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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.
*/
package com.android.net.module.util.netlink;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Objects;
/**
* struct nfgenmsg
*
* see <linux_src>/include/uapi/linux/netfilter/nfnetlink.h
*
* @hide
*/
public class StructNfGenMsg {
public static final int STRUCT_SIZE = 2 + Short.BYTES;
public static final int NFNETLINK_V0 = 0;
public final byte nfgen_family;
public final byte version;
public final short res_id; // N.B.: this is big endian in the kernel
/**
* Parse a netfilter netlink header from a {@link ByteBuffer}.
*
* @param byteBuffer The buffer from which to parse the netfilter netlink header.
* @return the parsed netfilter netlink header, or {@code null} if the netfilter netlink header
* could not be parsed successfully (for example, if it was truncated).
*/
@Nullable
public static StructNfGenMsg parse(@NonNull ByteBuffer byteBuffer) {
Objects.requireNonNull(byteBuffer);
if (!hasAvailableSpace(byteBuffer)) return null;
final byte nfgen_family = byteBuffer.get();
final byte version = byteBuffer.get();
final ByteOrder originalOrder = byteBuffer.order();
byteBuffer.order(ByteOrder.BIG_ENDIAN);
final short res_id = byteBuffer.getShort();
byteBuffer.order(originalOrder);
return new StructNfGenMsg(nfgen_family, version, res_id);
}
public StructNfGenMsg(byte family, byte ver, short id) {
nfgen_family = family;
version = ver;
res_id = id;
}
public StructNfGenMsg(byte family) {
nfgen_family = family;
version = (byte) NFNETLINK_V0;
res_id = (short) 0;
}
/**
* Write a netfilter netlink header to a {@link ByteBuffer}.
*/
public void pack(ByteBuffer byteBuffer) {
byteBuffer.put(nfgen_family);
byteBuffer.put(version);
final ByteOrder originalOrder = byteBuffer.order();
byteBuffer.order(ByteOrder.BIG_ENDIAN);
byteBuffer.putShort(res_id);
byteBuffer.order(originalOrder);
}
private static boolean hasAvailableSpace(@NonNull ByteBuffer byteBuffer) {
return byteBuffer.remaining() >= STRUCT_SIZE;
}
@Override
public String toString() {
final String familyStr = NetlinkConstants.stringForAddressFamily(nfgen_family);
return "NfGenMsg{ "
+ "nfgen_family{" + familyStr + "}, "
+ "version{" + Byte.toUnsignedInt(version) + "}, "
+ "res_id{" + Short.toUnsignedInt(res_id) + "} "
+ "}";
}
}
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