Import socket2 0.4.4 am: beba3e6188 am: 9fb7ef254d am: 6e3f4b48ba

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/socket2/+/2377156

Change-Id: Iea52674971c7a5769a5e4428320a70b55f03946d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

19 files changed, 6099 insertions, 0 deletions

diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..b0a8014
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,6 @@
+{
+  "git": {
+    "sha1": "ac391b27fe7ab6740a61b8d52c2920ee383d5817"
+  },
+  "path_in_vcs": ""
+}
\ No newline at end of file
diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..a39ddf5
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,27 @@
+// This file is generated by cargo2android.py --config cargo2android.json.
+// Do not modify this file as changes will be overridden on upgrade.
+
+
+
+rust_library {
+    name: "libsocket2",
+    // has rustc warnings
+    host_supported: true,
+    crate_name: "socket2",
+    cargo_env_compat: true,
+    cargo_pkg_version: "0.4.4",
+    srcs: ["src/lib.rs"],
+    edition: "2018",
+    features: ["all"],
+    rustlibs: [
+        "liblibc",
+    ],
+    apex_available: [
+        "//apex_available:platform",
+        "com.android.btservices",
+        "com.android.resolv",
+        "com.android.uwb",
+    ],
+    vendor_available: true,
+    min_sdk_version: "29",
+}
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..8fd3884
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,39 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+name = "socket2"
+version = "0.4.4"
+authors = ["Alex Crichton <alex@alexcrichton.com>", "Thomas de Zeeuw <thomasdezeeuw@gmail.com>"]
+include = ["Cargo.toml", "LICENSE-APACHE", "LICENSE-MIT", "README.md", "src/**/*.rs"]
+description = "Utilities for handling networking sockets with a maximal amount of configuration\npossible intended.\n"
+homepage = "https://github.com/rust-lang/socket2"
+documentation = "https://docs.rs/socket2"
+readme = "README.md"
+keywords = ["io", "socket", "network"]
+categories = ["api-bindings", "network-programming"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-lang/socket2"
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[package.metadata.playground]
+features = ["all"]
+
+[features]
+all = []
+[target."cfg(unix)".dependencies.libc]
+version = "0.2.114"
+[target."cfg(windows)".dependencies.winapi]
+version = "0.3.9"
+features = ["handleapi", "ws2ipdef", "ws2tcpip"]
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..6ca3422
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,43 @@
+[package]
+name          = "socket2"
+version       = "0.4.4"
+authors       = [
+  "Alex Crichton <alex@alexcrichton.com>",
+  "Thomas de Zeeuw <thomasdezeeuw@gmail.com>"
+]
+license       = "MIT OR Apache-2.0"
+readme        = "README.md"
+repository    = "https://github.com/rust-lang/socket2"
+homepage      = "https://github.com/rust-lang/socket2"
+documentation = "https://docs.rs/socket2"
+description = """
+Utilities for handling networking sockets with a maximal amount of configuration
+possible intended.
+"""
+keywords      = ["io", "socket", "network"]
+categories    = ["api-bindings", "network-programming"]
+edition       = "2018"
+include       = [
+  "Cargo.toml",
+  "LICENSE-APACHE",
+  "LICENSE-MIT",
+  "README.md",
+  "src/**/*.rs",
+]
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[package.metadata.playground]
+features = ["all"]
+
+[target."cfg(unix)".dependencies]
+libc = "0.2.114"
+
+[target."cfg(windows)".dependencies]
+winapi = { version = "0.3.9", features = ["handleapi", "ws2ipdef", "ws2tcpip"] }
+
+[features]
+# Enable all API, even ones not available on all OSs.
+all = []
diff --git a/LICENSE b/LICENSE
new file mode 120000
index 0000000..6b579aa
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1 @@
+LICENSE-APACHE
\ No newline at end of file
diff --git a/LICENSE-APACHE b/LICENSE-APACHE
new file mode 100644
index 0000000..16fe87b
--- /dev/null
+++ b/LICENSE-APACHE
@@ -0,0 +1,201 @@
+                              Apache License
+                        Version 2.0, January 2004
+                     http://www.apache.org/licenses/
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
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+   any Contribution intentionally submitted for inclusion in the Work
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+   the terms of any separate license agreement you may have executed
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+6. Trademarks. This License does not grant permission to use the trade
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+   agreed to in writing, Licensor provides the Work (and each
+   Contributor provides its Contributions) on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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+8. Limitation of Liability. In no event and under no legal theory,
+   whether in tort (including negligence), contract, or otherwise,
+   unless required by applicable law (such as deliberate and grossly
+   negligent acts) or agreed to in writing, shall any Contributor be
+   liable to You for damages, including any direct, indirect, special,
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+   of your accepting any such warranty or additional liability.
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+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work.
+
+   To apply the Apache License to your work, attach the following
+   boilerplate notice, with the fields enclosed by brackets "[]"
+   replaced with your own identifying information. (Don't include
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+   comment syntax for the file format. We also recommend that a
+   file or class name and description of purpose be included on the
+   same "printed page" as the copyright notice for easier
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+Copyright [yyyy] [name of copyright owner]
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+	http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
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diff --git a/LICENSE-MIT b/LICENSE-MIT
new file mode 100644
index 0000000..39e0ed6
--- /dev/null
+++ b/LICENSE-MIT
@@ -0,0 +1,25 @@
+Copyright (c) 2014 Alex Crichton
+
+Permission is hereby granted, free of charge, to any
+person obtaining a copy of this software and associated
+documentation files (the "Software"), to deal in the
+Software without restriction, including without
+limitation the rights to use, copy, modify, merge,
+publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software
+is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice
+shall be included in all copies or substantial portions
+of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF
+ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
+TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
+SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..7c214be
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,20 @@
+name: "socket2"
+description: "Utilities for handling networking sockets with a maximal amount of configuration possible intended."
+third_party {
+  url {
+    type: HOMEPAGE
+    value: "https://crates.io/crates/socket2"
+  }
+  url {
+    type: ARCHIVE
+    value: "https://static.crates.io/crates/socket2/socket2-0.4.4.crate"
+  }
+  version: "0.4.4"
+  # Dual-licensed, using the least restrictive per go/thirdpartylicenses#same.
+  license_type: NOTICE
+  last_upgrade_date {
+    year: 2022
+    month: 12
+    day: 12
+  }
+}
diff --git a/MODULE_LICENSE_APACHE2 b/MODULE_LICENSE_APACHE2
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_APACHE2
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..45dc4dd
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1 @@
+include platform/prebuilts/rust:master:/OWNERS
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..45f4cf8
--- /dev/null
+++ b/README.md
@@ -0,0 +1,84 @@
+# Socket2
+
+Socket2 is a crate that provides utilities for creating and using sockets.
+
+The goal of this crate is to create and use a socket using advanced
+configuration options (those that are not available in the types in the standard
+library) without using any unsafe code.
+
+This crate provides as direct as possible access to the system's functionality
+for sockets, this means little effort to provide cross-platform utilities. It is
+up to the user to know how to use sockets when using this crate. *If you don't
+know how to create a socket using libc/system calls then this crate is not for
+you*. Most, if not all, functions directly relate to the equivalent system call
+with no error handling applied, so no handling errors such as `EINTR`. As a
+result using this crate can be a little wordy, but it should give you maximal
+flexibility over configuration of sockets.
+
+See the [API documentation] for more.
+
+[API documentation]: https://docs.rs/socket2
+
+# Two branches
+
+Currently Socket2 supports two versions: v0.4 and v0.3. Version 0.4 is developed
+in the master branch, version 0.3 in the [v0.3.x branch].
+
+[v0.3.x branch]: https://github.com/rust-lang/socket2/tree/v0.3.x
+
+# OS support
+
+Socket2 attempts to support the same OS/architectures as Rust does, see
+https://doc.rust-lang.org/nightly/rustc/platform-support.html. However this is
+not always possible, below is current list of support OSs.
+
+*If your favorite OS is not on the list consider contributing it! See [issue
+#78].*
+
+[issue #78]: https://github.com/rust-lang/socket2/issues/78
+
+### Tier 1
+
+These OSs are tested with each commit in the CI and must always pass the tests.
+All functions/types/etc., excluding ones behind the `all` feature, must work on
+these OSs.
+
+* Linux
+* macOS
+* Windows
+
+### Tier 2
+
+These OSs are currently build in the CI, but not tested. Not all
+functions/types/etc. may work on these OSs, even ones **not** behind the `all`
+feature flag.
+
+* Android
+* FreeBSD
+* Fuchsia
+* iOS
+* illumos
+* NetBSD
+* Redox
+* Solaris
+
+# Minimum Supported Rust Version (MSRV)
+
+Socket2 uses 1.46.0 as MSRV.
+
+# License
+
+This project is licensed under either of
+
+ * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or
+   http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or
+   http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in this project by you, as defined in the Apache-2.0 license,
+shall be dual licensed as above, without any additional terms or conditions.
diff --git a/cargo.out b/cargo.out
new file mode 100644
index 0000000..cec2d0b
--- /dev/null
+++ b/cargo.out
@@ -0,0 +1,20 @@
+### Running: /usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/development/scripts/../../prebuilts/rust/linux-x86/1.64.0/bin/cargo -v clean --target-dir target.tmp >> ./cargo.out 2>&1
+    Removing /usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp
+### Running: /usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/development/scripts/../../prebuilts/rust/linux-x86/1.64.0/bin/cargo -v build --target x86_64-unknown-linux-gnu --no-default-features --features all --target-dir target.tmp >> ./cargo.out 2>&1
+    Updating crates.io index
+   Compiling libc v0.2.138
+     Running `rustc --crate-name build_script_build /usr/local/google/home/chriswailes/.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.138/build.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type bin --emit=dep-info,link -C embed-bitcode=no -C debuginfo=2 --cfg 'feature="default"' --cfg 'feature="std"' -C metadata=a91c13d3321fe99a -C extra-filename=-a91c13d3321fe99a --out-dir /usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/debug/build/libc-a91c13d3321fe99a -L dependency=/usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/debug/deps --cap-lints allow`
+     Running `/usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/debug/build/libc-a91c13d3321fe99a/build-script-build`
+     Running `rustc --crate-name libc /usr/local/google/home/chriswailes/.cargo/registry/src/github.com-1ecc6299db9ec823/libc-0.2.138/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debuginfo=2 --cfg 'feature="default"' --cfg 'feature="std"' -C metadata=c27f6107a08ccd2c -C extra-filename=-c27f6107a08ccd2c --out-dir /usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/x86_64-unknown-linux-gnu/debug/deps --target x86_64-unknown-linux-gnu -L dependency=/usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/x86_64-unknown-linux-gnu/debug/deps -L dependency=/usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/debug/deps --cap-lints allow --cfg freebsd11 --cfg libc_priv_mod_use --cfg libc_union --cfg libc_const_size_of --cfg libc_align --cfg libc_int128 --cfg libc_core_cvoid --cfg libc_packedN --cfg libc_cfg_target_vendor --cfg libc_non_exhaustive --cfg libc_ptr_addr_of --cfg libc_underscore_const_names --cfg libc_const_extern_fn`
+   Compiling socket2 v0.4.4 (/usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2)
+     Running `rustc --crate-name socket2 --edition=2018 src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts,future-incompat --crate-type lib --emit=dep-info,metadata,link -C embed-bitcode=no -C debuginfo=2 --cfg 'feature="all"' -C metadata=96fa3d53ddb1d7a8 -C extra-filename=-96fa3d53ddb1d7a8 --out-dir /usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/x86_64-unknown-linux-gnu/debug/deps --target x86_64-unknown-linux-gnu -C incremental=/usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/x86_64-unknown-linux-gnu/debug/incremental -L dependency=/usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/x86_64-unknown-linux-gnu/debug/deps -L dependency=/usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/debug/deps --extern libc=/usr/local/google/home/chriswailes/projects/android/aosp-plus-rust/external/rust/crates/socket2/target.tmp/x86_64-unknown-linux-gnu/debug/deps/liblibc-c27f6107a08ccd2c.rmeta`
+warning: unnecessary `unsafe` block
+    --> src/sys/unix.rs:1486:9
+     |
+1486 |         unsafe {
+     |         ^^^^^^ unnecessary `unsafe` block
+     |
+     = note: `#[warn(unused_unsafe)]` on by default
+
+warning: `socket2` (lib) generated 1 warning
+    Finished dev [unoptimized + debuginfo] target(s) in 2.18s
diff --git a/cargo2android.json b/cargo2android.json
new file mode 100644
index 0000000..5488125
--- /dev/null
+++ b/cargo2android.json
@@ -0,0 +1,13 @@
+{
+  "apex-available": [
+    "//apex_available:platform",
+    "com.android.btservices",
+    "com.android.resolv",
+    "com.android.uwb"
+  ],
+  "device": true,
+  "features": "all",
+  "min-sdk-version": "29",
+  "vendor-available": true,
+  "run": true
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..d01b652
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,442 @@
+// Copyright 2015 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Utilities for creating and using sockets.
+//!
+//! The goal of this crate is to create and use a socket using advanced
+//! configuration options (those that are not available in the types in the
+//! standard library) without using any unsafe code.
+//!
+//! This crate provides as direct as possible access to the system's
+//! functionality for sockets, this means little effort to provide
+//! cross-platform utilities. It is up to the user to know how to use sockets
+//! when using this crate. *If you don't know how to create a socket using
+//! libc/system calls then this crate is not for you*. Most, if not all,
+//! functions directly relate to the equivalent system call with no error
+//! handling applied, so no handling errors such as [`EINTR`]. As a result using
+//! this crate can be a little wordy, but it should give you maximal flexibility
+//! over configuration of sockets.
+//!
+//! [`EINTR`]: std::io::ErrorKind::Interrupted
+//!
+//! # Examples
+//!
+//! ```no_run
+//! # fn main() -> std::io::Result<()> {
+//! use std::net::{SocketAddr, TcpListener};
+//! use socket2::{Socket, Domain, Type};
+//!
+//! // Create a TCP listener bound to two addresses.
+//! let socket = Socket::new(Domain::IPV6, Type::STREAM, None)?;
+//!
+//! socket.set_only_v6(false)?;
+//! let address: SocketAddr = "[::1]:12345".parse().unwrap();
+//! socket.bind(&address.into())?;
+//! socket.listen(128)?;
+//!
+//! let listener: TcpListener = socket.into();
+//! // ...
+//! # drop(listener);
+//! # Ok(()) }
+//! ```
+//!
+//! ## Features
+//!
+//! This crate has a single feature `all`, which enables all functions even ones
+//! that are not available on all OSs.
+
+#![doc(html_root_url = "https://docs.rs/socket2/0.3")]
+#![deny(missing_docs, missing_debug_implementations, rust_2018_idioms)]
+// Show required OS/features on docs.rs.
+#![cfg_attr(docsrs, feature(doc_cfg))]
+// Disallow warnings when running tests.
+#![cfg_attr(test, deny(warnings))]
+// Disallow warnings in examples.
+#![doc(test(attr(deny(warnings))))]
+
+use std::fmt;
+use std::mem::MaybeUninit;
+use std::net::SocketAddr;
+use std::ops::{Deref, DerefMut};
+use std::time::Duration;
+
+/// Macro to implement `fmt::Debug` for a type, printing the constant names
+/// rather than a number.
+///
+/// Note this is used in the `sys` module and thus must be defined before
+/// defining the modules.
+macro_rules! impl_debug {
+    (
+        // Type name for which to implement `fmt::Debug`.
+        $type: path,
+        $(
+            $(#[$target: meta])*
+            // The flag(s) to check.
+            // Need to specific the libc crate because Windows doesn't use
+            // `libc` but `winapi`.
+            $libc: ident :: $flag: ident
+        ),+ $(,)*
+    ) => {
+        impl std::fmt::Debug for $type {
+            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                let string = match self.0 {
+                    $(
+                        $(#[$target])*
+                        $libc :: $flag => stringify!($flag),
+                    )+
+                    n => return write!(f, "{}", n),
+                };
+                f.write_str(string)
+            }
+        }
+    };
+}
+
+/// Macro to convert from one network type to another.
+macro_rules! from {
+    ($from: ty, $for: ty) => {
+        impl From<$from> for $for {
+            fn from(socket: $from) -> $for {
+                #[cfg(unix)]
+                unsafe {
+                    <$for>::from_raw_fd(socket.into_raw_fd())
+                }
+                #[cfg(windows)]
+                unsafe {
+                    <$for>::from_raw_socket(socket.into_raw_socket())
+                }
+            }
+        }
+    };
+}
+
+mod sockaddr;
+mod socket;
+mod sockref;
+
+#[cfg_attr(unix, path = "sys/unix.rs")]
+#[cfg_attr(windows, path = "sys/windows.rs")]
+mod sys;
+
+#[cfg(not(any(windows, unix)))]
+compile_error!("Socket2 doesn't support the compile target");
+
+use sys::c_int;
+
+pub use sockaddr::SockAddr;
+pub use socket::Socket;
+pub use sockref::SockRef;
+
+#[cfg(not(any(
+    target_os = "haiku",
+    target_os = "illumos",
+    target_os = "netbsd",
+    target_os = "redox",
+    target_os = "solaris",
+)))]
+pub use socket::InterfaceIndexOrAddress;
+
+/// Specification of the communication domain for a socket.
+///
+/// This is a newtype wrapper around an integer which provides a nicer API in
+/// addition to an injection point for documentation. Convenience constants such
+/// as [`Domain::IPV4`], [`Domain::IPV6`], etc, are provided to avoid reaching
+/// into libc for various constants.
+///
+/// This type is freely interconvertible with C's `int` type, however, if a raw
+/// value needs to be provided.
+#[derive(Copy, Clone, Eq, PartialEq)]
+pub struct Domain(c_int);
+
+impl Domain {
+    /// Domain for IPv4 communication, corresponding to `AF_INET`.
+    pub const IPV4: Domain = Domain(sys::AF_INET);
+
+    /// Domain for IPv6 communication, corresponding to `AF_INET6`.
+    pub const IPV6: Domain = Domain(sys::AF_INET6);
+
+    /// Returns the correct domain for `address`.
+    pub const fn for_address(address: SocketAddr) -> Domain {
+        match address {
+            SocketAddr::V4(_) => Domain::IPV4,
+            SocketAddr::V6(_) => Domain::IPV6,
+        }
+    }
+}
+
+impl From<c_int> for Domain {
+    fn from(d: c_int) -> Domain {
+        Domain(d)
+    }
+}
+
+impl From<Domain> for c_int {
+    fn from(d: Domain) -> c_int {
+        d.0
+    }
+}
+
+/// Specification of communication semantics on a socket.
+///
+/// This is a newtype wrapper around an integer which provides a nicer API in
+/// addition to an injection point for documentation. Convenience constants such
+/// as [`Type::STREAM`], [`Type::DGRAM`], etc, are provided to avoid reaching
+/// into libc for various constants.
+///
+/// This type is freely interconvertible with C's `int` type, however, if a raw
+/// value needs to be provided.
+#[derive(Copy, Clone, Eq, PartialEq)]
+pub struct Type(c_int);
+
+impl Type {
+    /// Type corresponding to `SOCK_STREAM`.
+    ///
+    /// Used for protocols such as TCP.
+    pub const STREAM: Type = Type(sys::SOCK_STREAM);
+
+    /// Type corresponding to `SOCK_DGRAM`.
+    ///
+    /// Used for protocols such as UDP.
+    pub const DGRAM: Type = Type(sys::SOCK_DGRAM);
+
+    /// Type corresponding to `SOCK_SEQPACKET`.
+    #[cfg(feature = "all")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "all")))]
+    pub const SEQPACKET: Type = Type(sys::SOCK_SEQPACKET);
+
+    /// Type corresponding to `SOCK_RAW`.
+    #[cfg(all(feature = "all", not(target_os = "redox")))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", not(target_os = "redox")))))]
+    pub const RAW: Type = Type(sys::SOCK_RAW);
+}
+
+impl From<c_int> for Type {
+    fn from(t: c_int) -> Type {
+        Type(t)
+    }
+}
+
+impl From<Type> for c_int {
+    fn from(t: Type) -> c_int {
+        t.0
+    }
+}
+
+/// Protocol specification used for creating sockets via `Socket::new`.
+///
+/// This is a newtype wrapper around an integer which provides a nicer API in
+/// addition to an injection point for documentation.
+///
+/// This type is freely interconvertible with C's `int` type, however, if a raw
+/// value needs to be provided.
+#[derive(Copy, Clone, Eq, PartialEq)]
+pub struct Protocol(c_int);
+
+impl Protocol {
+    /// Protocol corresponding to `ICMPv4`.
+    pub const ICMPV4: Protocol = Protocol(sys::IPPROTO_ICMP);
+
+    /// Protocol corresponding to `ICMPv6`.
+    pub const ICMPV6: Protocol = Protocol(sys::IPPROTO_ICMPV6);
+
+    /// Protocol corresponding to `TCP`.
+    pub const TCP: Protocol = Protocol(sys::IPPROTO_TCP);
+
+    /// Protocol corresponding to `UDP`.
+    pub const UDP: Protocol = Protocol(sys::IPPROTO_UDP);
+}
+
+impl From<c_int> for Protocol {
+    fn from(p: c_int) -> Protocol {
+        Protocol(p)
+    }
+}
+
+impl From<Protocol> for c_int {
+    fn from(p: Protocol) -> c_int {
+        p.0
+    }
+}
+
+/// Flags for incoming messages.
+///
+/// Flags provide additional information about incoming messages.
+#[cfg(not(target_os = "redox"))]
+#[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+#[derive(Copy, Clone, Eq, PartialEq)]
+pub struct RecvFlags(c_int);
+
+#[cfg(not(target_os = "redox"))]
+impl RecvFlags {
+    /// Check if the message contains a truncated datagram.
+    ///
+    /// This flag is only used for datagram-based sockets,
+    /// not for stream sockets.
+    ///
+    /// On Unix this corresponds to the `MSG_TRUNC` flag.
+    /// On Windows this corresponds to the `WSAEMSGSIZE` error code.
+    pub const fn is_truncated(self) -> bool {
+        self.0 & sys::MSG_TRUNC != 0
+    }
+}
+
+/// A version of [`IoSliceMut`] that allows the buffer to be uninitialised.
+///
+/// [`IoSliceMut`]: std::io::IoSliceMut
+#[repr(transparent)]
+pub struct MaybeUninitSlice<'a>(sys::MaybeUninitSlice<'a>);
+
+impl<'a> fmt::Debug for MaybeUninitSlice<'a> {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(self.0.as_slice(), fmt)
+    }
+}
+
+impl<'a> MaybeUninitSlice<'a> {
+    /// Creates a new `MaybeUninitSlice` wrapping a byte slice.
+    ///
+    /// # Panics
+    ///
+    /// Panics on Windows if the slice is larger than 4GB.
+    pub fn new(buf: &'a mut [MaybeUninit<u8>]) -> MaybeUninitSlice<'a> {
+        MaybeUninitSlice(sys::MaybeUninitSlice::new(buf))
+    }
+}
+
+impl<'a> Deref for MaybeUninitSlice<'a> {
+    type Target = [MaybeUninit<u8>];
+
+    fn deref(&self) -> &[MaybeUninit<u8>] {
+        self.0.as_slice()
+    }
+}
+
+impl<'a> DerefMut for MaybeUninitSlice<'a> {
+    fn deref_mut(&mut self) -> &mut [MaybeUninit<u8>] {
+        self.0.as_mut_slice()
+    }
+}
+
+/// Configures a socket's TCP keepalive parameters.
+///
+/// See [`Socket::set_tcp_keepalive`].
+#[derive(Debug, Clone)]
+pub struct TcpKeepalive {
+    time: Option<Duration>,
+    #[cfg(not(any(target_os = "redox", target_os = "solaris")))]
+    interval: Option<Duration>,
+    #[cfg(not(any(target_os = "redox", target_os = "solaris", target_os = "windows")))]
+    retries: Option<u32>,
+}
+
+impl TcpKeepalive {
+    /// Returns a new, empty set of TCP keepalive parameters.
+    pub const fn new() -> TcpKeepalive {
+        TcpKeepalive {
+            time: None,
+            #[cfg(not(any(target_os = "redox", target_os = "solaris")))]
+            interval: None,
+            #[cfg(not(any(target_os = "redox", target_os = "solaris", target_os = "windows")))]
+            retries: None,
+        }
+    }
+
+    /// Set the amount of time after which TCP keepalive probes will be sent on
+    /// idle connections.
+    ///
+    /// This will set `TCP_KEEPALIVE` on macOS and iOS, and
+    /// `TCP_KEEPIDLE` on all other Unix operating systems, except
+    /// OpenBSD and Haiku which don't support any way to set this
+    /// option. On Windows, this sets the value of the `tcp_keepalive`
+    /// struct's `keepalivetime` field.
+    ///
+    /// Some platforms specify this value in seconds, so sub-second
+    /// specifications may be omitted.
+    pub const fn with_time(self, time: Duration) -> Self {
+        Self {
+            time: Some(time),
+            ..self
+        }
+    }
+
+    /// Set the value of the `TCP_KEEPINTVL` option. On Windows, this sets the
+    /// value of the `tcp_keepalive` struct's `keepaliveinterval` field.
+    ///
+    /// Sets the time interval between TCP keepalive probes.
+    ///
+    /// Some platforms specify this value in seconds, so sub-second
+    /// specifications may be omitted.
+    #[cfg(all(
+        feature = "all",
+        any(
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_vendor = "apple",
+            windows,
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(
+                target_os = "freebsd",
+                target_os = "fuchsia",
+                target_os = "linux",
+                target_os = "netbsd",
+                target_vendor = "apple",
+                windows,
+            )
+        )))
+    )]
+    pub const fn with_interval(self, interval: Duration) -> Self {
+        Self {
+            interval: Some(interval),
+            ..self
+        }
+    }
+
+    /// Set the value of the `TCP_KEEPCNT` option.
+    ///
+    /// Set the maximum number of TCP keepalive probes that will be sent before
+    /// dropping a connection, if TCP keepalive is enabled on this socket.
+    #[cfg(all(
+        feature = "all",
+        any(
+            doc,
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_vendor = "apple",
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(
+                target_os = "freebsd",
+                target_os = "fuchsia",
+                target_os = "linux",
+                target_os = "netbsd",
+                target_vendor = "apple",
+            )
+        )))
+    )]
+    pub const fn with_retries(self, retries: u32) -> Self {
+        Self {
+            retries: Some(retries),
+            ..self
+        }
+    }
+}
diff --git a/src/sockaddr.rs b/src/sockaddr.rs
new file mode 100644
index 0000000..55951b6
--- /dev/null
+++ b/src/sockaddr.rs
@@ -0,0 +1,348 @@
+use std::mem::{self, size_of, MaybeUninit};
+use std::net::{SocketAddr, SocketAddrV4, SocketAddrV6};
+use std::{fmt, io};
+
+use crate::sys::{
+    sa_family_t, sockaddr, sockaddr_in, sockaddr_in6, sockaddr_storage, socklen_t, AF_INET,
+    AF_INET6,
+};
+#[cfg(windows)]
+use winapi::shared::ws2ipdef::SOCKADDR_IN6_LH_u;
+
+/// The address of a socket.
+///
+/// `SockAddr`s may be constructed directly to and from the standard library
+/// [`SocketAddr`], [`SocketAddrV4`], and [`SocketAddrV6`] types.
+pub struct SockAddr {
+    storage: sockaddr_storage,
+    len: socklen_t,
+}
+
+#[allow(clippy::len_without_is_empty)]
+impl SockAddr {
+    /// Create a `SockAddr` from the underlying storage and its length.
+    ///
+    /// # Safety
+    ///
+    /// Caller must ensure that the address family and length match the type of
+    /// storage address. For example if `storage.ss_family` is set to `AF_INET`
+    /// the `storage` must be initialised as `sockaddr_in`, setting the content
+    /// and length appropriately.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # fn main() -> std::io::Result<()> {
+    /// # #[cfg(unix)] {
+    /// use std::io;
+    /// use std::mem;
+    /// use std::os::unix::io::AsRawFd;
+    ///
+    /// use socket2::{SockAddr, Socket, Domain, Type};
+    ///
+    /// let socket = Socket::new(Domain::IPV4, Type::STREAM, None)?;
+    ///
+    /// // Initialise a `SocketAddr` byte calling `getsockname(2)`.
+    /// let mut addr_storage: libc::sockaddr_storage = unsafe { mem::zeroed() };
+    /// let mut len = mem::size_of_val(&addr_storage) as libc::socklen_t;
+    ///
+    /// // The `getsockname(2)` system call will intiliase `storage` for
+    /// // us, setting `len` to the correct length.
+    /// let res = unsafe {
+    ///     libc::getsockname(
+    ///         socket.as_raw_fd(),
+    ///         (&mut addr_storage as *mut libc::sockaddr_storage).cast(),
+    ///         &mut len,
+    ///     )
+    /// };
+    /// if res == -1 {
+    ///     return Err(io::Error::last_os_error());
+    /// }
+    ///
+    /// let address = unsafe { SockAddr::new(addr_storage, len) };
+    /// # drop(address);
+    /// # }
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub const unsafe fn new(storage: sockaddr_storage, len: socklen_t) -> SockAddr {
+        SockAddr { storage, len }
+    }
+
+    /// Initialise a `SockAddr` by calling the function `init`.
+    ///
+    /// The type of the address storage and length passed to the function `init`
+    /// is OS/architecture specific.
+    ///
+    /// The address is zeroed before `init` is called and is thus valid to
+    /// dereference and read from. The length initialised to the maximum length
+    /// of the storage.
+    ///
+    /// # Safety
+    ///
+    /// Caller must ensure that the address family and length match the type of
+    /// storage address. For example if `storage.ss_family` is set to `AF_INET`
+    /// the `storage` must be initialised as `sockaddr_in`, setting the content
+    /// and length appropriately.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # fn main() -> std::io::Result<()> {
+    /// # #[cfg(unix)] {
+    /// use std::io;
+    /// use std::os::unix::io::AsRawFd;
+    ///
+    /// use socket2::{SockAddr, Socket, Domain, Type};
+    ///
+    /// let socket = Socket::new(Domain::IPV4, Type::STREAM, None)?;
+    ///
+    /// // Initialise a `SocketAddr` byte calling `getsockname(2)`.
+    /// let (_, address) = unsafe {
+    ///     SockAddr::init(|addr_storage, len| {
+    ///         // The `getsockname(2)` system call will intiliase `storage` for
+    ///         // us, setting `len` to the correct length.
+    ///         if libc::getsockname(socket.as_raw_fd(), addr_storage.cast(), len) == -1 {
+    ///             Err(io::Error::last_os_error())
+    ///         } else {
+    ///             Ok(())
+    ///         }
+    ///     })
+    /// }?;
+    /// # drop(address);
+    /// # }
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub unsafe fn init<F, T>(init: F) -> io::Result<(T, SockAddr)>
+    where
+        F: FnOnce(*mut sockaddr_storage, *mut socklen_t) -> io::Result<T>,
+    {
+        const STORAGE_SIZE: socklen_t = size_of::<sockaddr_storage>() as socklen_t;
+        // NOTE: `SockAddr::unix` depends on the storage being zeroed before
+        // calling `init`.
+        // NOTE: calling `recvfrom` with an empty buffer also depends on the
+        // storage being zeroed before calling `init` as the OS might not
+        // initialise it.
+        let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
+        let mut len = STORAGE_SIZE;
+        init(storage.as_mut_ptr(), &mut len).map(|res| {
+            debug_assert!(len <= STORAGE_SIZE, "overflown address storage");
+            let addr = SockAddr {
+                // Safety: zeroed-out `sockaddr_storage` is valid, caller must
+                // ensure at least `len` bytes are valid.
+                storage: storage.assume_init(),
+                len,
+            };
+            (res, addr)
+        })
+    }
+
+    /// Returns this address's family.
+    pub const fn family(&self) -> sa_family_t {
+        self.storage.ss_family
+    }
+
+    /// Returns the size of this address in bytes.
+    pub const fn len(&self) -> socklen_t {
+        self.len
+    }
+
+    /// Returns a raw pointer to the address.
+    pub const fn as_ptr(&self) -> *const sockaddr {
+        &self.storage as *const _ as *const _
+    }
+
+    /// Returns a raw pointer to the address storage.
+    #[cfg(all(unix, not(target_os = "redox")))]
+    pub(crate) const fn as_storage_ptr(&self) -> *const sockaddr_storage {
+        &self.storage
+    }
+
+    /// Returns this address as a `SocketAddr` if it is in the `AF_INET` (IPv4)
+    /// or `AF_INET6` (IPv6) family, otherwise returns `None`.
+    pub fn as_socket(&self) -> Option<SocketAddr> {
+        if self.storage.ss_family == AF_INET as sa_family_t {
+            // Safety: if the ss_family field is AF_INET then storage must be a sockaddr_in.
+            let addr = unsafe { &*(&self.storage as *const _ as *const sockaddr_in) };
+
+            let ip = crate::sys::from_in_addr(addr.sin_addr);
+            let port = u16::from_be(addr.sin_port);
+            Some(SocketAddr::V4(SocketAddrV4::new(ip, port)))
+        } else if self.storage.ss_family == AF_INET6 as sa_family_t {
+            // Safety: if the ss_family field is AF_INET6 then storage must be a sockaddr_in6.
+            let addr = unsafe { &*(&self.storage as *const _ as *const sockaddr_in6) };
+
+            let ip = crate::sys::from_in6_addr(addr.sin6_addr);
+            let port = u16::from_be(addr.sin6_port);
+            Some(SocketAddr::V6(SocketAddrV6::new(
+                ip,
+                port,
+                addr.sin6_flowinfo,
+                #[cfg(unix)]
+                addr.sin6_scope_id,
+                #[cfg(windows)]
+                unsafe {
+                    *addr.u.sin6_scope_id()
+                },
+            )))
+        } else {
+            None
+        }
+    }
+
+    /// Returns this address as a [`SocketAddrV4`] if it is in the `AF_INET`
+    /// family.
+    pub fn as_socket_ipv4(&self) -> Option<SocketAddrV4> {
+        match self.as_socket() {
+            Some(SocketAddr::V4(addr)) => Some(addr),
+            _ => None,
+        }
+    }
+
+    /// Returns this address as a [`SocketAddrV6`] if it is in the `AF_INET6`
+    /// family.
+    pub fn as_socket_ipv6(&self) -> Option<SocketAddrV6> {
+        match self.as_socket() {
+            Some(SocketAddr::V6(addr)) => Some(addr),
+            _ => None,
+        }
+    }
+}
+
+impl From<SocketAddr> for SockAddr {
+    fn from(addr: SocketAddr) -> SockAddr {
+        match addr {
+            SocketAddr::V4(addr) => addr.into(),
+            SocketAddr::V6(addr) => addr.into(),
+        }
+    }
+}
+
+impl From<SocketAddrV4> for SockAddr {
+    fn from(addr: SocketAddrV4) -> SockAddr {
+        let sockaddr_in = sockaddr_in {
+            sin_family: AF_INET as sa_family_t,
+            sin_port: addr.port().to_be(),
+            sin_addr: crate::sys::to_in_addr(addr.ip()),
+            sin_zero: Default::default(),
+            #[cfg(any(
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "haiku",
+                target_os = "ios",
+                target_os = "macos",
+                target_os = "netbsd",
+                target_os = "openbsd"
+            ))]
+            sin_len: 0,
+        };
+        let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
+        // Safety: A `sockaddr_in` is memory compatible with a `sockaddr_storage`
+        unsafe { (storage.as_mut_ptr() as *mut sockaddr_in).write(sockaddr_in) };
+        SockAddr {
+            storage: unsafe { storage.assume_init() },
+            len: mem::size_of::<sockaddr_in>() as socklen_t,
+        }
+    }
+}
+
+impl From<SocketAddrV6> for SockAddr {
+    fn from(addr: SocketAddrV6) -> SockAddr {
+        #[cfg(windows)]
+        let u = unsafe {
+            let mut u = mem::zeroed::<SOCKADDR_IN6_LH_u>();
+            *u.sin6_scope_id_mut() = addr.scope_id();
+            u
+        };
+
+        let sockaddr_in6 = sockaddr_in6 {
+            sin6_family: AF_INET6 as sa_family_t,
+            sin6_port: addr.port().to_be(),
+            sin6_addr: crate::sys::to_in6_addr(addr.ip()),
+            sin6_flowinfo: addr.flowinfo(),
+            #[cfg(unix)]
+            sin6_scope_id: addr.scope_id(),
+            #[cfg(windows)]
+            u,
+            #[cfg(any(
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "haiku",
+                target_os = "ios",
+                target_os = "macos",
+                target_os = "netbsd",
+                target_os = "openbsd"
+            ))]
+            sin6_len: 0,
+            #[cfg(any(target_os = "solaris", target_os = "illumos"))]
+            __sin6_src_id: 0,
+        };
+        let mut storage = MaybeUninit::<sockaddr_storage>::zeroed();
+        // Safety: A `sockaddr_in6` is memory compatible with a `sockaddr_storage`
+        unsafe { (storage.as_mut_ptr() as *mut sockaddr_in6).write(sockaddr_in6) };
+        SockAddr {
+            storage: unsafe { storage.assume_init() },
+            len: mem::size_of::<sockaddr_in6>() as socklen_t,
+        }
+    }
+}
+
+impl fmt::Debug for SockAddr {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut f = fmt.debug_struct("SockAddr");
+        #[cfg(any(
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "haiku",
+            target_os = "hermit",
+            target_os = "ios",
+            target_os = "macos",
+            target_os = "netbsd",
+            target_os = "openbsd",
+            target_os = "vxworks",
+        ))]
+        f.field("ss_len", &self.storage.ss_len);
+        f.field("ss_family", &self.storage.ss_family)
+            .field("len", &self.len)
+            .finish()
+    }
+}
+
+#[test]
+fn ipv4() {
+    use std::net::Ipv4Addr;
+    let std = SocketAddrV4::new(Ipv4Addr::new(1, 2, 3, 4), 9876);
+    let addr = SockAddr::from(std);
+    assert_eq!(addr.family(), AF_INET as sa_family_t);
+    assert_eq!(addr.len(), size_of::<sockaddr_in>() as socklen_t);
+    assert_eq!(addr.as_socket(), Some(SocketAddr::V4(std)));
+    assert_eq!(addr.as_socket_ipv4(), Some(std));
+    assert!(addr.as_socket_ipv6().is_none());
+
+    let addr = SockAddr::from(SocketAddr::from(std));
+    assert_eq!(addr.family(), AF_INET as sa_family_t);
+    assert_eq!(addr.len(), size_of::<sockaddr_in>() as socklen_t);
+    assert_eq!(addr.as_socket(), Some(SocketAddr::V4(std)));
+    assert_eq!(addr.as_socket_ipv4(), Some(std));
+    assert!(addr.as_socket_ipv6().is_none());
+}
+
+#[test]
+fn ipv6() {
+    use std::net::Ipv6Addr;
+    let std = SocketAddrV6::new(Ipv6Addr::new(1, 2, 3, 4, 5, 6, 7, 8), 9876, 11, 12);
+    let addr = SockAddr::from(std);
+    assert_eq!(addr.family(), AF_INET6 as sa_family_t);
+    assert_eq!(addr.len(), size_of::<sockaddr_in6>() as socklen_t);
+    assert_eq!(addr.as_socket(), Some(SocketAddr::V6(std)));
+    assert!(addr.as_socket_ipv4().is_none());
+    assert_eq!(addr.as_socket_ipv6(), Some(std));
+
+    let addr = SockAddr::from(SocketAddr::from(std));
+    assert_eq!(addr.family(), AF_INET6 as sa_family_t);
+    assert_eq!(addr.len(), size_of::<sockaddr_in6>() as socklen_t);
+    assert_eq!(addr.as_socket(), Some(SocketAddr::V6(std)));
+    assert!(addr.as_socket_ipv4().is_none());
+    assert_eq!(addr.as_socket_ipv6(), Some(std));
+}
diff --git a/src/socket.rs b/src/socket.rs
new file mode 100644
index 0000000..028c4ae
--- /dev/null
+++ b/src/socket.rs
@@ -0,0 +1,1781 @@
+// Copyright 2015 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::fmt;
+use std::io::{self, Read, Write};
+#[cfg(not(target_os = "redox"))]
+use std::io::{IoSlice, IoSliceMut};
+use std::mem::MaybeUninit;
+use std::net::{self, Ipv4Addr, Ipv6Addr, Shutdown};
+#[cfg(unix)]
+use std::os::unix::io::{FromRawFd, IntoRawFd};
+#[cfg(windows)]
+use std::os::windows::io::{FromRawSocket, IntoRawSocket};
+use std::time::Duration;
+
+use crate::sys::{self, c_int, getsockopt, setsockopt, Bool};
+use crate::{Domain, Protocol, SockAddr, TcpKeepalive, Type};
+#[cfg(not(target_os = "redox"))]
+use crate::{MaybeUninitSlice, RecvFlags};
+
+/// Owned wrapper around a system socket.
+///
+/// This type simply wraps an instance of a file descriptor (`c_int`) on Unix
+/// and an instance of `SOCKET` on Windows. This is the main type exported by
+/// this crate and is intended to mirror the raw semantics of sockets on
+/// platforms as closely as possible. Almost all methods correspond to
+/// precisely one libc or OS API call which is essentially just a "Rustic
+/// translation" of what's below.
+///
+/// ## Converting to and from other types
+///
+/// This type can be freely converted into the network primitives provided by
+/// the standard library, such as [`TcpStream`] or [`UdpSocket`], using the
+/// [`From`] trait, see the example below.
+///
+/// [`TcpStream`]: std::net::TcpStream
+/// [`UdpSocket`]: std::net::UdpSocket
+///
+/// # Notes
+///
+/// Some methods that set options on `Socket` require two system calls to set
+/// there options without overwriting previously set options. We do this by
+/// first getting the current settings, applying the desired changes and than
+/// updating the settings. This means that the operation is **not** atomic. This
+/// can lead to a data race when two threads are changing options in parallel.
+///
+/// # Examples
+/// ```no_run
+/// # fn main() -> std::io::Result<()> {
+/// use std::net::{SocketAddr, TcpListener};
+/// use socket2::{Socket, Domain, Type};
+///
+/// // create a TCP listener bound to two addresses
+/// let socket = Socket::new(Domain::IPV4, Type::STREAM, None)?;
+///
+/// let address: SocketAddr = "[::1]:12345".parse().unwrap();
+/// let address = address.into();
+/// socket.bind(&address)?;
+/// socket.bind(&address)?;
+/// socket.listen(128)?;
+///
+/// let listener: TcpListener = socket.into();
+/// // ...
+/// # drop(listener);
+/// # Ok(()) }
+/// ```
+pub struct Socket {
+    inner: Inner,
+}
+
+/// Store a `TcpStream` internally to take advantage of its niche optimizations on Unix platforms.
+pub(crate) type Inner = std::net::TcpStream;
+
+impl Socket {
+    /// # Safety
+    ///
+    /// The caller must ensure `raw` is a valid file descriptor/socket. NOTE:
+    /// this should really be marked `unsafe`, but this being an internal
+    /// function, often passed as mapping function, it's makes it very
+    /// inconvenient to mark it as `unsafe`.
+    pub(crate) fn from_raw(raw: sys::Socket) -> Socket {
+        Socket {
+            inner: unsafe {
+                // SAFETY: the caller must ensure that `raw` is a valid file
+                // descriptor, but when it isn't it could return I/O errors, or
+                // potentially close a fd it doesn't own. All of that isn't
+                // memory unsafe, so it's not desired but never memory unsafe or
+                // causes UB.
+                //
+                // However there is one exception. We use `TcpStream` to
+                // represent the `Socket` internally (see `Inner` type),
+                // `TcpStream` has a layout optimisation that doesn't allow for
+                // negative file descriptors (as those are always invalid).
+                // Violating this assumption (fd never negative) causes UB,
+                // something we don't want. So check for that we have this
+                // `assert!`.
+                #[cfg(unix)]
+                assert!(raw >= 0, "tried to create a `Socket` with an invalid fd");
+                sys::socket_from_raw(raw)
+            },
+        }
+    }
+
+    pub(crate) fn as_raw(&self) -> sys::Socket {
+        sys::socket_as_raw(&self.inner)
+    }
+
+    pub(crate) fn into_raw(self) -> sys::Socket {
+        sys::socket_into_raw(self.inner)
+    }
+
+    /// Creates a new socket and sets common flags.
+    ///
+    /// This function corresponds to `socket(2)` on Unix and `WSASocketW` on
+    /// Windows.
+    ///
+    /// On Unix-like systems, the close-on-exec flag is set on the new socket.
+    /// Additionally, on Apple platforms `SOCK_NOSIGPIPE` is set. On Windows,
+    /// the socket is made non-inheritable.
+    ///
+    /// [`Socket::new_raw`] can be used if you don't want these flags to be set.
+    pub fn new(domain: Domain, ty: Type, protocol: Option<Protocol>) -> io::Result<Socket> {
+        let ty = set_common_type(ty);
+        Socket::new_raw(domain, ty, protocol).and_then(set_common_flags)
+    }
+
+    /// Creates a new socket ready to be configured.
+    ///
+    /// This function corresponds to `socket(2)` on Unix and `WSASocketW` on
+    /// Windows and simply creates a new socket, no other configuration is done.
+    pub fn new_raw(domain: Domain, ty: Type, protocol: Option<Protocol>) -> io::Result<Socket> {
+        let protocol = protocol.map(|p| p.0).unwrap_or(0);
+        sys::socket(domain.0, ty.0, protocol).map(Socket::from_raw)
+    }
+
+    /// Creates a pair of sockets which are connected to each other.
+    ///
+    /// This function corresponds to `socketpair(2)`.
+    ///
+    /// This function sets the same flags as in done for [`Socket::new`],
+    /// [`Socket::pair_raw`] can be used if you don't want to set those flags.
+    #[cfg(any(doc, all(feature = "all", unix)))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", unix))))]
+    pub fn pair(
+        domain: Domain,
+        ty: Type,
+        protocol: Option<Protocol>,
+    ) -> io::Result<(Socket, Socket)> {
+        let ty = set_common_type(ty);
+        let (a, b) = Socket::pair_raw(domain, ty, protocol)?;
+        let a = set_common_flags(a)?;
+        let b = set_common_flags(b)?;
+        Ok((a, b))
+    }
+
+    /// Creates a pair of sockets which are connected to each other.
+    ///
+    /// This function corresponds to `socketpair(2)`.
+    #[cfg(any(doc, all(feature = "all", unix)))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", unix))))]
+    pub fn pair_raw(
+        domain: Domain,
+        ty: Type,
+        protocol: Option<Protocol>,
+    ) -> io::Result<(Socket, Socket)> {
+        let protocol = protocol.map(|p| p.0).unwrap_or(0);
+        sys::socketpair(domain.0, ty.0, protocol)
+            .map(|[a, b]| (Socket::from_raw(a), Socket::from_raw(b)))
+    }
+
+    /// Binds this socket to the specified address.
+    ///
+    /// This function directly corresponds to the `bind(2)` function on Windows
+    /// and Unix.
+    pub fn bind(&self, address: &SockAddr) -> io::Result<()> {
+        sys::bind(self.as_raw(), address)
+    }
+
+    /// Initiate a connection on this socket to the specified address.
+    ///
+    /// This function directly corresponds to the `connect(2)` function on
+    /// Windows and Unix.
+    ///
+    /// An error will be returned if `listen` or `connect` has already been
+    /// called on this builder.
+    ///
+    /// # Notes
+    ///
+    /// When using a non-blocking connect (by setting the socket into
+    /// non-blocking mode before calling this function), socket option can't be
+    /// set *while connecting*. This will cause errors on Windows. Socket
+    /// options can be safely set before and after connecting the socket.
+    pub fn connect(&self, address: &SockAddr) -> io::Result<()> {
+        sys::connect(self.as_raw(), address)
+    }
+
+    /// Initiate a connection on this socket to the specified address, only
+    /// only waiting for a certain period of time for the connection to be
+    /// established.
+    ///
+    /// Unlike many other methods on `Socket`, this does *not* correspond to a
+    /// single C function. It sets the socket to nonblocking mode, connects via
+    /// connect(2), and then waits for the connection to complete with poll(2)
+    /// on Unix and select on Windows. When the connection is complete, the
+    /// socket is set back to blocking mode. On Unix, this will loop over
+    /// `EINTR` errors.
+    ///
+    /// # Warnings
+    ///
+    /// The non-blocking state of the socket is overridden by this function -
+    /// it will be returned in blocking mode on success, and in an indeterminate
+    /// state on failure.
+    ///
+    /// If the connection request times out, it may still be processing in the
+    /// background - a second call to `connect` or `connect_timeout` may fail.
+    pub fn connect_timeout(&self, addr: &SockAddr, timeout: Duration) -> io::Result<()> {
+        self.set_nonblocking(true)?;
+        let res = self.connect(addr);
+        self.set_nonblocking(false)?;
+
+        match res {
+            Ok(()) => return Ok(()),
+            Err(ref e) if e.kind() == io::ErrorKind::WouldBlock => {}
+            #[cfg(unix)]
+            Err(ref e) if e.raw_os_error() == Some(libc::EINPROGRESS) => {}
+            Err(e) => return Err(e),
+        }
+
+        sys::poll_connect(self, timeout)
+    }
+
+    /// Mark a socket as ready to accept incoming connection requests using
+    /// [`Socket::accept()`].
+    ///
+    /// This function directly corresponds to the `listen(2)` function on
+    /// Windows and Unix.
+    ///
+    /// An error will be returned if `listen` or `connect` has already been
+    /// called on this builder.
+    pub fn listen(&self, backlog: c_int) -> io::Result<()> {
+        sys::listen(self.as_raw(), backlog)
+    }
+
+    /// Accept a new incoming connection from this listener.
+    ///
+    /// This function uses `accept4(2)` on platforms that support it and
+    /// `accept(2)` platforms that do not.
+    ///
+    /// This function sets the same flags as in done for [`Socket::new`],
+    /// [`Socket::accept_raw`] can be used if you don't want to set those flags.
+    pub fn accept(&self) -> io::Result<(Socket, SockAddr)> {
+        // Use `accept4` on platforms that support it.
+        #[cfg(any(
+            target_os = "android",
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "illumos",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_os = "openbsd",
+        ))]
+        return self._accept4(libc::SOCK_CLOEXEC);
+
+        // Fall back to `accept` on platforms that do not support `accept4`.
+        #[cfg(not(any(
+            target_os = "android",
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "illumos",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_os = "openbsd",
+        )))]
+        {
+            let (socket, addr) = self.accept_raw()?;
+            let socket = set_common_flags(socket)?;
+            // `set_common_flags` does not disable inheritance on Windows because `Socket::new`
+            // unlike `accept` is able to create the socket with inheritance disabled.
+            #[cfg(windows)]
+            socket._set_no_inherit(true)?;
+            Ok((socket, addr))
+        }
+    }
+
+    /// Accept a new incoming connection from this listener.
+    ///
+    /// This function directly corresponds to the `accept(2)` function on
+    /// Windows and Unix.
+    pub fn accept_raw(&self) -> io::Result<(Socket, SockAddr)> {
+        sys::accept(self.as_raw()).map(|(inner, addr)| (Socket::from_raw(inner), addr))
+    }
+
+    /// Returns the socket address of the local half of this socket.
+    ///
+    /// # Notes
+    ///
+    /// Depending on the OS this may return an error if the socket is not
+    /// [bound].
+    ///
+    /// [bound]: Socket::bind
+    pub fn local_addr(&self) -> io::Result<SockAddr> {
+        sys::getsockname(self.as_raw())
+    }
+
+    /// Returns the socket address of the remote peer of this socket.
+    ///
+    /// # Notes
+    ///
+    /// This returns an error if the socket is not [`connect`ed].
+    ///
+    /// [`connect`ed]: Socket::connect
+    pub fn peer_addr(&self) -> io::Result<SockAddr> {
+        sys::getpeername(self.as_raw())
+    }
+
+    /// Returns the [`Type`] of this socket by checking the `SO_TYPE` option on
+    /// this socket.
+    pub fn r#type(&self) -> io::Result<Type> {
+        unsafe { getsockopt::<c_int>(self.as_raw(), sys::SOL_SOCKET, sys::SO_TYPE).map(Type) }
+    }
+
+    /// Creates a new independently owned handle to the underlying socket.
+    ///
+    /// # Notes
+    ///
+    /// On Unix this uses `F_DUPFD_CLOEXEC` and thus sets the `FD_CLOEXEC` on
+    /// the returned socket.
+    ///
+    /// On Windows this uses `WSA_FLAG_NO_HANDLE_INHERIT` setting inheriting to
+    /// false.
+    ///
+    /// On Windows this can **not** be used function cannot be used on a
+    /// QOS-enabled socket, see
+    /// <https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsaduplicatesocketw>.
+    pub fn try_clone(&self) -> io::Result<Socket> {
+        sys::try_clone(self.as_raw()).map(Socket::from_raw)
+    }
+
+    /// Moves this TCP stream into or out of nonblocking mode.
+    ///
+    /// # Notes
+    ///
+    /// On Unix this corresponds to calling `fcntl` (un)setting `O_NONBLOCK`.
+    ///
+    /// On Windows this corresponds to calling `ioctlsocket` (un)setting
+    /// `FIONBIO`.
+    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
+        sys::set_nonblocking(self.as_raw(), nonblocking)
+    }
+
+    /// Shuts down the read, write, or both halves of this connection.
+    ///
+    /// This function will cause all pending and future I/O on the specified
+    /// portions to return immediately with an appropriate value.
+    pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
+        sys::shutdown(self.as_raw(), how)
+    }
+
+    /// Receives data on the socket from the remote address to which it is
+    /// connected.
+    ///
+    /// The [`connect`] method will connect this socket to a remote address.
+    /// This method might fail if the socket is not connected.
+    ///
+    /// [`connect`]: Socket::connect
+    ///
+    /// # Safety
+    ///
+    /// Normally casting a `&mut [u8]` to `&mut [MaybeUninit<u8>]` would be
+    /// unsound, as that allows us to write uninitialised bytes to the buffer.
+    /// However this implementation promises to not write uninitialised bytes to
+    /// the `buf`fer and passes it directly to `recv(2)` system call. This
+    /// promise ensures that this function can be called using a `buf`fer of
+    /// type `&mut [u8]`.
+    ///
+    /// Note that the [`io::Read::read`] implementation calls this function with
+    /// a `buf`fer of type `&mut [u8]`, allowing initialised buffers to be used
+    /// without using `unsafe`.
+    pub fn recv(&self, buf: &mut [MaybeUninit<u8>]) -> io::Result<usize> {
+        self.recv_with_flags(buf, 0)
+    }
+
+    /// Receives out-of-band (OOB) data on the socket from the remote address to
+    /// which it is connected by setting the `MSG_OOB` flag for this call.
+    ///
+    /// For more information, see [`recv`], [`out_of_band_inline`].
+    ///
+    /// [`recv`]: Socket::recv
+    /// [`out_of_band_inline`]: Socket::out_of_band_inline
+    pub fn recv_out_of_band(&self, buf: &mut [MaybeUninit<u8>]) -> io::Result<usize> {
+        self.recv_with_flags(buf, sys::MSG_OOB)
+    }
+
+    /// Identical to [`recv`] but allows for specification of arbitrary flags to
+    /// the underlying `recv` call.
+    ///
+    /// [`recv`]: Socket::recv
+    pub fn recv_with_flags(
+        &self,
+        buf: &mut [MaybeUninit<u8>],
+        flags: sys::c_int,
+    ) -> io::Result<usize> {
+        sys::recv(self.as_raw(), buf, flags)
+    }
+
+    /// Receives data on the socket from the remote address to which it is
+    /// connected. Unlike [`recv`] this allows passing multiple buffers.
+    ///
+    /// The [`connect`] method will connect this socket to a remote address.
+    /// This method might fail if the socket is not connected.
+    ///
+    /// In addition to the number of bytes read, this function returns the flags
+    /// for the received message. See [`RecvFlags`] for more information about
+    /// the returned flags.
+    ///
+    /// [`recv`]: Socket::recv
+    /// [`connect`]: Socket::connect
+    ///
+    /// # Safety
+    ///
+    /// Normally casting a `IoSliceMut` to `MaybeUninitSlice` would be unsound,
+    /// as that allows us to write uninitialised bytes to the buffer. However
+    /// this implementation promises to not write uninitialised bytes to the
+    /// `bufs` and passes it directly to `recvmsg(2)` system call. This promise
+    /// ensures that this function can be called using `bufs` of type `&mut
+    /// [IoSliceMut]`.
+    ///
+    /// Note that the [`io::Read::read_vectored`] implementation calls this
+    /// function with `buf`s of type `&mut [IoSliceMut]`, allowing initialised
+    /// buffers to be used without using `unsafe`.
+    #[cfg(not(target_os = "redox"))]
+    #[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+    pub fn recv_vectored(
+        &self,
+        bufs: &mut [MaybeUninitSlice<'_>],
+    ) -> io::Result<(usize, RecvFlags)> {
+        self.recv_vectored_with_flags(bufs, 0)
+    }
+
+    /// Identical to [`recv_vectored`] but allows for specification of arbitrary
+    /// flags to the underlying `recvmsg`/`WSARecv` call.
+    ///
+    /// [`recv_vectored`]: Socket::recv_vectored
+    ///
+    /// # Safety
+    ///
+    /// `recv_from_vectored` makes the same safety guarantees regarding `bufs`
+    /// as [`recv_vectored`].
+    ///
+    /// [`recv_vectored`]: Socket::recv_vectored
+    #[cfg(not(target_os = "redox"))]
+    #[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+    pub fn recv_vectored_with_flags(
+        &self,
+        bufs: &mut [MaybeUninitSlice<'_>],
+        flags: c_int,
+    ) -> io::Result<(usize, RecvFlags)> {
+        sys::recv_vectored(self.as_raw(), bufs, flags)
+    }
+
+    /// Receives data on the socket from the remote adress to which it is
+    /// connected, without removing that data from the queue. On success,
+    /// returns the number of bytes peeked.
+    ///
+    /// Successive calls return the same data. This is accomplished by passing
+    /// `MSG_PEEK` as a flag to the underlying `recv` system call.
+    ///
+    /// # Safety
+    ///
+    /// `peek` makes the same safety guarantees regarding the `buf`fer as
+    /// [`recv`].
+    ///
+    /// [`recv`]: Socket::recv
+    pub fn peek(&self, buf: &mut [MaybeUninit<u8>]) -> io::Result<usize> {
+        self.recv_with_flags(buf, sys::MSG_PEEK)
+    }
+
+    /// Receives data from the socket. On success, returns the number of bytes
+    /// read and the address from whence the data came.
+    ///
+    /// # Safety
+    ///
+    /// `recv_from` makes the same safety guarantees regarding the `buf`fer as
+    /// [`recv`].
+    ///
+    /// [`recv`]: Socket::recv
+    pub fn recv_from(&self, buf: &mut [MaybeUninit<u8>]) -> io::Result<(usize, SockAddr)> {
+        self.recv_from_with_flags(buf, 0)
+    }
+
+    /// Identical to [`recv_from`] but allows for specification of arbitrary
+    /// flags to the underlying `recvfrom` call.
+    ///
+    /// [`recv_from`]: Socket::recv_from
+    pub fn recv_from_with_flags(
+        &self,
+        buf: &mut [MaybeUninit<u8>],
+        flags: c_int,
+    ) -> io::Result<(usize, SockAddr)> {
+        sys::recv_from(self.as_raw(), buf, flags)
+    }
+
+    /// Receives data from the socket. Returns the amount of bytes read, the
+    /// [`RecvFlags`] and the remote address from the data is coming. Unlike
+    /// [`recv_from`] this allows passing multiple buffers.
+    ///
+    /// [`recv_from`]: Socket::recv_from
+    ///
+    /// # Safety
+    ///
+    /// `recv_from_vectored` makes the same safety guarantees regarding `bufs`
+    /// as [`recv_vectored`].
+    ///
+    /// [`recv_vectored`]: Socket::recv_vectored
+    #[cfg(not(target_os = "redox"))]
+    #[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+    pub fn recv_from_vectored(
+        &self,
+        bufs: &mut [MaybeUninitSlice<'_>],
+    ) -> io::Result<(usize, RecvFlags, SockAddr)> {
+        self.recv_from_vectored_with_flags(bufs, 0)
+    }
+
+    /// Identical to [`recv_from_vectored`] but allows for specification of
+    /// arbitrary flags to the underlying `recvmsg`/`WSARecvFrom` call.
+    ///
+    /// [`recv_from_vectored`]: Socket::recv_from_vectored
+    ///
+    /// # Safety
+    ///
+    /// `recv_from_vectored` makes the same safety guarantees regarding `bufs`
+    /// as [`recv_vectored`].
+    ///
+    /// [`recv_vectored`]: Socket::recv_vectored
+    #[cfg(not(target_os = "redox"))]
+    #[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+    pub fn recv_from_vectored_with_flags(
+        &self,
+        bufs: &mut [MaybeUninitSlice<'_>],
+        flags: c_int,
+    ) -> io::Result<(usize, RecvFlags, SockAddr)> {
+        sys::recv_from_vectored(self.as_raw(), bufs, flags)
+    }
+
+    /// Receives data from the socket, without removing it from the queue.
+    ///
+    /// Successive calls return the same data. This is accomplished by passing
+    /// `MSG_PEEK` as a flag to the underlying `recvfrom` system call.
+    ///
+    /// On success, returns the number of bytes peeked and the address from
+    /// whence the data came.
+    ///
+    /// # Safety
+    ///
+    /// `peek_from` makes the same safety guarantees regarding the `buf`fer as
+    /// [`recv`].
+    ///
+    /// [`recv`]: Socket::recv
+    pub fn peek_from(&self, buf: &mut [MaybeUninit<u8>]) -> io::Result<(usize, SockAddr)> {
+        self.recv_from_with_flags(buf, sys::MSG_PEEK)
+    }
+
+    /// Sends data on the socket to a connected peer.
+    ///
+    /// This is typically used on TCP sockets or datagram sockets which have
+    /// been connected.
+    ///
+    /// On success returns the number of bytes that were sent.
+    pub fn send(&self, buf: &[u8]) -> io::Result<usize> {
+        self.send_with_flags(buf, 0)
+    }
+
+    /// Identical to [`send`] but allows for specification of arbitrary flags to the underlying
+    /// `send` call.
+    ///
+    /// [`send`]: #method.send
+    pub fn send_with_flags(&self, buf: &[u8], flags: c_int) -> io::Result<usize> {
+        sys::send(self.as_raw(), buf, flags)
+    }
+
+    /// Send data to the connected peer. Returns the amount of bytes written.
+    #[cfg(not(target_os = "redox"))]
+    #[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+    pub fn send_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        self.send_vectored_with_flags(bufs, 0)
+    }
+
+    /// Identical to [`send_vectored`] but allows for specification of arbitrary
+    /// flags to the underlying `sendmsg`/`WSASend` call.
+    ///
+    /// [`send_vectored`]: Socket::send_vectored
+    #[cfg(not(target_os = "redox"))]
+    #[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+    pub fn send_vectored_with_flags(
+        &self,
+        bufs: &[IoSlice<'_>],
+        flags: c_int,
+    ) -> io::Result<usize> {
+        sys::send_vectored(self.as_raw(), bufs, flags)
+    }
+
+    /// Sends out-of-band (OOB) data on the socket to connected peer
+    /// by setting the `MSG_OOB` flag for this call.
+    ///
+    /// For more information, see [`send`], [`out_of_band_inline`].
+    ///
+    /// [`send`]: #method.send
+    /// [`out_of_band_inline`]: #method.out_of_band_inline
+    pub fn send_out_of_band(&self, buf: &[u8]) -> io::Result<usize> {
+        self.send_with_flags(buf, sys::MSG_OOB)
+    }
+
+    /// Sends data on the socket to the given address. On success, returns the
+    /// number of bytes written.
+    ///
+    /// This is typically used on UDP or datagram-oriented sockets.
+    pub fn send_to(&self, buf: &[u8], addr: &SockAddr) -> io::Result<usize> {
+        self.send_to_with_flags(buf, addr, 0)
+    }
+
+    /// Identical to [`send_to`] but allows for specification of arbitrary flags
+    /// to the underlying `sendto` call.
+    ///
+    /// [`send_to`]: Socket::send_to
+    pub fn send_to_with_flags(
+        &self,
+        buf: &[u8],
+        addr: &SockAddr,
+        flags: c_int,
+    ) -> io::Result<usize> {
+        sys::send_to(self.as_raw(), buf, addr, flags)
+    }
+
+    /// Send data to a peer listening on `addr`. Returns the amount of bytes
+    /// written.
+    #[cfg(not(target_os = "redox"))]
+    #[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+    pub fn send_to_vectored(&self, bufs: &[IoSlice<'_>], addr: &SockAddr) -> io::Result<usize> {
+        self.send_to_vectored_with_flags(bufs, addr, 0)
+    }
+
+    /// Identical to [`send_to_vectored`] but allows for specification of
+    /// arbitrary flags to the underlying `sendmsg`/`WSASendTo` call.
+    ///
+    /// [`send_to_vectored`]: Socket::send_to_vectored
+    #[cfg(not(target_os = "redox"))]
+    #[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+    pub fn send_to_vectored_with_flags(
+        &self,
+        bufs: &[IoSlice<'_>],
+        addr: &SockAddr,
+        flags: c_int,
+    ) -> io::Result<usize> {
+        sys::send_to_vectored(self.as_raw(), bufs, addr, flags)
+    }
+}
+
+/// Set `SOCK_CLOEXEC` and `NO_HANDLE_INHERIT` on the `ty`pe on platforms that
+/// support it.
+#[inline(always)]
+fn set_common_type(ty: Type) -> Type {
+    // On platforms that support it set `SOCK_CLOEXEC`.
+    #[cfg(any(
+        target_os = "android",
+        target_os = "dragonfly",
+        target_os = "freebsd",
+        target_os = "fuchsia",
+        target_os = "illumos",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_os = "openbsd",
+    ))]
+    let ty = ty._cloexec();
+
+    // On windows set `NO_HANDLE_INHERIT`.
+    #[cfg(windows)]
+    let ty = ty._no_inherit();
+
+    ty
+}
+
+/// Set `FD_CLOEXEC` and `NOSIGPIPE` on the `socket` for platforms that need it.
+#[inline(always)]
+#[allow(clippy::unnecessary_wraps)]
+fn set_common_flags(socket: Socket) -> io::Result<Socket> {
+    // On platforms that don't have `SOCK_CLOEXEC` use `FD_CLOEXEC`.
+    #[cfg(all(
+        unix,
+        not(any(
+            target_os = "android",
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "illumos",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_os = "openbsd",
+        ))
+    ))]
+    socket._set_cloexec(true)?;
+
+    // On Apple platforms set `NOSIGPIPE`.
+    #[cfg(target_vendor = "apple")]
+    socket._set_nosigpipe(true)?;
+
+    Ok(socket)
+}
+
+/// A local interface specified by its index or an address assigned to it.
+///
+/// `Index(0)` and `Address(Ipv4Addr::UNSPECIFIED)` are equivalent and indicate
+/// that an appropriate interface should be selected by the system.
+#[cfg(not(any(
+    target_os = "haiku",
+    target_os = "illumos",
+    target_os = "netbsd",
+    target_os = "redox",
+    target_os = "solaris",
+)))]
+#[derive(Debug)]
+pub enum InterfaceIndexOrAddress {
+    /// An interface index.
+    Index(u32),
+    /// An address assigned to an interface.
+    Address(Ipv4Addr),
+}
+
+/// Socket options get/set using `SOL_SOCKET`.
+///
+/// Additional documentation can be found in documentation of the OS.
+/// * Linux: <https://man7.org/linux/man-pages/man7/socket.7.html>
+/// * Windows: <https://docs.microsoft.com/en-us/windows/win32/winsock/sol-socket-socket-options>
+impl Socket {
+    /// Get the value of the `SO_BROADCAST` option for this socket.
+    ///
+    /// For more information about this option, see [`set_broadcast`].
+    ///
+    /// [`set_broadcast`]: Socket::set_broadcast
+    pub fn broadcast(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::SOL_SOCKET, sys::SO_BROADCAST)
+                .map(|broadcast| broadcast != 0)
+        }
+    }
+
+    /// Set the value of the `SO_BROADCAST` option for this socket.
+    ///
+    /// When enabled, this socket is allowed to send packets to a broadcast
+    /// address.
+    pub fn set_broadcast(&self, broadcast: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::SOL_SOCKET,
+                sys::SO_BROADCAST,
+                broadcast as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `SO_ERROR` option on this socket.
+    ///
+    /// This will retrieve the stored error in the underlying socket, clearing
+    /// the field in the process. This can be useful for checking errors between
+    /// calls.
+    pub fn take_error(&self) -> io::Result<Option<io::Error>> {
+        match unsafe { getsockopt::<c_int>(self.as_raw(), sys::SOL_SOCKET, sys::SO_ERROR) } {
+            Ok(0) => Ok(None),
+            Ok(errno) => Ok(Some(io::Error::from_raw_os_error(errno))),
+            Err(err) => Err(err),
+        }
+    }
+
+    /// Get the value of the `SO_KEEPALIVE` option on this socket.
+    ///
+    /// For more information about this option, see [`set_keepalive`].
+    ///
+    /// [`set_keepalive`]: Socket::set_keepalive
+    pub fn keepalive(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<Bool>(self.as_raw(), sys::SOL_SOCKET, sys::SO_KEEPALIVE)
+                .map(|keepalive| keepalive != 0)
+        }
+    }
+
+    /// Set value for the `SO_KEEPALIVE` option on this socket.
+    ///
+    /// Enable sending of keep-alive messages on connection-oriented sockets.
+    pub fn set_keepalive(&self, keepalive: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::SOL_SOCKET,
+                sys::SO_KEEPALIVE,
+                keepalive as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `SO_LINGER` option on this socket.
+    ///
+    /// For more information about this option, see [`set_linger`].
+    ///
+    /// [`set_linger`]: Socket::set_linger
+    pub fn linger(&self) -> io::Result<Option<Duration>> {
+        unsafe {
+            getsockopt::<sys::linger>(self.as_raw(), sys::SOL_SOCKET, sys::SO_LINGER)
+                .map(from_linger)
+        }
+    }
+
+    /// Set value for the `SO_LINGER` option on this socket.
+    ///
+    /// If `linger` is not `None`, a close(2) or shutdown(2) will not return
+    /// until all queued messages for the socket have been successfully sent or
+    /// the linger timeout has been reached. Otherwise, the call returns
+    /// immediately and the closing is done in the background. When the socket
+    /// is closed as part of exit(2), it always lingers in the background.
+    ///
+    /// # Notes
+    ///
+    /// On most OSs the duration only has a precision of seconds and will be
+    /// silently truncated.
+    ///
+    /// On Apple platforms (e.g. macOS, iOS, etc) this uses `SO_LINGER_SEC`.
+    pub fn set_linger(&self, linger: Option<Duration>) -> io::Result<()> {
+        let linger = into_linger(linger);
+        unsafe { setsockopt(self.as_raw(), sys::SOL_SOCKET, sys::SO_LINGER, linger) }
+    }
+
+    /// Get value for the `SO_OOBINLINE` option on this socket.
+    ///
+    /// For more information about this option, see [`set_out_of_band_inline`].
+    ///
+    /// [`set_out_of_band_inline`]: Socket::set_out_of_band_inline
+    #[cfg(not(target_os = "redox"))]
+    #[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+    pub fn out_of_band_inline(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::SOL_SOCKET, sys::SO_OOBINLINE)
+                .map(|oob_inline| oob_inline != 0)
+        }
+    }
+
+    /// Set value for the `SO_OOBINLINE` option on this socket.
+    ///
+    /// If this option is enabled, out-of-band data is directly placed into the
+    /// receive data stream. Otherwise, out-of-band data is passed only when the
+    /// `MSG_OOB` flag is set during receiving. As per RFC6093, TCP sockets
+    /// using the Urgent mechanism are encouraged to set this flag.
+    #[cfg(not(target_os = "redox"))]
+    #[cfg_attr(docsrs, doc(cfg(not(target_os = "redox"))))]
+    pub fn set_out_of_band_inline(&self, oob_inline: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::SOL_SOCKET,
+                sys::SO_OOBINLINE,
+                oob_inline as c_int,
+            )
+        }
+    }
+
+    /// Get value for the `SO_RCVBUF` option on this socket.
+    ///
+    /// For more information about this option, see [`set_recv_buffer_size`].
+    ///
+    /// [`set_recv_buffer_size`]: Socket::set_recv_buffer_size
+    pub fn recv_buffer_size(&self) -> io::Result<usize> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::SOL_SOCKET, sys::SO_RCVBUF)
+                .map(|size| size as usize)
+        }
+    }
+
+    /// Set value for the `SO_RCVBUF` option on this socket.
+    ///
+    /// Changes the size of the operating system's receive buffer associated
+    /// with the socket.
+    pub fn set_recv_buffer_size(&self, size: usize) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::SOL_SOCKET,
+                sys::SO_RCVBUF,
+                size as c_int,
+            )
+        }
+    }
+
+    /// Get value for the `SO_RCVTIMEO` option on this socket.
+    ///
+    /// If the returned timeout is `None`, then `read` and `recv` calls will
+    /// block indefinitely.
+    pub fn read_timeout(&self) -> io::Result<Option<Duration>> {
+        sys::timeout_opt(self.as_raw(), sys::SOL_SOCKET, sys::SO_RCVTIMEO)
+    }
+
+    /// Set value for the `SO_RCVTIMEO` option on this socket.
+    ///
+    /// If `timeout` is `None`, then `read` and `recv` calls will block
+    /// indefinitely.
+    pub fn set_read_timeout(&self, duration: Option<Duration>) -> io::Result<()> {
+        sys::set_timeout_opt(self.as_raw(), sys::SOL_SOCKET, sys::SO_RCVTIMEO, duration)
+    }
+
+    /// Get the value of the `SO_REUSEADDR` option on this socket.
+    ///
+    /// For more information about this option, see [`set_reuse_address`].
+    ///
+    /// [`set_reuse_address`]: Socket::set_reuse_address
+    pub fn reuse_address(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::SOL_SOCKET, sys::SO_REUSEADDR)
+                .map(|reuse| reuse != 0)
+        }
+    }
+
+    /// Set value for the `SO_REUSEADDR` option on this socket.
+    ///
+    /// This indicates that futher calls to `bind` may allow reuse of local
+    /// addresses. For IPv4 sockets this means that a socket may bind even when
+    /// there's a socket already listening on this port.
+    pub fn set_reuse_address(&self, reuse: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::SOL_SOCKET,
+                sys::SO_REUSEADDR,
+                reuse as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `SO_SNDBUF` option on this socket.
+    ///
+    /// For more information about this option, see [`set_send_buffer_size`].
+    ///
+    /// [`set_send_buffer_size`]: Socket::set_send_buffer_size
+    pub fn send_buffer_size(&self) -> io::Result<usize> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::SOL_SOCKET, sys::SO_SNDBUF)
+                .map(|size| size as usize)
+        }
+    }
+
+    /// Set value for the `SO_SNDBUF` option on this socket.
+    ///
+    /// Changes the size of the operating system's send buffer associated with
+    /// the socket.
+    pub fn set_send_buffer_size(&self, size: usize) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::SOL_SOCKET,
+                sys::SO_SNDBUF,
+                size as c_int,
+            )
+        }
+    }
+
+    /// Get value for the `SO_SNDTIMEO` option on this socket.
+    ///
+    /// If the returned timeout is `None`, then `write` and `send` calls will
+    /// block indefinitely.
+    pub fn write_timeout(&self) -> io::Result<Option<Duration>> {
+        sys::timeout_opt(self.as_raw(), sys::SOL_SOCKET, sys::SO_SNDTIMEO)
+    }
+
+    /// Set value for the `SO_SNDTIMEO` option on this socket.
+    ///
+    /// If `timeout` is `None`, then `write` and `send` calls will block
+    /// indefinitely.
+    pub fn set_write_timeout(&self, duration: Option<Duration>) -> io::Result<()> {
+        sys::set_timeout_opt(self.as_raw(), sys::SOL_SOCKET, sys::SO_SNDTIMEO, duration)
+    }
+}
+
+fn from_linger(linger: sys::linger) -> Option<Duration> {
+    if linger.l_onoff == 0 {
+        None
+    } else {
+        Some(Duration::from_secs(linger.l_linger as u64))
+    }
+}
+
+fn into_linger(duration: Option<Duration>) -> sys::linger {
+    match duration {
+        Some(duration) => sys::linger {
+            l_onoff: 1,
+            l_linger: duration.as_secs() as _,
+        },
+        None => sys::linger {
+            l_onoff: 0,
+            l_linger: 0,
+        },
+    }
+}
+
+/// Socket options for IPv4 sockets, get/set using `IPPROTO_IP`.
+///
+/// Additional documentation can be found in documentation of the OS.
+/// * Linux: <https://man7.org/linux/man-pages/man7/ip.7.html>
+/// * Windows: <https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ip-socket-options>
+impl Socket {
+    /// Get the value of the `IP_HDRINCL` option on this socket.
+    ///
+    /// For more information about this option, see [`set_header_included`].
+    ///
+    /// [`set_header_included`]: Socket::set_header_included
+    #[cfg(all(feature = "all", not(target_os = "redox")))]
+    #[cfg_attr(docsrs, doc(all(feature = "all", not(target_os = "redox"))))]
+    pub fn header_included(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IP, sys::IP_HDRINCL)
+                .map(|included| included != 0)
+        }
+    }
+
+    /// Set the value of the `IP_HDRINCL` option on this socket.
+    ///
+    /// If enabled, the user supplies an IP header in front of the user data.
+    /// Valid only for [`SOCK_RAW`] sockets; see [raw(7)] for more information.
+    /// When this flag is enabled, the values set by `IP_OPTIONS`, [`IP_TTL`],
+    /// and [`IP_TOS`] are ignored.
+    ///
+    /// [`SOCK_RAW`]: Type::RAW
+    /// [raw(7)]: https://man7.org/linux/man-pages/man7/raw.7.html
+    /// [`IP_TTL`]: Socket::set_ttl
+    /// [`IP_TOS`]: Socket::set_tos
+    #[cfg(all(feature = "all", not(target_os = "redox")))]
+    #[cfg_attr(docsrs, doc(all(feature = "all", not(target_os = "redox"))))]
+    pub fn set_header_included(&self, included: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IP,
+                sys::IP_HDRINCL,
+                included as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `IP_TRANSPARENT` option on this socket.
+    ///
+    /// For more information about this option, see [`set_ip_transparent`].
+    ///
+    /// [`set_ip_transparent`]: Socket::set_ip_transparent
+    #[cfg(any(doc, all(feature = "all", target_os = "linux")))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", target_os = "linux"))))]
+    pub fn ip_transparent(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IP, libc::IP_TRANSPARENT)
+                .map(|transparent| transparent != 0)
+        }
+    }
+
+    /// Set the value of the `IP_TRANSPARENT` option on this socket.
+    ///
+    /// Setting this boolean option enables transparent proxying
+    /// on this socket.  This socket option allows the calling
+    /// application to bind to a nonlocal IP address and operate
+    /// both as a client and a server with the foreign address as
+    /// the local endpoint.  NOTE: this requires that routing be
+    /// set up in a way that packets going to the foreign address
+    /// are routed through the TProxy box (i.e., the system
+    /// hosting the application that employs the IP_TRANSPARENT
+    /// socket option).  Enabling this socket option requires
+    /// superuser privileges (the `CAP_NET_ADMIN` capability).
+    ///
+    /// TProxy redirection with the iptables TPROXY target also
+    /// requires that this option be set on the redirected socket.
+    #[cfg(any(doc, all(feature = "all", target_os = "linux")))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", target_os = "linux"))))]
+    pub fn set_ip_transparent(&self, transparent: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IP,
+                libc::IP_TRANSPARENT,
+                transparent as c_int,
+            )
+        }
+    }
+
+    /// Join a multicast group using `IP_ADD_MEMBERSHIP` option on this socket.
+    ///
+    /// This function specifies a new multicast group for this socket to join.
+    /// The address must be a valid multicast address, and `interface` is the
+    /// address of the local interface with which the system should join the
+    /// multicast group. If it's [`Ipv4Addr::UNSPECIFIED`] (`INADDR_ANY`) then
+    /// an appropriate interface is chosen by the system.
+    pub fn join_multicast_v4(&self, multiaddr: &Ipv4Addr, interface: &Ipv4Addr) -> io::Result<()> {
+        let mreq = sys::IpMreq {
+            imr_multiaddr: sys::to_in_addr(multiaddr),
+            imr_interface: sys::to_in_addr(interface),
+        };
+        unsafe { setsockopt(self.as_raw(), sys::IPPROTO_IP, sys::IP_ADD_MEMBERSHIP, mreq) }
+    }
+
+    /// Leave a multicast group using `IP_DROP_MEMBERSHIP` option on this socket.
+    ///
+    /// For more information about this option, see [`join_multicast_v4`].
+    ///
+    /// [`join_multicast_v4`]: Socket::join_multicast_v4
+    pub fn leave_multicast_v4(&self, multiaddr: &Ipv4Addr, interface: &Ipv4Addr) -> io::Result<()> {
+        let mreq = sys::IpMreq {
+            imr_multiaddr: sys::to_in_addr(multiaddr),
+            imr_interface: sys::to_in_addr(interface),
+        };
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IP,
+                sys::IP_DROP_MEMBERSHIP,
+                mreq,
+            )
+        }
+    }
+
+    /// Join a multicast group using `IP_ADD_MEMBERSHIP` option on this socket.
+    ///
+    /// This function specifies a new multicast group for this socket to join.
+    /// The address must be a valid multicast address, and `interface` specifies
+    /// the local interface with which the system should join the multicast
+    /// group. See [`InterfaceIndexOrAddress`].
+    #[cfg(not(any(
+        target_os = "haiku",
+        target_os = "illumos",
+        target_os = "netbsd",
+        target_os = "redox",
+        target_os = "solaris",
+    )))]
+    pub fn join_multicast_v4_n(
+        &self,
+        multiaddr: &Ipv4Addr,
+        interface: &InterfaceIndexOrAddress,
+    ) -> io::Result<()> {
+        let mreqn = sys::to_mreqn(multiaddr, interface);
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IP,
+                sys::IP_ADD_MEMBERSHIP,
+                mreqn,
+            )
+        }
+    }
+
+    /// Leave a multicast group using `IP_DROP_MEMBERSHIP` option on this socket.
+    ///
+    /// For more information about this option, see [`join_multicast_v4_n`].
+    ///
+    /// [`join_multicast_v4_n`]: Socket::join_multicast_v4_n
+    #[cfg(not(any(
+        target_os = "haiku",
+        target_os = "illumos",
+        target_os = "netbsd",
+        target_os = "redox",
+        target_os = "solaris",
+    )))]
+    pub fn leave_multicast_v4_n(
+        &self,
+        multiaddr: &Ipv4Addr,
+        interface: &InterfaceIndexOrAddress,
+    ) -> io::Result<()> {
+        let mreqn = sys::to_mreqn(multiaddr, interface);
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IP,
+                sys::IP_DROP_MEMBERSHIP,
+                mreqn,
+            )
+        }
+    }
+
+    /// Get the value of the `IP_MULTICAST_IF` option for this socket.
+    ///
+    /// For more information about this option, see [`set_multicast_if_v4`].
+    ///
+    /// [`set_multicast_if_v4`]: Socket::set_multicast_if_v4
+    pub fn multicast_if_v4(&self) -> io::Result<Ipv4Addr> {
+        unsafe {
+            getsockopt(self.as_raw(), sys::IPPROTO_IP, sys::IP_MULTICAST_IF).map(sys::from_in_addr)
+        }
+    }
+
+    /// Set the value of the `IP_MULTICAST_IF` option for this socket.
+    ///
+    /// Specifies the interface to use for routing multicast packets.
+    pub fn set_multicast_if_v4(&self, interface: &Ipv4Addr) -> io::Result<()> {
+        let interface = sys::to_in_addr(interface);
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IP,
+                sys::IP_MULTICAST_IF,
+                interface,
+            )
+        }
+    }
+
+    /// Get the value of the `IP_MULTICAST_LOOP` option for this socket.
+    ///
+    /// For more information about this option, see [`set_multicast_loop_v4`].
+    ///
+    /// [`set_multicast_loop_v4`]: Socket::set_multicast_loop_v4
+    pub fn multicast_loop_v4(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IP, sys::IP_MULTICAST_LOOP)
+                .map(|loop_v4| loop_v4 != 0)
+        }
+    }
+
+    /// Set the value of the `IP_MULTICAST_LOOP` option for this socket.
+    ///
+    /// If enabled, multicast packets will be looped back to the local socket.
+    /// Note that this may not have any affect on IPv6 sockets.
+    pub fn set_multicast_loop_v4(&self, loop_v4: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IP,
+                sys::IP_MULTICAST_LOOP,
+                loop_v4 as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `IP_MULTICAST_TTL` option for this socket.
+    ///
+    /// For more information about this option, see [`set_multicast_ttl_v4`].
+    ///
+    /// [`set_multicast_ttl_v4`]: Socket::set_multicast_ttl_v4
+    pub fn multicast_ttl_v4(&self) -> io::Result<u32> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IP, sys::IP_MULTICAST_TTL)
+                .map(|ttl| ttl as u32)
+        }
+    }
+
+    /// Set the value of the `IP_MULTICAST_TTL` option for this socket.
+    ///
+    /// Indicates the time-to-live value of outgoing multicast packets for
+    /// this socket. The default value is 1 which means that multicast packets
+    /// don't leave the local network unless explicitly requested.
+    ///
+    /// Note that this may not have any affect on IPv6 sockets.
+    pub fn set_multicast_ttl_v4(&self, ttl: u32) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IP,
+                sys::IP_MULTICAST_TTL,
+                ttl as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `IP_TTL` option for this socket.
+    ///
+    /// For more information about this option, see [`set_ttl`].
+    ///
+    /// [`set_ttl`]: Socket::set_ttl
+    pub fn ttl(&self) -> io::Result<u32> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IP, sys::IP_TTL).map(|ttl| ttl as u32)
+        }
+    }
+
+    /// Set the value of the `IP_TTL` option for this socket.
+    ///
+    /// This value sets the time-to-live field that is used in every packet sent
+    /// from this socket.
+    pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
+        unsafe { setsockopt(self.as_raw(), sys::IPPROTO_IP, sys::IP_TTL, ttl as c_int) }
+    }
+
+    /// Set the value of the `IP_TOS` option for this socket.
+    ///
+    /// This value sets the type-of-service field that is used in every packet
+    /// sent from this socket.
+    ///
+    /// NOTE: <https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ip-socket-options>
+    /// documents that not all versions of windows support `IP_TOS`.
+    #[cfg(not(any(
+        target_os = "fuschia",
+        target_os = "redox",
+        target_os = "solaris",
+        target_os = "illumos",
+    )))]
+    pub fn set_tos(&self, tos: u32) -> io::Result<()> {
+        unsafe { setsockopt(self.as_raw(), sys::IPPROTO_IP, sys::IP_TOS, tos as c_int) }
+    }
+
+    /// Get the value of the `IP_TOS` option for this socket.
+    ///
+    /// For more information about this option, see [`set_tos`].
+    ///
+    /// NOTE: <https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ip-socket-options>
+    /// documents that not all versions of windows support `IP_TOS`.
+    ///
+    /// [`set_tos`]: Socket::set_tos
+    #[cfg(not(any(
+        target_os = "fuschia",
+        target_os = "redox",
+        target_os = "solaris",
+        target_os = "illumos",
+    )))]
+    pub fn tos(&self) -> io::Result<u32> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IP, sys::IP_TOS).map(|tos| tos as u32)
+        }
+    }
+}
+
+/// Socket options for IPv6 sockets, get/set using `IPPROTO_IPV6`.
+///
+/// Additional documentation can be found in documentation of the OS.
+/// * Linux: <https://man7.org/linux/man-pages/man7/ipv6.7.html>
+/// * Windows: <https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ipv6-socket-options>
+impl Socket {
+    /// Join a multicast group using `IPV6_ADD_MEMBERSHIP` option on this socket.
+    ///
+    /// Some OSs use `IPV6_JOIN_GROUP` for this option.
+    ///
+    /// This function specifies a new multicast group for this socket to join.
+    /// The address must be a valid multicast address, and `interface` is the
+    /// index of the interface to join/leave (or 0 to indicate any interface).
+    pub fn join_multicast_v6(&self, multiaddr: &Ipv6Addr, interface: u32) -> io::Result<()> {
+        let mreq = sys::Ipv6Mreq {
+            ipv6mr_multiaddr: sys::to_in6_addr(multiaddr),
+            // NOTE: some OSs use `c_int`, others use `c_uint`.
+            ipv6mr_interface: interface as _,
+        };
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IPV6,
+                sys::IPV6_ADD_MEMBERSHIP,
+                mreq,
+            )
+        }
+    }
+
+    /// Leave a multicast group using `IPV6_DROP_MEMBERSHIP` option on this socket.
+    ///
+    /// Some OSs use `IPV6_LEAVE_GROUP` for this option.
+    ///
+    /// For more information about this option, see [`join_multicast_v6`].
+    ///
+    /// [`join_multicast_v6`]: Socket::join_multicast_v6
+    pub fn leave_multicast_v6(&self, multiaddr: &Ipv6Addr, interface: u32) -> io::Result<()> {
+        let mreq = sys::Ipv6Mreq {
+            ipv6mr_multiaddr: sys::to_in6_addr(multiaddr),
+            // NOTE: some OSs use `c_int`, others use `c_uint`.
+            ipv6mr_interface: interface as _,
+        };
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IPV6,
+                sys::IPV6_DROP_MEMBERSHIP,
+                mreq,
+            )
+        }
+    }
+
+    /// Get the value of the `IPV6_MULTICAST_HOPS` option for this socket
+    ///
+    /// For more information about this option, see [`set_multicast_hops_v6`].
+    ///
+    /// [`set_multicast_hops_v6`]: Socket::set_multicast_hops_v6
+    pub fn multicast_hops_v6(&self) -> io::Result<u32> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IPV6, sys::IPV6_MULTICAST_HOPS)
+                .map(|hops| hops as u32)
+        }
+    }
+
+    /// Set the value of the `IPV6_MULTICAST_HOPS` option for this socket
+    ///
+    /// Indicates the number of "routers" multicast packets will transit for
+    /// this socket. The default value is 1 which means that multicast packets
+    /// don't leave the local network unless explicitly requested.
+    pub fn set_multicast_hops_v6(&self, hops: u32) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IPV6,
+                sys::IPV6_MULTICAST_HOPS,
+                hops as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `IPV6_MULTICAST_IF` option for this socket.
+    ///
+    /// For more information about this option, see [`set_multicast_if_v6`].
+    ///
+    /// [`set_multicast_if_v6`]: Socket::set_multicast_if_v6
+    pub fn multicast_if_v6(&self) -> io::Result<u32> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IPV6, sys::IPV6_MULTICAST_IF)
+                .map(|interface| interface as u32)
+        }
+    }
+
+    /// Set the value of the `IPV6_MULTICAST_IF` option for this socket.
+    ///
+    /// Specifies the interface to use for routing multicast packets. Unlike
+    /// ipv4, this is generally required in ipv6 contexts where network routing
+    /// prefixes may overlap.
+    pub fn set_multicast_if_v6(&self, interface: u32) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IPV6,
+                sys::IPV6_MULTICAST_IF,
+                interface as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `IPV6_MULTICAST_LOOP` option for this socket.
+    ///
+    /// For more information about this option, see [`set_multicast_loop_v6`].
+    ///
+    /// [`set_multicast_loop_v6`]: Socket::set_multicast_loop_v6
+    pub fn multicast_loop_v6(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IPV6, sys::IPV6_MULTICAST_LOOP)
+                .map(|loop_v6| loop_v6 != 0)
+        }
+    }
+
+    /// Set the value of the `IPV6_MULTICAST_LOOP` option for this socket.
+    ///
+    /// Controls whether this socket sees the multicast packets it sends itself.
+    /// Note that this may not have any affect on IPv4 sockets.
+    pub fn set_multicast_loop_v6(&self, loop_v6: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IPV6,
+                sys::IPV6_MULTICAST_LOOP,
+                loop_v6 as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `IPV6_UNICAST_HOPS` option for this socket.
+    ///
+    /// Specifies the hop limit for ipv6 unicast packets
+    pub fn unicast_hops_v6(&self) -> io::Result<u32> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IPV6, sys::IPV6_UNICAST_HOPS)
+                .map(|hops| hops as u32)
+        }
+    }
+
+    /// Set the value for the `IPV6_UNICAST_HOPS` option on this socket.
+    ///
+    /// Specifies the hop limit for ipv6 unicast packets
+    pub fn set_unicast_hops_v6(&self, hops: u32) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IPV6,
+                sys::IPV6_UNICAST_HOPS,
+                hops as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `IPV6_V6ONLY` option for this socket.
+    ///
+    /// For more information about this option, see [`set_only_v6`].
+    ///
+    /// [`set_only_v6`]: Socket::set_only_v6
+    pub fn only_v6(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_IPV6, sys::IPV6_V6ONLY)
+                .map(|only_v6| only_v6 != 0)
+        }
+    }
+
+    /// Set the value for the `IPV6_V6ONLY` option on this socket.
+    ///
+    /// If this is set to `true` then the socket is restricted to sending and
+    /// receiving IPv6 packets only. In this case two IPv4 and IPv6 applications
+    /// can bind the same port at the same time.
+    ///
+    /// If this is set to `false` then the socket can be used to send and
+    /// receive packets from an IPv4-mapped IPv6 address.
+    pub fn set_only_v6(&self, only_v6: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_IPV6,
+                sys::IPV6_V6ONLY,
+                only_v6 as c_int,
+            )
+        }
+    }
+}
+
+/// Socket options for TCP sockets, get/set using `IPPROTO_TCP`.
+///
+/// Additional documentation can be found in documentation of the OS.
+/// * Linux: <https://man7.org/linux/man-pages/man7/tcp.7.html>
+/// * Windows: <https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-tcp-socket-options>
+impl Socket {
+    /// Get the value of the `TCP_KEEPIDLE` option on this socket.
+    ///
+    /// This returns the value of `TCP_KEEPALIVE` on macOS and iOS and `TCP_KEEPIDLE` on all other
+    /// supported Unix operating systems.
+    #[cfg(any(
+        doc,
+        all(
+            feature = "all",
+            not(any(windows, target_os = "haiku", target_os = "openbsd"))
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            not(any(windows, target_os = "haiku", target_os = "openbsd"))
+        )))
+    )]
+    pub fn keepalive_time(&self) -> io::Result<Duration> {
+        sys::keepalive_time(self.as_raw())
+    }
+
+    /// Get the value of the `TCP_KEEPINTVL` option on this socket.
+    ///
+    /// For more information about this option, see [`set_tcp_keepalive`].
+    ///
+    /// [`set_tcp_keepalive`]: Socket::set_tcp_keepalive
+    #[cfg(all(
+        feature = "all",
+        any(
+            doc,
+            target_os = "android",
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "illumos",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_vendor = "apple",
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(
+                target_os = "android",
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "fuchsia",
+                target_os = "illumos",
+                target_os = "linux",
+                target_os = "netbsd",
+                target_vendor = "apple",
+            )
+        )))
+    )]
+    pub fn keepalive_interval(&self) -> io::Result<Duration> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_TCP, sys::TCP_KEEPINTVL)
+                .map(|secs| Duration::from_secs(secs as u64))
+        }
+    }
+
+    /// Get the value of the `TCP_KEEPCNT` option on this socket.
+    ///
+    /// For more information about this option, see [`set_tcp_keepalive`].
+    ///
+    /// [`set_tcp_keepalive`]: Socket::set_tcp_keepalive
+    #[cfg(all(
+        feature = "all",
+        any(
+            doc,
+            target_os = "android",
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "illumos",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_vendor = "apple",
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(
+                target_os = "android",
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "fuchsia",
+                target_os = "illumos",
+                target_os = "linux",
+                target_os = "netbsd",
+                target_vendor = "apple",
+            )
+        )))
+    )]
+    pub fn keepalive_retries(&self) -> io::Result<u32> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), sys::IPPROTO_TCP, sys::TCP_KEEPCNT)
+                .map(|retries| retries as u32)
+        }
+    }
+
+    /// Set parameters configuring TCP keepalive probes for this socket.
+    ///
+    /// The supported parameters depend on the operating system, and are
+    /// configured using the [`TcpKeepalive`] struct. At a minimum, all systems
+    /// support configuring the [keepalive time]: the time after which the OS
+    /// will start sending keepalive messages on an idle connection.
+    ///
+    /// [keepalive time]: TcpKeepalive::with_time
+    ///
+    /// # Notes
+    ///
+    /// * This will enable `SO_KEEPALIVE` on this socket, if it is not already
+    ///   enabled.
+    /// * On some platforms, such as Windows, any keepalive parameters *not*
+    ///   configured by the `TcpKeepalive` struct passed to this function may be
+    ///   overwritten with their default values. Therefore, this function should
+    ///   either only be called once per socket, or the same parameters should
+    ///   be passed every time it is called.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::time::Duration;
+    ///
+    /// use socket2::{Socket, TcpKeepalive, Domain, Type};
+    ///
+    /// # fn main() -> std::io::Result<()> {
+    /// let socket = Socket::new(Domain::IPV4, Type::STREAM, None)?;
+    /// let keepalive = TcpKeepalive::new()
+    ///     .with_time(Duration::from_secs(4));
+    ///     // Depending on the target operating system, we may also be able to
+    ///     // configure the keepalive probe interval and/or the number of
+    ///     // retries here as well.
+    ///
+    /// socket.set_tcp_keepalive(&keepalive)?;
+    /// # Ok(()) }
+    /// ```
+    ///
+    pub fn set_tcp_keepalive(&self, params: &TcpKeepalive) -> io::Result<()> {
+        self.set_keepalive(true)?;
+        sys::set_tcp_keepalive(self.as_raw(), params)
+    }
+
+    /// Get the value of the `TCP_NODELAY` option on this socket.
+    ///
+    /// For more information about this option, see [`set_nodelay`].
+    ///
+    /// [`set_nodelay`]: Socket::set_nodelay
+    pub fn nodelay(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<Bool>(self.as_raw(), sys::IPPROTO_TCP, sys::TCP_NODELAY)
+                .map(|nodelay| nodelay != 0)
+        }
+    }
+
+    /// Set the value of the `TCP_NODELAY` option on this socket.
+    ///
+    /// If set, this option disables the Nagle algorithm. This means that
+    /// segments are always sent as soon as possible, even if there is only a
+    /// small amount of data. When not set, data is buffered until there is a
+    /// sufficient amount to send out, thereby avoiding the frequent sending of
+    /// small packets.
+    pub fn set_nodelay(&self, nodelay: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                sys::IPPROTO_TCP,
+                sys::TCP_NODELAY,
+                nodelay as c_int,
+            )
+        }
+    }
+}
+
+impl Read for Socket {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        // Safety: the `recv` implementation promises not to write uninitialised
+        // bytes to the `buf`fer, so this casting is safe.
+        let buf = unsafe { &mut *(buf as *mut [u8] as *mut [MaybeUninit<u8>]) };
+        self.recv(buf)
+    }
+
+    #[cfg(not(target_os = "redox"))]
+    fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
+        // Safety: both `IoSliceMut` and `MaybeUninitSlice` promise to have the
+        // same layout, that of `iovec`/`WSABUF`. Furthermore `recv_vectored`
+        // promises to not write unitialised bytes to the `bufs` and pass it
+        // directly to the `recvmsg` system call, so this is safe.
+        let bufs = unsafe { &mut *(bufs as *mut [IoSliceMut<'_>] as *mut [MaybeUninitSlice<'_>]) };
+        self.recv_vectored(bufs).map(|(n, _)| n)
+    }
+}
+
+impl<'a> Read for &'a Socket {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        // Safety: see other `Read::read` impl.
+        let buf = unsafe { &mut *(buf as *mut [u8] as *mut [MaybeUninit<u8>]) };
+        self.recv(buf)
+    }
+
+    #[cfg(not(target_os = "redox"))]
+    fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
+        // Safety: see other `Read::read` impl.
+        let bufs = unsafe { &mut *(bufs as *mut [IoSliceMut<'_>] as *mut [MaybeUninitSlice<'_>]) };
+        self.recv_vectored(bufs).map(|(n, _)| n)
+    }
+}
+
+impl Write for Socket {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.send(buf)
+    }
+
+    #[cfg(not(target_os = "redox"))]
+    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        self.send_vectored(bufs)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+impl<'a> Write for &'a Socket {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.send(buf)
+    }
+
+    #[cfg(not(target_os = "redox"))]
+    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
+        self.send_vectored(bufs)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+}
+
+impl fmt::Debug for Socket {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Socket")
+            .field("raw", &self.as_raw())
+            .field("local_addr", &self.local_addr().ok())
+            .field("peer_addr", &self.peer_addr().ok())
+            .finish()
+    }
+}
+
+from!(net::TcpStream, Socket);
+from!(net::TcpListener, Socket);
+from!(net::UdpSocket, Socket);
+from!(Socket, net::TcpStream);
+from!(Socket, net::TcpListener);
+from!(Socket, net::UdpSocket);
diff --git a/src/sockref.rs b/src/sockref.rs
new file mode 100644
index 0000000..257323b
--- /dev/null
+++ b/src/sockref.rs
@@ -0,0 +1,147 @@
+use std::fmt;
+use std::marker::PhantomData;
+use std::mem::ManuallyDrop;
+use std::ops::Deref;
+#[cfg(unix)]
+use std::os::unix::io::{AsRawFd, FromRawFd};
+#[cfg(windows)]
+use std::os::windows::io::{AsRawSocket, FromRawSocket};
+
+use crate::Socket;
+
+/// A reference to a [`Socket`] that can be used to configure socket types other
+/// than the `Socket` type itself.
+///
+/// This allows for example a [`TcpStream`], found in the standard library, to
+/// be configured using all the additional methods found in the [`Socket`] API.
+///
+/// `SockRef` can be created from any socket type that implements [`AsRawFd`]
+/// (Unix) or [`AsRawSocket`] (Windows) using the [`From`] implementation, but
+/// the caller must ensure the file descriptor/socket is a valid.
+///
+/// [`TcpStream`]: std::net::TcpStream
+// Don't use intra-doc links because they won't build on every platform.
+/// [`AsRawFd`]: https://doc.rust-lang.org/stable/std/os/unix/io/trait.AsRawFd.html
+/// [`AsRawSocket`]: https://doc.rust-lang.org/stable/std/os/windows/io/trait.AsRawSocket.html
+///
+/// # Examples
+///
+/// Below is an example of converting a [`TcpStream`] into a [`SockRef`].
+///
+/// ```
+/// use std::net::{TcpStream, SocketAddr};
+///
+/// use socket2::SockRef;
+///
+/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+/// // Create `TcpStream` from the standard library.
+/// let address: SocketAddr = "127.0.0.1:1234".parse()?;
+/// # let b1 = std::sync::Arc::new(std::sync::Barrier::new(2));
+/// # let b2 = b1.clone();
+/// # let handle = std::thread::spawn(move || {
+/// #    let listener = std::net::TcpListener::bind(address).unwrap();
+/// #    b2.wait();
+/// #    let (stream, _) = listener.accept().unwrap();
+/// #    std::thread::sleep(std::time::Duration::from_millis(10));
+/// #    drop(stream);
+/// # });
+/// # b1.wait();
+/// let stream = TcpStream::connect(address)?;
+///
+/// // Create a `SockRef`erence to the stream.
+/// let socket_ref = SockRef::from(&stream);
+/// // Use `Socket::set_nodelay` on the stream.
+/// socket_ref.set_nodelay(true)?;
+/// drop(socket_ref);
+///
+/// assert_eq!(stream.nodelay()?, true);
+/// # handle.join().unwrap();
+/// # Ok(())
+/// # }
+/// ```
+///
+/// Below is an example of **incorrect usage** of `SockRef::from`, which is
+/// currently possible (but not intended and will be fixed in future versions).
+///
+/// ```compile_fail
+/// use socket2::SockRef;
+///
+/// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+/// /// THIS USAGE IS NOT VALID!
+/// let socket_ref = SockRef::from(&123);
+/// // The above line is overseen possibility when using `SockRef::from`, it
+/// // uses the `RawFd` (on Unix), which is a type alias for `c_int`/`i32`,
+/// // which implements `AsRawFd`. However it may be clear that this usage is
+/// // invalid as it doesn't guarantee that `123` is a valid file descriptor.
+///
+/// // Using `Socket::set_nodelay` now will call it on a file descriptor we
+/// // don't own! We don't even not if the file descriptor is valid or a socket.
+/// socket_ref.set_nodelay(true)?;
+/// drop(socket_ref);
+/// # Ok(())
+/// # }
+/// # DO_NOT_COMPILE
+/// ```
+pub struct SockRef<'s> {
+    /// Because this is a reference we don't own the `Socket`, however `Socket`
+    /// closes itself when dropped, so we use `ManuallyDrop` to prevent it from
+    /// closing itself.
+    socket: ManuallyDrop<Socket>,
+    /// Because we don't own the socket we need to ensure the socket remains
+    /// open while we have a "reference" to it, the lifetime `'s` ensures this.
+    _lifetime: PhantomData<&'s Socket>,
+}
+
+impl<'s> Deref for SockRef<'s> {
+    type Target = Socket;
+
+    fn deref(&self) -> &Self::Target {
+        &self.socket
+    }
+}
+
+/// On Windows, a corresponding `From<&impl AsRawSocket>` implementation exists.
+#[cfg(unix)]
+#[cfg_attr(docsrs, doc(cfg(unix)))]
+impl<'s, S> From<&'s S> for SockRef<'s>
+where
+    S: AsRawFd,
+{
+    /// The caller must ensure `S` is actually a socket.
+    fn from(socket: &'s S) -> Self {
+        let fd = socket.as_raw_fd();
+        assert!(fd >= 0);
+        SockRef {
+            socket: ManuallyDrop::new(unsafe { Socket::from_raw_fd(fd) }),
+            _lifetime: PhantomData,
+        }
+    }
+}
+
+/// On Unix, a corresponding `From<&impl AsRawFd>` implementation exists.
+#[cfg(windows)]
+#[cfg_attr(docsrs, doc(cfg(windows)))]
+impl<'s, S> From<&'s S> for SockRef<'s>
+where
+    S: AsRawSocket,
+{
+    /// See the `From<&impl AsRawFd>` implementation.
+    fn from(socket: &'s S) -> Self {
+        let socket = socket.as_raw_socket();
+        assert!(socket != winapi::um::winsock2::INVALID_SOCKET as _);
+        SockRef {
+            socket: ManuallyDrop::new(unsafe { Socket::from_raw_socket(socket) }),
+            _lifetime: PhantomData,
+        }
+    }
+}
+
+impl fmt::Debug for SockRef<'_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("SockRef")
+            .field("raw", &self.socket.as_raw())
+            .field("local_addr", &self.socket.local_addr().ok())
+            .field("peer_addr", &self.socket.peer_addr().ok())
+            .finish()
+    }
+}
diff --git a/src/sys/unix.rs b/src/sys/unix.rs
new file mode 100644
index 0000000..873b323
--- /dev/null
+++ b/src/sys/unix.rs
@@ -0,0 +1,2053 @@
+// Copyright 2015 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::cmp::min;
+#[cfg(not(target_os = "redox"))]
+use std::io::IoSlice;
+use std::marker::PhantomData;
+use std::mem::{self, size_of, MaybeUninit};
+use std::net::Shutdown;
+use std::net::{Ipv4Addr, Ipv6Addr};
+#[cfg(all(feature = "all", target_vendor = "apple"))]
+use std::num::NonZeroU32;
+#[cfg(all(
+    feature = "all",
+    any(
+        target_os = "android",
+        target_os = "freebsd",
+        target_os = "linux",
+        target_vendor = "apple",
+    )
+))]
+use std::num::NonZeroUsize;
+#[cfg(feature = "all")]
+use std::os::unix::ffi::OsStrExt;
+#[cfg(all(
+    feature = "all",
+    any(
+        target_os = "android",
+        target_os = "freebsd",
+        target_os = "linux",
+        target_vendor = "apple",
+    )
+))]
+use std::os::unix::io::RawFd;
+use std::os::unix::io::{AsRawFd, FromRawFd, IntoRawFd};
+#[cfg(feature = "all")]
+use std::os::unix::net::{UnixDatagram, UnixListener, UnixStream};
+#[cfg(feature = "all")]
+use std::path::Path;
+#[cfg(not(all(target_os = "redox", not(feature = "all"))))]
+use std::ptr;
+use std::time::{Duration, Instant};
+use std::{io, slice};
+
+#[cfg(not(target_vendor = "apple"))]
+use libc::ssize_t;
+use libc::{c_void, in6_addr, in_addr};
+
+#[cfg(not(target_os = "redox"))]
+use crate::RecvFlags;
+use crate::{Domain, Protocol, SockAddr, TcpKeepalive, Type};
+
+pub(crate) use libc::c_int;
+
+// Used in `Domain`.
+pub(crate) use libc::{AF_INET, AF_INET6};
+// Used in `Type`.
+#[cfg(all(feature = "all", not(target_os = "redox")))]
+pub(crate) use libc::SOCK_RAW;
+#[cfg(feature = "all")]
+pub(crate) use libc::SOCK_SEQPACKET;
+pub(crate) use libc::{SOCK_DGRAM, SOCK_STREAM};
+// Used in `Protocol`.
+pub(crate) use libc::{IPPROTO_ICMP, IPPROTO_ICMPV6, IPPROTO_TCP, IPPROTO_UDP};
+// Used in `SockAddr`.
+pub(crate) use libc::{
+    sa_family_t, sockaddr, sockaddr_in, sockaddr_in6, sockaddr_storage, socklen_t,
+};
+// Used in `RecvFlags`.
+#[cfg(not(target_os = "redox"))]
+pub(crate) use libc::{MSG_TRUNC, SO_OOBINLINE};
+// Used in `Socket`.
+#[cfg(all(feature = "all", not(target_os = "redox")))]
+pub(crate) use libc::IP_HDRINCL;
+#[cfg(not(any(
+    target_os = "fuschia",
+    target_os = "redox",
+    target_os = "solaris",
+    target_os = "illumos",
+)))]
+pub(crate) use libc::IP_TOS;
+#[cfg(not(target_vendor = "apple"))]
+pub(crate) use libc::SO_LINGER;
+#[cfg(target_vendor = "apple")]
+pub(crate) use libc::SO_LINGER_SEC as SO_LINGER;
+pub(crate) use libc::{
+    ip_mreq as IpMreq, ipv6_mreq as Ipv6Mreq, linger, IPPROTO_IP, IPPROTO_IPV6,
+    IPV6_MULTICAST_HOPS, IPV6_MULTICAST_IF, IPV6_MULTICAST_LOOP, IPV6_UNICAST_HOPS, IPV6_V6ONLY,
+    IP_ADD_MEMBERSHIP, IP_DROP_MEMBERSHIP, IP_MULTICAST_IF, IP_MULTICAST_LOOP, IP_MULTICAST_TTL,
+    IP_TTL, MSG_OOB, MSG_PEEK, SOL_SOCKET, SO_BROADCAST, SO_ERROR, SO_KEEPALIVE, SO_RCVBUF,
+    SO_RCVTIMEO, SO_REUSEADDR, SO_SNDBUF, SO_SNDTIMEO, SO_TYPE, TCP_NODELAY,
+};
+#[cfg(not(any(
+    target_os = "dragonfly",
+    target_os = "freebsd",
+    target_os = "haiku",
+    target_os = "illumos",
+    target_os = "netbsd",
+    target_os = "openbsd",
+    target_os = "solaris",
+    target_vendor = "apple"
+)))]
+pub(crate) use libc::{IPV6_ADD_MEMBERSHIP, IPV6_DROP_MEMBERSHIP};
+#[cfg(any(
+    target_os = "dragonfly",
+    target_os = "freebsd",
+    target_os = "haiku",
+    target_os = "illumos",
+    target_os = "netbsd",
+    target_os = "openbsd",
+    target_os = "solaris",
+    target_vendor = "apple",
+))]
+pub(crate) use libc::{
+    IPV6_JOIN_GROUP as IPV6_ADD_MEMBERSHIP, IPV6_LEAVE_GROUP as IPV6_DROP_MEMBERSHIP,
+};
+#[cfg(all(
+    feature = "all",
+    any(
+        target_os = "android",
+        target_os = "dragonfly",
+        target_os = "freebsd",
+        target_os = "fuchsia",
+        target_os = "illumos",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    )
+))]
+pub(crate) use libc::{TCP_KEEPCNT, TCP_KEEPINTVL};
+
+// See this type in the Windows file.
+pub(crate) type Bool = c_int;
+
+#[cfg(target_vendor = "apple")]
+use libc::TCP_KEEPALIVE as KEEPALIVE_TIME;
+#[cfg(not(any(target_vendor = "apple", target_os = "haiku", target_os = "openbsd")))]
+use libc::TCP_KEEPIDLE as KEEPALIVE_TIME;
+
+/// Helper macro to execute a system call that returns an `io::Result`.
+macro_rules! syscall {
+    ($fn: ident ( $($arg: expr),* $(,)* ) ) => {{
+        #[allow(unused_unsafe)]
+        let res = unsafe { libc::$fn($($arg, )*) };
+        if res == -1 {
+            Err(std::io::Error::last_os_error())
+        } else {
+            Ok(res)
+        }
+    }};
+}
+
+/// Maximum size of a buffer passed to system call like `recv` and `send`.
+#[cfg(not(target_vendor = "apple"))]
+const MAX_BUF_LEN: usize = <ssize_t>::max_value() as usize;
+
+// The maximum read limit on most posix-like systems is `SSIZE_MAX`, with the
+// man page quoting that if the count of bytes to read is greater than
+// `SSIZE_MAX` the result is "unspecified".
+//
+// On macOS, however, apparently the 64-bit libc is either buggy or
+// intentionally showing odd behavior by rejecting any read with a size larger
+// than or equal to INT_MAX. To handle both of these the read size is capped on
+// both platforms.
+#[cfg(target_vendor = "apple")]
+const MAX_BUF_LEN: usize = <c_int>::max_value() as usize - 1;
+
+#[cfg(any(
+    all(
+        target_os = "linux",
+        any(
+            target_env = "gnu",
+            all(target_env = "uclibc", target_pointer_width = "64")
+        )
+    ),
+    target_os = "android",
+))]
+type IovLen = usize;
+
+#[cfg(any(
+    all(
+        target_os = "linux",
+        any(
+            target_env = "musl",
+            all(target_env = "uclibc", target_pointer_width = "32")
+        )
+    ),
+    target_os = "dragonfly",
+    target_os = "freebsd",
+    target_os = "fuchsia",
+    target_os = "haiku",
+    target_os = "illumos",
+    target_os = "netbsd",
+    target_os = "openbsd",
+    target_os = "solaris",
+    target_vendor = "apple",
+))]
+type IovLen = c_int;
+
+/// Unix only API.
+impl Domain {
+    /// Domain for Unix socket communication, corresponding to `AF_UNIX`.
+    #[cfg_attr(docsrs, doc(cfg(unix)))]
+    pub const UNIX: Domain = Domain(libc::AF_UNIX);
+
+    /// Domain for low-level packet interface, corresponding to `AF_PACKET`.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub const PACKET: Domain = Domain(libc::AF_PACKET);
+
+    /// Domain for low-level VSOCK interface, corresponding to `AF_VSOCK`.
+    #[cfg(all(feature = "all", any(target_os = "android", target_os = "linux")))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(feature = "all", any(target_os = "android", target_os = "linux"))))
+    )]
+    pub const VSOCK: Domain = Domain(libc::AF_VSOCK);
+}
+
+impl_debug!(
+    Domain,
+    libc::AF_INET,
+    libc::AF_INET6,
+    libc::AF_UNIX,
+    #[cfg(any(target_os = "android", target_os = "fuchsia", target_os = "linux"))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(any(target_os = "android", target_os = "fuchsia", target_os = "linux")))
+    )]
+    libc::AF_PACKET,
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    #[cfg_attr(docsrs, doc(cfg(any(target_os = "android", target_os = "linux"))))]
+    libc::AF_VSOCK,
+    libc::AF_UNSPEC, // = 0.
+);
+
+/// Unix only API.
+impl Type {
+    /// Set `SOCK_NONBLOCK` on the `Type`.
+    #[cfg(all(
+        feature = "all",
+        any(
+            target_os = "android",
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "illumos",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_os = "openbsd"
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(
+                target_os = "android",
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "fuchsia",
+                target_os = "illumos",
+                target_os = "linux",
+                target_os = "netbsd",
+                target_os = "openbsd"
+            )
+        )))
+    )]
+    pub const fn nonblocking(self) -> Type {
+        Type(self.0 | libc::SOCK_NONBLOCK)
+    }
+
+    /// Set `SOCK_CLOEXEC` on the `Type`.
+    #[cfg(all(
+        feature = "all",
+        any(
+            target_os = "android",
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "illumos",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_os = "openbsd"
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(
+                target_os = "android",
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "fuchsia",
+                target_os = "illumos",
+                target_os = "linux",
+                target_os = "netbsd",
+                target_os = "openbsd"
+            )
+        )))
+    )]
+    pub const fn cloexec(self) -> Type {
+        self._cloexec()
+    }
+
+    #[cfg(any(
+        target_os = "android",
+        target_os = "dragonfly",
+        target_os = "freebsd",
+        target_os = "fuchsia",
+        target_os = "illumos",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_os = "openbsd"
+    ))]
+    pub(crate) const fn _cloexec(self) -> Type {
+        Type(self.0 | libc::SOCK_CLOEXEC)
+    }
+}
+
+impl_debug!(
+    Type,
+    libc::SOCK_STREAM,
+    libc::SOCK_DGRAM,
+    #[cfg(not(target_os = "redox"))]
+    libc::SOCK_RAW,
+    #[cfg(not(any(target_os = "redox", target_os = "haiku")))]
+    libc::SOCK_RDM,
+    libc::SOCK_SEQPACKET,
+    /* TODO: add these optional bit OR-ed flags:
+    #[cfg(any(
+        target_os = "android",
+        target_os = "dragonfly",
+        target_os = "freebsd",
+        target_os = "fuchsia",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_os = "openbsd"
+    ))]
+    libc::SOCK_NONBLOCK,
+    #[cfg(any(
+        target_os = "android",
+        target_os = "dragonfly",
+        target_os = "freebsd",
+        target_os = "fuchsia",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_os = "openbsd"
+    ))]
+    libc::SOCK_CLOEXEC,
+    */
+);
+
+impl_debug!(
+    Protocol,
+    libc::IPPROTO_ICMP,
+    libc::IPPROTO_ICMPV6,
+    libc::IPPROTO_TCP,
+    libc::IPPROTO_UDP,
+);
+
+/// Unix-only API.
+#[cfg(not(target_os = "redox"))]
+impl RecvFlags {
+    /// Check if the message terminates a record.
+    ///
+    /// Not all socket types support the notion of records.
+    /// For socket types that do support it (such as [`SEQPACKET`][Type::SEQPACKET]),
+    /// a record is terminated by sending a message with the end-of-record flag set.
+    ///
+    /// On Unix this corresponds to the MSG_EOR flag.
+    pub const fn is_end_of_record(self) -> bool {
+        self.0 & libc::MSG_EOR != 0
+    }
+
+    /// Check if the message contains out-of-band data.
+    ///
+    /// This is useful for protocols where you receive out-of-band data
+    /// mixed in with the normal data stream.
+    ///
+    /// On Unix this corresponds to the MSG_OOB flag.
+    pub const fn is_out_of_band(self) -> bool {
+        self.0 & libc::MSG_OOB != 0
+    }
+}
+
+#[cfg(not(target_os = "redox"))]
+impl std::fmt::Debug for RecvFlags {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("RecvFlags")
+            .field("is_end_of_record", &self.is_end_of_record())
+            .field("is_out_of_band", &self.is_out_of_band())
+            .field("is_truncated", &self.is_truncated())
+            .finish()
+    }
+}
+
+#[repr(transparent)]
+pub struct MaybeUninitSlice<'a> {
+    vec: libc::iovec,
+    _lifetime: PhantomData<&'a mut [MaybeUninit<u8>]>,
+}
+
+unsafe impl<'a> Send for MaybeUninitSlice<'a> {}
+
+unsafe impl<'a> Sync for MaybeUninitSlice<'a> {}
+
+impl<'a> MaybeUninitSlice<'a> {
+    pub(crate) fn new(buf: &'a mut [MaybeUninit<u8>]) -> MaybeUninitSlice<'a> {
+        MaybeUninitSlice {
+            vec: libc::iovec {
+                iov_base: buf.as_mut_ptr().cast(),
+                iov_len: buf.len(),
+            },
+            _lifetime: PhantomData,
+        }
+    }
+
+    pub(crate) fn as_slice(&self) -> &[MaybeUninit<u8>] {
+        unsafe { slice::from_raw_parts(self.vec.iov_base.cast(), self.vec.iov_len) }
+    }
+
+    pub(crate) fn as_mut_slice(&mut self) -> &mut [MaybeUninit<u8>] {
+        unsafe { slice::from_raw_parts_mut(self.vec.iov_base.cast(), self.vec.iov_len) }
+    }
+}
+
+/// Unix only API.
+impl SockAddr {
+    /// Constructs a `SockAddr` with the family `AF_UNIX` and the provided path.
+    ///
+    /// # Failure
+    ///
+    /// Returns an error if the path is longer than `SUN_LEN`.
+    #[cfg(feature = "all")]
+    #[cfg_attr(docsrs, doc(cfg(all(unix, feature = "all"))))]
+    #[allow(unused_unsafe)] // TODO: replace with `unsafe_op_in_unsafe_fn` once stable.
+    pub fn unix<P>(path: P) -> io::Result<SockAddr>
+    where
+        P: AsRef<Path>,
+    {
+        unsafe {
+            SockAddr::init(|storage, len| {
+                // Safety: `SockAddr::init` zeros the address, which is a valid
+                // representation.
+                let storage: &mut libc::sockaddr_un = unsafe { &mut *storage.cast() };
+                let len: &mut socklen_t = unsafe { &mut *len };
+
+                let bytes = path.as_ref().as_os_str().as_bytes();
+                let too_long = match bytes.first() {
+                    None => false,
+                    // linux abstract namespaces aren't null-terminated
+                    Some(&0) => bytes.len() > storage.sun_path.len(),
+                    Some(_) => bytes.len() >= storage.sun_path.len(),
+                };
+                if too_long {
+                    return Err(io::Error::new(
+                        io::ErrorKind::InvalidInput,
+                        "path must be shorter than SUN_LEN",
+                    ));
+                }
+
+                storage.sun_family = libc::AF_UNIX as sa_family_t;
+                // Safety: `bytes` and `addr.sun_path` are not overlapping and
+                // both point to valid memory.
+                // `SockAddr::init` zeroes the memory, so the path is already
+                // null terminated.
+                unsafe {
+                    ptr::copy_nonoverlapping(
+                        bytes.as_ptr(),
+                        storage.sun_path.as_mut_ptr() as *mut u8,
+                        bytes.len(),
+                    )
+                };
+
+                let base = storage as *const _ as usize;
+                let path = &storage.sun_path as *const _ as usize;
+                let sun_path_offset = path - base;
+                let length = sun_path_offset
+                    + bytes.len()
+                    + match bytes.first() {
+                        Some(&0) | None => 0,
+                        Some(_) => 1,
+                    };
+                *len = length as socklen_t;
+
+                Ok(())
+            })
+        }
+        .map(|(_, addr)| addr)
+    }
+}
+
+impl SockAddr {
+    /// Constructs a `SockAddr` with the family `AF_VSOCK` and the provided CID/port.
+    ///
+    /// # Errors
+    ///
+    /// This function can never fail. In a future version of this library it will be made
+    /// infallible.
+    #[allow(unused_unsafe)] // TODO: replace with `unsafe_op_in_unsafe_fn` once stable.
+    #[cfg(all(feature = "all", any(target_os = "android", target_os = "linux")))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(feature = "all", any(target_os = "android", target_os = "linux"))))
+    )]
+    pub fn vsock(cid: u32, port: u32) -> io::Result<SockAddr> {
+        unsafe {
+            SockAddr::init(|storage, len| {
+                // Safety: `SockAddr::init` zeros the address, which is a valid
+                // representation.
+                let storage: &mut libc::sockaddr_vm = unsafe { &mut *storage.cast() };
+                let len: &mut socklen_t = unsafe { &mut *len };
+
+                storage.svm_family = libc::AF_VSOCK as sa_family_t;
+                storage.svm_cid = cid;
+                storage.svm_port = port;
+
+                *len = mem::size_of::<libc::sockaddr_vm>() as socklen_t;
+
+                Ok(())
+            })
+        }
+        .map(|(_, addr)| addr)
+    }
+
+    /// Returns this address VSOCK CID/port if it is in the `AF_VSOCK` family,
+    /// otherwise return `None`.
+    #[cfg(all(feature = "all", any(target_os = "android", target_os = "linux")))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(feature = "all", any(target_os = "android", target_os = "linux"))))
+    )]
+    pub fn vsock_address(&self) -> Option<(u32, u32)> {
+        if self.family() == libc::AF_VSOCK as sa_family_t {
+            // Safety: if the ss_family field is AF_VSOCK then storage must be a sockaddr_vm.
+            let addr = unsafe { &*(self.as_ptr() as *const libc::sockaddr_vm) };
+            Some((addr.svm_cid, addr.svm_port))
+        } else {
+            None
+        }
+    }
+}
+
+pub(crate) type Socket = c_int;
+
+pub(crate) unsafe fn socket_from_raw(socket: Socket) -> crate::socket::Inner {
+    crate::socket::Inner::from_raw_fd(socket)
+}
+
+pub(crate) fn socket_as_raw(socket: &crate::socket::Inner) -> Socket {
+    socket.as_raw_fd()
+}
+
+pub(crate) fn socket_into_raw(socket: crate::socket::Inner) -> Socket {
+    socket.into_raw_fd()
+}
+
+pub(crate) fn socket(family: c_int, ty: c_int, protocol: c_int) -> io::Result<Socket> {
+    syscall!(socket(family, ty, protocol))
+}
+
+#[cfg(feature = "all")]
+pub(crate) fn socketpair(family: c_int, ty: c_int, protocol: c_int) -> io::Result<[Socket; 2]> {
+    let mut fds = [0, 0];
+    syscall!(socketpair(family, ty, protocol, fds.as_mut_ptr())).map(|_| fds)
+}
+
+pub(crate) fn bind(fd: Socket, addr: &SockAddr) -> io::Result<()> {
+    syscall!(bind(fd, addr.as_ptr(), addr.len() as _)).map(|_| ())
+}
+
+pub(crate) fn connect(fd: Socket, addr: &SockAddr) -> io::Result<()> {
+    syscall!(connect(fd, addr.as_ptr(), addr.len())).map(|_| ())
+}
+
+pub(crate) fn poll_connect(socket: &crate::Socket, timeout: Duration) -> io::Result<()> {
+    let start = Instant::now();
+
+    let mut pollfd = libc::pollfd {
+        fd: socket.as_raw(),
+        events: libc::POLLIN | libc::POLLOUT,
+        revents: 0,
+    };
+
+    loop {
+        let elapsed = start.elapsed();
+        if elapsed >= timeout {
+            return Err(io::ErrorKind::TimedOut.into());
+        }
+
+        let timeout = (timeout - elapsed).as_millis();
+        let timeout = clamp(timeout, 1, c_int::max_value() as u128) as c_int;
+
+        match syscall!(poll(&mut pollfd, 1, timeout)) {
+            Ok(0) => return Err(io::ErrorKind::TimedOut.into()),
+            Ok(_) => {
+                // Error or hang up indicates an error (or failure to connect).
+                if (pollfd.revents & libc::POLLHUP) != 0 || (pollfd.revents & libc::POLLERR) != 0 {
+                    match socket.take_error() {
+                        Ok(Some(err)) => return Err(err),
+                        Ok(None) => {
+                            return Err(io::Error::new(
+                                io::ErrorKind::Other,
+                                "no error set after POLLHUP",
+                            ))
+                        }
+                        Err(err) => return Err(err),
+                    }
+                }
+                return Ok(());
+            }
+            // Got interrupted, try again.
+            Err(ref err) if err.kind() == io::ErrorKind::Interrupted => continue,
+            Err(err) => return Err(err),
+        }
+    }
+}
+
+// TODO: use clamp from std lib, stable since 1.50.
+fn clamp<T>(value: T, min: T, max: T) -> T
+where
+    T: Ord,
+{
+    if value <= min {
+        min
+    } else if value >= max {
+        max
+    } else {
+        value
+    }
+}
+
+pub(crate) fn listen(fd: Socket, backlog: c_int) -> io::Result<()> {
+    syscall!(listen(fd, backlog)).map(|_| ())
+}
+
+pub(crate) fn accept(fd: Socket) -> io::Result<(Socket, SockAddr)> {
+    // Safety: `accept` initialises the `SockAddr` for us.
+    unsafe { SockAddr::init(|storage, len| syscall!(accept(fd, storage.cast(), len))) }
+}
+
+pub(crate) fn getsockname(fd: Socket) -> io::Result<SockAddr> {
+    // Safety: `accept` initialises the `SockAddr` for us.
+    unsafe { SockAddr::init(|storage, len| syscall!(getsockname(fd, storage.cast(), len))) }
+        .map(|(_, addr)| addr)
+}
+
+pub(crate) fn getpeername(fd: Socket) -> io::Result<SockAddr> {
+    // Safety: `accept` initialises the `SockAddr` for us.
+    unsafe { SockAddr::init(|storage, len| syscall!(getpeername(fd, storage.cast(), len))) }
+        .map(|(_, addr)| addr)
+}
+
+pub(crate) fn try_clone(fd: Socket) -> io::Result<Socket> {
+    syscall!(fcntl(fd, libc::F_DUPFD_CLOEXEC, 0))
+}
+
+pub(crate) fn set_nonblocking(fd: Socket, nonblocking: bool) -> io::Result<()> {
+    if nonblocking {
+        fcntl_add(fd, libc::F_GETFL, libc::F_SETFL, libc::O_NONBLOCK)
+    } else {
+        fcntl_remove(fd, libc::F_GETFL, libc::F_SETFL, libc::O_NONBLOCK)
+    }
+}
+
+pub(crate) fn shutdown(fd: Socket, how: Shutdown) -> io::Result<()> {
+    let how = match how {
+        Shutdown::Write => libc::SHUT_WR,
+        Shutdown::Read => libc::SHUT_RD,
+        Shutdown::Both => libc::SHUT_RDWR,
+    };
+    syscall!(shutdown(fd, how)).map(|_| ())
+}
+
+pub(crate) fn recv(fd: Socket, buf: &mut [MaybeUninit<u8>], flags: c_int) -> io::Result<usize> {
+    syscall!(recv(
+        fd,
+        buf.as_mut_ptr().cast(),
+        min(buf.len(), MAX_BUF_LEN),
+        flags,
+    ))
+    .map(|n| n as usize)
+}
+
+pub(crate) fn recv_from(
+    fd: Socket,
+    buf: &mut [MaybeUninit<u8>],
+    flags: c_int,
+) -> io::Result<(usize, SockAddr)> {
+    // Safety: `recvfrom` initialises the `SockAddr` for us.
+    unsafe {
+        SockAddr::init(|addr, addrlen| {
+            syscall!(recvfrom(
+                fd,
+                buf.as_mut_ptr().cast(),
+                min(buf.len(), MAX_BUF_LEN),
+                flags,
+                addr.cast(),
+                addrlen
+            ))
+            .map(|n| n as usize)
+        })
+    }
+}
+
+#[cfg(not(target_os = "redox"))]
+pub(crate) fn recv_vectored(
+    fd: Socket,
+    bufs: &mut [crate::MaybeUninitSlice<'_>],
+    flags: c_int,
+) -> io::Result<(usize, RecvFlags)> {
+    recvmsg(fd, ptr::null_mut(), bufs, flags).map(|(n, _, recv_flags)| (n, recv_flags))
+}
+
+#[cfg(not(target_os = "redox"))]
+pub(crate) fn recv_from_vectored(
+    fd: Socket,
+    bufs: &mut [crate::MaybeUninitSlice<'_>],
+    flags: c_int,
+) -> io::Result<(usize, RecvFlags, SockAddr)> {
+    // Safety: `recvmsg` initialises the address storage and we set the length
+    // manually.
+    unsafe {
+        SockAddr::init(|storage, len| {
+            recvmsg(fd, storage, bufs, flags).map(|(n, addrlen, recv_flags)| {
+                // Set the correct address length.
+                *len = addrlen;
+                (n, recv_flags)
+            })
+        })
+    }
+    .map(|((n, recv_flags), addr)| (n, recv_flags, addr))
+}
+
+/// Returns the (bytes received, sending address len, `RecvFlags`).
+#[cfg(not(target_os = "redox"))]
+fn recvmsg(
+    fd: Socket,
+    msg_name: *mut sockaddr_storage,
+    bufs: &mut [crate::MaybeUninitSlice<'_>],
+    flags: c_int,
+) -> io::Result<(usize, libc::socklen_t, RecvFlags)> {
+    let msg_namelen = if msg_name.is_null() {
+        0
+    } else {
+        size_of::<sockaddr_storage>() as libc::socklen_t
+    };
+    // libc::msghdr contains unexported padding fields on Fuchsia.
+    let mut msg: libc::msghdr = unsafe { mem::zeroed() };
+    msg.msg_name = msg_name.cast();
+    msg.msg_namelen = msg_namelen;
+    msg.msg_iov = bufs.as_mut_ptr().cast();
+    msg.msg_iovlen = min(bufs.len(), IovLen::MAX as usize) as IovLen;
+    syscall!(recvmsg(fd, &mut msg, flags))
+        .map(|n| (n as usize, msg.msg_namelen, RecvFlags(msg.msg_flags)))
+}
+
+pub(crate) fn send(fd: Socket, buf: &[u8], flags: c_int) -> io::Result<usize> {
+    syscall!(send(
+        fd,
+        buf.as_ptr().cast(),
+        min(buf.len(), MAX_BUF_LEN),
+        flags,
+    ))
+    .map(|n| n as usize)
+}
+
+#[cfg(not(target_os = "redox"))]
+pub(crate) fn send_vectored(fd: Socket, bufs: &[IoSlice<'_>], flags: c_int) -> io::Result<usize> {
+    sendmsg(fd, ptr::null(), 0, bufs, flags)
+}
+
+pub(crate) fn send_to(fd: Socket, buf: &[u8], addr: &SockAddr, flags: c_int) -> io::Result<usize> {
+    syscall!(sendto(
+        fd,
+        buf.as_ptr().cast(),
+        min(buf.len(), MAX_BUF_LEN),
+        flags,
+        addr.as_ptr(),
+        addr.len(),
+    ))
+    .map(|n| n as usize)
+}
+
+#[cfg(not(target_os = "redox"))]
+pub(crate) fn send_to_vectored(
+    fd: Socket,
+    bufs: &[IoSlice<'_>],
+    addr: &SockAddr,
+    flags: c_int,
+) -> io::Result<usize> {
+    sendmsg(fd, addr.as_storage_ptr(), addr.len(), bufs, flags)
+}
+
+/// Returns the (bytes received, sending address len, `RecvFlags`).
+#[cfg(not(target_os = "redox"))]
+fn sendmsg(
+    fd: Socket,
+    msg_name: *const sockaddr_storage,
+    msg_namelen: socklen_t,
+    bufs: &[IoSlice<'_>],
+    flags: c_int,
+) -> io::Result<usize> {
+    // libc::msghdr contains unexported padding fields on Fuchsia.
+    let mut msg: libc::msghdr = unsafe { mem::zeroed() };
+    // Safety: we're creating a `*mut` pointer from a reference, which is UB
+    // once actually used. However the OS should not write to it in the
+    // `sendmsg` system call.
+    msg.msg_name = (msg_name as *mut sockaddr_storage).cast();
+    msg.msg_namelen = msg_namelen;
+    // Safety: Same as above about `*const` -> `*mut`.
+    msg.msg_iov = bufs.as_ptr() as *mut _;
+    msg.msg_iovlen = min(bufs.len(), IovLen::MAX as usize) as IovLen;
+    syscall!(sendmsg(fd, &msg, flags)).map(|n| n as usize)
+}
+
+/// Wrapper around `getsockopt` to deal with platform specific timeouts.
+pub(crate) fn timeout_opt(fd: Socket, opt: c_int, val: c_int) -> io::Result<Option<Duration>> {
+    unsafe { getsockopt(fd, opt, val).map(from_timeval) }
+}
+
+fn from_timeval(duration: libc::timeval) -> Option<Duration> {
+    if duration.tv_sec == 0 && duration.tv_usec == 0 {
+        None
+    } else {
+        let sec = duration.tv_sec as u64;
+        let nsec = (duration.tv_usec as u32) * 1000;
+        Some(Duration::new(sec, nsec))
+    }
+}
+
+/// Wrapper around `setsockopt` to deal with platform specific timeouts.
+pub(crate) fn set_timeout_opt(
+    fd: Socket,
+    opt: c_int,
+    val: c_int,
+    duration: Option<Duration>,
+) -> io::Result<()> {
+    let duration = into_timeval(duration);
+    unsafe { setsockopt(fd, opt, val, duration) }
+}
+
+fn into_timeval(duration: Option<Duration>) -> libc::timeval {
+    match duration {
+        // https://github.com/rust-lang/libc/issues/1848
+        #[cfg_attr(target_env = "musl", allow(deprecated))]
+        Some(duration) => libc::timeval {
+            tv_sec: min(duration.as_secs(), libc::time_t::max_value() as u64) as libc::time_t,
+            tv_usec: duration.subsec_micros() as libc::suseconds_t,
+        },
+        None => libc::timeval {
+            tv_sec: 0,
+            tv_usec: 0,
+        },
+    }
+}
+
+#[cfg(feature = "all")]
+#[cfg(not(any(target_os = "haiku", target_os = "openbsd")))]
+pub(crate) fn keepalive_time(fd: Socket) -> io::Result<Duration> {
+    unsafe {
+        getsockopt::<c_int>(fd, IPPROTO_TCP, KEEPALIVE_TIME)
+            .map(|secs| Duration::from_secs(secs as u64))
+    }
+}
+
+#[allow(unused_variables)]
+pub(crate) fn set_tcp_keepalive(fd: Socket, keepalive: &TcpKeepalive) -> io::Result<()> {
+    #[cfg(not(any(target_os = "haiku", target_os = "openbsd")))]
+    if let Some(time) = keepalive.time {
+        let secs = into_secs(time);
+        unsafe { setsockopt(fd, libc::IPPROTO_TCP, KEEPALIVE_TIME, secs)? }
+    }
+
+    #[cfg(any(
+        target_os = "android",
+        target_os = "dragonfly",
+        target_os = "freebsd",
+        target_os = "fuchsia",
+        target_os = "illumos",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_vendor = "apple",
+    ))]
+    {
+        if let Some(interval) = keepalive.interval {
+            let secs = into_secs(interval);
+            unsafe { setsockopt(fd, libc::IPPROTO_TCP, libc::TCP_KEEPINTVL, secs)? }
+        }
+
+        if let Some(retries) = keepalive.retries {
+            unsafe { setsockopt(fd, libc::IPPROTO_TCP, libc::TCP_KEEPCNT, retries as c_int)? }
+        }
+    }
+
+    Ok(())
+}
+
+#[cfg(not(any(target_os = "haiku", target_os = "openbsd")))]
+fn into_secs(duration: Duration) -> c_int {
+    min(duration.as_secs(), c_int::max_value() as u64) as c_int
+}
+
+/// Add `flag` to the current set flags of `F_GETFD`.
+fn fcntl_add(fd: Socket, get_cmd: c_int, set_cmd: c_int, flag: c_int) -> io::Result<()> {
+    let previous = syscall!(fcntl(fd, get_cmd))?;
+    let new = previous | flag;
+    if new != previous {
+        syscall!(fcntl(fd, set_cmd, new)).map(|_| ())
+    } else {
+        // Flag was already set.
+        Ok(())
+    }
+}
+
+/// Remove `flag` to the current set flags of `F_GETFD`.
+fn fcntl_remove(fd: Socket, get_cmd: c_int, set_cmd: c_int, flag: c_int) -> io::Result<()> {
+    let previous = syscall!(fcntl(fd, get_cmd))?;
+    let new = previous & !flag;
+    if new != previous {
+        syscall!(fcntl(fd, set_cmd, new)).map(|_| ())
+    } else {
+        // Flag was already set.
+        Ok(())
+    }
+}
+
+/// Caller must ensure `T` is the correct type for `opt` and `val`.
+pub(crate) unsafe fn getsockopt<T>(fd: Socket, opt: c_int, val: c_int) -> io::Result<T> {
+    let mut payload: MaybeUninit<T> = MaybeUninit::uninit();
+    let mut len = size_of::<T>() as libc::socklen_t;
+    syscall!(getsockopt(
+        fd,
+        opt,
+        val,
+        payload.as_mut_ptr().cast(),
+        &mut len,
+    ))
+    .map(|_| {
+        debug_assert_eq!(len as usize, size_of::<T>());
+        // Safety: `getsockopt` initialised `payload` for us.
+        payload.assume_init()
+    })
+}
+
+/// Caller must ensure `T` is the correct type for `opt` and `val`.
+pub(crate) unsafe fn setsockopt<T>(
+    fd: Socket,
+    opt: c_int,
+    val: c_int,
+    payload: T,
+) -> io::Result<()> {
+    let payload = &payload as *const T as *const c_void;
+    syscall!(setsockopt(
+        fd,
+        opt,
+        val,
+        payload,
+        mem::size_of::<T>() as libc::socklen_t,
+    ))
+    .map(|_| ())
+}
+
+pub(crate) fn to_in_addr(addr: &Ipv4Addr) -> in_addr {
+    // `s_addr` is stored as BE on all machines, and the array is in BE order.
+    // So the native endian conversion method is used so that it's never
+    // swapped.
+    in_addr {
+        s_addr: u32::from_ne_bytes(addr.octets()),
+    }
+}
+
+pub(crate) fn from_in_addr(in_addr: in_addr) -> Ipv4Addr {
+    Ipv4Addr::from(in_addr.s_addr.to_ne_bytes())
+}
+
+pub(crate) fn to_in6_addr(addr: &Ipv6Addr) -> in6_addr {
+    in6_addr {
+        s6_addr: addr.octets(),
+    }
+}
+
+pub(crate) fn from_in6_addr(addr: in6_addr) -> Ipv6Addr {
+    Ipv6Addr::from(addr.s6_addr)
+}
+
+#[cfg(not(any(
+    target_os = "haiku",
+    target_os = "illumos",
+    target_os = "netbsd",
+    target_os = "redox",
+    target_os = "solaris",
+)))]
+pub(crate) fn to_mreqn(
+    multiaddr: &Ipv4Addr,
+    interface: &crate::socket::InterfaceIndexOrAddress,
+) -> libc::ip_mreqn {
+    match interface {
+        crate::socket::InterfaceIndexOrAddress::Index(interface) => libc::ip_mreqn {
+            imr_multiaddr: to_in_addr(multiaddr),
+            imr_address: to_in_addr(&Ipv4Addr::UNSPECIFIED),
+            imr_ifindex: *interface as _,
+        },
+        crate::socket::InterfaceIndexOrAddress::Address(interface) => libc::ip_mreqn {
+            imr_multiaddr: to_in_addr(multiaddr),
+            imr_address: to_in_addr(interface),
+            imr_ifindex: 0,
+        },
+    }
+}
+
+/// Unix only API.
+impl crate::Socket {
+    /// Accept a new incoming connection from this listener.
+    ///
+    /// This function directly corresponds to the `accept4(2)` function.
+    ///
+    /// This function will block the calling thread until a new connection is
+    /// established. When established, the corresponding `Socket` and the remote
+    /// peer's address will be returned.
+    #[cfg(all(
+        feature = "all",
+        any(
+            target_os = "android",
+            target_os = "dragonfly",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "illumos",
+            target_os = "linux",
+            target_os = "netbsd",
+            target_os = "openbsd"
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(
+                target_os = "android",
+                target_os = "dragonfly",
+                target_os = "freebsd",
+                target_os = "fuchsia",
+                target_os = "illumos",
+                target_os = "linux",
+                target_os = "netbsd",
+                target_os = "openbsd"
+            )
+        )))
+    )]
+    pub fn accept4(&self, flags: c_int) -> io::Result<(crate::Socket, SockAddr)> {
+        self._accept4(flags)
+    }
+
+    #[cfg(any(
+        target_os = "android",
+        target_os = "dragonfly",
+        target_os = "freebsd",
+        target_os = "fuchsia",
+        target_os = "illumos",
+        target_os = "linux",
+        target_os = "netbsd",
+        target_os = "openbsd"
+    ))]
+    pub(crate) fn _accept4(&self, flags: c_int) -> io::Result<(crate::Socket, SockAddr)> {
+        // Safety: `accept4` initialises the `SockAddr` for us.
+        unsafe {
+            SockAddr::init(|storage, len| {
+                syscall!(accept4(self.as_raw(), storage.cast(), len, flags))
+                    .map(crate::Socket::from_raw)
+            })
+        }
+    }
+
+    /// Sets `CLOEXEC` on the socket.
+    ///
+    /// # Notes
+    ///
+    /// On supported platforms you can use [`Type::cloexec`].
+    #[cfg(feature = "all")]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", unix))))]
+    pub fn set_cloexec(&self, close_on_exec: bool) -> io::Result<()> {
+        self._set_cloexec(close_on_exec)
+    }
+
+    pub(crate) fn _set_cloexec(&self, close_on_exec: bool) -> io::Result<()> {
+        if close_on_exec {
+            fcntl_add(
+                self.as_raw(),
+                libc::F_GETFD,
+                libc::F_SETFD,
+                libc::FD_CLOEXEC,
+            )
+        } else {
+            fcntl_remove(
+                self.as_raw(),
+                libc::F_GETFD,
+                libc::F_SETFD,
+                libc::FD_CLOEXEC,
+            )
+        }
+    }
+
+    /// Sets `SO_NOSIGPIPE` on the socket.
+    #[cfg(all(feature = "all", any(doc, target_vendor = "apple")))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", target_vendor = "apple"))))]
+    pub fn set_nosigpipe(&self, nosigpipe: bool) -> io::Result<()> {
+        self._set_nosigpipe(nosigpipe)
+    }
+
+    #[cfg(target_vendor = "apple")]
+    pub(crate) fn _set_nosigpipe(&self, nosigpipe: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::SOL_SOCKET,
+                libc::SO_NOSIGPIPE,
+                nosigpipe as c_int,
+            )
+        }
+    }
+
+    /// Gets the value of the `TCP_MAXSEG` option on this socket.
+    ///
+    /// For more information about this option, see [`set_mss`].
+    ///
+    /// [`set_mss`]: crate::Socket::set_mss
+    #[cfg(all(feature = "all", not(target_os = "redox")))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", unix, not(target_os = "redox")))))]
+    pub fn mss(&self) -> io::Result<u32> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), libc::IPPROTO_TCP, libc::TCP_MAXSEG)
+                .map(|mss| mss as u32)
+        }
+    }
+
+    /// Sets the value of the `TCP_MAXSEG` option on this socket.
+    ///
+    /// The `TCP_MAXSEG` option denotes the TCP Maximum Segment Size and is only
+    /// available on TCP sockets.
+    #[cfg(all(feature = "all", not(target_os = "redox")))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", unix, not(target_os = "redox")))))]
+    pub fn set_mss(&self, mss: u32) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::IPPROTO_TCP,
+                libc::TCP_MAXSEG,
+                mss as c_int,
+            )
+        }
+    }
+
+    /// Returns `true` if `listen(2)` was called on this socket by checking the
+    /// `SO_ACCEPTCONN` option on this socket.
+    #[cfg(all(
+        feature = "all",
+        any(
+            target_os = "android",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "linux",
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(
+                target_os = "android",
+                target_os = "freebsd",
+                target_os = "fuchsia",
+                target_os = "linux",
+            )
+        )))
+    )]
+    pub fn is_listener(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), libc::SOL_SOCKET, libc::SO_ACCEPTCONN)
+                .map(|v| v != 0)
+        }
+    }
+
+    /// Returns the [`Domain`] of this socket by checking the `SO_DOMAIN` option
+    /// on this socket.
+    #[cfg(all(
+        feature = "all",
+        any(
+            target_os = "android",
+            // TODO: add FreeBSD.
+            // target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "linux",
+        )
+    ))]
+    #[cfg_attr(docsrs, doc(cfg(all(
+        feature = "all",
+        any(
+            target_os = "android",
+            // TODO: add FreeBSD.
+            // target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "linux",
+        )
+    ))))]
+    pub fn domain(&self) -> io::Result<Domain> {
+        unsafe { getsockopt::<c_int>(self.as_raw(), libc::SOL_SOCKET, libc::SO_DOMAIN).map(Domain) }
+    }
+
+    /// Returns the [`Protocol`] of this socket by checking the `SO_PROTOCOL`
+    /// option on this socket.
+    #[cfg(all(
+        feature = "all",
+        any(
+            target_os = "android",
+            target_os = "freebsd",
+            target_os = "fuchsia",
+            target_os = "linux",
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(
+                target_os = "android",
+                target_os = "freebsd",
+                target_os = "fuchsia",
+                target_os = "linux",
+            )
+        )))
+    )]
+    pub fn protocol(&self) -> io::Result<Option<Protocol>> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), libc::SOL_SOCKET, libc::SO_PROTOCOL).map(|v| match v
+            {
+                0 => None,
+                p => Some(Protocol(p)),
+            })
+        }
+    }
+
+    /// Gets the value for the `SO_MARK` option on this socket.
+    ///
+    /// This value gets the socket mark field for each packet sent through
+    /// this socket.
+    ///
+    /// On Linux this function requires the `CAP_NET_ADMIN` capability.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn mark(&self) -> io::Result<u32> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), libc::SOL_SOCKET, libc::SO_MARK)
+                .map(|mark| mark as u32)
+        }
+    }
+
+    /// Sets the value for the `SO_MARK` option on this socket.
+    ///
+    /// This value sets the socket mark field for each packet sent through
+    /// this socket. Changing the mark can be used for mark-based routing
+    /// without netfilter or for packet filtering.
+    ///
+    /// On Linux this function requires the `CAP_NET_ADMIN` capability.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn set_mark(&self, mark: u32) -> io::Result<()> {
+        unsafe {
+            setsockopt::<c_int>(
+                self.as_raw(),
+                libc::SOL_SOCKET,
+                libc::SO_MARK,
+                mark as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `TCP_CORK` option on this socket.
+    ///
+    /// For more information about this option, see [`set_cork`].
+    ///
+    /// [`set_cork`]: Socket::set_cork
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn cork(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<Bool>(self.as_raw(), libc::IPPROTO_TCP, libc::TCP_CORK)
+                .map(|cork| cork != 0)
+        }
+    }
+
+    /// Set the value of the `TCP_CORK` option on this socket.
+    ///
+    /// If set, don't send out partial frames. All queued partial frames are
+    /// sent when the option is cleared again. There is a 200 millisecond ceiling on
+    /// the time for which output is corked by `TCP_CORK`. If this ceiling is reached,
+    /// then queued data is automatically transmitted.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn set_cork(&self, cork: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::IPPROTO_TCP,
+                libc::TCP_CORK,
+                cork as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `TCP_QUICKACK` option on this socket.
+    ///
+    /// For more information about this option, see [`set_quickack`].
+    ///
+    /// [`set_quickack`]: Socket::set_quickack
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn quickack(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<Bool>(self.as_raw(), libc::IPPROTO_TCP, libc::TCP_QUICKACK)
+                .map(|quickack| quickack != 0)
+        }
+    }
+
+    /// Set the value of the `TCP_QUICKACK` option on this socket.
+    ///
+    /// If set, acks are sent immediately, rather than delayed if needed in accordance to normal
+    /// TCP operation. This flag is not permanent, it only enables a switch to or from quickack mode.
+    /// Subsequent operation of the TCP protocol will once again enter/leave quickack mode depending on
+    /// internal protocol processing and factors such as delayed ack timeouts occurring and data transfer.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn set_quickack(&self, quickack: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::IPPROTO_TCP,
+                libc::TCP_QUICKACK,
+                quickack as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `TCP_THIN_LINEAR_TIMEOUTS` option on this socket.
+    ///
+    /// For more information about this option, see [`set_thin_linear_timeouts`].
+    ///
+    /// [`set_thin_linear_timeouts`]: Socket::set_thin_linear_timeouts
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn thin_linear_timeouts(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<Bool>(
+                self.as_raw(),
+                libc::IPPROTO_TCP,
+                libc::TCP_THIN_LINEAR_TIMEOUTS,
+            )
+            .map(|timeouts| timeouts != 0)
+        }
+    }
+
+    /// Set the value of the `TCP_THIN_LINEAR_TIMEOUTS` option on this socket.
+    ///    
+    /// If set, the kernel will dynamically detect a thin-stream connection if there are less than four packets in flight.
+    /// With less than four packets in flight the normal TCP fast retransmission will not be effective.
+    /// The kernel will modify the retransmission to avoid the very high latencies that thin stream suffer because of exponential backoff.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn set_thin_linear_timeouts(&self, timeouts: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::IPPROTO_TCP,
+                libc::TCP_THIN_LINEAR_TIMEOUTS,
+                timeouts as c_int,
+            )
+        }
+    }
+
+    /// Gets the value for the `SO_BINDTODEVICE` option on this socket.
+    ///
+    /// This value gets the socket binded device's interface name.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn device(&self) -> io::Result<Option<Vec<u8>>> {
+        // TODO: replace with `MaybeUninit::uninit_array` once stable.
+        let mut buf: [MaybeUninit<u8>; libc::IFNAMSIZ] =
+            unsafe { MaybeUninit::uninit().assume_init() };
+        let mut len = buf.len() as libc::socklen_t;
+        unsafe {
+            syscall!(getsockopt(
+                self.as_raw(),
+                libc::SOL_SOCKET,
+                libc::SO_BINDTODEVICE,
+                buf.as_mut_ptr().cast(),
+                &mut len,
+            ))?;
+        }
+        if len == 0 {
+            Ok(None)
+        } else {
+            let buf = &buf[..len as usize - 1];
+            // TODO: use `MaybeUninit::slice_assume_init_ref` once stable.
+            Ok(Some(unsafe { &*(buf as *const [_] as *const [u8]) }.into()))
+        }
+    }
+
+    /// Sets the value for the `SO_BINDTODEVICE` option on this socket.
+    ///
+    /// If a socket is bound to an interface, only packets received from that
+    /// particular interface are processed by the socket. Note that this only
+    /// works for some socket types, particularly `AF_INET` sockets.
+    ///
+    /// If `interface` is `None` or an empty string it removes the binding.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn bind_device(&self, interface: Option<&[u8]>) -> io::Result<()> {
+        let (value, len) = if let Some(interface) = interface {
+            (interface.as_ptr(), interface.len())
+        } else {
+            (ptr::null(), 0)
+        };
+        syscall!(setsockopt(
+            self.as_raw(),
+            libc::SOL_SOCKET,
+            libc::SO_BINDTODEVICE,
+            value.cast(),
+            len as libc::socklen_t,
+        ))
+        .map(|_| ())
+    }
+
+    /// Sets the value for the `SO_SETFIB` option on this socket.
+    ///
+    /// Bind socket to the specified forwarding table (VRF) on a FreeBSD.
+    #[cfg(all(feature = "all", any(target_os = "freebsd")))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", any(target_os = "freebsd")))))]
+    pub fn set_fib(&self, fib: u32) -> io::Result<()> {
+        syscall!(setsockopt(
+            self.as_raw(),
+            libc::SOL_SOCKET,
+            libc::SO_SETFIB,
+            (&fib as *const u32).cast(),
+            mem::size_of::<u32>() as libc::socklen_t,
+        ))
+        .map(|_| ())
+    }
+
+    /// Sets the value for `IP_BOUND_IF` option on this socket.
+    ///
+    /// If a socket is bound to an interface, only packets received from that
+    /// particular interface are processed by the socket.
+    ///
+    /// If `interface` is `None`, the binding is removed. If the `interface`
+    /// index is not valid, an error is returned.
+    ///
+    /// One can use `libc::if_nametoindex` to convert an interface alias to an
+    /// index.
+    #[cfg(all(feature = "all", target_vendor = "apple"))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", target_vendor = "apple"))))]
+    pub fn bind_device_by_index(&self, interface: Option<NonZeroU32>) -> io::Result<()> {
+        let index = interface.map(NonZeroU32::get).unwrap_or(0);
+        unsafe { setsockopt(self.as_raw(), IPPROTO_IP, libc::IP_BOUND_IF, index) }
+    }
+
+    /// Gets the value for `IP_BOUND_IF` option on this socket, i.e. the index
+    /// for the interface to which the socket is bound.
+    ///
+    /// Returns `None` if the socket is not bound to any interface, otherwise
+    /// returns an interface index.
+    #[cfg(all(feature = "all", target_vendor = "apple"))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", target_vendor = "apple"))))]
+    pub fn device_index(&self) -> io::Result<Option<NonZeroU32>> {
+        let index =
+            unsafe { getsockopt::<libc::c_uint>(self.as_raw(), IPPROTO_IP, libc::IP_BOUND_IF)? };
+        Ok(NonZeroU32::new(index))
+    }
+
+    /// Get the value of the `SO_INCOMING_CPU` option on this socket.
+    ///
+    /// For more information about this option, see [`set_cpu_affinity`].
+    ///
+    /// [`set_cpu_affinity`]: crate::Socket::set_cpu_affinity
+    #[cfg(all(feature = "all", target_os = "linux"))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", target_os = "linux"))))]
+    pub fn cpu_affinity(&self) -> io::Result<usize> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), libc::SOL_SOCKET, libc::SO_INCOMING_CPU)
+                .map(|cpu| cpu as usize)
+        }
+    }
+
+    /// Set value for the `SO_INCOMING_CPU` option on this socket.
+    ///
+    /// Sets the CPU affinity of the socket.
+    #[cfg(all(feature = "all", target_os = "linux"))]
+    #[cfg_attr(docsrs, doc(cfg(all(feature = "all", target_os = "linux"))))]
+    pub fn set_cpu_affinity(&self, cpu: usize) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::SOL_SOCKET,
+                libc::SO_INCOMING_CPU,
+                cpu as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `SO_REUSEPORT` option on this socket.
+    ///
+    /// For more information about this option, see [`set_reuse_port`].
+    ///
+    /// [`set_reuse_port`]: crate::Socket::set_reuse_port
+    #[cfg(all(
+        feature = "all",
+        not(any(target_os = "solaris", target_os = "illumos"))
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            unix,
+            not(any(target_os = "solaris", target_os = "illumos"))
+        )))
+    )]
+    pub fn reuse_port(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), libc::SOL_SOCKET, libc::SO_REUSEPORT)
+                .map(|reuse| reuse != 0)
+        }
+    }
+
+    /// Set value for the `SO_REUSEPORT` option on this socket.
+    ///
+    /// This indicates that further calls to `bind` may allow reuse of local
+    /// addresses. For IPv4 sockets this means that a socket may bind even when
+    /// there's a socket already listening on this port.
+    #[cfg(all(
+        feature = "all",
+        not(any(target_os = "solaris", target_os = "illumos"))
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            unix,
+            not(any(target_os = "solaris", target_os = "illumos"))
+        )))
+    )]
+    pub fn set_reuse_port(&self, reuse: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::SOL_SOCKET,
+                libc::SO_REUSEPORT,
+                reuse as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `IP_FREEBIND` option on this socket.
+    ///
+    /// For more information about this option, see [`set_freebind`].
+    ///
+    /// [`set_freebind`]: crate::Socket::set_freebind
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn freebind(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), libc::SOL_IP, libc::IP_FREEBIND)
+                .map(|freebind| freebind != 0)
+        }
+    }
+
+    /// Set value for the `IP_FREEBIND` option on this socket.
+    ///
+    /// If enabled, this boolean option allows binding to an IP address that is
+    /// nonlocal or does not (yet) exist.  This permits listening on a socket,
+    /// without requiring the underlying network interface or the specified
+    /// dynamic IP address to be up at the time that the application is trying
+    /// to bind to it.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn set_freebind(&self, freebind: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::SOL_IP,
+                libc::IP_FREEBIND,
+                freebind as c_int,
+            )
+        }
+    }
+
+    /// Get the value of the `IPV6_FREEBIND` option on this socket.
+    ///
+    /// This is an IPv6 counterpart of `IP_FREEBIND` socket option on
+    /// Android/Linux. For more information about this option, see
+    /// [`set_freebind`].
+    ///
+    /// [`set_freebind`]: crate::Socket::set_freebind
+    #[cfg(all(feature = "all", any(target_os = "android", target_os = "linux")))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(feature = "all", any(target_os = "android", target_os = "linux"))))
+    )]
+    pub fn freebind_ipv6(&self) -> io::Result<bool> {
+        unsafe {
+            getsockopt::<c_int>(self.as_raw(), libc::SOL_IPV6, libc::IPV6_FREEBIND)
+                .map(|freebind| freebind != 0)
+        }
+    }
+
+    /// Set value for the `IPV6_FREEBIND` option on this socket.
+    ///
+    /// This is an IPv6 counterpart of `IP_FREEBIND` socket option on
+    /// Android/Linux. For more information about this option, see
+    /// [`set_freebind`].
+    ///
+    /// [`set_freebind`]: crate::Socket::set_freebind
+    ///
+    /// # Examples
+    ///
+    /// On Linux:
+    ///
+    /// ```
+    /// use socket2::{Domain, Socket, Type};
+    /// use std::io::{self, Error, ErrorKind};
+    ///
+    /// fn enable_freebind(socket: &Socket) -> io::Result<()> {
+    ///     match socket.domain()? {
+    ///         Domain::IPV4 => socket.set_freebind(true)?,
+    ///         Domain::IPV6 => socket.set_freebind_ipv6(true)?,
+    ///         _ => return Err(Error::new(ErrorKind::Other, "unsupported domain")),
+    ///     };
+    ///     Ok(())
+    /// }
+    ///
+    /// # fn main() -> io::Result<()> {
+    /// #     let socket = Socket::new(Domain::IPV6, Type::STREAM, None)?;
+    /// #     enable_freebind(&socket)
+    /// # }
+    /// ```
+    #[cfg(all(feature = "all", any(target_os = "android", target_os = "linux")))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(feature = "all", any(target_os = "android", target_os = "linux"))))
+    )]
+    pub fn set_freebind_ipv6(&self, freebind: bool) -> io::Result<()> {
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::SOL_IPV6,
+                libc::IPV6_FREEBIND,
+                freebind as c_int,
+            )
+        }
+    }
+
+    /// Copies data between a `file` and this socket using the `sendfile(2)`
+    /// system call. Because this copying is done within the kernel,
+    /// `sendfile()` is more efficient than the combination of `read(2)` and
+    /// `write(2)`, which would require transferring data to and from user
+    /// space.
+    ///
+    /// Different OSs support different kinds of `file`s, see the OS
+    /// documentation for what kind of files are supported. Generally *regular*
+    /// files are supported by all OSs.
+    ///
+    /// The `offset` is the absolute offset into the `file` to use as starting
+    /// point.
+    ///
+    /// Depending on the OS this function *may* change the offset of `file`. For
+    /// the best results reset the offset of the file before using it again.
+    ///
+    /// The `length` determines how many bytes to send, where a length of `None`
+    /// means it will try to send all bytes.
+    #[cfg(all(
+        feature = "all",
+        any(
+            target_os = "android",
+            target_os = "freebsd",
+            target_os = "linux",
+            target_vendor = "apple",
+        )
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(
+                target_os = "android",
+                target_os = "freebsd",
+                target_os = "linux",
+                target_vendor = "apple",
+            )
+        )))
+    )]
+    pub fn sendfile<F>(
+        &self,
+        file: &F,
+        offset: usize,
+        length: Option<NonZeroUsize>,
+    ) -> io::Result<usize>
+    where
+        F: AsRawFd,
+    {
+        self._sendfile(file.as_raw_fd(), offset as _, length)
+    }
+
+    #[cfg(all(feature = "all", target_vendor = "apple"))]
+    fn _sendfile(
+        &self,
+        file: RawFd,
+        offset: libc::off_t,
+        length: Option<NonZeroUsize>,
+    ) -> io::Result<usize> {
+        // On macOS `length` is value-result parameter. It determines the number
+        // of bytes to write and returns the number of bytes written.
+        let mut length = match length {
+            Some(n) => n.get() as libc::off_t,
+            // A value of `0` means send all bytes.
+            None => 0,
+        };
+        syscall!(sendfile(
+            file,
+            self.as_raw(),
+            offset,
+            &mut length,
+            ptr::null_mut(),
+            0,
+        ))
+        .map(|_| length as usize)
+    }
+
+    #[cfg(all(feature = "all", any(target_os = "android", target_os = "linux")))]
+    fn _sendfile(
+        &self,
+        file: RawFd,
+        offset: libc::off_t,
+        length: Option<NonZeroUsize>,
+    ) -> io::Result<usize> {
+        let count = match length {
+            Some(n) => n.get() as libc::size_t,
+            // The maximum the Linux kernel will write in a single call.
+            None => 0x7ffff000, // 2,147,479,552 bytes.
+        };
+        let mut offset = offset;
+        syscall!(sendfile(self.as_raw(), file, &mut offset, count)).map(|n| n as usize)
+    }
+
+    #[cfg(all(feature = "all", target_os = "freebsd"))]
+    fn _sendfile(
+        &self,
+        file: RawFd,
+        offset: libc::off_t,
+        length: Option<NonZeroUsize>,
+    ) -> io::Result<usize> {
+        let nbytes = match length {
+            Some(n) => n.get() as libc::size_t,
+            // A value of `0` means send all bytes.
+            None => 0,
+        };
+        let mut sbytes: libc::off_t = 0;
+        syscall!(sendfile(
+            file,
+            self.as_raw(),
+            offset,
+            nbytes,
+            ptr::null_mut(),
+            &mut sbytes,
+            0,
+        ))
+        .map(|_| sbytes as usize)
+    }
+
+    /// Set the value of the `TCP_USER_TIMEOUT` option on this socket.
+    ///
+    /// If set, this specifies the maximum amount of time that transmitted data may remain
+    /// unacknowledged or buffered data may remain untransmitted before TCP will forcibly close the
+    /// corresponding connection.
+    ///
+    /// Setting `timeout` to `None` or a zero duration causes the system default timeouts to
+    /// be used. If `timeout` in milliseconds is larger than `c_uint::MAX`, the timeout is clamped
+    /// to `c_uint::MAX`. For example, when `c_uint` is a 32-bit value, this limits the timeout to
+    /// approximately 49.71 days.
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn set_tcp_user_timeout(&self, timeout: Option<Duration>) -> io::Result<()> {
+        let timeout = timeout
+            .map(|to| min(to.as_millis(), libc::c_uint::MAX as u128) as libc::c_uint)
+            .unwrap_or(0);
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::IPPROTO_TCP,
+                libc::TCP_USER_TIMEOUT,
+                timeout,
+            )
+        }
+    }
+
+    /// Get the value of the `TCP_USER_TIMEOUT` option on this socket.
+    ///
+    /// For more information about this option, see [`set_tcp_user_timeout`].
+    ///
+    /// [`set_tcp_user_timeout`]: Socket::set_tcp_user_timeout
+    #[cfg(all(
+        feature = "all",
+        any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+    ))]
+    #[cfg_attr(
+        docsrs,
+        doc(cfg(all(
+            feature = "all",
+            any(target_os = "android", target_os = "fuchsia", target_os = "linux")
+        )))
+    )]
+    pub fn tcp_user_timeout(&self) -> io::Result<Option<Duration>> {
+        unsafe {
+            getsockopt::<libc::c_uint>(self.as_raw(), libc::IPPROTO_TCP, libc::TCP_USER_TIMEOUT)
+                .map(|millis| {
+                    if millis == 0 {
+                        None
+                    } else {
+                        Some(Duration::from_millis(millis as u64))
+                    }
+                })
+        }
+    }
+
+    /// Attach Berkeley Packet Filter(BPF) on this socket.
+    ///
+    /// BPF allows a user-space program to attach a filter onto any socket
+    /// and allow or disallow certain types of data to come through the socket.
+    ///
+    /// For more information about this option, see [filter](https://www.kernel.org/doc/html/v5.12/networking/filter.html)
+    #[cfg(all(feature = "all", any(target_os = "linux", target_os = "android")))]
+    pub fn attach_filter(&self, filters: &[libc::sock_filter]) -> io::Result<()> {
+        let prog = libc::sock_fprog {
+            len: filters.len() as u16,
+            filter: filters.as_ptr() as *mut _,
+        };
+
+        unsafe {
+            setsockopt(
+                self.as_raw(),
+                libc::SOL_SOCKET,
+                libc::SO_ATTACH_FILTER,
+                prog,
+            )
+        }
+    }
+
+    /// Detach Berkeley Packet Filter(BPF) from this socket.
+    ///
+    /// For more information about this option, see [`attach_filter`]
+    #[cfg(all(feature = "all", any(target_os = "linux", target_os = "android")))]
+    pub fn detach_filter(&self) -> io::Result<()> {
+        unsafe { setsockopt(self.as_raw(), libc::SOL_SOCKET, libc::SO_DETACH_FILTER, 0) }
+    }
+}
+
+#[cfg_attr(docsrs, doc(cfg(unix)))]
+impl AsRawFd for crate::Socket {
+    fn as_raw_fd(&self) -> c_int {
+        self.as_raw()
+    }
+}
+
+#[cfg_attr(docsrs, doc(cfg(unix)))]
+impl IntoRawFd for crate::Socket {
+    fn into_raw_fd(self) -> c_int {
+        self.into_raw()
+    }
+}
+
+#[cfg_attr(docsrs, doc(cfg(unix)))]
+impl FromRawFd for crate::Socket {
+    unsafe fn from_raw_fd(fd: c_int) -> crate::Socket {
+        crate::Socket::from_raw(fd)
+    }
+}
+
+#[cfg(feature = "all")]
+from!(UnixStream, crate::Socket);
+#[cfg(feature = "all")]
+from!(UnixListener, crate::Socket);
+#[cfg(feature = "all")]
+from!(UnixDatagram, crate::Socket);
+#[cfg(feature = "all")]
+from!(crate::Socket, UnixStream);
+#[cfg(feature = "all")]
+from!(crate::Socket, UnixListener);
+#[cfg(feature = "all")]
+from!(crate::Socket, UnixDatagram);
+
+#[test]
+fn in_addr_convertion() {
+    let ip = Ipv4Addr::new(127, 0, 0, 1);
+    let raw = to_in_addr(&ip);
+    // NOTE: `in_addr` is packed on NetBSD and it's unsafe to borrow.
+    let a = raw.s_addr;
+    assert_eq!(a, u32::from_ne_bytes([127, 0, 0, 1]));
+    assert_eq!(from_in_addr(raw), ip);
+
+    let ip = Ipv4Addr::new(127, 34, 4, 12);
+    let raw = to_in_addr(&ip);
+    let a = raw.s_addr;
+    assert_eq!(a, u32::from_ne_bytes([127, 34, 4, 12]));
+    assert_eq!(from_in_addr(raw), ip);
+}
+
+#[test]
+fn in6_addr_convertion() {
+    let ip = Ipv6Addr::new(0x2000, 1, 2, 3, 4, 5, 6, 7);
+    let raw = to_in6_addr(&ip);
+    let want = [32, 0, 0, 1, 0, 2, 0, 3, 0, 4, 0, 5, 0, 6, 0, 7];
+    assert_eq!(raw.s6_addr, want);
+    assert_eq!(from_in6_addr(raw), ip);
+}
diff --git a/src/sys/windows.rs b/src/sys/windows.rs
new file mode 100644
index 0000000..ab59839
--- /dev/null
+++ b/src/sys/windows.rs
@@ -0,0 +1,848 @@
+// Copyright 2015 The Rust Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::cmp::min;
+use std::io::{self, IoSlice};
+use std::marker::PhantomData;
+use std::mem::{self, size_of, MaybeUninit};
+use std::net::{self, Ipv4Addr, Ipv6Addr, Shutdown};
+use std::os::windows::prelude::*;
+use std::sync::Once;
+use std::time::{Duration, Instant};
+use std::{ptr, slice};
+
+use winapi::ctypes::c_long;
+use winapi::shared::in6addr::*;
+use winapi::shared::inaddr::*;
+use winapi::shared::minwindef::DWORD;
+use winapi::shared::minwindef::ULONG;
+use winapi::shared::mstcpip::{tcp_keepalive, SIO_KEEPALIVE_VALS};
+use winapi::shared::ntdef::HANDLE;
+use winapi::shared::ws2def;
+use winapi::shared::ws2def::WSABUF;
+use winapi::um::handleapi::SetHandleInformation;
+use winapi::um::processthreadsapi::GetCurrentProcessId;
+use winapi::um::winbase::{self, INFINITE};
+use winapi::um::winsock2::{
+    self as sock, u_long, POLLERR, POLLHUP, POLLRDNORM, POLLWRNORM, SD_BOTH, SD_RECEIVE, SD_SEND,
+    WSAPOLLFD,
+};
+
+use crate::{RecvFlags, SockAddr, TcpKeepalive, Type};
+
+pub(crate) use winapi::ctypes::c_int;
+
+/// Fake MSG_TRUNC flag for the [`RecvFlags`] struct.
+///
+/// The flag is enabled when a `WSARecv[From]` call returns `WSAEMSGSIZE`. The
+/// value of the flag is defined by us.
+pub(crate) const MSG_TRUNC: c_int = 0x01;
+
+// Used in `Domain`.
+pub(crate) use winapi::shared::ws2def::{AF_INET, AF_INET6};
+// Used in `Type`.
+pub(crate) use winapi::shared::ws2def::{SOCK_DGRAM, SOCK_STREAM};
+#[cfg(feature = "all")]
+pub(crate) use winapi::shared::ws2def::{SOCK_RAW, SOCK_SEQPACKET};
+// Used in `Protocol`.
+pub(crate) const IPPROTO_ICMP: c_int = winapi::shared::ws2def::IPPROTO_ICMP as c_int;
+pub(crate) const IPPROTO_ICMPV6: c_int = winapi::shared::ws2def::IPPROTO_ICMPV6 as c_int;
+pub(crate) const IPPROTO_TCP: c_int = winapi::shared::ws2def::IPPROTO_TCP as c_int;
+pub(crate) const IPPROTO_UDP: c_int = winapi::shared::ws2def::IPPROTO_UDP as c_int;
+// Used in `SockAddr`.
+pub(crate) use winapi::shared::ws2def::{
+    ADDRESS_FAMILY as sa_family_t, SOCKADDR as sockaddr, SOCKADDR_IN as sockaddr_in,
+    SOCKADDR_STORAGE as sockaddr_storage,
+};
+pub(crate) use winapi::shared::ws2ipdef::SOCKADDR_IN6_LH as sockaddr_in6;
+pub(crate) use winapi::um::ws2tcpip::socklen_t;
+// Used in `Socket`.
+pub(crate) use winapi::shared::ws2def::{
+    IPPROTO_IP, SOL_SOCKET, SO_BROADCAST, SO_ERROR, SO_KEEPALIVE, SO_LINGER, SO_OOBINLINE,
+    SO_RCVBUF, SO_RCVTIMEO, SO_REUSEADDR, SO_SNDBUF, SO_SNDTIMEO, SO_TYPE, TCP_NODELAY,
+};
+#[cfg(feature = "all")]
+pub(crate) use winapi::shared::ws2ipdef::IP_HDRINCL;
+pub(crate) use winapi::shared::ws2ipdef::{
+    IPV6_ADD_MEMBERSHIP, IPV6_DROP_MEMBERSHIP, IPV6_MREQ as Ipv6Mreq, IPV6_MULTICAST_HOPS,
+    IPV6_MULTICAST_IF, IPV6_MULTICAST_LOOP, IPV6_UNICAST_HOPS, IPV6_V6ONLY, IP_ADD_MEMBERSHIP,
+    IP_DROP_MEMBERSHIP, IP_MREQ as IpMreq, IP_MULTICAST_IF, IP_MULTICAST_LOOP, IP_MULTICAST_TTL,
+    IP_TOS, IP_TTL,
+};
+pub(crate) use winapi::um::winsock2::{linger, MSG_OOB, MSG_PEEK};
+pub(crate) const IPPROTO_IPV6: c_int = winapi::shared::ws2def::IPPROTO_IPV6 as c_int;
+
+/// Type used in set/getsockopt to retrieve the `TCP_NODELAY` option.
+///
+/// NOTE: <https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-getsockopt>
+/// documents that options such as `TCP_NODELAY` and `SO_KEEPALIVE` expect a
+/// `BOOL` (alias for `c_int`, 4 bytes), however in practice this turns out to
+/// be false (or misleading) as a `BOOLEAN` (`c_uchar`, 1 byte) is returned by
+/// `getsockopt`.
+pub(crate) type Bool = winapi::shared::ntdef::BOOLEAN;
+
+/// Maximum size of a buffer passed to system call like `recv` and `send`.
+const MAX_BUF_LEN: usize = <c_int>::max_value() as usize;
+
+/// Helper macro to execute a system call that returns an `io::Result`.
+macro_rules! syscall {
+    ($fn: ident ( $($arg: expr),* $(,)* ), $err_test: path, $err_value: expr) => {{
+        #[allow(unused_unsafe)]
+        let res = unsafe { sock::$fn($($arg, )*) };
+        if $err_test(&res, &$err_value) {
+            Err(io::Error::last_os_error())
+        } else {
+            Ok(res)
+        }
+    }};
+}
+
+impl_debug!(
+    crate::Domain,
+    ws2def::AF_INET,
+    ws2def::AF_INET6,
+    ws2def::AF_UNIX,
+    ws2def::AF_UNSPEC, // = 0.
+);
+
+/// Windows only API.
+impl Type {
+    /// Our custom flag to set `WSA_FLAG_NO_HANDLE_INHERIT` on socket creation.
+    /// Trying to mimic `Type::cloexec` on windows.
+    const NO_INHERIT: c_int = 1 << ((size_of::<c_int>() * 8) - 1); // Last bit.
+
+    /// Set `WSA_FLAG_NO_HANDLE_INHERIT` on the socket.
+    #[cfg(feature = "all")]
+    #[cfg_attr(docsrs, doc(cfg(all(windows, feature = "all"))))]
+    pub const fn no_inherit(self) -> Type {
+        self._no_inherit()
+    }
+
+    pub(crate) const fn _no_inherit(self) -> Type {
+        Type(self.0 | Type::NO_INHERIT)
+    }
+}
+
+impl_debug!(
+    crate::Type,
+    ws2def::SOCK_STREAM,
+    ws2def::SOCK_DGRAM,
+    ws2def::SOCK_RAW,
+    ws2def::SOCK_RDM,
+    ws2def::SOCK_SEQPACKET,
+);
+
+impl_debug!(
+    crate::Protocol,
+    self::IPPROTO_ICMP,
+    self::IPPROTO_ICMPV6,
+    self::IPPROTO_TCP,
+    self::IPPROTO_UDP,
+);
+
+impl std::fmt::Debug for RecvFlags {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("RecvFlags")
+            .field("is_truncated", &self.is_truncated())
+            .finish()
+    }
+}
+
+#[repr(transparent)]
+pub struct MaybeUninitSlice<'a> {
+    vec: WSABUF,
+    _lifetime: PhantomData<&'a mut [MaybeUninit<u8>]>,
+}
+
+unsafe impl<'a> Send for MaybeUninitSlice<'a> {}
+
+unsafe impl<'a> Sync for MaybeUninitSlice<'a> {}
+
+impl<'a> MaybeUninitSlice<'a> {
+    pub fn new(buf: &'a mut [MaybeUninit<u8>]) -> MaybeUninitSlice<'a> {
+        assert!(buf.len() <= ULONG::MAX as usize);
+        MaybeUninitSlice {
+            vec: WSABUF {
+                len: buf.len() as ULONG,
+                buf: buf.as_mut_ptr().cast(),
+            },
+            _lifetime: PhantomData,
+        }
+    }
+
+    pub fn as_slice(&self) -> &[MaybeUninit<u8>] {
+        unsafe { slice::from_raw_parts(self.vec.buf.cast(), self.vec.len as usize) }
+    }
+
+    pub fn as_mut_slice(&mut self) -> &mut [MaybeUninit<u8>] {
+        unsafe { slice::from_raw_parts_mut(self.vec.buf.cast(), self.vec.len as usize) }
+    }
+}
+
+fn init() {
+    static INIT: Once = Once::new();
+
+    INIT.call_once(|| {
+        // Initialize winsock through the standard library by just creating a
+        // dummy socket. Whether this is successful or not we drop the result as
+        // libstd will be sure to have initialized winsock.
+        let _ = net::UdpSocket::bind("127.0.0.1:34254");
+    });
+}
+
+pub(crate) type Socket = sock::SOCKET;
+
+pub(crate) unsafe fn socket_from_raw(socket: Socket) -> crate::socket::Inner {
+    crate::socket::Inner::from_raw_socket(socket as RawSocket)
+}
+
+pub(crate) fn socket_as_raw(socket: &crate::socket::Inner) -> Socket {
+    socket.as_raw_socket() as Socket
+}
+
+pub(crate) fn socket_into_raw(socket: crate::socket::Inner) -> Socket {
+    socket.into_raw_socket() as Socket
+}
+
+pub(crate) fn socket(family: c_int, mut ty: c_int, protocol: c_int) -> io::Result<Socket> {
+    init();
+
+    // Check if we set our custom flag.
+    let flags = if ty & Type::NO_INHERIT != 0 {
+        ty = ty & !Type::NO_INHERIT;
+        sock::WSA_FLAG_NO_HANDLE_INHERIT
+    } else {
+        0
+    };
+
+    syscall!(
+        WSASocketW(
+            family,
+            ty,
+            protocol,
+            ptr::null_mut(),
+            0,
+            sock::WSA_FLAG_OVERLAPPED | flags,
+        ),
+        PartialEq::eq,
+        sock::INVALID_SOCKET
+    )
+}
+
+pub(crate) fn bind(socket: Socket, addr: &SockAddr) -> io::Result<()> {
+    syscall!(bind(socket, addr.as_ptr(), addr.len()), PartialEq::ne, 0).map(|_| ())
+}
+
+pub(crate) fn connect(socket: Socket, addr: &SockAddr) -> io::Result<()> {
+    syscall!(connect(socket, addr.as_ptr(), addr.len()), PartialEq::ne, 0).map(|_| ())
+}
+
+pub(crate) fn poll_connect(socket: &crate::Socket, timeout: Duration) -> io::Result<()> {
+    let start = Instant::now();
+
+    let mut fd_array = WSAPOLLFD {
+        fd: socket.as_raw(),
+        events: POLLRDNORM | POLLWRNORM,
+        revents: 0,
+    };
+
+    loop {
+        let elapsed = start.elapsed();
+        if elapsed >= timeout {
+            return Err(io::ErrorKind::TimedOut.into());
+        }
+
+        let timeout = (timeout - elapsed).as_millis();
+        let timeout = clamp(timeout, 1, c_int::max_value() as u128) as c_int;
+
+        match syscall!(
+            WSAPoll(&mut fd_array, 1, timeout),
+            PartialEq::eq,
+            sock::SOCKET_ERROR
+        ) {
+            Ok(0) => return Err(io::ErrorKind::TimedOut.into()),
+            Ok(_) => {
+                // Error or hang up indicates an error (or failure to connect).
+                if (fd_array.revents & POLLERR) != 0 || (fd_array.revents & POLLHUP) != 0 {
+                    match socket.take_error() {
+                        Ok(Some(err)) => return Err(err),
+                        Ok(None) => {
+                            return Err(io::Error::new(
+                                io::ErrorKind::Other,
+                                "no error set after POLLHUP",
+                            ))
+                        }
+                        Err(err) => return Err(err),
+                    }
+                }
+                return Ok(());
+            }
+            // Got interrupted, try again.
+            Err(ref err) if err.kind() == io::ErrorKind::Interrupted => continue,
+            Err(err) => return Err(err),
+        }
+    }
+}
+
+// TODO: use clamp from std lib, stable since 1.50.
+fn clamp<T>(value: T, min: T, max: T) -> T
+where
+    T: Ord,
+{
+    if value <= min {
+        min
+    } else if value >= max {
+        max
+    } else {
+        value
+    }
+}
+
+pub(crate) fn listen(socket: Socket, backlog: c_int) -> io::Result<()> {
+    syscall!(listen(socket, backlog), PartialEq::ne, 0).map(|_| ())
+}
+
+pub(crate) fn accept(socket: Socket) -> io::Result<(Socket, SockAddr)> {
+    // Safety: `accept` initialises the `SockAddr` for us.
+    unsafe {
+        SockAddr::init(|storage, len| {
+            syscall!(
+                accept(socket, storage.cast(), len),
+                PartialEq::eq,
+                sock::INVALID_SOCKET
+            )
+        })
+    }
+}
+
+pub(crate) fn getsockname(socket: Socket) -> io::Result<SockAddr> {
+    // Safety: `getsockname` initialises the `SockAddr` for us.
+    unsafe {
+        SockAddr::init(|storage, len| {
+            syscall!(
+                getsockname(socket, storage.cast(), len),
+                PartialEq::eq,
+                sock::SOCKET_ERROR
+            )
+        })
+    }
+    .map(|(_, addr)| addr)
+}
+
+pub(crate) fn getpeername(socket: Socket) -> io::Result<SockAddr> {
+    // Safety: `getpeername` initialises the `SockAddr` for us.
+    unsafe {
+        SockAddr::init(|storage, len| {
+            syscall!(
+                getpeername(socket, storage.cast(), len),
+                PartialEq::eq,
+                sock::SOCKET_ERROR
+            )
+        })
+    }
+    .map(|(_, addr)| addr)
+}
+
+pub(crate) fn try_clone(socket: Socket) -> io::Result<Socket> {
+    let mut info: MaybeUninit<sock::WSAPROTOCOL_INFOW> = MaybeUninit::uninit();
+    syscall!(
+        WSADuplicateSocketW(socket, GetCurrentProcessId(), info.as_mut_ptr()),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    )?;
+    // Safety: `WSADuplicateSocketW` intialised `info` for us.
+    let mut info = unsafe { info.assume_init() };
+
+    syscall!(
+        WSASocketW(
+            info.iAddressFamily,
+            info.iSocketType,
+            info.iProtocol,
+            &mut info,
+            0,
+            sock::WSA_FLAG_OVERLAPPED | sock::WSA_FLAG_NO_HANDLE_INHERIT,
+        ),
+        PartialEq::eq,
+        sock::INVALID_SOCKET
+    )
+}
+
+pub(crate) fn set_nonblocking(socket: Socket, nonblocking: bool) -> io::Result<()> {
+    let mut nonblocking = nonblocking as u_long;
+    ioctlsocket(socket, sock::FIONBIO, &mut nonblocking)
+}
+
+pub(crate) fn shutdown(socket: Socket, how: Shutdown) -> io::Result<()> {
+    let how = match how {
+        Shutdown::Write => SD_SEND,
+        Shutdown::Read => SD_RECEIVE,
+        Shutdown::Both => SD_BOTH,
+    };
+    syscall!(shutdown(socket, how), PartialEq::eq, sock::SOCKET_ERROR).map(|_| ())
+}
+
+pub(crate) fn recv(socket: Socket, buf: &mut [MaybeUninit<u8>], flags: c_int) -> io::Result<usize> {
+    let res = syscall!(
+        recv(
+            socket,
+            buf.as_mut_ptr().cast(),
+            min(buf.len(), MAX_BUF_LEN) as c_int,
+            flags,
+        ),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    );
+    match res {
+        Ok(n) => Ok(n as usize),
+        Err(ref err) if err.raw_os_error() == Some(sock::WSAESHUTDOWN as i32) => Ok(0),
+        Err(err) => Err(err),
+    }
+}
+
+pub(crate) fn recv_vectored(
+    socket: Socket,
+    bufs: &mut [crate::MaybeUninitSlice<'_>],
+    flags: c_int,
+) -> io::Result<(usize, RecvFlags)> {
+    let mut nread = 0;
+    let mut flags = flags as DWORD;
+    let res = syscall!(
+        WSARecv(
+            socket,
+            bufs.as_mut_ptr().cast(),
+            min(bufs.len(), DWORD::max_value() as usize) as DWORD,
+            &mut nread,
+            &mut flags,
+            ptr::null_mut(),
+            None,
+        ),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    );
+    match res {
+        Ok(_) => Ok((nread as usize, RecvFlags(0))),
+        Err(ref err) if err.raw_os_error() == Some(sock::WSAESHUTDOWN as i32) => {
+            Ok((0, RecvFlags(0)))
+        }
+        Err(ref err) if err.raw_os_error() == Some(sock::WSAEMSGSIZE as i32) => {
+            Ok((nread as usize, RecvFlags(MSG_TRUNC)))
+        }
+        Err(err) => Err(err),
+    }
+}
+
+pub(crate) fn recv_from(
+    socket: Socket,
+    buf: &mut [MaybeUninit<u8>],
+    flags: c_int,
+) -> io::Result<(usize, SockAddr)> {
+    // Safety: `recvfrom` initialises the `SockAddr` for us.
+    unsafe {
+        SockAddr::init(|storage, addrlen| {
+            let res = syscall!(
+                recvfrom(
+                    socket,
+                    buf.as_mut_ptr().cast(),
+                    min(buf.len(), MAX_BUF_LEN) as c_int,
+                    flags,
+                    storage.cast(),
+                    addrlen,
+                ),
+                PartialEq::eq,
+                sock::SOCKET_ERROR
+            );
+            match res {
+                Ok(n) => Ok(n as usize),
+                Err(ref err) if err.raw_os_error() == Some(sock::WSAESHUTDOWN as i32) => Ok(0),
+                Err(err) => Err(err),
+            }
+        })
+    }
+}
+
+pub(crate) fn recv_from_vectored(
+    socket: Socket,
+    bufs: &mut [crate::MaybeUninitSlice<'_>],
+    flags: c_int,
+) -> io::Result<(usize, RecvFlags, SockAddr)> {
+    // Safety: `recvfrom` initialises the `SockAddr` for us.
+    unsafe {
+        SockAddr::init(|storage, addrlen| {
+            let mut nread = 0;
+            let mut flags = flags as DWORD;
+            let res = syscall!(
+                WSARecvFrom(
+                    socket,
+                    bufs.as_mut_ptr().cast(),
+                    min(bufs.len(), DWORD::max_value() as usize) as DWORD,
+                    &mut nread,
+                    &mut flags,
+                    storage.cast(),
+                    addrlen,
+                    ptr::null_mut(),
+                    None,
+                ),
+                PartialEq::eq,
+                sock::SOCKET_ERROR
+            );
+            match res {
+                Ok(_) => Ok((nread as usize, RecvFlags(0))),
+                Err(ref err) if err.raw_os_error() == Some(sock::WSAESHUTDOWN as i32) => {
+                    Ok((nread as usize, RecvFlags(0)))
+                }
+                Err(ref err) if err.raw_os_error() == Some(sock::WSAEMSGSIZE as i32) => {
+                    Ok((nread as usize, RecvFlags(MSG_TRUNC)))
+                }
+                Err(err) => Err(err),
+            }
+        })
+    }
+    .map(|((n, recv_flags), addr)| (n, recv_flags, addr))
+}
+
+pub(crate) fn send(socket: Socket, buf: &[u8], flags: c_int) -> io::Result<usize> {
+    syscall!(
+        send(
+            socket,
+            buf.as_ptr().cast(),
+            min(buf.len(), MAX_BUF_LEN) as c_int,
+            flags,
+        ),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    )
+    .map(|n| n as usize)
+}
+
+pub(crate) fn send_vectored(
+    socket: Socket,
+    bufs: &[IoSlice<'_>],
+    flags: c_int,
+) -> io::Result<usize> {
+    let mut nsent = 0;
+    syscall!(
+        WSASend(
+            socket,
+            // FIXME: From the `WSASend` docs [1]:
+            // > For a Winsock application, once the WSASend function is called,
+            // > the system owns these buffers and the application may not
+            // > access them.
+            //
+            // So what we're doing is actually UB as `bufs` needs to be `&mut
+            // [IoSlice<'_>]`.
+            //
+            // Tracking issue: https://github.com/rust-lang/socket2-rs/issues/129.
+            //
+            // NOTE: `send_to_vectored` has the same problem.
+            //
+            // [1] https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsasend
+            bufs.as_ptr() as *mut _,
+            min(bufs.len(), DWORD::max_value() as usize) as DWORD,
+            &mut nsent,
+            flags as DWORD,
+            std::ptr::null_mut(),
+            None,
+        ),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    )
+    .map(|_| nsent as usize)
+}
+
+pub(crate) fn send_to(
+    socket: Socket,
+    buf: &[u8],
+    addr: &SockAddr,
+    flags: c_int,
+) -> io::Result<usize> {
+    syscall!(
+        sendto(
+            socket,
+            buf.as_ptr().cast(),
+            min(buf.len(), MAX_BUF_LEN) as c_int,
+            flags,
+            addr.as_ptr(),
+            addr.len(),
+        ),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    )
+    .map(|n| n as usize)
+}
+
+pub(crate) fn send_to_vectored(
+    socket: Socket,
+    bufs: &[IoSlice<'_>],
+    addr: &SockAddr,
+    flags: c_int,
+) -> io::Result<usize> {
+    let mut nsent = 0;
+    syscall!(
+        WSASendTo(
+            socket,
+            // FIXME: Same problem as in `send_vectored`.
+            bufs.as_ptr() as *mut _,
+            bufs.len().min(DWORD::MAX as usize) as DWORD,
+            &mut nsent,
+            flags as DWORD,
+            addr.as_ptr(),
+            addr.len(),
+            ptr::null_mut(),
+            None,
+        ),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    )
+    .map(|_| nsent as usize)
+}
+
+/// Wrapper around `getsockopt` to deal with platform specific timeouts.
+pub(crate) fn timeout_opt(fd: Socket, lvl: c_int, name: c_int) -> io::Result<Option<Duration>> {
+    unsafe { getsockopt(fd, lvl, name).map(from_ms) }
+}
+
+fn from_ms(duration: DWORD) -> Option<Duration> {
+    if duration == 0 {
+        None
+    } else {
+        let secs = duration / 1000;
+        let nsec = (duration % 1000) * 1000000;
+        Some(Duration::new(secs as u64, nsec as u32))
+    }
+}
+
+/// Wrapper around `setsockopt` to deal with platform specific timeouts.
+pub(crate) fn set_timeout_opt(
+    fd: Socket,
+    level: c_int,
+    optname: c_int,
+    duration: Option<Duration>,
+) -> io::Result<()> {
+    let duration = into_ms(duration);
+    unsafe { setsockopt(fd, level, optname, duration) }
+}
+
+fn into_ms(duration: Option<Duration>) -> DWORD {
+    // Note that a duration is a (u64, u32) (seconds, nanoseconds) pair, and the
+    // timeouts in windows APIs are typically u32 milliseconds. To translate, we
+    // have two pieces to take care of:
+    //
+    // * Nanosecond precision is rounded up
+    // * Greater than u32::MAX milliseconds (50 days) is rounded up to
+    //   INFINITE (never time out).
+    duration
+        .map(|duration| min(duration.as_millis(), INFINITE as u128) as DWORD)
+        .unwrap_or(0)
+}
+
+pub(crate) fn set_tcp_keepalive(socket: Socket, keepalive: &TcpKeepalive) -> io::Result<()> {
+    let mut keepalive = tcp_keepalive {
+        onoff: 1,
+        keepalivetime: into_ms(keepalive.time),
+        keepaliveinterval: into_ms(keepalive.interval),
+    };
+    let mut out = 0;
+    syscall!(
+        WSAIoctl(
+            socket,
+            SIO_KEEPALIVE_VALS,
+            &mut keepalive as *mut _ as *mut _,
+            size_of::<tcp_keepalive>() as _,
+            ptr::null_mut(),
+            0,
+            &mut out,
+            ptr::null_mut(),
+            None,
+        ),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    )
+    .map(|_| ())
+}
+
+/// Caller must ensure `T` is the correct type for `level` and `optname`.
+pub(crate) unsafe fn getsockopt<T>(socket: Socket, level: c_int, optname: c_int) -> io::Result<T> {
+    let mut optval: MaybeUninit<T> = MaybeUninit::uninit();
+    let mut optlen = mem::size_of::<T>() as c_int;
+    syscall!(
+        getsockopt(
+            socket,
+            level,
+            optname,
+            optval.as_mut_ptr().cast(),
+            &mut optlen,
+        ),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    )
+    .map(|_| {
+        debug_assert_eq!(optlen as usize, mem::size_of::<T>());
+        // Safety: `getsockopt` initialised `optval` for us.
+        optval.assume_init()
+    })
+}
+
+/// Caller must ensure `T` is the correct type for `level` and `optname`.
+pub(crate) unsafe fn setsockopt<T>(
+    socket: Socket,
+    level: c_int,
+    optname: c_int,
+    optval: T,
+) -> io::Result<()> {
+    syscall!(
+        setsockopt(
+            socket,
+            level,
+            optname,
+            (&optval as *const T).cast(),
+            mem::size_of::<T>() as c_int,
+        ),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    )
+    .map(|_| ())
+}
+
+fn ioctlsocket(socket: Socket, cmd: c_long, payload: &mut u_long) -> io::Result<()> {
+    syscall!(
+        ioctlsocket(socket, cmd, payload),
+        PartialEq::eq,
+        sock::SOCKET_ERROR
+    )
+    .map(|_| ())
+}
+
+pub(crate) fn to_in_addr(addr: &Ipv4Addr) -> IN_ADDR {
+    let mut s_un: in_addr_S_un = unsafe { mem::zeroed() };
+    // `S_un` is stored as BE on all machines, and the array is in BE order. So
+    // the native endian conversion method is used so that it's never swapped.
+    unsafe { *(s_un.S_addr_mut()) = u32::from_ne_bytes(addr.octets()) };
+    IN_ADDR { S_un: s_un }
+}
+
+pub(crate) fn from_in_addr(in_addr: IN_ADDR) -> Ipv4Addr {
+    Ipv4Addr::from(unsafe { *in_addr.S_un.S_addr() }.to_ne_bytes())
+}
+
+pub(crate) fn to_in6_addr(addr: &Ipv6Addr) -> in6_addr {
+    let mut ret_addr: in6_addr_u = unsafe { mem::zeroed() };
+    unsafe { *(ret_addr.Byte_mut()) = addr.octets() };
+    let mut ret: in6_addr = unsafe { mem::zeroed() };
+    ret.u = ret_addr;
+    ret
+}
+
+pub(crate) fn from_in6_addr(addr: in6_addr) -> Ipv6Addr {
+    Ipv6Addr::from(*unsafe { addr.u.Byte() })
+}
+
+pub(crate) fn to_mreqn(
+    multiaddr: &Ipv4Addr,
+    interface: &crate::socket::InterfaceIndexOrAddress,
+) -> IpMreq {
+    IpMreq {
+        imr_multiaddr: to_in_addr(multiaddr),
+        // Per https://docs.microsoft.com/en-us/windows/win32/api/ws2ipdef/ns-ws2ipdef-ip_mreq#members:
+        //
+        // imr_interface
+        //
+        // The local IPv4 address of the interface or the interface index on
+        // which the multicast group should be joined or dropped. This value is
+        // in network byte order. If this member specifies an IPv4 address of
+        // 0.0.0.0, the default IPv4 multicast interface is used.
+        //
+        // To use an interface index of 1 would be the same as an IP address of
+        // 0.0.0.1.
+        imr_interface: match interface {
+            crate::socket::InterfaceIndexOrAddress::Index(interface) => {
+                to_in_addr(&(*interface).into())
+            }
+            crate::socket::InterfaceIndexOrAddress::Address(interface) => to_in_addr(interface),
+        },
+    }
+}
+
+/// Windows only API.
+impl crate::Socket {
+    /// Sets `HANDLE_FLAG_INHERIT` using `SetHandleInformation`.
+    #[cfg(feature = "all")]
+    #[cfg_attr(docsrs, doc(cfg(all(windows, feature = "all"))))]
+    pub fn set_no_inherit(&self, no_inherit: bool) -> io::Result<()> {
+        self._set_no_inherit(no_inherit)
+    }
+
+    pub(crate) fn _set_no_inherit(&self, no_inherit: bool) -> io::Result<()> {
+        // NOTE: can't use `syscall!` because it expects the function in the
+        // `sock::` path.
+        let res = unsafe {
+            SetHandleInformation(
+                self.as_raw() as HANDLE,
+                winbase::HANDLE_FLAG_INHERIT,
+                !no_inherit as _,
+            )
+        };
+        if res == 0 {
+            // Zero means error.
+            Err(io::Error::last_os_error())
+        } else {
+            Ok(())
+        }
+    }
+}
+
+impl AsRawSocket for crate::Socket {
+    fn as_raw_socket(&self) -> RawSocket {
+        self.as_raw() as RawSocket
+    }
+}
+
+impl IntoRawSocket for crate::Socket {
+    fn into_raw_socket(self) -> RawSocket {
+        self.into_raw() as RawSocket
+    }
+}
+
+impl FromRawSocket for crate::Socket {
+    unsafe fn from_raw_socket(socket: RawSocket) -> crate::Socket {
+        crate::Socket::from_raw(socket as Socket)
+    }
+}
+
+#[test]
+fn in_addr_convertion() {
+    let ip = Ipv4Addr::new(127, 0, 0, 1);
+    let raw = to_in_addr(&ip);
+    assert_eq!(unsafe { *raw.S_un.S_addr() }, 127 << 0 | 1 << 24);
+    assert_eq!(from_in_addr(raw), ip);
+
+    let ip = Ipv4Addr::new(127, 34, 4, 12);
+    let raw = to_in_addr(&ip);
+    assert_eq!(
+        unsafe { *raw.S_un.S_addr() },
+        127 << 0 | 34 << 8 | 4 << 16 | 12 << 24
+    );
+    assert_eq!(from_in_addr(raw), ip);
+}
+
+#[test]
+fn in6_addr_convertion() {
+    let ip = Ipv6Addr::new(0x2000, 1, 2, 3, 4, 5, 6, 7);
+    let raw = to_in6_addr(&ip);
+    let want = [
+        0x2000u16.to_be(),
+        1u16.to_be(),
+        2u16.to_be(),
+        3u16.to_be(),
+        4u16.to_be(),
+        5u16.to_be(),
+        6u16.to_be(),
+        7u16.to_be(),
+    ];
+    assert_eq!(unsafe { *raw.u.Word() }, want);
+    assert_eq!(from_in6_addr(raw), ip);
+}