1 files changed, 180 insertions, 0 deletions
diff --git a/Tethering/src/android/net/ip/NeighborPacketForwarder.java b/Tethering/src/android/net/ip/NeighborPacketForwarder.java
new file mode 100644
index 0000000000..73fc833fab
--- /dev/null
+++ b/Tethering/src/android/net/ip/NeighborPacketForwarder.java
@@ -0,0 +1,180 @@
+/*
+ * 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.InterfaceParams;
+import android.net.util.PacketReader;
+import android.net.util.SocketUtils;
+import android.net.util.TetheringUtils;
+import android.os.Handler;
+import android.system.ErrnoException;
+import android.system.Os;
+import android.util.Log;
+
+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);
+        }
+    }
+}