android-34/com/android/testutils/PacketReflector.java - platform/prebuilts/fullsdk/sources - Git at Google

 /*
  * Copyright (C) 2014 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 com.android.testutils;

 import static android.system.OsConstants.ICMP6_ECHO_REPLY;
 import static android.system.OsConstants.ICMP6_ECHO_REQUEST;

 import android.annotation.NonNull;
 import android.net.TestNetworkInterface;
 import android.system.ErrnoException;
 import android.system.Os;
 import android.util.Log;

 import java.io.FileDescriptor;
 import java.io.IOException;
 import java.util.Objects;

 /**
  * A class that echoes packets received on a {@link TestNetworkInterface} back to itself.
  *
  * For testing purposes, sometimes a mocked environment to simulate a simple echo from the
  * server side is needed. This is particularly useful if the test, e.g. VpnTest, is
  * heavily relying on the outside world.
  *
  * This class reads packets from the {@link FileDescriptor} of a {@link TestNetworkInterface}, and:
  *   1. For TCP and UDP packets, simply swaps the source address and the destination
  *      address, then send it back to the {@link FileDescriptor}.
  *   2. For ICMP ping packets, composes a ping reply and sends it back to the sender.
  *   3. Ignore all other packets.
  */
 public class PacketReflector extends Thread {

     static final int IPV4_HEADER_LENGTH = 20;
     static final int IPV6_HEADER_LENGTH = 40;

     static final int IPV4_ADDR_OFFSET = 12;
     static final int IPV6_ADDR_OFFSET = 8;
     static final int IPV4_ADDR_LENGTH = 4;
     static final int IPV6_ADDR_LENGTH = 16;

     static final int IPV4_PROTO_OFFSET = 9;
     static final int IPV6_PROTO_OFFSET = 6;

     static final byte IPPROTO_ICMP = 1;
     static final byte IPPROTO_TCP = 6;
     static final byte IPPROTO_UDP = 17;
     private static final byte IPPROTO_ICMPV6 = 58;

     private static final int ICMP_HEADER_LENGTH = 8;
     static final int TCP_HEADER_LENGTH = 20;
     static final int UDP_HEADER_LENGTH = 8;

     private static final byte ICMP_ECHO = 8;
     private static final byte ICMP_ECHOREPLY = 0;

     private static String TAG = "PacketReflector";

     @NonNull
     private final FileDescriptor mFd;
     @NonNull
     private final byte[] mBuf;

     /**
      * Construct a {@link PacketReflector} from the given {@code fd} of
      * a {@link TestNetworkInterface}.
      *
      * @param fd {@link FileDescriptor} to read/write packets.
      * @param mtu MTU of the test network.
      */
     public PacketReflector(@NonNull FileDescriptor fd, int mtu) {
         super("PacketReflector");
         mFd = Objects.requireNonNull(fd);
         mBuf = new byte[mtu];
     }

     private static void swapBytes(@NonNull byte[] buf, int pos1, int pos2, int len) {
         for (int i = 0; i < len; i++) {
             byte b = buf[pos1 + i];
             buf[pos1 + i] = buf[pos2 + i];
             buf[pos2 + i] = b;
         }
     }

     private static void swapAddresses(@NonNull byte[] buf, int version) {
         int addrPos, addrLen;
         switch (version) {
             case 4:
                 addrPos = IPV4_ADDR_OFFSET;
                 addrLen = IPV4_ADDR_LENGTH;
                 break;
             case 6:
                 addrPos = IPV6_ADDR_OFFSET;
                 addrLen = IPV6_ADDR_LENGTH;
                 break;
             default:
                 throw new IllegalArgumentException();
         }
         swapBytes(buf, addrPos, addrPos + addrLen, addrLen);
     }

     // Reflect TCP packets: swap the source and destination addresses, but don't change the ports.
     // This is used by the test to "connect to itself" through the VPN.
     private void processTcpPacket(@NonNull byte[] buf, int version, int len, int hdrLen) {
         if (len < hdrLen + TCP_HEADER_LENGTH) {
             return;
         }

         // Swap src and dst IP addresses.
         swapAddresses(buf, version);

         // Send the packet back.
         writePacket(buf, len);
     }

     // Echo UDP packets: swap source and destination addresses, and source and destination ports.
     // This is used by the test to check that the bytes it sends are echoed back.
     private void processUdpPacket(@NonNull byte[] buf, int version, int len, int hdrLen) {
         if (len < hdrLen + UDP_HEADER_LENGTH) {
             return;
         }

         // Swap src and dst IP addresses.
         swapAddresses(buf, version);

         // Swap dst and src ports.
         int portOffset = hdrLen;
         swapBytes(buf, portOffset, portOffset + 2, 2);

         // Send the packet back.
         writePacket(buf, len);
     }

     private void processIcmpPacket(@NonNull byte[] buf, int version, int len, int hdrLen) {
         if (len < hdrLen + ICMP_HEADER_LENGTH) {
             return;
         }

         byte type = buf[hdrLen];
         if (!(version == 4 && type == ICMP_ECHO) &&
                 !(version == 6 && type == (byte) ICMP6_ECHO_REQUEST)) {
             return;
         }

         // Save the ping packet we received.
         byte[] request = buf.clone();

         // Swap src and dst IP addresses, and send the packet back.
         // This effectively pings the device to see if it replies.
         swapAddresses(buf, version);
         writePacket(buf, len);

         // The device should have replied, and buf should now contain a ping response.
         int received = PacketReflectorUtil.readPacket(mFd, buf);
         if (received != len) {
             Log.i(TAG, "Reflecting ping did not result in ping response: " +
                     "read=" + received + " expected=" + len);
             return;
         }

         byte replyType = buf[hdrLen];
         if ((type == ICMP_ECHO && replyType != ICMP_ECHOREPLY)
                 || (type == (byte) ICMP6_ECHO_REQUEST && replyType != (byte) ICMP6_ECHO_REPLY)) {
             Log.i(TAG, "Received unexpected ICMP reply: original " + type
                     + ", reply " + replyType);
             return;
         }

         // Compare the response we got with the original packet.
         // The only thing that should have changed are addresses, type and checksum.
         // Overwrite them with the received bytes and see if the packet is otherwise identical.
         request[hdrLen] = buf[hdrLen];          // Type
         request[hdrLen + 2] = buf[hdrLen + 2];  // Checksum byte 1.
         request[hdrLen + 3] = buf[hdrLen + 3];  // Checksum byte 2.

         // Since Linux kernel 4.2, net.ipv6.auto_flowlabels is set by default, and therefore
         // the request and reply may have different IPv6 flow label: ignore that as well.
         if (version == 6) {
             request[1] = (byte) (request[1] & 0xf0 | buf[1] & 0x0f);
             request[2] = buf[2];
             request[3] = buf[3];
         }

         for (int i = 0; i < len; i++) {
             if (buf[i] != request[i]) {
                 Log.i(TAG, "Received non-matching packet when expecting ping response.");
                 return;
             }
         }

         // Now swap the addresses again and reflect the packet. This sends a ping reply.
         swapAddresses(buf, version);
         writePacket(buf, len);
     }

     private void writePacket(@NonNull byte[] buf, int len) {
         try {
             Os.write(mFd, buf, 0, len);
         } catch (ErrnoException | IOException e) {
             Log.e(TAG, "Error writing packet: " + e.getMessage());
         }
     }

     // Reads one packet from our mFd, and possibly writes the packet back.
     private void processPacket() {
         int len = PacketReflectorUtil.readPacket(mFd, mBuf);
         if (len < 1) {
             // Usually happens when socket read is being interrupted, e.g. stopping PacketReflector.
             return;
         }

         int version = mBuf[0] >> 4;
         int protoPos, hdrLen;
         if (version == 4) {
             hdrLen = IPV4_HEADER_LENGTH;
             protoPos = IPV4_PROTO_OFFSET;
         } else if (version == 6) {
             hdrLen = IPV6_HEADER_LENGTH;
             protoPos = IPV6_PROTO_OFFSET;
         } else {
             throw new IllegalStateException("Unexpected version: " + version);
         }

         if (len < hdrLen) {
             throw new IllegalStateException("Unexpected buffer length: " + len);
         }

         byte proto = mBuf[protoPos];
         switch (proto) {
             case IPPROTO_ICMP:
                 // fall through
             case IPPROTO_ICMPV6:
                 processIcmpPacket(mBuf, version, len, hdrLen);
                 break;
             case IPPROTO_TCP:
                 processTcpPacket(mBuf, version, len, hdrLen);
                 break;
             case IPPROTO_UDP:
                 processUdpPacket(mBuf, version, len, hdrLen);
                 break;
         }
     }

     public void run() {
         Log.i(TAG, "starting fd=" + mFd + " valid=" + mFd.valid());
         while (!interrupted() && mFd.valid()) {
             processPacket();
         }
         Log.i(TAG, "exiting fd=" + mFd + " valid=" + mFd.valid());
     }
 }
	/*
	* Copyright (C) 2014 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 com.android.testutils;

	import static android.system.OsConstants.ICMP6_ECHO_REPLY;
	import static android.system.OsConstants.ICMP6_ECHO_REQUEST;

	import android.annotation.NonNull;
	import android.net.TestNetworkInterface;
	import android.system.ErrnoException;
	import android.system.Os;
	import android.util.Log;

	import java.io.FileDescriptor;
	import java.io.IOException;
	import java.util.Objects;

	/**
	* A class that echoes packets received on a {@link TestNetworkInterface} back to itself.
	*
	* For testing purposes, sometimes a mocked environment to simulate a simple echo from the
	* server side is needed. This is particularly useful if the test, e.g. VpnTest, is
	* heavily relying on the outside world.
	*
	* This class reads packets from the {@link FileDescriptor} of a {@link TestNetworkInterface}, and:
	* 1. For TCP and UDP packets, simply swaps the source address and the destination
	* address, then send it back to the {@link FileDescriptor}.
	* 2. For ICMP ping packets, composes a ping reply and sends it back to the sender.
	* 3. Ignore all other packets.
	*/
	public class PacketReflector extends Thread {

	static final int IPV4_HEADER_LENGTH = 20;
	static final int IPV6_HEADER_LENGTH = 40;

	static final int IPV4_ADDR_OFFSET = 12;
	static final int IPV6_ADDR_OFFSET = 8;
	static final int IPV4_ADDR_LENGTH = 4;
	static final int IPV6_ADDR_LENGTH = 16;

	static final int IPV4_PROTO_OFFSET = 9;
	static final int IPV6_PROTO_OFFSET = 6;

	static final byte IPPROTO_ICMP = 1;
	static final byte IPPROTO_TCP = 6;
	static final byte IPPROTO_UDP = 17;
	private static final byte IPPROTO_ICMPV6 = 58;

	private static final int ICMP_HEADER_LENGTH = 8;
	static final int TCP_HEADER_LENGTH = 20;
	static final int UDP_HEADER_LENGTH = 8;

	private static final byte ICMP_ECHO = 8;
	private static final byte ICMP_ECHOREPLY = 0;

	private static String TAG = "PacketReflector";

	@NonNull
	private final FileDescriptor mFd;
	@NonNull
	private final byte[] mBuf;

	/**
	* Construct a {@link PacketReflector} from the given {@code fd} of
	* a {@link TestNetworkInterface}.
	*
	* @param fd {@link FileDescriptor} to read/write packets.
	* @param mtu MTU of the test network.
	*/
	public PacketReflector(@NonNull FileDescriptor fd, int mtu) {
	super("PacketReflector");
	mFd = Objects.requireNonNull(fd);
	mBuf = new byte[mtu];
	}

	private static void swapBytes(@NonNull byte[] buf, int pos1, int pos2, int len) {
	for (int i = 0; i < len; i++) {
	byte b = buf[pos1 + i];
	buf[pos1 + i] = buf[pos2 + i];
	buf[pos2 + i] = b;
	}
	}

	private static void swapAddresses(@NonNull byte[] buf, int version) {
	int addrPos, addrLen;
	switch (version) {
	case 4:
	addrPos = IPV4_ADDR_OFFSET;
	addrLen = IPV4_ADDR_LENGTH;
	break;
	case 6:
	addrPos = IPV6_ADDR_OFFSET;
	addrLen = IPV6_ADDR_LENGTH;
	break;
	default:
	throw new IllegalArgumentException();
	}
	swapBytes(buf, addrPos, addrPos + addrLen, addrLen);
	}

	// Reflect TCP packets: swap the source and destination addresses, but don't change the ports.
	// This is used by the test to "connect to itself" through the VPN.
	private void processTcpPacket(@NonNull byte[] buf, int version, int len, int hdrLen) {
	if (len < hdrLen + TCP_HEADER_LENGTH) {
	return;
	}

	// Swap src and dst IP addresses.
	swapAddresses(buf, version);

	// Send the packet back.
	writePacket(buf, len);
	}

	// Echo UDP packets: swap source and destination addresses, and source and destination ports.
	// This is used by the test to check that the bytes it sends are echoed back.
	private void processUdpPacket(@NonNull byte[] buf, int version, int len, int hdrLen) {
	if (len < hdrLen + UDP_HEADER_LENGTH) {
	return;
	}

	// Swap src and dst IP addresses.
	swapAddresses(buf, version);

	// Swap dst and src ports.
	int portOffset = hdrLen;
	swapBytes(buf, portOffset, portOffset + 2, 2);

	// Send the packet back.
	writePacket(buf, len);
	}

	private void processIcmpPacket(@NonNull byte[] buf, int version, int len, int hdrLen) {
	if (len < hdrLen + ICMP_HEADER_LENGTH) {
	return;
	}

	byte type = buf[hdrLen];
	if (!(version == 4 && type == ICMP_ECHO) &&
	!(version == 6 && type == (byte) ICMP6_ECHO_REQUEST)) {
	return;
	}

	// Save the ping packet we received.
	byte[] request = buf.clone();

	// Swap src and dst IP addresses, and send the packet back.
	// This effectively pings the device to see if it replies.
	swapAddresses(buf, version);
	writePacket(buf, len);

	// The device should have replied, and buf should now contain a ping response.
	int received = PacketReflectorUtil.readPacket(mFd, buf);
	if (received != len) {
	Log.i(TAG, "Reflecting ping did not result in ping response: " +
	"read=" + received + " expected=" + len);
	return;
	}

	byte replyType = buf[hdrLen];
	if ((type == ICMP_ECHO && replyType != ICMP_ECHOREPLY)
	\|\| (type == (byte) ICMP6_ECHO_REQUEST && replyType != (byte) ICMP6_ECHO_REPLY)) {
	Log.i(TAG, "Received unexpected ICMP reply: original " + type
	+ ", reply " + replyType);
	return;
	}

	// Compare the response we got with the original packet.
	// The only thing that should have changed are addresses, type and checksum.
	// Overwrite them with the received bytes and see if the packet is otherwise identical.
	request[hdrLen] = buf[hdrLen]; // Type
	request[hdrLen + 2] = buf[hdrLen + 2]; // Checksum byte 1.
	request[hdrLen + 3] = buf[hdrLen + 3]; // Checksum byte 2.

	// Since Linux kernel 4.2, net.ipv6.auto_flowlabels is set by default, and therefore
	// the request and reply may have different IPv6 flow label: ignore that as well.
	if (version == 6) {
	request[1] = (byte) (request[1] & 0xf0 \| buf[1] & 0x0f);
	request[2] = buf[2];
	request[3] = buf[3];
	}

	for (int i = 0; i < len; i++) {
	if (buf[i] != request[i]) {
	Log.i(TAG, "Received non-matching packet when expecting ping response.");
	return;
	}
	}

	// Now swap the addresses again and reflect the packet. This sends a ping reply.
	swapAddresses(buf, version);
	writePacket(buf, len);
	}

	private void writePacket(@NonNull byte[] buf, int len) {
	try {
	Os.write(mFd, buf, 0, len);
	} catch (ErrnoException \| IOException e) {
	Log.e(TAG, "Error writing packet: " + e.getMessage());
	}
	}

	// Reads one packet from our mFd, and possibly writes the packet back.
	private void processPacket() {
	int len = PacketReflectorUtil.readPacket(mFd, mBuf);
	if (len < 1) {
	// Usually happens when socket read is being interrupted, e.g. stopping PacketReflector.
	return;
	}

	int version = mBuf[0] >> 4;
	int protoPos, hdrLen;
	if (version == 4) {
	hdrLen = IPV4_HEADER_LENGTH;
	protoPos = IPV4_PROTO_OFFSET;
	} else if (version == 6) {
	hdrLen = IPV6_HEADER_LENGTH;
	protoPos = IPV6_PROTO_OFFSET;
	} else {
	throw new IllegalStateException("Unexpected version: " + version);
	}

	if (len < hdrLen) {
	throw new IllegalStateException("Unexpected buffer length: " + len);
	}

	byte proto = mBuf[protoPos];
	switch (proto) {
	case IPPROTO_ICMP:
	// fall through
	case IPPROTO_ICMPV6:
	processIcmpPacket(mBuf, version, len, hdrLen);
	break;
	case IPPROTO_TCP:
	processTcpPacket(mBuf, version, len, hdrLen);
	break;
	case IPPROTO_UDP:
	processUdpPacket(mBuf, version, len, hdrLen);
	break;
	}
	}

	public void run() {
	Log.i(TAG, "starting fd=" + mFd + " valid=" + mFd.valid());
	while (!interrupted() && mFd.valid()) {
	processPacket();
	}
	Log.i(TAG, "exiting fd=" + mFd + " valid=" + mFd.valid());
	}
	}