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/*
* Copyright (C) 2016 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 android.net.ip;
import static android.net.util.SocketUtils.makePacketSocketAddress;
import static android.system.OsConstants.AF_PACKET;
import static android.system.OsConstants.ARPHRD_ETHER;
import static android.system.OsConstants.ETH_P_ALL;
import static android.system.OsConstants.SOCK_NONBLOCK;
import static android.system.OsConstants.SOCK_RAW;
import android.net.util.ConnectivityPacketSummary;
import android.net.util.InterfaceParams;
import android.net.util.NetworkStackUtils;
import android.net.util.PacketReader;
import android.os.Handler;
import android.os.SystemClock;
import android.system.ErrnoException;
import android.system.Os;
import android.text.TextUtils;
import android.util.LocalLog;
import android.util.Log;
import com.android.internal.util.HexDump;
import com.android.internal.util.TokenBucket;
import java.io.FileDescriptor;
import java.io.IOException;
/**
* Critical connectivity packet tracking daemon.
*
* Tracks ARP, DHCPv4, and IPv6 RS/RA/NS/NA packets.
*
* This class's constructor, start() and stop() methods must only be called
* from the same thread on which the passed in |log| is accessed.
*
* Log lines include a hexdump of the packet, which can be decoded via:
*
* echo -n H3XSTR1NG | sed -e 's/\([0-9A-F][0-9A-F]\)/\1 /g' -e 's/^/000000 /'
* | text2pcap - -
* | tcpdump -n -vv -e -r -
*
* @hide
*/
public class ConnectivityPacketTracker {
private static final String TAG = ConnectivityPacketTracker.class.getSimpleName();
private static final boolean DBG = false;
private static final String MARK_START = "--- START ---";
private static final String MARK_STOP = "--- STOP ---";
private static final String MARK_NAMED_START = "--- START (%s) ---";
private static final String MARK_NAMED_STOP = "--- STOP (%s) ---";
// Use a TokenBucket to limit CPU usage of logging packets in steady state.
private static final int TOKEN_FILL_RATE = 50; // Maximum one packet every 20ms.
private static final int MAX_BURST_LENGTH = 100; // Maximum burst 100 packets.
private final String mTag;
private final LocalLog mLog;
private final PacketReader mPacketListener;
private final TokenBucket mTokenBucket = new TokenBucket(TOKEN_FILL_RATE, MAX_BURST_LENGTH);
private long mLastRateLimitLogTimeMs = 0;
private boolean mRunning;
private String mDisplayName;
public ConnectivityPacketTracker(Handler h, InterfaceParams ifParams, LocalLog log) {
if (ifParams == null) throw new IllegalArgumentException("null InterfaceParams");
mTag = TAG + "." + ifParams.name;
mLog = log;
mPacketListener = new PacketListener(h, ifParams);
}
public void start(String displayName) {
mRunning = true;
mDisplayName = displayName;
mPacketListener.start();
}
public void stop() {
mPacketListener.stop();
mRunning = false;
mDisplayName = null;
}
private final class PacketListener extends PacketReader {
private final InterfaceParams mInterface;
PacketListener(Handler h, InterfaceParams ifParams) {
super(h, ifParams.defaultMtu);
mInterface = ifParams;
}
@Override
protected FileDescriptor createFd() {
FileDescriptor s = null;
try {
s = Os.socket(AF_PACKET, SOCK_RAW | SOCK_NONBLOCK, 0);
NetworkStackUtils.attachControlPacketFilter(s, ARPHRD_ETHER);
Os.bind(s, makePacketSocketAddress(ETH_P_ALL, mInterface.index));
} catch (ErrnoException | IOException e) {
logError("Failed to create packet tracking socket: ", e);
closeFd(s);
return null;
}
return s;
}
@Override
protected void handlePacket(byte[] recvbuf, int length) {
if (!mTokenBucket.get()) {
// Rate limited. Log once every second so the user knows packets are missing.
final long now = SystemClock.elapsedRealtime();
if (now >= mLastRateLimitLogTimeMs + 1000) {
addLogEntry("Warning: too many packets, rate-limiting to one every " +
TOKEN_FILL_RATE + "ms");
mLastRateLimitLogTimeMs = now;
}
return;
}
final String summary;
try {
summary = ConnectivityPacketSummary.summarize(mInterface.macAddr, recvbuf, length);
if (summary == null) return;
} catch (Exception e) {
if (DBG) Log.d(mTag, "Error creating packet summary", e);
return;
}
if (DBG) Log.d(mTag, summary);
addLogEntry(summary + "\n[" + HexDump.toHexString(recvbuf, 0, length) + "]");
}
@Override
protected void onStart() {
final String msg = TextUtils.isEmpty(mDisplayName)
? MARK_START
: String.format(MARK_NAMED_START, mDisplayName);
mLog.log(msg);
}
@Override
protected void onStop() {
String msg = TextUtils.isEmpty(mDisplayName)
? MARK_STOP
: String.format(MARK_NAMED_STOP, mDisplayName);
if (!mRunning) msg += " (packet listener stopped unexpectedly)";
mLog.log(msg);
}
@Override
protected void logError(String msg, Exception e) {
Log.e(mTag, msg, e);
addLogEntry(msg + e);
}
private void addLogEntry(String entry) {
mLog.log(entry);
}
}
}
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