| /* |
| * 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.cts.net.hostside; |
| |
| import android.system.Os; |
| import android.system.ErrnoException; |
| import android.util.Log; |
| |
| import java.io.FileDescriptor; |
| import java.io.IOException; |
| |
| public class UdpReflector extends Thread { |
| |
| private static int IPV4_HEADER_LENGTH = 20; |
| private static int IPV6_HEADER_LENGTH = 40; |
| private static int UDP_HEADER_LENGTH = 8; |
| |
| private static int IPV4_PROTO_OFFSET = 9; |
| private static int IPV6_PROTO_OFFSET = 6; |
| private static int IPPROTO_UDP = 17; |
| |
| private static int IPV4_ADDR_OFFSET = 12; |
| private static int IPV6_ADDR_OFFSET = 8; |
| private static int IPV4_ADDR_LENGTH = 4; |
| private static int IPV6_ADDR_LENGTH = 16; |
| |
| private static String TAG = "UdpReflector"; |
| |
| private FileDescriptor mFd; |
| private byte[] mBuf; |
| |
| public UdpReflector(FileDescriptor fd, int mtu) { |
| super("UdpReflector"); |
| mFd = fd; |
| mBuf = new byte[mtu]; |
| } |
| |
| private static void swapBytes(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; |
| } |
| } |
| |
| /** Reads one packet from our mFd, and possibly writes the packet back. */ |
| private void processPacket() { |
| int len; |
| try { |
| len = Os.read(mFd, mBuf, 0, mBuf.length); |
| } catch (ErrnoException|IOException e) { |
| Log.e(TAG, "Error reading packet: " + e.getMessage()); |
| return; |
| } |
| |
| int version = mBuf[0] >> 4; |
| int addressOffset, protoOffset, headerLength, addressLength; |
| if (version == 4) { |
| headerLength = IPV4_HEADER_LENGTH; |
| protoOffset = IPV4_PROTO_OFFSET; |
| addressOffset = IPV4_ADDR_OFFSET; |
| addressLength = IPV4_ADDR_LENGTH; |
| } else if (version == 6) { |
| headerLength = IPV6_HEADER_LENGTH; |
| protoOffset = IPV6_PROTO_OFFSET; |
| addressOffset = IPV6_ADDR_OFFSET; |
| addressLength = IPV6_ADDR_LENGTH; |
| } else { |
| return; |
| } |
| |
| if (len < headerLength + UDP_HEADER_LENGTH || mBuf[protoOffset] != IPPROTO_UDP) { |
| return; |
| } |
| |
| // Swap src and dst IP addresses. |
| swapBytes(mBuf, addressOffset, addressOffset + addressLength, addressLength); |
| |
| // Swap dst and src ports. |
| int portOffset = headerLength; |
| swapBytes(mBuf, portOffset, portOffset + 2, 2); |
| |
| // Send the packet back. We don't need to recalculate the checksum because we didn't change |
| // the packet bytes, we only moved them around. |
| try { |
| len = Os.write(mFd, mBuf, 0, len); |
| } catch (ErrnoException|IOException e) { |
| Log.e(TAG, "Error writing packet: " + e.getMessage()); |
| } |
| } |
| |
| public void run() { |
| Log.i(TAG, "UdpReflector starting fd=" + mFd + " valid=" + mFd.valid()); |
| while (!interrupted() && mFd.valid()) { |
| processPacket(); |
| } |
| Log.i(TAG, "UdpReflector exiting fd=" + mFd + " valid=" + mFd.valid()); |
| } |
| } |