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/*
* Copyright (C) 2023 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.
*/
@file:JvmName("PacketReflectorUtil")
package com.android.testutils
import android.system.ErrnoException
import android.system.Os
import android.system.OsConstants
import com.android.net.module.util.IpUtils
import com.android.testutils.PacketReflector.IPV4_HEADER_LENGTH
import com.android.testutils.PacketReflector.IPV6_HEADER_LENGTH
import java.io.FileDescriptor
import java.io.InterruptedIOException
import java.net.InetAddress
import java.nio.ByteBuffer
fun readPacket(fd: FileDescriptor, buf: ByteArray): Int {
return try {
Os.read(fd, buf, 0, buf.size)
} catch (e: ErrnoException) {
// Ignore normal use cases such as the EAGAIN error indicates that the read operation
// cannot be completed immediately, or the EINTR error indicates that the read
// operation was interrupted by a signal.
if (e.errno == OsConstants.EAGAIN || e.errno == OsConstants.EINTR) {
-1
} else {
throw e
}
} catch (e: InterruptedIOException) {
-1
}
}
fun getInetAddressAt(buf: ByteArray, pos: Int, len: Int): InetAddress =
InetAddress.getByAddress(buf.copyOfRange(pos, pos + len))
/**
* Reads a 16-bit unsigned int at pos in big endian, with no alignment requirements.
*/
fun getPortAt(buf: ByteArray, pos: Int): Int {
return (buf[pos].toInt() and 0xff shl 8) + (buf[pos + 1].toInt() and 0xff)
}
fun setPortAt(port: Int, buf: ByteArray, pos: Int) {
buf[pos] = (port ushr 8).toByte()
buf[pos + 1] = (port and 0xff).toByte()
}
fun getAddressPositionAndLength(version: Int) = when (version) {
4 -> PacketReflector.IPV4_ADDR_OFFSET to PacketReflector.IPV4_ADDR_LENGTH
6 -> PacketReflector.IPV6_ADDR_OFFSET to PacketReflector.IPV6_ADDR_LENGTH
else -> throw IllegalArgumentException("Unknown IP version $version")
}
private const val IPV4_CHKSUM_OFFSET = 10
private const val UDP_CHECKSUM_OFFSET = 6
private const val TCP_CHECKSUM_OFFSET = 16
fun fixPacketChecksum(buf: ByteArray, len: Int, version: Int, protocol: Byte) {
// Fill Ip checksum for IPv4. IPv6 header doesn't have a checksum field.
if (version == 4) {
val checksum = IpUtils.ipChecksum(ByteBuffer.wrap(buf), 0)
// Place checksum in Big-endian order.
buf[IPV4_CHKSUM_OFFSET] = (checksum.toInt() ushr 8).toByte()
buf[IPV4_CHKSUM_OFFSET + 1] = (checksum.toInt() and 0xff).toByte()
}
// Fill transport layer checksum.
val transportOffset = if (version == 4) IPV4_HEADER_LENGTH else IPV6_HEADER_LENGTH
when (protocol) {
PacketReflector.IPPROTO_UDP -> {
val checksumPos = transportOffset + UDP_CHECKSUM_OFFSET
// Clear before calculate.
buf[checksumPos + 1] = 0x00
buf[checksumPos] = buf[checksumPos + 1]
val checksum = IpUtils.udpChecksum(
ByteBuffer.wrap(buf), 0,
transportOffset
)
buf[checksumPos] = (checksum.toInt() ushr 8).toByte()
buf[checksumPos + 1] = (checksum.toInt() and 0xff).toByte()
}
PacketReflector.IPPROTO_TCP -> {
val checksumPos = transportOffset + TCP_CHECKSUM_OFFSET
// Clear before calculate.
buf[checksumPos + 1] = 0x00
buf[checksumPos] = buf[checksumPos + 1]
val transportLen: Int = len - transportOffset
val checksum = IpUtils.tcpChecksum(
ByteBuffer.wrap(buf), 0, transportOffset,
transportLen
)
buf[checksumPos] = (checksum.toInt() ushr 8).toByte()
buf[checksumPos + 1] = (checksum.toInt() and 0xff).toByte()
}
// TODO: Support ICMP.
else -> throw IllegalArgumentException("Unsupported protocol: $protocol")
}
}
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