// Copyright 2020 The gVisor Authors.
//
// 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 testbench

import (
	"bytes"
	"net"
	"testing"

	"github.com/mohae/deepcopy"
	"gvisor.dev/gvisor/pkg/tcpip"
	"gvisor.dev/gvisor/pkg/tcpip/header"
)

func TestLayerMatch(t *testing.T) {
	var nilPayload *Payload
	noPayload := &Payload{}
	emptyPayload := &Payload{Bytes: []byte{}}
	fullPayload := &Payload{Bytes: []byte{1, 2, 3}}
	emptyTCP := &TCP{SrcPort: Uint16(1234), LayerBase: LayerBase{nextLayer: emptyPayload}}
	fullTCP := &TCP{SrcPort: Uint16(1234), LayerBase: LayerBase{nextLayer: fullPayload}}
	for _, tt := range []struct {
		a, b Layer
		want bool
	}{
		{nilPayload, nilPayload, true},
		{nilPayload, noPayload, true},
		{nilPayload, emptyPayload, true},
		{nilPayload, fullPayload, true},
		{noPayload, noPayload, true},
		{noPayload, emptyPayload, true},
		{noPayload, fullPayload, true},
		{emptyPayload, emptyPayload, true},
		{emptyPayload, fullPayload, false},
		{fullPayload, fullPayload, true},
		{emptyTCP, fullTCP, true},
	} {
		if got := tt.a.match(tt.b); got != tt.want {
			t.Errorf("%s.match(%s) = %t, want %t", tt.a, tt.b, got, tt.want)
		}
		if got := tt.b.match(tt.a); got != tt.want {
			t.Errorf("%s.match(%s) = %t, want %t", tt.b, tt.a, got, tt.want)
		}
	}
}

func TestLayerMergeMismatch(t *testing.T) {
	tcp := &TCP{}
	otherTCP := &TCP{}
	ipv4 := &IPv4{}
	ether := &Ether{}
	for _, tt := range []struct {
		a, b    Layer
		success bool
	}{
		{tcp, tcp, true},
		{tcp, otherTCP, true},
		{tcp, ipv4, false},
		{tcp, ether, false},
		{tcp, nil, true},

		{otherTCP, otherTCP, true},
		{otherTCP, ipv4, false},
		{otherTCP, ether, false},
		{otherTCP, nil, true},

		{ipv4, ipv4, true},
		{ipv4, ether, false},
		{ipv4, nil, true},

		{ether, ether, true},
		{ether, nil, true},
	} {
		if err := tt.a.merge(tt.b); (err == nil) != tt.success {
			t.Errorf("%s.merge(%s) got %s, wanted the opposite", tt.a, tt.b, err)
		}
		if tt.b != nil {
			if err := tt.b.merge(tt.a); (err == nil) != tt.success {
				t.Errorf("%s.merge(%s) got %s, wanted the opposite", tt.b, tt.a, err)
			}
		}
	}
}

func TestLayerMerge(t *testing.T) {
	zero := Uint32(0)
	one := Uint32(1)
	two := Uint32(2)
	empty := []byte{}
	foo := []byte("foo")
	bar := []byte("bar")
	for _, tt := range []struct {
		a, b Layer
		want Layer
	}{
		{&TCP{AckNum: nil}, &TCP{AckNum: nil}, &TCP{AckNum: nil}},
		{&TCP{AckNum: nil}, &TCP{AckNum: zero}, &TCP{AckNum: zero}},
		{&TCP{AckNum: nil}, &TCP{AckNum: one}, &TCP{AckNum: one}},
		{&TCP{AckNum: nil}, &TCP{AckNum: two}, &TCP{AckNum: two}},
		{&TCP{AckNum: nil}, nil, &TCP{AckNum: nil}},

		{&TCP{AckNum: zero}, &TCP{AckNum: nil}, &TCP{AckNum: zero}},
		{&TCP{AckNum: zero}, &TCP{AckNum: zero}, &TCP{AckNum: zero}},
		{&TCP{AckNum: zero}, &TCP{AckNum: one}, &TCP{AckNum: one}},
		{&TCP{AckNum: zero}, &TCP{AckNum: two}, &TCP{AckNum: two}},
		{&TCP{AckNum: zero}, nil, &TCP{AckNum: zero}},

		{&TCP{AckNum: one}, &TCP{AckNum: nil}, &TCP{AckNum: one}},
		{&TCP{AckNum: one}, &TCP{AckNum: zero}, &TCP{AckNum: zero}},
		{&TCP{AckNum: one}, &TCP{AckNum: one}, &TCP{AckNum: one}},
		{&TCP{AckNum: one}, &TCP{AckNum: two}, &TCP{AckNum: two}},
		{&TCP{AckNum: one}, nil, &TCP{AckNum: one}},

		{&TCP{AckNum: two}, &TCP{AckNum: nil}, &TCP{AckNum: two}},
		{&TCP{AckNum: two}, &TCP{AckNum: zero}, &TCP{AckNum: zero}},
		{&TCP{AckNum: two}, &TCP{AckNum: one}, &TCP{AckNum: one}},
		{&TCP{AckNum: two}, &TCP{AckNum: two}, &TCP{AckNum: two}},
		{&TCP{AckNum: two}, nil, &TCP{AckNum: two}},

		{&Payload{Bytes: nil}, &Payload{Bytes: nil}, &Payload{Bytes: nil}},
		{&Payload{Bytes: nil}, &Payload{Bytes: empty}, &Payload{Bytes: empty}},
		{&Payload{Bytes: nil}, &Payload{Bytes: foo}, &Payload{Bytes: foo}},
		{&Payload{Bytes: nil}, &Payload{Bytes: bar}, &Payload{Bytes: bar}},
		{&Payload{Bytes: nil}, nil, &Payload{Bytes: nil}},

		{&Payload{Bytes: empty}, &Payload{Bytes: nil}, &Payload{Bytes: empty}},
		{&Payload{Bytes: empty}, &Payload{Bytes: empty}, &Payload{Bytes: empty}},
		{&Payload{Bytes: empty}, &Payload{Bytes: foo}, &Payload{Bytes: foo}},
		{&Payload{Bytes: empty}, &Payload{Bytes: bar}, &Payload{Bytes: bar}},
		{&Payload{Bytes: empty}, nil, &Payload{Bytes: empty}},

		{&Payload{Bytes: foo}, &Payload{Bytes: nil}, &Payload{Bytes: foo}},
		{&Payload{Bytes: foo}, &Payload{Bytes: empty}, &Payload{Bytes: empty}},
		{&Payload{Bytes: foo}, &Payload{Bytes: foo}, &Payload{Bytes: foo}},
		{&Payload{Bytes: foo}, &Payload{Bytes: bar}, &Payload{Bytes: bar}},
		{&Payload{Bytes: foo}, nil, &Payload{Bytes: foo}},

		{&Payload{Bytes: bar}, &Payload{Bytes: nil}, &Payload{Bytes: bar}},
		{&Payload{Bytes: bar}, &Payload{Bytes: empty}, &Payload{Bytes: empty}},
		{&Payload{Bytes: bar}, &Payload{Bytes: foo}, &Payload{Bytes: foo}},
		{&Payload{Bytes: bar}, &Payload{Bytes: bar}, &Payload{Bytes: bar}},
		{&Payload{Bytes: bar}, nil, &Payload{Bytes: bar}},
	} {
		a := deepcopy.Copy(tt.a).(Layer)
		if err := a.merge(tt.b); err != nil {
			t.Errorf("%s.merge(%s) = %s, wanted nil", tt.a, tt.b, err)
			continue
		}
		if a.String() != tt.want.String() {
			t.Errorf("%s.merge(%s) merge result got %s, want %s", tt.a, tt.b, a, tt.want)
		}
	}
}

func TestLayerStringFormat(t *testing.T) {
	for _, tt := range []struct {
		name string
		l    Layer
		want string
	}{
		{
			name: "TCP",
			l: &TCP{
				SrcPort:    Uint16(34785),
				DstPort:    Uint16(47767),
				SeqNum:     Uint32(3452155723),
				AckNum:     Uint32(2596996163),
				DataOffset: Uint8(5),
				Flags:      Uint8(20),
				WindowSize: Uint16(64240),
				Checksum:   Uint16(0x2e2b),
			},
			want: "&testbench.TCP{" +
				"SrcPort:34785 " +
				"DstPort:47767 " +
				"SeqNum:3452155723 " +
				"AckNum:2596996163 " +
				"DataOffset:5 " +
				"Flags:20 " +
				"WindowSize:64240 " +
				"Checksum:11819" +
				"}",
		},
		{
			name: "UDP",
			l: &UDP{
				SrcPort: Uint16(34785),
				DstPort: Uint16(47767),
				Length:  Uint16(12),
			},
			want: "&testbench.UDP{" +
				"SrcPort:34785 " +
				"DstPort:47767 " +
				"Length:12" +
				"}",
		},
		{
			name: "IPv4",
			l: &IPv4{
				IHL:            Uint8(5),
				TOS:            Uint8(0),
				TotalLength:    Uint16(44),
				ID:             Uint16(0),
				Flags:          Uint8(2),
				FragmentOffset: Uint16(0),
				TTL:            Uint8(64),
				Protocol:       Uint8(6),
				Checksum:       Uint16(0x2e2b),
				SrcAddr:        Address(tcpip.Address([]byte{197, 34, 63, 10})),
				DstAddr:        Address(tcpip.Address([]byte{197, 34, 63, 20})),
			},
			want: "&testbench.IPv4{" +
				"IHL:5 " +
				"TOS:0 " +
				"TotalLength:44 " +
				"ID:0 " +
				"Flags:2 " +
				"FragmentOffset:0 " +
				"TTL:64 " +
				"Protocol:6 " +
				"Checksum:11819 " +
				"SrcAddr:197.34.63.10 " +
				"DstAddr:197.34.63.20" +
				"}",
		},
		{
			name: "Ether",
			l: &Ether{
				SrcAddr: LinkAddress(tcpip.LinkAddress([]byte{0x02, 0x42, 0xc5, 0x22, 0x3f, 0x0a})),
				DstAddr: LinkAddress(tcpip.LinkAddress([]byte{0x02, 0x42, 0xc5, 0x22, 0x3f, 0x14})),
				Type:    NetworkProtocolNumber(4),
			},
			want: "&testbench.Ether{" +
				"SrcAddr:02:42:c5:22:3f:0a " +
				"DstAddr:02:42:c5:22:3f:14 " +
				"Type:4" +
				"}",
		},
		{
			name: "Payload",
			l: &Payload{
				Bytes: []byte("Hooray for packetimpact."),
			},
			want: "&testbench.Payload{Bytes:\n" +
				"00000000  48 6f 6f 72 61 79 20 66  6f 72 20 70 61 63 6b 65  |Hooray for packe|\n" +
				"00000010  74 69 6d 70 61 63 74 2e                           |timpact.|\n" +
				"}",
		},
	} {
		t.Run(tt.name, func(t *testing.T) {
			if got := tt.l.String(); got != tt.want {
				t.Errorf("%s.String() = %s, want: %s", tt.name, got, tt.want)
			}
		})
	}
}

func TestConnectionMatch(t *testing.T) {
	conn := Connection{
		layerStates: []layerState{&etherState{}},
	}
	protoNum0 := tcpip.NetworkProtocolNumber(0)
	protoNum1 := tcpip.NetworkProtocolNumber(1)
	for _, tt := range []struct {
		description        string
		override, received Layers
		wantMatch          bool
	}{
		{
			description: "shorter override",
			override:    []Layer{&Ether{}},
			received:    []Layer{&Ether{}, &Payload{Bytes: []byte("hello")}},
			wantMatch:   true,
		},
		{
			description: "longer override",
			override:    []Layer{&Ether{}, &Payload{Bytes: []byte("hello")}},
			received:    []Layer{&Ether{}},
			wantMatch:   false,
		},
		{
			description: "ether layer mismatch",
			override:    []Layer{&Ether{Type: &protoNum0}},
			received:    []Layer{&Ether{Type: &protoNum1}},
			wantMatch:   false,
		},
		{
			description: "both nil",
			override:    nil,
			received:    nil,
			wantMatch:   false,
		},
		{
			description: "nil override",
			override:    nil,
			received:    []Layer{&Ether{}},
			wantMatch:   true,
		},
	} {
		t.Run(tt.description, func(t *testing.T) {
			if gotMatch := conn.match(tt.override, tt.received); gotMatch != tt.wantMatch {
				t.Fatalf("conn.match(%s, %s) = %t, want %t", tt.override, tt.received, gotMatch, tt.wantMatch)
			}
		})
	}
}

func TestLayersDiff(t *testing.T) {
	for _, tt := range []struct {
		x, y Layers
		want string
	}{
		{
			Layers{&Ether{Type: NetworkProtocolNumber(12)}, &TCP{DataOffset: Uint8(5), SeqNum: Uint32(5)}},
			Layers{&Ether{Type: NetworkProtocolNumber(13)}, &TCP{DataOffset: Uint8(7), SeqNum: Uint32(6)}},
			"Ether:       Type: 12 13\n" +
				"  TCP:     SeqNum:  5  6\n" +
				"       DataOffset:  5  7\n",
		},
		{
			Layers{&Ether{Type: NetworkProtocolNumber(12)}, &UDP{SrcPort: Uint16(123)}},
			Layers{&Ether{Type: NetworkProtocolNumber(13)}, &TCP{DataOffset: Uint8(7), SeqNum: Uint32(6)}},
			"Ether:       Type:  12 13\n" +
				"(UDP doesn't match TCP)\n" +
				"  UDP:    SrcPort: 123   \n" +
				"  TCP:     SeqNum:      6\n" +
				"       DataOffset:      7\n",
		},
		{
			Layers{&UDP{SrcPort: Uint16(123)}},
			Layers{&Ether{Type: NetworkProtocolNumber(13)}, &TCP{DataOffset: Uint8(7), SeqNum: Uint32(6)}},
			"(UDP doesn't match Ether)\n" +
				"  UDP: SrcPort: 123   \n" +
				"Ether:    Type:     13\n" +
				"(missing matches TCP)\n",
		},
		{
			Layers{nil, &UDP{SrcPort: Uint16(123)}},
			Layers{&Ether{Type: NetworkProtocolNumber(13)}, &TCP{DataOffset: Uint8(7), SeqNum: Uint32(6)}},
			"(nil matches Ether)\n" +
				"(UDP doesn't match TCP)\n" +
				"UDP:    SrcPort: 123  \n" +
				"TCP:     SeqNum:     6\n" +
				"     DataOffset:     7\n",
		},
		{
			Layers{&Ether{Type: NetworkProtocolNumber(13)}, &IPv4{IHL: Uint8(4)}, &TCP{DataOffset: Uint8(7), SeqNum: Uint32(6)}},
			Layers{&Ether{Type: NetworkProtocolNumber(13)}, &IPv4{IHL: Uint8(6)}, &TCP{DataOffset: Uint8(7), SeqNum: Uint32(6)}},
			"(Ether matches Ether)\n" +
				"IPv4: IHL: 4 6\n" +
				"(TCP matches TCP)\n",
		},
		{
			Layers{&Payload{Bytes: []byte("foo")}},
			Layers{&Payload{Bytes: []byte("bar")}},
			"Payload: Bytes: [102 111 111] [98 97 114]\n",
		},
		{
			Layers{&Payload{Bytes: []byte("")}},
			Layers{&Payload{}},
			"",
		},
		{
			Layers{&Payload{Bytes: []byte("")}},
			Layers{&Payload{Bytes: []byte("")}},
			"",
		},
		{
			Layers{&UDP{}},
			Layers{&TCP{}},
			"(UDP doesn't match TCP)\n" +
				"(UDP)\n" +
				"(TCP)\n",
		},
	} {
		if got := tt.x.diff(tt.y); got != tt.want {
			t.Errorf("%s.diff(%s) = %q, want %q", tt.x, tt.y, got, tt.want)
		}
		if tt.x.match(tt.y) != (tt.x.diff(tt.y) == "") {
			t.Errorf("match and diff of %s and %s disagree", tt.x, tt.y)
		}
		if tt.y.match(tt.x) != (tt.y.diff(tt.x) == "") {
			t.Errorf("match and diff of %s and %s disagree", tt.y, tt.x)
		}
	}
}

func TestTCPOptions(t *testing.T) {
	for _, tt := range []struct {
		description string
		wantBytes   []byte
		wantLayers  Layers
	}{
		{
			description: "without payload",
			wantBytes: []byte{
				// IPv4 Header
				0x45, 0x00, 0x00, 0x2c, 0x00, 0x01, 0x00, 0x00, 0x40, 0x06,
				0xf9, 0x77, 0xc0, 0xa8, 0x00, 0x02, 0xc0, 0xa8, 0x00, 0x01,
				// TCP Header
				0x30, 0x39, 0xd4, 0x31, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
				0x00, 0x00, 0x60, 0x02, 0x20, 0x00, 0xf5, 0x1c, 0x00, 0x00,
				// WindowScale Option
				0x03, 0x03, 0x02,
				// NOP Option
				0x00,
			},
			wantLayers: []Layer{
				&IPv4{
					IHL:            Uint8(20),
					TOS:            Uint8(0),
					TotalLength:    Uint16(44),
					ID:             Uint16(1),
					Flags:          Uint8(0),
					FragmentOffset: Uint16(0),
					TTL:            Uint8(64),
					Protocol:       Uint8(uint8(header.TCPProtocolNumber)),
					Checksum:       Uint16(0xf977),
					SrcAddr:        Address(tcpip.Address(net.ParseIP("192.168.0.2").To4())),
					DstAddr:        Address(tcpip.Address(net.ParseIP("192.168.0.1").To4())),
				},
				&TCP{
					SrcPort:       Uint16(12345),
					DstPort:       Uint16(54321),
					SeqNum:        Uint32(0),
					AckNum:        Uint32(0),
					Flags:         Uint8(header.TCPFlagSyn),
					WindowSize:    Uint16(8192),
					Checksum:      Uint16(0xf51c),
					UrgentPointer: Uint16(0),
					Options:       []byte{3, 3, 2, 0},
				},
				&Payload{Bytes: nil},
			},
		},
		{
			description: "with payload",
			wantBytes: []byte{
				// IPv4 header
				0x45, 0x00, 0x00, 0x37, 0x00, 0x01, 0x00, 0x00, 0x40, 0x06,
				0xf9, 0x6c, 0xc0, 0xa8, 0x00, 0x02, 0xc0, 0xa8, 0x00, 0x01,
				// TCP header
				0x30, 0x39, 0xd4, 0x31, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
				0x00, 0x00, 0x60, 0x02, 0x20, 0x00, 0xe5, 0x21, 0x00, 0x00,
				// WindowScale Option
				0x03, 0x03, 0x02,
				// NOP Option
				0x00,
				// Payload: "Sample Data"
				0x53, 0x61, 0x6d, 0x70, 0x6c, 0x65, 0x20, 0x44, 0x61, 0x74, 0x61,
			},
			wantLayers: []Layer{
				&IPv4{
					IHL:            Uint8(20),
					TOS:            Uint8(0),
					TotalLength:    Uint16(55),
					ID:             Uint16(1),
					Flags:          Uint8(0),
					FragmentOffset: Uint16(0),
					TTL:            Uint8(64),
					Protocol:       Uint8(uint8(header.TCPProtocolNumber)),
					Checksum:       Uint16(0xf96c),
					SrcAddr:        Address(tcpip.Address(net.ParseIP("192.168.0.2").To4())),
					DstAddr:        Address(tcpip.Address(net.ParseIP("192.168.0.1").To4())),
				},
				&TCP{
					SrcPort:       Uint16(12345),
					DstPort:       Uint16(54321),
					SeqNum:        Uint32(0),
					AckNum:        Uint32(0),
					Flags:         Uint8(header.TCPFlagSyn),
					WindowSize:    Uint16(8192),
					Checksum:      Uint16(0xe521),
					UrgentPointer: Uint16(0),
					Options:       []byte{3, 3, 2, 0},
				},
				&Payload{Bytes: []byte("Sample Data")},
			},
		},
	} {
		t.Run(tt.description, func(t *testing.T) {
			layers := parse(parseIPv4, tt.wantBytes)
			if !layers.match(tt.wantLayers) {
				t.Fatalf("match failed with diff: %s", layers.diff(tt.wantLayers))
			}
			gotBytes, err := layers.ToBytes()
			if err != nil {
				t.Fatalf("ToBytes() failed on %s: %s", &layers, err)
			}
			if !bytes.Equal(tt.wantBytes, gotBytes) {
				t.Fatalf("mismatching bytes, gotBytes: %x, wantBytes: %x", gotBytes, tt.wantBytes)
			}
		})
	}
}

func TestIPv6ExtHdrOptions(t *testing.T) {
	for _, tt := range []struct {
		description string
		wantBytes   []byte
		wantLayers  Layers
	}{
		{
			description: "IPv6/HopByHop",
			wantBytes: []byte{
				// IPv6 Header
				0x60, 0x00, 0x00, 0x00, 0x00, 0x08, 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
				0x3b, 0x00, 0x05, 0x02, 0x00, 0x00, 0x01, 0x00,
			},
			wantLayers: []Layer{
				&IPv6{
					SrcAddr: Address(tcpip.Address(net.ParseIP("::1"))),
					DstAddr: Address(tcpip.Address(net.ParseIP("fe80::dead:beef"))),
				},
				&IPv6HopByHopOptionsExtHdr{
					NextHeader: IPv6ExtHdrIdent(header.IPv6NoNextHeaderIdentifier),
					Options:    []byte{0x05, 0x02, 0x00, 0x00, 0x01, 0x00},
				},
				&Payload{
					Bytes: nil,
				},
			},
		},
		{
			description: "IPv6/HopByHop/Payload",
			wantBytes: []byte{
				// IPv6 Header
				0x60, 0x00, 0x00, 0x00, 0x00, 0x13, 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
				0x3b, 0x00, 0x05, 0x02, 0x00, 0x00, 0x01, 0x00,
				// 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"))),
				},
				&IPv6HopByHopOptionsExtHdr{
					NextHeader: IPv6ExtHdrIdent(header.IPv6NoNextHeaderIdentifier),
					Options:    []byte{0x05, 0x02, 0x00, 0x00, 0x01, 0x00},
				},
				&Payload{
					Bytes: []byte("Sample Data"),
				},
			},
		},
		{
			description: "IPv6/HopByHop/Destination/ICMPv6",
			wantBytes: []byte{
				// IPv6 Header
				0x60, 0x00, 0x00, 0x00, 0x00, 0x18, 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
				0x3c, 0x00, 0x05, 0x02, 0x00, 0x00, 0x01, 0x00,
				// Destination Options
				0x3a, 0x00, 0x05, 0x02, 0x00, 0x00, 0x01, 0x00,
				// ICMPv6 Param Problem
				0x04, 0x00, 0x5f, 0x98, 0x00, 0x00, 0x00, 0x06,
			},
			wantLayers: []Layer{
				&IPv6{
					SrcAddr: Address(tcpip.Address(net.ParseIP("::1"))),
					DstAddr: Address(tcpip.Address(net.ParseIP("fe80::dead:beef"))),
				},
				&IPv6HopByHopOptionsExtHdr{
					NextHeader: IPv6ExtHdrIdent(header.IPv6DestinationOptionsExtHdrIdentifier),
					Options:    []byte{0x05, 0x02, 0x00, 0x00, 0x01, 0x00},
				},
				&IPv6DestinationOptionsExtHdr{
					NextHeader: IPv6ExtHdrIdent(header.IPv6ExtensionHeaderIdentifier(header.ICMPv6ProtocolNumber)),
					Options:    []byte{0x05, 0x02, 0x00, 0x00, 0x01, 0x00},
				},
				&ICMPv6{
					Type:     ICMPv6Type(header.ICMPv6ParamProblem),
					Code:     ICMPv6Code(header.ICMPv6ErroneousHeader),
					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"),
				},
			},
		},
	} {
		t.Run(tt.description, func(t *testing.T) {
			layers := parse(parseIPv6, tt.wantBytes)
			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)
			}
			if !bytes.Equal(tt.wantBytes, gotBytes) {
				t.Fatalf("mismatching bytes, gotBytes: %x, wantBytes: %x", gotBytes, tt.wantBytes)
			}
		})
	}
}