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      1 /*
      2  * Copyright (C) 2016 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 android.net.ip;
     18 
     19 import static android.system.OsConstants.*;
     20 
     21 import android.net.NetworkUtils;
     22 import android.net.util.BlockingSocketReader;
     23 import android.net.util.ConnectivityPacketSummary;
     24 import android.os.Handler;
     25 import android.system.ErrnoException;
     26 import android.system.Os;
     27 import android.system.PacketSocketAddress;
     28 import android.util.Log;
     29 import android.util.LocalLog;
     30 
     31 import libcore.io.IoBridge;
     32 import libcore.util.HexEncoding;
     33 
     34 import java.io.FileDescriptor;
     35 import java.io.InterruptedIOException;
     36 import java.io.IOException;
     37 import java.net.NetworkInterface;
     38 import java.net.SocketException;
     39 
     40 
     41 /**
     42  * Critical connectivity packet tracking daemon.
     43  *
     44  * Tracks ARP, DHCPv4, and IPv6 RS/RA/NS/NA packets.
     45  *
     46  * This class's constructor, start() and stop() methods must only be called
     47  * from the same thread on which the passed in |log| is accessed.
     48  *
     49  * Log lines include a hexdump of the packet, which can be decoded via:
     50  *
     51  *     echo -n H3XSTR1NG | sed -e 's/\([0-9A-F][0-9A-F]\)/\1 /g' -e 's/^/000000 /'
     52  *                       | text2pcap - -
     53  *                       | tcpdump -n -vv -e -r -
     54  *
     55  * @hide
     56  */
     57 public class ConnectivityPacketTracker {
     58     private static final String TAG = ConnectivityPacketTracker.class.getSimpleName();
     59     private static final boolean DBG = false;
     60     private static final String MARK_START = "--- START ---";
     61     private static final String MARK_STOP = "--- STOP ---";
     62 
     63     private final String mTag;
     64     private final Handler mHandler;
     65     private final LocalLog mLog;
     66     private final BlockingSocketReader mPacketListener;
     67 
     68     public ConnectivityPacketTracker(NetworkInterface netif, LocalLog log) {
     69         final String ifname;
     70         final int ifindex;
     71         final byte[] hwaddr;
     72         final int mtu;
     73 
     74         try {
     75             ifname = netif.getName();
     76             ifindex = netif.getIndex();
     77             hwaddr = netif.getHardwareAddress();
     78             mtu = netif.getMTU();
     79         } catch (NullPointerException|SocketException e) {
     80             throw new IllegalArgumentException("bad network interface", e);
     81         }
     82 
     83         mTag = TAG + "." + ifname;
     84         mHandler = new Handler();
     85         mLog = log;
     86         mPacketListener = new PacketListener(ifindex, hwaddr, mtu);
     87     }
     88 
     89     public void start() {
     90         mLog.log(MARK_START);
     91         mPacketListener.start();
     92     }
     93 
     94     public void stop() {
     95         mPacketListener.stop();
     96         mLog.log(MARK_STOP);
     97     }
     98 
     99     private final class PacketListener extends BlockingSocketReader {
    100         private final int mIfIndex;
    101         private final byte mHwAddr[];
    102 
    103         PacketListener(int ifindex, byte[] hwaddr, int mtu) {
    104             super(mtu);
    105             mIfIndex = ifindex;
    106             mHwAddr = hwaddr;
    107         }
    108 
    109         @Override
    110         protected FileDescriptor createSocket() {
    111             FileDescriptor s = null;
    112             try {
    113                 // TODO: Evaluate switching to SOCK_DGRAM and changing the
    114                 // BlockingSocketReader's read() to recvfrom(), so that this
    115                 // might work on non-ethernet-like links (via SLL).
    116                 s = Os.socket(AF_PACKET, SOCK_RAW, 0);
    117                 NetworkUtils.attachControlPacketFilter(s, ARPHRD_ETHER);
    118                 Os.bind(s, new PacketSocketAddress((short) ETH_P_ALL, mIfIndex));
    119             } catch (ErrnoException | IOException e) {
    120                 logError("Failed to create packet tracking socket: ", e);
    121                 closeSocket(s);
    122                 return null;
    123             }
    124             return s;
    125         }
    126 
    127         @Override
    128         protected void handlePacket(byte[] recvbuf, int length) {
    129             final String summary = ConnectivityPacketSummary.summarize(
    130                     mHwAddr, recvbuf, length);
    131             if (summary == null) return;
    132 
    133             if (DBG) Log.d(mTag, summary);
    134             addLogEntry(summary +
    135                         "\n[" + new String(HexEncoding.encode(recvbuf, 0, length)) + "]");
    136         }
    137 
    138         @Override
    139         protected void logError(String msg, Exception e) {
    140             Log.e(mTag, msg, e);
    141             addLogEntry(msg + e);
    142         }
    143 
    144         private void addLogEntry(String entry) {
    145             mHandler.post(() -> mLog.log(entry));
    146         }
    147     }
    148 }
    149