Abandon reassembly of a packet if fragments overlap

However, receiving duplicated fragments will not cause reassembly to
fail. This is what Linux does too:
https://github.com/torvalds/linux/blob/38525c6/net/ipv4/inet_fragment.c#L355

PiperOrigin-RevId: 345309546

2 files changed, 99 insertions, 18 deletions

diff --git a/test/packetimpact/tests/ipv4_fragment_reassembly_test.go b/test/packetimpact/tests/ipv4_fragment_reassembly_test.go
index e00a7aba2..d2203082d 100644
--- a/test/packetimpact/tests/ipv4_fragment_reassembly_test.go
+++ b/test/packetimpact/tests/ipv4_fragment_reassembly_test.go
@@ -34,10 +34,10 @@ type fragmentInfo struct {
 	offset uint16
 	size   uint16
 	more   uint8
+	id     uint16
 }
 
 func TestIPv4FragmentReassembly(t *testing.T) {
-	const fragmentID = 42
 	icmpv4ProtoNum := uint8(header.ICMPv4ProtocolNumber)
 
 	tests := []struct {
@@ -45,28 +45,75 @@ func TestIPv4FragmentReassembly(t *testing.T) {
 		ipPayloadLen int
 		fragments    []fragmentInfo
 		expectReply  bool
+		skip         bool
+		skipReason   string
 	}{
 		{
 			description:  "basic reassembly",
-			ipPayloadLen: 2000,
+			ipPayloadLen: 3000,
 			fragments: []fragmentInfo{
-				{offset: 0, size: 1000, more: header.IPv4FlagMoreFragments},
-				{offset: 1000, size: 1000, more: 0},
+				{offset: 0, size: 1000, id: 5, more: header.IPv4FlagMoreFragments},
+				{offset: 1000, size: 1000, id: 5, more: header.IPv4FlagMoreFragments},
+				{offset: 2000, size: 1000, id: 5, more: 0},
 			},
 			expectReply: true,
 		},
 		{
 			description:  "out of order fragments",
-			ipPayloadLen: 2000,
+			ipPayloadLen: 3000,
 			fragments: []fragmentInfo{
-				{offset: 1000, size: 1000, more: 0},
-				{offset: 0, size: 1000, more: header.IPv4FlagMoreFragments},
+				{offset: 2000, size: 1000, id: 6, more: 0},
+				{offset: 0, size: 1000, id: 6, more: header.IPv4FlagMoreFragments},
+				{offset: 1000, size: 1000, id: 6, more: header.IPv4FlagMoreFragments},
 			},
 			expectReply: true,
 		},
+		{
+			description:  "duplicated fragments",
+			ipPayloadLen: 3000,
+			fragments: []fragmentInfo{
+				{offset: 0, size: 1000, id: 7, more: header.IPv4FlagMoreFragments},
+				{offset: 1000, size: 1000, id: 7, more: header.IPv4FlagMoreFragments},
+				{offset: 1000, size: 1000, id: 7, more: header.IPv4FlagMoreFragments},
+				{offset: 2000, size: 1000, id: 7, more: 0},
+			},
+			expectReply: true,
+			skip:        true,
+			skipReason:  "gvisor.dev/issues/4971",
+		},
+		{
+			description:  "fragment subset",
+			ipPayloadLen: 3000,
+			fragments: []fragmentInfo{
+				{offset: 0, size: 1000, id: 8, more: header.IPv4FlagMoreFragments},
+				{offset: 1000, size: 1000, id: 8, more: header.IPv4FlagMoreFragments},
+				{offset: 512, size: 256, id: 8, more: header.IPv4FlagMoreFragments},
+				{offset: 2000, size: 1000, id: 8, more: 0},
+			},
+			expectReply: true,
+			skip:        true,
+			skipReason:  "gvisor.dev/issues/4971",
+		},
+		{
+			description:  "fragment overlap",
+			ipPayloadLen: 3000,
+			fragments: []fragmentInfo{
+				{offset: 0, size: 1000, id: 9, more: header.IPv4FlagMoreFragments},
+				{offset: 1512, size: 1000, id: 9, more: header.IPv4FlagMoreFragments},
+				{offset: 1000, size: 1000, id: 9, more: header.IPv4FlagMoreFragments},
+				{offset: 2000, size: 1000, id: 9, more: 0},
+			},
+			expectReply: false,
+			skip:        true,
+			skipReason:  "gvisor.dev/issues/4971",
+		},
 	}
 
 	for _, test := range tests {
+		if test.skip {
+			t.Skip("%s test skipped: %s", test.description, test.skipReason)
+			continue
+		}
 		t.Run(test.description, func(t *testing.T) {
 			dut := testbench.NewDUT(t)
 			conn := dut.Net.NewIPv4Conn(t, testbench.IPv4{}, testbench.IPv4{})
@@ -95,7 +142,7 @@ func TestIPv4FragmentReassembly(t *testing.T) {
 						Protocol:       &icmpv4ProtoNum,
 						FragmentOffset: testbench.Uint16(fragment.offset),
 						Flags:          testbench.Uint8(fragment.more),
-						ID:             testbench.Uint16(fragmentID),
+						ID:             testbench.Uint16(fragment.id),
 					},
 					&testbench.Payload{
 						Bytes: data[fragment.offset:][:fragment.size],
@@ -114,7 +161,7 @@ func TestIPv4FragmentReassembly(t *testing.T) {
 				}, time.Second)
 				if err != nil {
 					// Either an unexpected frame was received, or none at all.
-					if bytesReceived < test.ipPayloadLen {
+					if test.expectReply && bytesReceived < test.ipPayloadLen {
 						t.Fatalf("received %d bytes out of %d, then conn.ExpectFrame(_, _, time.Second) failed with %s", bytesReceived, test.ipPayloadLen, err)
 					}
 					break
diff --git a/test/packetimpact/tests/ipv6_fragment_reassembly_test.go b/test/packetimpact/tests/ipv6_fragment_reassembly_test.go
index 65f742f55..dd98ee7a1 100644
--- a/test/packetimpact/tests/ipv6_fragment_reassembly_test.go
+++ b/test/packetimpact/tests/ipv6_fragment_reassembly_test.go
@@ -35,10 +35,10 @@ type fragmentInfo struct {
 	offset uint16
 	size   uint16
 	more   bool
+	id     uint32
 }
 
 func TestIPv6FragmentReassembly(t *testing.T) {
-	const fragmentID = 42
 	icmpv6ProtoNum := header.IPv6ExtensionHeaderIdentifier(header.ICMPv6ProtocolNumber)
 
 	tests := []struct {
@@ -49,10 +49,11 @@ func TestIPv6FragmentReassembly(t *testing.T) {
 	}{
 		{
 			description:  "basic reassembly",
-			ipPayloadLen: 1500,
+			ipPayloadLen: 3000,
 			fragments: []fragmentInfo{
-				{offset: 0, size: 760, more: true},
-				{offset: 760, size: 740, more: false},
+				{offset: 0, size: 1000, id: 100, more: true},
+				{offset: 1000, size: 1000, id: 100, more: true},
+				{offset: 2000, size: 1000, id: 100, more: false},
 			},
 			expectReply: true,
 		},
@@ -60,12 +61,45 @@ func TestIPv6FragmentReassembly(t *testing.T) {
 			description:  "out of order fragments",
 			ipPayloadLen: 3000,
 			fragments: []fragmentInfo{
-				{offset: 0, size: 1024, more: true},
-				{offset: 2048, size: 952, more: false},
-				{offset: 1024, size: 1024, more: true},
+				{offset: 0, size: 1000, id: 101, more: true},
+				{offset: 2000, size: 1000, id: 101, more: false},
+				{offset: 1000, size: 1000, id: 101, more: true},
+			},
+			expectReply: true,
+		},
+		{
+			description:  "duplicated fragments",
+			ipPayloadLen: 3000,
+			fragments: []fragmentInfo{
+				{offset: 0, size: 1000, id: 102, more: true},
+				{offset: 1000, size: 1000, id: 102, more: true},
+				{offset: 1000, size: 1000, id: 102, more: true},
+				{offset: 2000, size: 1000, id: 102, more: false},
+			},
+			expectReply: true,
+		},
+		{
+			description:  "fragment subset",
+			ipPayloadLen: 3000,
+			fragments: []fragmentInfo{
+				{offset: 0, size: 1000, id: 103, more: true},
+				{offset: 1000, size: 1000, id: 103, more: true},
+				{offset: 512, size: 256, id: 103, more: true},
+				{offset: 2000, size: 1000, id: 103, more: false},
 			},
 			expectReply: true,
 		},
+		{
+			description:  "fragment overlap",
+			ipPayloadLen: 3000,
+			fragments: []fragmentInfo{
+				{offset: 0, size: 1000, id: 104, more: true},
+				{offset: 1512, size: 1000, id: 104, more: true},
+				{offset: 1000, size: 1000, id: 104, more: true},
+				{offset: 2000, size: 1000, id: 104, more: false},
+			},
+			expectReply: false,
+		},
 	}
 
 	for _, test := range tests {
@@ -101,7 +135,7 @@ func TestIPv6FragmentReassembly(t *testing.T) {
 						NextHeader:     &icmpv6ProtoNum,
 						FragmentOffset: testbench.Uint16(fragment.offset / header.IPv6FragmentExtHdrFragmentOffsetBytesPerUnit),
 						MoreFragments:  testbench.Bool(fragment.more),
-						Identification: testbench.Uint32(fragmentID),
+						Identification: testbench.Uint32(fragment.id),
 					},
 					&testbench.Payload{
 						Bytes: data[fragment.offset:][:fragment.size],
@@ -118,7 +152,7 @@ func TestIPv6FragmentReassembly(t *testing.T) {
 				}, time.Second)
 				if err != nil {
 					// Either an unexpected frame was received, or none at all.
-					if bytesReceived < test.ipPayloadLen {
+					if test.expectReply && bytesReceived < test.ipPayloadLen {
 						t.Fatalf("received %d bytes out of %d, then conn.ExpectFrame(_, _, time.Second) failed with %s", bytesReceived, test.ipPayloadLen, err)
 					}
 					break