Test IPv6 fragment reassembly

A packetimpact test for: "A node must be able to accept a fragmented packet
that, after reassembly, is as large as 1500 octets."

PiperOrigin-RevId: 321210729

2 files changed, 252 insertions, 38 deletions

diff --git a/test/packetimpact/testbench/layers.go b/test/packetimpact/testbench/layers.go
index 95bafa876..645f6c1a9 100644
--- a/test/packetimpact/testbench/layers.go
+++ b/test/packetimpact/testbench/layers.go
@@ -15,6 +15,7 @@
 package testbench
 
 import (
+	"encoding/binary"
 	"encoding/hex"
 	"fmt"
 	"reflect"
@@ -470,21 +471,11 @@ func (l *IPv6) ToBytes() ([]byte, error) {
 	if l.NextHeader != nil {
 		fields.NextHeader = *l.NextHeader
 	} else {
-		switch n := l.next().(type) {
-		case *TCP:
-			fields.NextHeader = uint8(header.TCPProtocolNumber)
-		case *UDP:
-			fields.NextHeader = uint8(header.UDPProtocolNumber)
-		case *ICMPv6:
-			fields.NextHeader = uint8(header.ICMPv6ProtocolNumber)
-		case *IPv6HopByHopOptionsExtHdr:
-			fields.NextHeader = uint8(header.IPv6HopByHopOptionsExtHdrIdentifier)
-		case *IPv6DestinationOptionsExtHdr:
-			fields.NextHeader = uint8(header.IPv6DestinationOptionsExtHdrIdentifier)
-		default:
-			// TODO(b/150301488): Support more protocols as needed.
-			return nil, fmt.Errorf("ToBytes can't deduce the IPv6 header's next protocol: %#v", n)
+		nh, err := nextHeaderByLayer(l.next())
+		if err != nil {
+			return nil, err
 		}
+		fields.NextHeader = nh
 	}
 	if l.HopLimit != nil {
 		fields.HopLimit = *l.HopLimit
@@ -514,6 +505,8 @@ func nextIPv6PayloadParser(nextHeader uint8) layerParser {
 		return parseIPv6HopByHopOptionsExtHdr
 	case header.IPv6DestinationOptionsExtHdrIdentifier:
 		return parseIPv6DestinationOptionsExtHdr
+	case header.IPv6FragmentExtHdrIdentifier:
+		return parseIPv6FragmentExtHdr
 	}
 	return parsePayload
 }
@@ -566,14 +559,56 @@ type IPv6DestinationOptionsExtHdr struct {
 	Options    []byte
 }
 
+// IPv6FragmentExtHdr can construct and match an IPv6 Fragment Extension Header.
+type IPv6FragmentExtHdr struct {
+	LayerBase
+	NextHeader     *header.IPv6ExtensionHeaderIdentifier
+	FragmentOffset *uint16
+	MoreFragments  *bool
+	Identification *uint32
+}
+
+// nextHeaderByLayer finds the correct next header protocol value for layer l.
+func nextHeaderByLayer(l Layer) (uint8, error) {
+	if l == nil {
+		return uint8(header.IPv6NoNextHeaderIdentifier), nil
+	}
+	switch l.(type) {
+	case *TCP:
+		return uint8(header.TCPProtocolNumber), nil
+	case *UDP:
+		return uint8(header.UDPProtocolNumber), nil
+	case *ICMPv6:
+		return uint8(header.ICMPv6ProtocolNumber), nil
+	case *Payload:
+		return uint8(header.IPv6NoNextHeaderIdentifier), nil
+	case *IPv6HopByHopOptionsExtHdr:
+		return uint8(header.IPv6HopByHopOptionsExtHdrIdentifier), nil
+	case *IPv6DestinationOptionsExtHdr:
+		return uint8(header.IPv6DestinationOptionsExtHdrIdentifier), nil
+	case *IPv6FragmentExtHdr:
+		return uint8(header.IPv6FragmentExtHdrIdentifier), nil
+	default:
+		// TODO(b/161005083): Support more protocols as needed.
+		return 0, fmt.Errorf("failed to deduce the IPv6 header's next protocol: %T", l)
+	}
+}
+
 // ipv6OptionsExtHdrToBytes serializes an options extension header into bytes.
-func ipv6OptionsExtHdrToBytes(nextHeader *header.IPv6ExtensionHeaderIdentifier, options []byte) []byte {
+func ipv6OptionsExtHdrToBytes(nextHeader *header.IPv6ExtensionHeaderIdentifier, nextLayer Layer, options []byte) ([]byte, error) {
 	length := len(options) + 2
+	if length%8 != 0 {
+		return nil, fmt.Errorf("IPv6 extension headers must be a multiple of 8 octets long, but the length given: %d, options: %s", length, hex.Dump(options))
+	}
 	bytes := make([]byte, length)
-	if nextHeader == nil {
-		bytes[0] = byte(header.IPv6NoNextHeaderIdentifier)
-	} else {
+	if nextHeader != nil {
 		bytes[0] = byte(*nextHeader)
+	} else {
+		nh, err := nextHeaderByLayer(nextLayer)
+		if err != nil {
+			return nil, err
+		}
+		bytes[0] = nh
 	}
 	// ExtHdrLen field is the length of the extension header
 	// in 8-octet unit, ignoring the first 8 octets.
@@ -581,7 +616,7 @@ func ipv6OptionsExtHdrToBytes(nextHeader *header.IPv6ExtensionHeaderIdentifier,
 	// https://tools.ietf.org/html/rfc2460#section-4.6
 	bytes[1] = uint8((length - 8) / 8)
 	copy(bytes[2:], options)
-	return bytes
+	return bytes, nil
 }
 
 // IPv6ExtHdrIdent is a helper routine that allocates a new
@@ -591,14 +626,45 @@ func IPv6ExtHdrIdent(id header.IPv6ExtensionHeaderIdentifier) *header.IPv6Extens
 	return &id
 }
 
-// ToBytes implements Layer.ToBytes
+// ToBytes implements Layer.ToBytes.
 func (l *IPv6HopByHopOptionsExtHdr) ToBytes() ([]byte, error) {
-	return ipv6OptionsExtHdrToBytes(l.NextHeader, l.Options), nil
+	return ipv6OptionsExtHdrToBytes(l.NextHeader, l.next(), l.Options)
 }
 
-// ToBytes implements Layer.ToBytes
+// ToBytes implements Layer.ToBytes.
 func (l *IPv6DestinationOptionsExtHdr) ToBytes() ([]byte, error) {
-	return ipv6OptionsExtHdrToBytes(l.NextHeader, l.Options), nil
+	return ipv6OptionsExtHdrToBytes(l.NextHeader, l.next(), l.Options)
+}
+
+// ToBytes implements Layer.ToBytes.
+func (l *IPv6FragmentExtHdr) ToBytes() ([]byte, error) {
+	var offset, mflag uint16
+	var ident uint32
+	bytes := make([]byte, header.IPv6FragmentExtHdrLength)
+	if l.NextHeader != nil {
+		bytes[0] = byte(*l.NextHeader)
+	} else {
+		nh, err := nextHeaderByLayer(l.next())
+		if err != nil {
+			return nil, err
+		}
+		bytes[0] = nh
+	}
+	bytes[1] = 0 // reserved
+	if l.MoreFragments != nil && *l.MoreFragments {
+		mflag = 1
+	}
+	if l.FragmentOffset != nil {
+		offset = *l.FragmentOffset
+	}
+	if l.Identification != nil {
+		ident = *l.Identification
+	}
+	offsetAndMflag := offset<<3 | mflag
+	binary.BigEndian.PutUint16(bytes[2:], offsetAndMflag)
+	binary.BigEndian.PutUint32(bytes[4:], ident)
+
+	return bytes, nil
 }
 
 // parseIPv6ExtHdr parses an IPv6 extension header and returns the NextHeader
@@ -631,6 +697,26 @@ func parseIPv6DestinationOptionsExtHdr(b []byte) (Layer, layerParser) {
 	return &IPv6DestinationOptionsExtHdr{NextHeader: &nextHeader, Options: options}, nextParser
 }
 
+// Bool is a helper routine that allocates a new
+// bool value to store v and returns a pointer to it.
+func Bool(v bool) *bool {
+	return &v
+}
+
+// parseIPv6FragmentExtHdr parses the bytes assuming that they start
+// with an IPv6 Fragment Extension Header.
+func parseIPv6FragmentExtHdr(b []byte) (Layer, layerParser) {
+	nextHeader := b[0]
+	var extHdr header.IPv6FragmentExtHdr
+	copy(extHdr[:], b[2:])
+	return &IPv6FragmentExtHdr{
+		NextHeader:     IPv6ExtHdrIdent(header.IPv6ExtensionHeaderIdentifier(nextHeader)),
+		FragmentOffset: Uint16(extHdr.FragmentOffset()),
+		MoreFragments:  Bool(extHdr.More()),
+		Identification: Uint32(extHdr.ID()),
+	}, nextIPv6PayloadParser(nextHeader)
+}
+
 func (l *IPv6HopByHopOptionsExtHdr) length() int {
 	return len(l.Options) + 2
 }
@@ -667,13 +753,31 @@ func (l *IPv6DestinationOptionsExtHdr) String() string {
 	return stringLayer(l)
 }
 
+func (*IPv6FragmentExtHdr) length() int {
+	return header.IPv6FragmentExtHdrLength
+}
+
+func (l *IPv6FragmentExtHdr) match(other Layer) bool {
+	return equalLayer(l, other)
+}
+
+// merge overrides the values in l with the values from other but only in fields
+// where the value is not nil.
+func (l *IPv6FragmentExtHdr) merge(other Layer) error {
+	return mergeLayer(l, other)
+}
+
+func (l *IPv6FragmentExtHdr) String() string {
+	return stringLayer(l)
+}
+
 // ICMPv6 can construct and match an ICMPv6 encapsulation.
 type ICMPv6 struct {
 	LayerBase
-	Type       *header.ICMPv6Type
-	Code       *byte
-	Checksum   *uint16
-	NDPPayload []byte
+	Type     *header.ICMPv6Type
+	Code     *byte
+	Checksum *uint16
+	Payload  []byte
 }
 
 func (l *ICMPv6) String() string {
@@ -684,7 +788,7 @@ func (l *ICMPv6) String() string {
 
 // ToBytes implements Layer.ToBytes.
 func (l *ICMPv6) ToBytes() ([]byte, error) {
-	b := make([]byte, header.ICMPv6HeaderSize+len(l.NDPPayload))
+	b := make([]byte, header.ICMPv6HeaderSize+len(l.Payload))
 	h := header.ICMPv6(b)
 	if l.Type != nil {
 		h.SetType(*l.Type)
@@ -692,7 +796,7 @@ func (l *ICMPv6) ToBytes() ([]byte, error) {
 	if l.Code != nil {
 		h.SetCode(*l.Code)
 	}
-	copy(h.NDPPayload(), l.NDPPayload)
+	copy(h.NDPPayload(), l.Payload)
 	if l.Checksum != nil {
 		h.SetChecksum(*l.Checksum)
 	} else {
@@ -725,10 +829,10 @@ func Byte(v byte) *byte {
 func parseICMPv6(b []byte) (Layer, layerParser) {
 	h := header.ICMPv6(b)
 	icmpv6 := ICMPv6{
-		Type:       ICMPv6Type(h.Type()),
-		Code:       Byte(h.Code()),
-		Checksum:   Uint16(h.Checksum()),
-		NDPPayload: h.NDPPayload(),
+		Type:     ICMPv6Type(h.Type()),
+		Code:     Byte(h.Code()),
+		Checksum: Uint16(h.Checksum()),
+		Payload:  h.NDPPayload(),
 	}
 	return &icmpv6, nil
 }
@@ -738,7 +842,7 @@ func (l *ICMPv6) match(other Layer) bool {
 }
 
 func (l *ICMPv6) length() int {
-	return header.ICMPv6HeaderSize + len(l.NDPPayload)
+	return header.ICMPv6HeaderSize + len(l.Payload)
 }
 
 // merge overrides the values in l with the values from other but only in fields
diff --git a/test/packetimpact/testbench/layers_test.go b/test/packetimpact/testbench/layers_test.go
index 382a983a1..a2a763034 100644
--- a/test/packetimpact/testbench/layers_test.go
+++ b/test/packetimpact/testbench/layers_test.go
@@ -593,10 +593,107 @@ func TestIPv6ExtHdrOptions(t *testing.T) {
 					Options:    []byte{0x05, 0x02, 0x00, 0x00, 0x01, 0x00},
 				},
 				&ICMPv6{
-					Type:       ICMPv6Type(header.ICMPv6ParamProblem),
-					Code:       Byte(0),
-					Checksum:   Uint16(0x5f98),
-					NDPPayload: []byte{0x00, 0x00, 0x00, 0x06},
+					Type:     ICMPv6Type(header.ICMPv6ParamProblem),
+					Code:     Byte(0),
+					Checksum: Uint16(0x5f98),
+					Payload:  []byte{0x00, 0x00, 0x00, 0x06},
+				},
+			},
+		},
+		{
+			description: "IPv6/HopByHop/Fragment",
+			wantBytes: []byte{
+				// IPv6 Header
+				0x60, 0x00, 0x00, 0x00, 0x00, 0x10, 0x00, 0x40, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x01, 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xde, 0xad, 0xbe, 0xef,
+				// HopByHop Options
+				0x2c, 0x00, 0x05, 0x02, 0x00, 0x00, 0x01, 0x00,
+				// Fragment ExtHdr
+				0x3b, 0x00, 0x03, 0x20, 0x00, 0x00, 0x00, 0x2a,
+			},
+			wantLayers: []Layer{
+				&IPv6{
+					SrcAddr: Address(tcpip.Address(net.ParseIP("::1"))),
+					DstAddr: Address(tcpip.Address(net.ParseIP("fe80::dead:beef"))),
+				},
+				&IPv6HopByHopOptionsExtHdr{
+					NextHeader: IPv6ExtHdrIdent(header.IPv6FragmentExtHdrIdentifier),
+					Options:    []byte{0x05, 0x02, 0x00, 0x00, 0x01, 0x00},
+				},
+				&IPv6FragmentExtHdr{
+					NextHeader:     IPv6ExtHdrIdent(header.IPv6NoNextHeaderIdentifier),
+					FragmentOffset: Uint16(100),
+					MoreFragments:  Bool(false),
+					Identification: Uint32(42),
+				},
+				&Payload{
+					Bytes: nil,
+				},
+			},
+		},
+		{
+			description: "IPv6/DestOpt/Fragment/Payload",
+			wantBytes: []byte{
+				// IPv6 Header
+				0x60, 0x00, 0x00, 0x00, 0x00, 0x1b, 0x3c, 0x40, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x01, 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xde, 0xad, 0xbe, 0xef,
+				// Destination Options
+				0x2c, 0x00, 0x05, 0x02, 0x00, 0x00, 0x01, 0x00,
+				// Fragment ExtHdr
+				0x3b, 0x00, 0x03, 0x21, 0x00, 0x00, 0x00, 0x2a,
+				// Sample Data
+				0x53, 0x61, 0x6d, 0x70, 0x6c, 0x65, 0x20, 0x44, 0x61, 0x74, 0x61,
+			},
+			wantLayers: []Layer{
+				&IPv6{
+					SrcAddr: Address(tcpip.Address(net.ParseIP("::1"))),
+					DstAddr: Address(tcpip.Address(net.ParseIP("fe80::dead:beef"))),
+				},
+				&IPv6DestinationOptionsExtHdr{
+					NextHeader: IPv6ExtHdrIdent(header.IPv6FragmentExtHdrIdentifier),
+					Options:    []byte{0x05, 0x02, 0x00, 0x00, 0x01, 0x00},
+				},
+				&IPv6FragmentExtHdr{
+					NextHeader:     IPv6ExtHdrIdent(header.IPv6NoNextHeaderIdentifier),
+					FragmentOffset: Uint16(100),
+					MoreFragments:  Bool(true),
+					Identification: Uint32(42),
+				},
+				&Payload{
+					Bytes: []byte("Sample Data"),
+				},
+			},
+		},
+		{
+			description: "IPv6/Fragment/Payload",
+			wantBytes: []byte{
+				// IPv6 Header
+				0x60, 0x00, 0x00, 0x00, 0x00, 0x13, 0x2c, 0x40, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x01, 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xde, 0xad, 0xbe, 0xef,
+				// Fragment ExtHdr
+				0x3b, 0x00, 0x03, 0x21, 0x00, 0x00, 0x00, 0x2a,
+				// Sample Data
+				0x53, 0x61, 0x6d, 0x70, 0x6c, 0x65, 0x20, 0x44, 0x61, 0x74, 0x61,
+			},
+			wantLayers: []Layer{
+				&IPv6{
+					SrcAddr: Address(tcpip.Address(net.ParseIP("::1"))),
+					DstAddr: Address(tcpip.Address(net.ParseIP("fe80::dead:beef"))),
+				},
+				&IPv6FragmentExtHdr{
+					NextHeader:     IPv6ExtHdrIdent(header.IPv6NoNextHeaderIdentifier),
+					FragmentOffset: Uint16(100),
+					MoreFragments:  Bool(true),
+					Identification: Uint32(42),
+				},
+				&Payload{
+					Bytes: []byte("Sample Data"),
 				},
 			},
 		},
@@ -606,6 +703,19 @@ func TestIPv6ExtHdrOptions(t *testing.T) {
 			if !layers.match(tt.wantLayers) {
 				t.Fatalf("match failed with diff: %s", layers.diff(tt.wantLayers))
 			}
+			// Make sure we can generate correct next header values and checksums
+			for _, layer := range layers {
+				switch layer := layer.(type) {
+				case *IPv6HopByHopOptionsExtHdr:
+					layer.NextHeader = nil
+				case *IPv6DestinationOptionsExtHdr:
+					layer.NextHeader = nil
+				case *IPv6FragmentExtHdr:
+					layer.NextHeader = nil
+				case *ICMPv6:
+					layer.Checksum = nil
+				}
+			}
 			gotBytes, err := layers.ToBytes()
 			if err != nil {
 				t.Fatalf("ToBytes() failed on %s: %s", &layers, err)