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/*
* Copyright (C) 2020 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.system.OsConstants.AF_INET6;
import static android.system.OsConstants.AF_PACKET;
import static android.system.OsConstants.ETH_P_IPV6;
import static android.system.OsConstants.IPPROTO_RAW;
import static android.system.OsConstants.SOCK_DGRAM;
import static android.system.OsConstants.SOCK_NONBLOCK;
import static android.system.OsConstants.SOCK_RAW;
import android.net.util.SocketUtils;
import android.os.Handler;
import android.system.ErrnoException;
import android.system.Os;
import android.util.Log;
import com.android.net.module.util.InterfaceParams;
import com.android.net.module.util.PacketReader;
import com.android.networkstack.tethering.util.TetheringUtils;
import java.io.FileDescriptor;
import java.io.IOException;
import java.net.Inet6Address;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.SocketException;
import java.net.UnknownHostException;
import java.util.Arrays;
/**
* Basic IPv6 Neighbor Advertisement Forwarder.
*
* Forward NA packets from upstream iface to tethered iface
* and NS packets from tethered iface to upstream iface.
*
* @hide
*/
public class NeighborPacketForwarder extends PacketReader {
private final String mTag;
private FileDescriptor mFd;
// TODO: get these from NetworkStackConstants.
private static final int IPV6_ADDR_LEN = 16;
private static final int IPV6_DST_ADDR_OFFSET = 24;
private static final int IPV6_HEADER_LEN = 40;
private static final int ETH_HEADER_LEN = 14;
private InterfaceParams mListenIfaceParams, mSendIfaceParams;
private final int mType;
public static final int ICMPV6_NEIGHBOR_ADVERTISEMENT = 136;
public static final int ICMPV6_NEIGHBOR_SOLICITATION = 135;
public NeighborPacketForwarder(Handler h, InterfaceParams tetheredInterface, int type) {
super(h);
mTag = NeighborPacketForwarder.class.getSimpleName() + "-"
+ tetheredInterface.name + "-" + type;
mType = type;
if (mType == ICMPV6_NEIGHBOR_ADVERTISEMENT) {
mSendIfaceParams = tetheredInterface;
} else {
mListenIfaceParams = tetheredInterface;
}
}
/** Set new upstream iface and start/stop based on new params. */
public void setUpstreamIface(InterfaceParams upstreamParams) {
final InterfaceParams oldUpstreamParams;
if (mType == ICMPV6_NEIGHBOR_ADVERTISEMENT) {
oldUpstreamParams = mListenIfaceParams;
mListenIfaceParams = upstreamParams;
} else {
oldUpstreamParams = mSendIfaceParams;
mSendIfaceParams = upstreamParams;
}
if (oldUpstreamParams == null && upstreamParams != null) {
start();
} else if (oldUpstreamParams != null && upstreamParams == null) {
stop();
} else if (oldUpstreamParams != null && upstreamParams != null
&& oldUpstreamParams.index != upstreamParams.index) {
stop();
start();
}
}
// TODO: move NetworkStackUtils.closeSocketQuietly to
// frameworks/libs/net/common/device/com/android/net/module/util/[someclass].
private void closeSocketQuietly(FileDescriptor fd) {
try {
SocketUtils.closeSocket(fd);
} catch (IOException ignored) {
}
}
@Override
protected FileDescriptor createFd() {
try {
// ICMPv6 packets from modem do not have eth header, so RAW socket cannot be used.
// To keep uniformity in both directions PACKET socket can be used.
mFd = Os.socket(AF_PACKET, SOCK_DGRAM | SOCK_NONBLOCK, 0);
// TODO: convert setup*Socket to setupICMPv6BpfFilter with filter type?
if (mType == ICMPV6_NEIGHBOR_ADVERTISEMENT) {
TetheringUtils.setupNaSocket(mFd);
} else if (mType == ICMPV6_NEIGHBOR_SOLICITATION) {
TetheringUtils.setupNsSocket(mFd);
}
SocketAddress bindAddress = SocketUtils.makePacketSocketAddress(
ETH_P_IPV6, mListenIfaceParams.index);
Os.bind(mFd, bindAddress);
} catch (ErrnoException | SocketException e) {
Log.wtf(mTag, "Failed to create socket", e);
closeSocketQuietly(mFd);
return null;
}
return mFd;
}
private Inet6Address getIpv6DestinationAddress(byte[] recvbuf) {
Inet6Address dstAddr;
try {
dstAddr = (Inet6Address) Inet6Address.getByAddress(Arrays.copyOfRange(recvbuf,
IPV6_DST_ADDR_OFFSET, IPV6_DST_ADDR_OFFSET + IPV6_ADDR_LEN));
} catch (UnknownHostException | ClassCastException impossible) {
throw new AssertionError("16-byte array not valid IPv6 address?");
}
return dstAddr;
}
@Override
protected void handlePacket(byte[] recvbuf, int length) {
if (mSendIfaceParams == null) {
return;
}
// The BPF filter should already have checked the length of the packet, but...
if (length < IPV6_HEADER_LEN) {
return;
}
Inet6Address destv6 = getIpv6DestinationAddress(recvbuf);
if (!destv6.isMulticastAddress()) {
return;
}
InetSocketAddress dest = new InetSocketAddress(destv6, 0);
FileDescriptor fd = null;
try {
fd = Os.socket(AF_INET6, SOCK_RAW | SOCK_NONBLOCK, IPPROTO_RAW);
SocketUtils.bindSocketToInterface(fd, mSendIfaceParams.name);
int ret = Os.sendto(fd, recvbuf, 0, length, 0, dest);
} catch (ErrnoException | SocketException e) {
Log.e(mTag, "handlePacket error: " + e);
} finally {
closeSocketQuietly(fd);
}
}
}
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