Added ipv6 checksum tests and fixed ipv6 + transport layer checksums

compscidr · Oct 15, 2024 · 35f9936 · 35f9936
1 parent 9b06c61
commit 35f9936
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Showing 2 changed files with 65 additions and 2 deletions.
diff --git a/knet/src/main/kotlin/com/jasonernst/knet/transport/TransportHeader.kt b/knet/src/main/kotlin/com/jasonernst/knet/transport/TransportHeader.kt
@@ -4,6 +4,7 @@ import com.jasonernst.icmp_common.Checksum
 import com.jasonernst.icmp_common.PacketHeaderException
 import com.jasonernst.knet.network.ip.IpHeader
 import com.jasonernst.knet.network.ip.v4.Ipv4Header
+import com.jasonernst.knet.network.ip.v6.Ipv6Header
 import com.jasonernst.knet.network.ip.v6.Ipv6Header.Companion.IP6_HEADER_SIZE
 import com.jasonernst.knet.network.nextheader.NextHeader
 import com.jasonernst.knet.transport.tcp.TcpHeader
@@ -48,9 +49,18 @@ interface TransportHeader : NextHeader {
             pseudoHeader.put(0)
             pseudoHeader.put(ipHeader.protocol.toByte())
             pseudoHeader.putShort(ipHeader.getPayloadLength().toShort())
-        } else {
+        } else if (ipHeader is Ipv6Header) {
+            val extensionHeaderLength = ipHeader.extensionHeaders.sumOf { it.getExtensionLengthInBytes() }
+            val tcpLength = ipHeader.getPayloadLength().toInt() - extensionHeaderLength
             // https://en.wikipedia.org/wiki/Transmission_Control_Protocol#TCP_checksum_for_IPv6
-            pseudoHeader = ByteBuffer.allocate(IP6_HEADER_SIZE.toInt())
+            pseudoHeader = ByteBuffer.allocate(IP6_HEADER_SIZE.toInt() + tcpLength)
+            pseudoHeader.put(ipHeader.sourceAddress.address)
+            pseudoHeader.put(ipHeader.destinationAddress.address)
+            pseudoHeader.putInt(tcpLength)
+            val nextHeader = (ipHeader.extensionHeaders.lastOrNull()?.nextHeader ?: ipHeader.protocol).toInt()
+            pseudoHeader.putInt(nextHeader)
+        } else {
+            throw IllegalArgumentException("Unknown IP header type")
         }
         val pseudoHeaderTransportStart = pseudoHeader.position()
         pseudoHeader.put(toByteArray())

diff --git a/knet/src/test/kotlin/com/jasonernst/knet/ChecksumTests.kt b/knet/src/test/kotlin/com/jasonernst/knet/ChecksumTests.kt
@@ -1,6 +1,7 @@
 package com.jasonernst.knet
 
 import com.jasonernst.icmp_common.PacketHeaderException
+import com.jasonernst.knet.datalink.EthernetHeader
 import com.jasonernst.knet.network.ip.IpHeader
 import com.jasonernst.knet.network.nextheader.NextHeader
 import com.jasonernst.knet.transport.TransportHeader
@@ -117,4 +118,56 @@ class ChecksumTests {
 
         udpHeader.computeChecksum(ipHeader, payload, true)
     }
+
+    @Test fun ipv6TcpBadChecksum() {
+        val filename = "/test_packets/ipv6_tcp_badchecksum.dump"
+        val resource =
+            javaClass.getResource(filename)
+                ?: throw FileNotFoundException("Could not find test dump: $filename")
+        val stream = TextFilePacketDumper.parseFile(resource.file, true)
+        logger.debug("Read buffer length: {}", stream.limit())
+
+        EthernetHeader.fromStream(stream)
+        val ipHeader = IpHeader.fromStream(stream)
+        logger.debug("IP Header: {}", ipHeader)
+        val nextHeader = NextHeader.fromStream(stream, ipHeader.protocol)
+        assertTrue(nextHeader is TransportHeader)
+        assertTrue(nextHeader is TcpHeader)
+        val tcpHeader = nextHeader as TcpHeader
+
+        // this may be a bad checksum because the length of the payload is truncated, so we'll
+        // do a min check to prevent buffer underflow
+        val remainingPayloadSize = min(stream.remaining(), ipHeader.getPayloadLength().toInt() - tcpHeader.getHeaderLength().toInt())
+        val payload = ByteArray(remainingPayloadSize)
+        stream.get(payload)
+
+        assertThrows<PacketHeaderException> {
+            tcpHeader.computeChecksum(ipHeader, payload, true)
+        }
+    }
+
+    @Test fun ipv6TcpGoodChecksum() {
+        val filename = "/test_packets/ipv6_tcp_goodchecksum.dump"
+        val resource =
+            javaClass.getResource(filename)
+                ?: throw FileNotFoundException("Could not find test dump: $filename")
+        val stream = TextFilePacketDumper.parseFile(resource.file, true)
+        logger.debug("Read buffer length: {}", stream.limit())
+
+        EthernetHeader.fromStream(stream)
+        val ipHeader = IpHeader.fromStream(stream)
+        logger.debug("IP Header: {}", ipHeader)
+        val nextHeader = NextHeader.fromStream(stream, ipHeader.protocol)
+        assertTrue(nextHeader is TransportHeader)
+        assertTrue(nextHeader is TcpHeader)
+        val tcpHeader = nextHeader as TcpHeader
+
+        // this may be a bad checksum because the length of the payload is truncated, so we'll
+        // do a min check to prevent buffer underflow
+        val remainingPayloadSize = min(stream.remaining(), ipHeader.getPayloadLength().toInt() - tcpHeader.getHeaderLength().toInt())
+        val payload = ByteArray(remainingPayloadSize)
+        stream.get(payload)
+
+        tcpHeader.computeChecksum(ipHeader, payload, true)
+    }
 }