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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 android.net.ip;
import android.net.netlink.NetlinkConstants;
import android.net.netlink.NetlinkErrorMessage;
import android.net.netlink.NetlinkMessage;
import android.net.netlink.NetlinkSocket;
import android.net.netlink.RtNetlinkNeighborMessage;
import android.net.netlink.StructNdMsg;
import android.net.netlink.StructNlMsgHdr;
import android.net.util.PacketReader;
import android.net.util.SharedLog;
import android.os.Handler;
import android.os.SystemClock;
import android.system.ErrnoException;
import android.system.NetlinkSocketAddress;
import android.system.Os;
import android.system.OsConstants;
import android.util.Log;
import com.android.internal.util.BitUtils;
import libcore.io.IoUtils;
import libcore.io.Libcore;
import java.io.FileDescriptor;
import java.net.InetAddress;
import java.net.SocketAddress;
import java.net.SocketException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.StringJoiner;
/**
* IpNeighborMonitor.
*
* Monitors the kernel rtnetlink neighbor notifications and presents to callers
* NeighborEvents describing each event. Callers can provide a consumer instance
* to both filter (e.g. by interface index and IP address) and handle the
* generated NeighborEvents.
*
* @hide
*/
public class IpNeighborMonitor extends PacketReader {
private static final String TAG = IpNeighborMonitor.class.getSimpleName();
private static final boolean DBG = false;
private static final boolean VDBG = false;
/**
* Make the kernel perform neighbor reachability detection (IPv4 ARP or IPv6 ND)
* for the given IP address on the specified interface index.
*
* @return 0 if the request was successfully passed to the kernel; otherwise return
* a non-zero error code.
*/
public static int startKernelNeighborProbe(int ifIndex, InetAddress ip) {
final String msgSnippet = "probing ip=" + ip.getHostAddress() + "%" + ifIndex;
if (DBG) { Log.d(TAG, msgSnippet); }
final byte[] msg = RtNetlinkNeighborMessage.newNewNeighborMessage(
1, ip, StructNdMsg.NUD_PROBE, ifIndex, null);
try {
NetlinkSocket.sendOneShotKernelMessage(OsConstants.NETLINK_ROUTE, msg);
} catch (ErrnoException e) {
Log.e(TAG, "Error " + msgSnippet + ": " + e);
return -e.errno;
}
return 0;
}
public static class NeighborEvent {
final long elapsedMs;
final short msgType;
final int ifindex;
final InetAddress ip;
final short nudState;
final byte[] linkLayerAddr;
public NeighborEvent(long elapsedMs, short msgType, int ifindex, InetAddress ip,
short nudState, byte[] linkLayerAddr) {
this.elapsedMs = elapsedMs;
this.msgType = msgType;
this.ifindex = ifindex;
this.ip = ip;
this.nudState = nudState;
this.linkLayerAddr = linkLayerAddr;
}
boolean isConnected() {
return (msgType != NetlinkConstants.RTM_DELNEIGH) &&
StructNdMsg.isNudStateConnected(nudState);
}
boolean isValid() {
return (msgType != NetlinkConstants.RTM_DELNEIGH) &&
StructNdMsg.isNudStateValid(nudState);
}
@Override
public String toString() {
final StringJoiner j = new StringJoiner(",", "NeighborEvent{", "}");
return j.add("@" + elapsedMs)
.add(NetlinkConstants.stringForNlMsgType(msgType))
.add("if=" + ifindex)
.add(ip.getHostAddress())
.add(StructNdMsg.stringForNudState(nudState))
.add("[" + NetlinkConstants.hexify(linkLayerAddr) + "]")
.toString();
}
}
public interface NeighborEventConsumer {
// Every neighbor event received on the netlink socket is passed in
// here. Subclasses should filter for events of interest.
public void accept(NeighborEvent event);
}
private final SharedLog mLog;
private final NeighborEventConsumer mConsumer;
public IpNeighborMonitor(Handler h, SharedLog log, NeighborEventConsumer cb) {
super(h, NetlinkSocket.DEFAULT_RECV_BUFSIZE);
mLog = log.forSubComponent(TAG);
mConsumer = (cb != null) ? cb : (event) -> { /* discard */ };
}
@Override
protected FileDescriptor createFd() {
FileDescriptor fd = null;
try {
fd = NetlinkSocket.forProto(OsConstants.NETLINK_ROUTE);
Os.bind(fd, (SocketAddress)(new NetlinkSocketAddress(0, OsConstants.RTMGRP_NEIGH)));
Os.connect(fd, (SocketAddress)(new NetlinkSocketAddress(0, 0)));
if (VDBG) {
final NetlinkSocketAddress nlAddr = (NetlinkSocketAddress) Os.getsockname(fd);
Log.d(TAG, "bound to sockaddr_nl{"
+ BitUtils.uint32(nlAddr.getPortId()) + ", "
+ nlAddr.getGroupsMask()
+ "}");
}
} catch (ErrnoException|SocketException e) {
logError("Failed to create rtnetlink socket", e);
IoUtils.closeQuietly(fd);
return null;
}
return fd;
}
@Override
protected void handlePacket(byte[] recvbuf, int length) {
final long whenMs = SystemClock.elapsedRealtime();
final ByteBuffer byteBuffer = ByteBuffer.wrap(recvbuf, 0, length);
byteBuffer.order(ByteOrder.nativeOrder());
parseNetlinkMessageBuffer(byteBuffer, whenMs);
}
private void parseNetlinkMessageBuffer(ByteBuffer byteBuffer, long whenMs) {
while (byteBuffer.remaining() > 0) {
final int position = byteBuffer.position();
final NetlinkMessage nlMsg = NetlinkMessage.parse(byteBuffer);
if (nlMsg == null || nlMsg.getHeader() == null) {
byteBuffer.position(position);
mLog.e("unparsable netlink msg: " + NetlinkConstants.hexify(byteBuffer));
break;
}
final int srcPortId = nlMsg.getHeader().nlmsg_pid;
if (srcPortId != 0) {
mLog.e("non-kernel source portId: " + BitUtils.uint32(srcPortId));
break;
}
if (nlMsg instanceof NetlinkErrorMessage) {
mLog.e("netlink error: " + nlMsg);
continue;
} else if (!(nlMsg instanceof RtNetlinkNeighborMessage)) {
mLog.i("non-rtnetlink neighbor msg: " + nlMsg);
continue;
}
evaluateRtNetlinkNeighborMessage((RtNetlinkNeighborMessage) nlMsg, whenMs);
}
}
private void evaluateRtNetlinkNeighborMessage(
RtNetlinkNeighborMessage neighMsg, long whenMs) {
final short msgType = neighMsg.getHeader().nlmsg_type;
final StructNdMsg ndMsg = neighMsg.getNdHeader();
if (ndMsg == null) {
mLog.e("RtNetlinkNeighborMessage without ND message header!");
return;
}
final int ifindex = ndMsg.ndm_ifindex;
final InetAddress destination = neighMsg.getDestination();
final short nudState =
(msgType == NetlinkConstants.RTM_DELNEIGH)
? StructNdMsg.NUD_NONE
: ndMsg.ndm_state;
final NeighborEvent event = new NeighborEvent(
whenMs, msgType, ifindex, destination, nudState, neighMsg.getLinkLayerAddress());
if (VDBG) {
Log.d(TAG, neighMsg.toString());
}
if (DBG) {
Log.d(TAG, event.toString());
}
mConsumer.accept(event);
}
}
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