Additions to ICMP and IPv4 parsers

Teach ICMP.Parser/ToBytes to handle some non echo ICMP packets.
Teach IPv4.Parser that fragments only have a payload, not an upper layer.
Fix IPv4 and IPv6 reassembly tests to handle the change.

Fixes #4758

PiperOrigin-RevId: 341549665

2 files changed, 7 insertions, 5 deletions

diff --git a/test/packetimpact/tests/ipv4_fragment_reassembly_test.go b/test/packetimpact/tests/ipv4_fragment_reassembly_test.go
index 65c0df140..40f899065 100644
--- a/test/packetimpact/tests/ipv4_fragment_reassembly_test.go
+++ b/test/packetimpact/tests/ipv4_fragment_reassembly_test.go
@@ -105,11 +105,13 @@ func TestIPv4FragmentReassembly(t *testing.T) {
 
 			var bytesReceived int
 			reassembledPayload := make([]byte, test.ipPayloadLen)
+			// We are sending a packet fragmented into smaller parts but the
+			// response may also be large enough to require fragmentation.
+			// Therefore we only look for payload for an IPv4 packet not ICMP.
 			for {
 				incomingFrame, err := conn.ExpectFrame(t, testbench.Layers{
 					&testbench.Ether{},
 					&testbench.IPv4{},
-					&testbench.ICMPv4{},
 				}, time.Second)
 				if err != nil {
 					// Either an unexpected frame was received, or none at all.
@@ -121,9 +123,10 @@ func TestIPv4FragmentReassembly(t *testing.T) {
 				if !test.expectReply {
 					t.Fatalf("unexpected reply received:\n%s", incomingFrame)
 				}
-				ipPayload, err := incomingFrame[2 /* ICMPv4 */].ToBytes()
+				// We only asked for Ethernet and IPv4 so the rest should be payload.
+				ipPayload, err := incomingFrame[2 /* Payload */].ToBytes()
 				if err != nil {
-					t.Fatalf("failed to parse ICMPv4 header: incomingPacket[2].ToBytes() = (_, %s)", err)
+					t.Fatalf("failed to parse payload: incomingPacket[2].ToBytes() = (_, %s)", err)
 				}
 				offset := *incomingFrame[1 /* IPv4 */].(*testbench.IPv4).FragmentOffset
 				if copied := copy(reassembledPayload[offset:], ipPayload); copied != len(ipPayload) {
diff --git a/test/packetimpact/tests/ipv6_fragment_reassembly_test.go b/test/packetimpact/tests/ipv6_fragment_reassembly_test.go
index 4a29de688..eb56a53f7 100644
--- a/test/packetimpact/tests/ipv6_fragment_reassembly_test.go
+++ b/test/packetimpact/tests/ipv6_fragment_reassembly_test.go
@@ -117,7 +117,6 @@ func TestIPv6FragmentReassembly(t *testing.T) {
 					&testbench.Ether{},
 					&testbench.IPv6{},
 					&testbench.IPv6FragmentExtHdr{},
-					&testbench.ICMPv6{},
 				}, time.Second)
 				if err != nil {
 					// Either an unexpected frame was received, or none at all.
@@ -129,7 +128,7 @@ func TestIPv6FragmentReassembly(t *testing.T) {
 				if !test.expectReply {
 					t.Fatalf("unexpected reply received:\n%s", incomingFrame)
 				}
-				ipPayload, err := incomingFrame[3 /* ICMPv6 */].ToBytes()
+				ipPayload, err := incomingFrame[3 /* Payload */].ToBytes()
 				if err != nil {
 					t.Fatalf("failed to parse ICMPv6 header: incomingPacket[3].ToBytes() = (_, %s)", err)
 				}