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/*
* Copyright (C) 2017 The Android Open Source Project
*
* 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
* limitations under the License.
*/
#ifndef NETLINK_LISTENER_H
#define NETLINK_LISTENER_H
#include <functional>
#include <map>
#include <mutex>
#include <thread>
#include <android-base/thread_annotations.h>
#include <netdutils/Netlink.h>
#include <netdutils/Slice.h>
#include <netdutils/Status.h>
#include <netdutils/UniqueFd.h>
namespace android {
namespace netdutils {
class NetlinkListenerInterface {
public:
using DispatchFn = std::function<void(const nlmsghdr& nlmsg, const netdutils::Slice msg)>;
using SkErrorHandler = std::function<void(const int fd, const int err)>;
virtual ~NetlinkListenerInterface() = default;
// Send message to the kernel using the underlying netlink socket
virtual netdutils::Status send(const netdutils::Slice msg) = 0;
// Deliver future messages with nlmsghdr.nlmsg_type == type to fn.
//
// Threadsafe.
// All dispatch functions invoked on a single service thread.
// subscribe() and join() must not be called from the stack of fn().
virtual netdutils::Status subscribe(uint16_t type, const DispatchFn& fn) = 0;
// Halt delivery of future messages with nlmsghdr.nlmsg_type == type.
// Threadsafe.
virtual netdutils::Status unsubscribe(uint16_t type) = 0;
virtual void registerSkErrorHandler(const SkErrorHandler& handler) = 0;
};
// NetlinkListener manages a netlink socket and associated blocking
// service thread.
//
// This class is written in a generic way to allow multiple different
// netlink subsystems to share this common infrastructure. If multiple
// subsystems share the same message delivery requirements (drops ok,
// no drops) they may share a single listener by calling subscribe()
// with multiple types.
//
// This class is suitable for moderate performance message
// processing. In particular it avoids extra copies of received
// message data and allows client code to control which message
// attributes are processed.
//
// Note that NetlinkListener is capable of processing multiple batched
// netlink messages in a single system call. This is useful to
// netfilter extensions that allow batching of events like NFLOG.
class NetlinkListener : public NetlinkListenerInterface {
public:
NetlinkListener(netdutils::UniqueFd event, netdutils::UniqueFd sock, const std::string& name);
~NetlinkListener() override;
netdutils::Status send(const netdutils::Slice msg) override;
netdutils::Status subscribe(uint16_t type, const DispatchFn& fn) override EXCLUDES(mMutex);
netdutils::Status unsubscribe(uint16_t type) override EXCLUDES(mMutex);
void registerSkErrorHandler(const SkErrorHandler& handler) override;
private:
netdutils::Status run();
const netdutils::UniqueFd mEvent;
const netdutils::UniqueFd mSock;
const std::string mThreadName;
std::mutex mMutex;
std::map<uint16_t, DispatchFn> mDispatchMap GUARDED_BY(mMutex);
std::thread mWorker;
SkErrorHandler mErrorHandler;
};
} // namespace netdutils
} // namespace android
#endif /* NETLINK_LISTENER_H */
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