1 /* 2 * Copyright (C) 2022 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.server.connectivity.mdns; 18 19 import static com.android.server.connectivity.mdns.util.MdnsUtils.ensureRunningOnHandlerThread; 20 21 import android.annotation.NonNull; 22 import android.os.Handler; 23 import android.os.ParcelFileDescriptor; 24 import android.system.Os; 25 import android.util.ArraySet; 26 27 import com.android.net.module.util.FdEventsReader; 28 29 import java.io.FileDescriptor; 30 import java.net.InetSocketAddress; 31 import java.util.Set; 32 33 /** Simple reader for mDNS packets. */ 34 public class MulticastPacketReader extends FdEventsReader<MulticastPacketReader.RecvBuffer> { 35 @NonNull 36 private final String mLogTag; 37 @NonNull 38 private final ParcelFileDescriptor mSocket; 39 @NonNull 40 private final Handler mHandler; 41 @NonNull 42 private final Set<PacketHandler> mPacketHandlers = new ArraySet<>(); 43 44 interface PacketHandler { handlePacket(byte[] recvbuf, int length, InetSocketAddress src)45 void handlePacket(byte[] recvbuf, int length, InetSocketAddress src); 46 } 47 48 public static final class RecvBuffer { 49 final byte[] data; 50 final InetSocketAddress src; 51 RecvBuffer(byte[] data, InetSocketAddress src)52 private RecvBuffer(byte[] data, InetSocketAddress src) { 53 this.data = data; 54 this.src = src; 55 } 56 } 57 58 /** 59 * Create a new {@link MulticastPacketReader}. 60 * @param socket Socket to read from. This will *not* be closed when the reader terminates. 61 * @param buffer Buffer to read packets into. Will only be used from the handler thread. 62 * @param port the port number for the socket 63 */ MulticastPacketReader(@onNull String interfaceTag, @NonNull ParcelFileDescriptor socket, @NonNull Handler handler, @NonNull byte[] buffer)64 protected MulticastPacketReader(@NonNull String interfaceTag, 65 @NonNull ParcelFileDescriptor socket, @NonNull Handler handler, 66 @NonNull byte[] buffer) { 67 // Set the port to zero as placeholder as the recvfrom() call will fill the actual port 68 // value later. 69 super(handler, new RecvBuffer(buffer, new InetSocketAddress(0 /* port */))); 70 mLogTag = MulticastPacketReader.class.getSimpleName() + "/" + interfaceTag; 71 mSocket = socket; 72 mHandler = handler; 73 } 74 75 @Override recvBufSize(@onNull RecvBuffer buffer)76 protected int recvBufSize(@NonNull RecvBuffer buffer) { 77 return buffer.data.length; 78 } 79 80 @Override createFd()81 protected FileDescriptor createFd() { 82 // Keep a reference to the PFD as it would close the fd in its finalizer otherwise 83 return mSocket.getFileDescriptor(); 84 } 85 86 @Override onStop()87 protected void onStop() { 88 // Do nothing (do not close the FD) 89 } 90 91 @Override readPacket(@onNull FileDescriptor fd, @NonNull RecvBuffer buffer)92 protected int readPacket(@NonNull FileDescriptor fd, @NonNull RecvBuffer buffer) 93 throws Exception { 94 return Os.recvfrom( 95 fd, buffer.data, 0, buffer.data.length, 0 /* flags */, buffer.src); 96 } 97 98 @Override handlePacket(@onNull RecvBuffer recvbuf, int length)99 protected void handlePacket(@NonNull RecvBuffer recvbuf, int length) { 100 for (PacketHandler handler : mPacketHandlers) { 101 handler.handlePacket(recvbuf.data, length, recvbuf.src); 102 } 103 } 104 105 /** 106 * Add a packet handler to deal with received packets. If the handler is already set, 107 * this is a no-op. 108 */ addPacketHandler(@onNull PacketHandler handler)109 public void addPacketHandler(@NonNull PacketHandler handler) { 110 ensureRunningOnHandlerThread(mHandler); 111 mPacketHandlers.add(handler); 112 } 113 114 /** 115 * Remove a packet handler added via {@link #addPacketHandler}. If the handler was not set, 116 * this is a no-op. 117 */ removePacketHandler(@onNull PacketHandler handler)118 public void removePacketHandler(@NonNull PacketHandler handler) { 119 ensureRunningOnHandlerThread(mHandler); 120 mPacketHandlers.remove(handler); 121 } 122 } 123 124