Add a class to build IPv4 TCP packet
Note that IPv4 and TCP options are not supported.
Test: atest NetworkStaticLibTests
Change-Id: Ie62b95bf759b74d72a5e85d312d17978422f633b
diff --git a/staticlibs/Android.bp b/staticlibs/Android.bp
index 0585c09..4c58228 100644
--- a/staticlibs/Android.bp
+++ b/staticlibs/Android.bp
@@ -139,6 +139,7 @@
srcs: [
"device/com/android/net/module/util/HexDump.java",
"device/com/android/net/module/util/Ipv6Utils.java",
+ "device/com/android/net/module/util/PacketBuilder.java",
"device/com/android/net/module/util/Struct.java",
"device/com/android/net/module/util/structs/*.java",
],
diff --git a/staticlibs/device/com/android/net/module/util/PacketBuilder.java b/staticlibs/device/com/android/net/module/util/PacketBuilder.java
new file mode 100644
index 0000000..e9ecb94
--- /dev/null
+++ b/staticlibs/device/com/android/net/module/util/PacketBuilder.java
@@ -0,0 +1,222 @@
+/*
+ * Copyright (C) 2021 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.net.module.util;
+
+import static android.system.OsConstants.IPPROTO_IP;
+import static android.system.OsConstants.IPPROTO_TCP;
+
+import static com.android.net.module.util.IpUtils.ipChecksum;
+import static com.android.net.module.util.IpUtils.tcpChecksum;
+import static com.android.net.module.util.NetworkStackConstants.IPV4_CHECKSUM_OFFSET;
+import static com.android.net.module.util.NetworkStackConstants.IPV4_LENGTH_OFFSET;
+import static com.android.net.module.util.NetworkStackConstants.TCP_CHECKSUM_OFFSET;
+
+import android.net.MacAddress;
+
+import androidx.annotation.NonNull;
+
+import com.android.net.module.util.structs.EthernetHeader;
+import com.android.net.module.util.structs.Ipv4Header;
+import com.android.net.module.util.structs.TcpHeader;
+
+import java.io.IOException;
+import java.net.Inet4Address;
+import java.nio.BufferOverflowException;
+import java.nio.ByteBuffer;
+
+/**
+ * The class is used to build a packet.
+ *
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Layer 2 header (EthernetHeader) | (optional)
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Layer 3 header (Ipv4Header) |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Layer 4 header (TcpHeader) |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Payload | (optional)
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * Below is a sample code to build a packet.
+ *
+ * // Initialize builder
+ * final ByteBuffer buf = ByteBuffer.allocate(...);
+ * final PacketBuilder pb = new PacketBuilder(buf);
+ * // Write headers
+ * pb.writeL2Header(...);
+ * pb.writeIpHeader(...);
+ * pb.writeTcpHeader(...);
+ * // Write payload
+ * buf.putInt(...);
+ * buf.putShort(...);
+ * buf.putByte(...);
+ * // Finalize and use the packet
+ * pb.finalizePacket();
+ * sendPacket(buf);
+ */
+public class PacketBuilder {
+ private final ByteBuffer mBuffer;
+
+ private int mIpv4HeaderOffset = -1;
+ private int mTcpHeaderOffset = -1;
+
+ public PacketBuilder(@NonNull ByteBuffer buffer) {
+ mBuffer = buffer;
+ }
+
+ /**
+ * Write an ethernet header.
+ *
+ * @param srcMac source MAC address
+ * @param dstMac destination MAC address
+ * @param etherType ether type
+ */
+ public void writeL2Header(MacAddress srcMac, MacAddress dstMac, short etherType) throws
+ IOException {
+ final EthernetHeader ethv4Header = new EthernetHeader(dstMac, srcMac, etherType);
+ try {
+ ethv4Header.writeToByteBuffer(mBuffer);
+ } catch (IllegalArgumentException | BufferOverflowException e) {
+ throw new IOException("Error writing to buffer: ", e);
+ }
+ }
+
+ /**
+ * Write an IPv4 header.
+ * The IP header length and checksum are calculated and written back in #finalizePacket.
+ *
+ * @param tos type of service
+ * @param id the identification
+ * @param flagsAndFragmentOffset flags and fragment offset
+ * @param ttl time to live
+ * @param protocol protocol
+ * @param srcIp source IP address
+ * @param dstIp destination IP address
+ */
+ public void writeIpv4Header(byte tos, short id, short flagsAndFragmentOffset, byte ttl,
+ byte protocol, @NonNull final Inet4Address srcIp, @NonNull final Inet4Address dstIp)
+ throws IOException {
+ mIpv4HeaderOffset = mBuffer.position();
+ final Ipv4Header ipv4Header = new Ipv4Header(tos,
+ (short) 0 /* totalLength, calculate in #finalizePacket */, id,
+ flagsAndFragmentOffset, ttl, protocol,
+ (short) 0 /* checksum, calculate in #finalizePacket */, srcIp, dstIp);
+
+ try {
+ ipv4Header.writeToByteBuffer(mBuffer);
+ } catch (IllegalArgumentException | BufferOverflowException e) {
+ throw new IOException("Error writing to buffer: ", e);
+ }
+ }
+
+ /**
+ * Write a TCP header.
+ * The TCP header checksum is calculated and written back in #finalizePacket.
+ *
+ * @param srcPort source port
+ * @param dstPort destination port
+ * @param seq sequence number
+ * @param ack acknowledgement number
+ * @param tcpFlags tcp flags
+ * @param window window size
+ * @param urgentPointer urgent pointer
+ */
+ public void writeTcpHeader(short srcPort, short dstPort, short seq, short ack,
+ byte tcpFlags, short window, short urgentPointer) throws IOException {
+ mTcpHeaderOffset = mBuffer.position();
+ final TcpHeader tcpHeader = new TcpHeader(srcPort, dstPort, seq, ack,
+ (short) ((short) 0x5000 | ((byte) 0x3f & tcpFlags)) /* dataOffsetAndControlBits,
+ dataOffset is always 5(*4bytes) because options not supported */, window,
+ (short) 0 /* checksum, calculate in #finalizePacket */,
+ urgentPointer);
+
+ try {
+ tcpHeader.writeToByteBuffer(mBuffer);
+ } catch (IllegalArgumentException | BufferOverflowException e) {
+ throw new IOException("Error writing to buffer: ", e);
+ }
+ }
+
+ /**
+ * Finalize the packet.
+ *
+ * Call after writing L4 header (no payload) or payload to the buffer used by the builder.
+ * L3 header length, L3 header checksum and L4 header checksum are calculated and written back
+ * after finalization.
+ */
+ @NonNull
+ public ByteBuffer finalizePacket() throws IOException {
+ if (mIpv4HeaderOffset < 0) {
+ // TODO: add support for IPv6
+ throw new IOException("Packet is missing IPv4 header");
+ }
+
+ // Populate the IPv4 totalLength field.
+ mBuffer.putShort(mIpv4HeaderOffset + IPV4_LENGTH_OFFSET,
+ (short) (mBuffer.position() - mIpv4HeaderOffset));
+
+ // Populate the IPv4 header checksum field.
+ mBuffer.putShort(mIpv4HeaderOffset + IPV4_CHECKSUM_OFFSET,
+ ipChecksum(mBuffer, mIpv4HeaderOffset /* headerOffset */));
+
+ // Populate the TCP header checksum field.
+ if (mTcpHeaderOffset > 0) {
+ mBuffer.putShort(mTcpHeaderOffset + TCP_CHECKSUM_OFFSET, tcpChecksum(mBuffer,
+ mIpv4HeaderOffset /* ipOffset */, mTcpHeaderOffset /* transportOffset */,
+ mBuffer.position() - mTcpHeaderOffset /* transportLen */));
+ } else { // TODO: add support for UDP
+ throw new IOException("Packet is missing TCP header");
+ }
+
+ mBuffer.flip();
+ return mBuffer;
+ }
+
+ /**
+ * Allocate bytebuffer for building the packet.
+ *
+ * @param hasEther has ethernet header. Set this flag to indicate that the packet has an
+ * ethernet header.
+ * @param l3proto the layer 3 protocol. Only {@code IPPROTO_IP} currently supported.
+ * @param l4proto the layer 4 protocol. Only {@code IPPROTO_TCP} currently supported.
+ * @param payloadLen length of the payload.
+ */
+ @NonNull
+ public static ByteBuffer allocate(boolean hasEther, int l3proto, int l4proto, int payloadLen) {
+ if (l3proto != IPPROTO_IP) {
+ // TODO: add support for IPv6
+ throw new IllegalArgumentException("Unsupported layer 3 protocol " + l3proto);
+ }
+
+ if (l4proto != IPPROTO_TCP) {
+ // TODO: add support for UDP
+ throw new IllegalArgumentException("Unsupported layer 4 protocol " + l4proto);
+ }
+
+ if (payloadLen < 0) {
+ throw new IllegalArgumentException("Invalid payload length " + payloadLen);
+ }
+
+ int packetLen = 0;
+ if (hasEther) packetLen += Struct.getSize(EthernetHeader.class);
+ packetLen += Struct.getSize(Ipv4Header.class);
+ packetLen += Struct.getSize(TcpHeader.class);
+ packetLen += payloadLen;
+
+ return ByteBuffer.allocate(packetLen);
+ }
+}
diff --git a/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java b/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java
index f7151d7..378e485 100644
--- a/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java
+++ b/staticlibs/framework/com/android/net/module/util/NetworkStackConstants.java
@@ -89,9 +89,11 @@
public static final int IPV4_MAX_MTU = 65_535;
public static final int IPV4_HEADER_MIN_LEN = 20;
public static final int IPV4_IHL_MASK = 0xf;
+ public static final int IPV4_LENGTH_OFFSET = 2;
public static final int IPV4_FLAGS_OFFSET = 6;
public static final int IPV4_FRAGMENT_MASK = 0x1fff;
public static final int IPV4_PROTOCOL_OFFSET = 9;
+ public static final int IPV4_CHECKSUM_OFFSET = 10;
public static final int IPV4_SRC_ADDR_OFFSET = 12;
public static final int IPV4_DST_ADDR_OFFSET = 16;
public static final int IPV4_ADDR_LEN = 4;
@@ -164,6 +166,21 @@
public static final byte PIO_FLAG_AUTONOMOUS = (byte) (1 << 6);
/**
+ * TCP constants.
+ *
+ * See also:
+ * - https://tools.ietf.org/html/rfc793
+ */
+ public static final int TCP_HEADER_MIN_LEN = 20;
+ public static final int TCP_CHECKSUM_OFFSET = 16;
+ public static final byte TCPHDR_FIN = (byte) (1 << 0);
+ public static final byte TCPHDR_SYN = (byte) (1 << 1);
+ public static final byte TCPHDR_RST = (byte) (1 << 2);
+ public static final byte TCPHDR_PSH = (byte) (1 << 3);
+ public static final byte TCPHDR_ACK = (byte) (1 << 4);
+ public static final byte TCPHDR_URG = (byte) (1 << 5);
+
+ /**
* UDP constants.
*
* See also:
diff --git a/staticlibs/tests/unit/src/com/android/net/module/util/PacketBuilderTest.java b/staticlibs/tests/unit/src/com/android/net/module/util/PacketBuilderTest.java
new file mode 100644
index 0000000..275aa84
--- /dev/null
+++ b/staticlibs/tests/unit/src/com/android/net/module/util/PacketBuilderTest.java
@@ -0,0 +1,336 @@
+/*
+ * Copyright (C) 2021 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.net.module.util;
+
+import static android.system.OsConstants.IPPROTO_IP;
+import static android.system.OsConstants.IPPROTO_TCP;
+
+import static com.android.net.module.util.NetworkStackConstants.ETHER_TYPE_IPV4;
+import static com.android.net.module.util.NetworkStackConstants.IPV4_HEADER_MIN_LEN;
+import static com.android.net.module.util.NetworkStackConstants.TCPHDR_ACK;
+import static com.android.net.module.util.NetworkStackConstants.TCP_HEADER_MIN_LEN;
+import static com.android.testutils.MiscAsserts.assertThrows;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+
+import android.net.InetAddresses;
+import android.net.MacAddress;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import com.android.net.module.util.structs.EthernetHeader;
+import com.android.net.module.util.structs.Ipv4Header;
+import com.android.net.module.util.structs.TcpHeader;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.io.IOException;
+import java.net.Inet4Address;
+import java.nio.ByteBuffer;
+
+@RunWith(AndroidJUnit4.class)
+@SmallTest
+public class PacketBuilderTest {
+ private static final MacAddress SRC_MAC = MacAddress.fromString("11:22:33:44:55:66");
+ private static final MacAddress DST_MAC = MacAddress.fromString("aa:bb:cc:dd:ee:ff");
+ private static final Inet4Address IPV4_SRC_ADDR = addr("192.0.2.1");
+ private static final Inet4Address IPV4_DST_ADDR = addr("198.51.100.1");
+ private static final short SRC_PORT = 9876;
+ private static final short DST_PORT = 433;
+ private static final short SEQ_NO = 13579;
+ private static final short ACK_NO = 24680;
+ private static final byte TYPE_OF_SERVICE = 0;
+ private static final short ID = 27149;
+ private static final short FLAGS_AND_FRAGMENT_OFFSET = (short) 0x4000; // flags=DF, offset=0
+ private static final byte TIME_TO_LIVE = (byte) 0x40;
+ private static final short WINDOW = (short) 0x2000;
+ private static final short URGENT_POINTER = 0;
+ private static final ByteBuffer DATA = ByteBuffer.wrap(new byte[] {
+ (byte) 0xde, (byte) 0xad, (byte) 0xbe, (byte) 0xef
+ });
+
+ private static final byte[] TEST_PACKET_ETHERHDR_IPV4HDR_TCPHDR =
+ new byte[] {
+ // packet = (scapy.Ether(src="11:22:33:44:55:66", dst="aa:bb:cc:dd:ee:ff",
+ // type='IPv4') /
+ // scapy.IP(src="192.0.2.1", dst="198.51.100.1",
+ // tos=0, id=27149, flags='DF') /
+ // scapy.TCP(sport=9876, dport=433, seq=13579, ack=24680,
+ // flags='A', window=8192, urgptr=0))
+ // Ether header
+ (byte) 0xaa, (byte) 0xbb, (byte) 0xcc, (byte) 0xdd,
+ (byte) 0xee, (byte) 0xff, (byte) 0x11, (byte) 0x22,
+ (byte) 0x33, (byte) 0x44, (byte) 0x55, (byte) 0x66,
+ (byte) 0x08, (byte) 0x00,
+ // IPv4 header
+ (byte) 0x45, (byte) 0x00, (byte) 0x00, (byte) 0x28,
+ (byte) 0x6a, (byte) 0x0d, (byte) 0x40, (byte) 0x00,
+ (byte) 0x40, (byte) 0x06, (byte) 0xe4, (byte) 0x8c,
+ (byte) 0xc0, (byte) 0x00, (byte) 0x02, (byte) 0x01,
+ (byte) 0xc6, (byte) 0x33, (byte) 0x64, (byte) 0x01,
+ // TCP header
+ (byte) 0x26, (byte) 0x94, (byte) 0x01, (byte) 0xb1,
+ (byte) 0x00, (byte) 0x00, (byte) 0x35, (byte) 0x0b,
+ (byte) 0x00, (byte) 0x00, (byte) 0x60, (byte) 0x68,
+ (byte) 0x50, (byte) 0x10, (byte) 0x20, (byte) 0x00,
+ (byte) 0xe5, (byte) 0xe5, (byte) 0x00, (byte) 0x00
+ };
+
+ private static final byte[] TEST_PACKET_ETHERHDR_IPV4HDR_TCPHDR_DATA =
+ new byte[] {
+ // packet = (scapy.Ether(src="11:22:33:44:55:66", dst="aa:bb:cc:dd:ee:ff",
+ // type='IPv4') /
+ // scapy.IP(src="192.0.2.1", dst="198.51.100.1",
+ // tos=0, id=27149, flags='DF') /
+ // scapy.TCP(sport=9876, dport=433, seq=13579, ack=24680,
+ // flags='A', window=8192, urgptr=0) /
+ // b'\xde\xad\xbe\xef')
+ // Ether header
+ (byte) 0xaa, (byte) 0xbb, (byte) 0xcc, (byte) 0xdd,
+ (byte) 0xee, (byte) 0xff, (byte) 0x11, (byte) 0x22,
+ (byte) 0x33, (byte) 0x44, (byte) 0x55, (byte) 0x66,
+ (byte) 0x08, (byte) 0x00,
+ // IPv4 header
+ (byte) 0x45, (byte) 0x00, (byte) 0x00, (byte) 0x2c,
+ (byte) 0x6a, (byte) 0x0d, (byte) 0x40, (byte) 0x00,
+ (byte) 0x40, (byte) 0x06, (byte) 0xe4, (byte) 0x88,
+ (byte) 0xc0, (byte) 0x00, (byte) 0x02, (byte) 0x01,
+ (byte) 0xc6, (byte) 0x33, (byte) 0x64, (byte) 0x01,
+ // TCP header
+ (byte) 0x26, (byte) 0x94, (byte) 0x01, (byte) 0xb1,
+ (byte) 0x00, (byte) 0x00, (byte) 0x35, (byte) 0x0b,
+ (byte) 0x00, (byte) 0x00, (byte) 0x60, (byte) 0x68,
+ (byte) 0x50, (byte) 0x10, (byte) 0x20, (byte) 0x00,
+ (byte) 0x48, (byte) 0x44, (byte) 0x00, (byte) 0x00,
+ // Data
+ (byte) 0xde, (byte) 0xad, (byte) 0xbe, (byte) 0xef
+ };
+
+ private static final byte[] TEST_PACKET_IPV4HDR_TCPHDR =
+ new byte[] {
+ // packet = (scapy.IP(src="192.0.2.1", dst="198.51.100.1",
+ // tos=0, id=27149, flags='DF') /
+ // scapy.TCP(sport=9876, dport=433, seq=13579, ack=24680,
+ // flags='A', window=8192, urgptr=0))
+ // IPv4 header
+ (byte) 0x45, (byte) 0x00, (byte) 0x00, (byte) 0x28,
+ (byte) 0x6a, (byte) 0x0d, (byte) 0x40, (byte) 0x00,
+ (byte) 0x40, (byte) 0x06, (byte) 0xe4, (byte) 0x8c,
+ (byte) 0xc0, (byte) 0x00, (byte) 0x02, (byte) 0x01,
+ (byte) 0xc6, (byte) 0x33, (byte) 0x64, (byte) 0x01,
+ // TCP header
+ (byte) 0x26, (byte) 0x94, (byte) 0x01, (byte) 0xb1,
+ (byte) 0x00, (byte) 0x00, (byte) 0x35, (byte) 0x0b,
+ (byte) 0x00, (byte) 0x00, (byte) 0x60, (byte) 0x68,
+ (byte) 0x50, (byte) 0x10, (byte) 0x20, (byte) 0x00,
+ (byte) 0xe5, (byte) 0xe5, (byte) 0x00, (byte) 0x00
+ };
+
+ private static final byte[] TEST_PACKET_IPV4HDR_TCPHDR_DATA =
+ new byte[] {
+ // packet = (scapy.IP(src="192.0.2.1", dst="198.51.100.1",
+ // tos=0, id=27149, flags='DF') /
+ // scapy.TCP(sport=9876, dport=433, seq=13579, ack=24680,
+ // flags='A', window=8192, urgptr=0) /
+ // b'\xde\xad\xbe\xef')
+ // IPv4 header
+ (byte) 0x45, (byte) 0x00, (byte) 0x00, (byte) 0x2c,
+ (byte) 0x6a, (byte) 0x0d, (byte) 0x40, (byte) 0x00,
+ (byte) 0x40, (byte) 0x06, (byte) 0xe4, (byte) 0x88,
+ (byte) 0xc0, (byte) 0x00, (byte) 0x02, (byte) 0x01,
+ (byte) 0xc6, (byte) 0x33, (byte) 0x64, (byte) 0x01,
+ // TCP header
+ (byte) 0x26, (byte) 0x94, (byte) 0x01, (byte) 0xb1,
+ (byte) 0x00, (byte) 0x00, (byte) 0x35, (byte) 0x0b,
+ (byte) 0x00, (byte) 0x00, (byte) 0x60, (byte) 0x68,
+ (byte) 0x50, (byte) 0x10, (byte) 0x20, (byte) 0x00,
+ (byte) 0x48, (byte) 0x44, (byte) 0x00, (byte) 0x00,
+ // Data
+ (byte) 0xde, (byte) 0xad, (byte) 0xbe, (byte) 0xef
+ };
+
+ /**
+ * Build a TCPv4 packet which has ether header, IPv4 header, TCP header and data.
+ * The ethernet header and data are optional. Note that both source mac address and
+ * destination mac address are required for ethernet header.
+ *
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Layer 2 header (EthernetHeader) | (optional)
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Layer 3 header (Ipv4Header) |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Layer 4 header (TcpHeader) |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Payload | (optional)
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * @param srcMac source MAC address. used by L2 ether header.
+ * @param dstMac destination MAC address. used by L2 ether header.
+ * @param payload the payload.
+ */
+ @NonNull
+ private ByteBuffer buildTcpv4Packet(@Nullable final MacAddress srcMac,
+ @Nullable final MacAddress dstMac, @Nullable final ByteBuffer payload)
+ throws Exception {
+ final boolean hasEther = (srcMac != null && dstMac != null);
+ final int payloadLen = (payload == null) ? 0 : payload.limit();
+ final ByteBuffer buffer = PacketBuilder.allocate(hasEther, IPPROTO_IP, IPPROTO_TCP,
+ payloadLen);
+ final PacketBuilder packetBuilder = new PacketBuilder(buffer);
+
+ if (hasEther) packetBuilder.writeL2Header(srcMac, dstMac, (short) ETHER_TYPE_IPV4);
+ packetBuilder.writeIpv4Header(TYPE_OF_SERVICE, ID, FLAGS_AND_FRAGMENT_OFFSET,
+ TIME_TO_LIVE, (byte) IPPROTO_TCP, IPV4_SRC_ADDR, IPV4_DST_ADDR);
+ packetBuilder.writeTcpHeader(SRC_PORT, DST_PORT, SEQ_NO, ACK_NO,
+ TCPHDR_ACK, WINDOW, URGENT_POINTER);
+ if (payload != null) {
+ buffer.put(payload);
+ // in case data might be reused by caller, restore the position and
+ // limit of bytebuffer.
+ payload.clear();
+ }
+
+ return packetBuilder.finalizePacket();
+ }
+
+ private void checkEtherHeader(final ByteBuffer actual) {
+ final EthernetHeader eth = Struct.parse(EthernetHeader.class, actual);
+ assertEquals(SRC_MAC, eth.srcMac);
+ assertEquals(DST_MAC, eth.dstMac);
+ assertEquals(ETHER_TYPE_IPV4, eth.etherType);
+ }
+
+ private void checkIpv4Header(final boolean hasData, final ByteBuffer actual) {
+ final Ipv4Header ipv4Header = Struct.parse(Ipv4Header.class, actual);
+ assertEquals(Ipv4Header.IPHDR_VERSION_IHL, ipv4Header.vi);
+ assertEquals(TYPE_OF_SERVICE, ipv4Header.tos);
+ assertEquals(ID, ipv4Header.id);
+ assertEquals(FLAGS_AND_FRAGMENT_OFFSET, ipv4Header.flagsAndFragmentOffset);
+ assertEquals(TIME_TO_LIVE, ipv4Header.ttl);
+ assertEquals(IPV4_SRC_ADDR, ipv4Header.srcIp);
+ assertEquals(IPV4_DST_ADDR, ipv4Header.dstIp);
+
+ final int dataLength = hasData ? DATA.limit() : 0;
+ assertEquals(IPV4_HEADER_MIN_LEN + TCP_HEADER_MIN_LEN + dataLength,
+ ipv4Header.totalLength);
+ assertEquals((byte) IPPROTO_TCP, ipv4Header.protocol);
+ assertEquals(hasData ? (short) 0xe488 : (short) 0xe48c, ipv4Header.checksum);
+ }
+
+ private void checkTcpv4Packet(final boolean hasEther, final boolean hasData,
+ final ByteBuffer actual) {
+ if (hasEther) {
+ checkEtherHeader(actual);
+ }
+ checkIpv4Header(hasData, actual);
+
+ final TcpHeader tcpHeader = Struct.parse(TcpHeader.class, actual);
+ assertEquals(SRC_PORT, tcpHeader.srcPort);
+ assertEquals(DST_PORT, tcpHeader.dstPort);
+ assertEquals(SEQ_NO, tcpHeader.seq);
+ assertEquals(ACK_NO, tcpHeader.ack);
+ assertEquals((short) 0x5010 /* offset=5(*4bytes), control bits=ACK */,
+ tcpHeader.dataOffsetAndControlBits);
+ assertEquals(WINDOW, tcpHeader.window);
+ assertEquals(hasData ? (short) 0x4844 : (short) 0xe5e5, tcpHeader.checksum);
+ assertEquals(URGENT_POINTER, tcpHeader.urgentPointer);
+ }
+
+ @Test
+ public void testBuildPacketEtherIPv4Tcp() throws Exception {
+ final ByteBuffer packet = buildTcpv4Packet(SRC_MAC, DST_MAC, null /* data */);
+ checkTcpv4Packet(true /* hasEther */, false /* hasData */, packet);
+ assertArrayEquals(TEST_PACKET_ETHERHDR_IPV4HDR_TCPHDR, packet.array());
+ }
+
+ @Test
+ public void testBuildPacketEtherIPv4TcpData() throws Exception {
+ final ByteBuffer packet = buildTcpv4Packet(SRC_MAC, DST_MAC, DATA);
+ checkTcpv4Packet(true /* hasEther */, true /* hasData */, packet);
+ assertArrayEquals(TEST_PACKET_ETHERHDR_IPV4HDR_TCPHDR_DATA,
+ packet.array());
+ }
+
+ @Test
+ public void testBuildPacketIPv4Tcp() throws Exception {
+ final ByteBuffer packet = buildTcpv4Packet(null /* srcMac */, null /* dstMac */,
+ null /* data */);
+ checkTcpv4Packet(false /* hasEther */, false /* hasData */, packet);
+ assertArrayEquals(TEST_PACKET_IPV4HDR_TCPHDR, packet.array());
+ }
+
+ @Test
+ public void testBuildPacketIPv4TcpData() throws Exception {
+ final ByteBuffer packet = buildTcpv4Packet(null /* srcMac */, null /* dstMac */, DATA);
+ checkTcpv4Packet(false /* hasEther */, true /* hasData */, packet);
+ assertArrayEquals(TEST_PACKET_IPV4HDR_TCPHDR_DATA, packet.array());
+ }
+
+ @Test
+ public void testFinalizePacketWithoutIpv4Header() throws Exception {
+ final ByteBuffer buffer = PacketBuilder.allocate(false /* hasEther */, IPPROTO_IP,
+ IPPROTO_TCP, 0 /* payloadLen */);
+ final PacketBuilder packetBuilder = new PacketBuilder(buffer);
+ packetBuilder.writeTcpHeader(SRC_PORT, DST_PORT, SEQ_NO, ACK_NO,
+ TCPHDR_ACK, WINDOW, URGENT_POINTER);
+ assertThrows("java.io.IOException: Packet is missing IPv4 header", IOException.class,
+ () -> packetBuilder.finalizePacket());
+ }
+
+ @Test
+ public void testFinalizePacketWithoutTcpHeader() throws Exception {
+ final ByteBuffer buffer = PacketBuilder.allocate(false /* hasEther */, IPPROTO_IP,
+ IPPROTO_TCP, 0 /* payloadLen */);
+ final PacketBuilder packetBuilder = new PacketBuilder(buffer);
+ packetBuilder.writeIpv4Header(TYPE_OF_SERVICE, ID, FLAGS_AND_FRAGMENT_OFFSET,
+ TIME_TO_LIVE, (byte) IPPROTO_TCP, IPV4_SRC_ADDR, IPV4_DST_ADDR);
+ assertThrows("java.io.IOException: Packet is missing TCP headers", IOException.class,
+ () -> packetBuilder.finalizePacket());
+ }
+
+ @Test
+ public void testWriteL2HeaderToInsufficientBuffer() throws Exception {
+ final PacketBuilder packetBuilder = new PacketBuilder(ByteBuffer.allocate(1));
+ assertThrows(IOException.class,
+ () -> packetBuilder.writeL2Header(SRC_MAC, DST_MAC, (short) ETHER_TYPE_IPV4));
+ }
+
+ @Test
+ public void testWriteIpv4HeaderToInsufficientBuffer() throws Exception {
+ final PacketBuilder packetBuilder = new PacketBuilder(ByteBuffer.allocate(1));
+ assertThrows(IOException.class,
+ () -> packetBuilder.writeIpv4Header(TYPE_OF_SERVICE, ID, FLAGS_AND_FRAGMENT_OFFSET,
+ TIME_TO_LIVE, (byte) IPPROTO_TCP, IPV4_SRC_ADDR, IPV4_DST_ADDR));
+ }
+
+ @Test
+ public void testWriteTcpHeaderToInsufficientBuffer() throws Exception {
+ final PacketBuilder packetBuilder = new PacketBuilder(ByteBuffer.allocate(1));
+ assertThrows(IOException.class,
+ () -> packetBuilder.writeTcpHeader(SRC_PORT, DST_PORT, SEQ_NO, ACK_NO,
+ TCPHDR_ACK, WINDOW, URGENT_POINTER));
+ }
+
+ private static Inet4Address addr(String addr) {
+ return (Inet4Address) InetAddresses.parseNumericAddress(addr);
+ }
+}