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TUN-6791: Calculate ICMPv6 checksum

This commit is contained in:
cthuang 2022-09-22 10:49:19 +01:00 committed by Chung-Ting Huang
parent 7f487c2651
commit 3449ea35f2
5 changed files with 134 additions and 7 deletions
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7
ingress/origin_icmp_proxy_test.go
View File

@ -299,12 +299,7 @@ func (efr *echoFlowResponder) validate(t *testing.T, echoReq *packet.ICMP) {
require.Equal(t, ipv6.ICMPTypeEchoReply, decoded.Type)
}
require.Equal(t, 0, decoded.Code)
if echoReq.Type == ipv4.ICMPTypeEcho {
require.NotZero(t, decoded.Checksum)
} else {
// For ICMPv6, the kernel will compute the checksum during transmission unless pseudo header is not nil
require.Zero(t, decoded.Checksum)
}
require.NotZero(t, decoded.Checksum)
require.Equal(t, echoReq.Body, decoded.Body)
}

1
packet/decoder_test.go
View File

@ -152,6 +152,7 @@ func TestDecodeICMP(t *testing.T) {
require.Equal(t, test.packet.Type, icmpPacket.Type)
require.Equal(t, test.packet.Code, icmpPacket.Code)
assertICMPChecksum(t, icmpPacket)
require.Equal(t, test.packet.Body, icmpPacket.Body)
expectedBody, err := test.packet.Body.Marshal(test.packet.Type.Protocol())
require.NoError(t, err)

39
packet/packet.go
View File

@ -1,6 +1,7 @@
package packet
import (
"encoding/binary"
"fmt"
"net/netip"
@ -21,6 +22,7 @@ const (
// 0 = ttl exceed in transit, 1 = fragment reassembly time exceeded
icmpTTLExceedInTransitCode = 0
DefaultTTL uint8 = 255
pseudoHeaderLen = 40
)
// Packet represents an IP packet or a packet that is encapsulated by IP
@ -117,7 +119,18 @@ func (i *ICMP) EncodeLayers() ([]gopacket.SerializableLayer, error) {
return nil, err
}
msg, err := i.Marshal(nil)
var serializedPsh []byte = nil
if i.Protocol == layers.IPProtocolICMPv6 {
psh := &PseudoHeader{
SrcIP: i.Src.As16(),
DstIP: i.Dst.As16(),
// i.Marshal re-calculates the UpperLayerPacketLength
UpperLayerPacketLength: 0,
NextHeader: uint8(i.Protocol),
}
serializedPsh = psh.Marshal()
}
msg, err := i.Marshal(serializedPsh)
if err != nil {
return nil, err
}
@ -125,6 +138,29 @@ func (i *ICMP) EncodeLayers() ([]gopacket.SerializableLayer, error) {
return append(ipLayers, icmpLayer), nil
}
// https://www.rfc-editor.org/rfc/rfc2460#section-8.1
type PseudoHeader struct {
SrcIP [16]byte
DstIP [16]byte
UpperLayerPacketLength uint32
zero [3]byte
NextHeader uint8
}
func (ph *PseudoHeader) Marshal() []byte {
buf := make([]byte, pseudoHeaderLen)
index := 0
copy(buf, ph.SrcIP[:])
index += 16
copy(buf[index:], ph.DstIP[:])
index += 16
binary.BigEndian.PutUint32(buf[index:], ph.UpperLayerPacketLength)
index += 4
copy(buf[index:], ph.zero[:])
buf[pseudoHeaderLen-1] = ph.NextHeader
return buf
}
func NewICMPTTLExceedPacket(originalIP *IP, originalPacket RawPacket, routerIP netip.Addr) *ICMP {
var (
protocol layers.IPProtocol
@ -137,6 +173,7 @@ func NewICMPTTLExceedPacket(originalIP *IP, originalPacket RawPacket, routerIP n
protocol = layers.IPProtocolICMPv6
icmpType = ipv6.ICMPTypeTimeExceeded
}
return &ICMP{
IP: &IP{
Src: routerIP,

93
packet/packet_test.go
View File

@ -5,6 +5,7 @@ import (
"net/netip"
"testing"
"github.com/google/gopacket"
"github.com/google/gopacket/layers"
"github.com/stretchr/testify/require"
"golang.org/x/net/icmp"
@ -101,4 +102,96 @@ func assertTTLExceedPacket(t *testing.T, pk *ICMP) {
require.Len(t, rawTTLExceedPacket.Data, headerLen+icmpHeaderLen+len(rawPacket.Data))
require.True(t, bytes.Equal(rawPacket.Data, rawTTLExceedPacket.Data[headerLen+icmpHeaderLen:]))
}
decoder := NewICMPDecoder()
decodedPacket, err := decoder.Decode(rawTTLExceedPacket)
require.NoError(t, err)
assertICMPChecksum(t, decodedPacket)
}
func assertICMPChecksum(t *testing.T, icmpPacket *ICMP) {
buf := gopacket.NewSerializeBuffer()
if icmpPacket.Protocol == layers.IPProtocolICMPv4 {
icmpv4 := layers.ICMPv4{
TypeCode: layers.CreateICMPv4TypeCode(uint8(icmpPacket.Type.(ipv4.ICMPType)), uint8(icmpPacket.Code)),
}
switch body := icmpPacket.Body.(type) {
case *icmp.Echo:
icmpv4.Id = uint16(body.ID)
icmpv4.Seq = uint16(body.Seq)
payload := gopacket.Payload(body.Data)
require.NoError(t, payload.SerializeTo(buf, serializeOpts))
default:
require.NoError(t, serializeICMPAsPayload(icmpPacket.Message, buf))
}
// SerializeTo sets the checksum in icmpv4
require.NoError(t, icmpv4.SerializeTo(buf, serializeOpts))
require.Equal(t, icmpv4.Checksum, uint16(icmpPacket.Checksum))
} else {
switch body := icmpPacket.Body.(type) {
case *icmp.Echo:
payload := gopacket.Payload(body.Data)
require.NoError(t, payload.SerializeTo(buf, serializeOpts))
echo := layers.ICMPv6Echo{
Identifier: uint16(body.ID),
SeqNumber: uint16(body.Seq),
}
require.NoError(t, echo.SerializeTo(buf, serializeOpts))
default:
require.NoError(t, serializeICMPAsPayload(icmpPacket.Message, buf))
}
icmpv6 := layers.ICMPv6{
TypeCode: layers.CreateICMPv6TypeCode(uint8(icmpPacket.Type.(ipv6.ICMPType)), uint8(icmpPacket.Code)),
}
ipLayer := layers.IPv6{
Version: 6,
SrcIP: icmpPacket.Src.AsSlice(),
DstIP: icmpPacket.Dst.AsSlice(),
NextHeader: icmpPacket.Protocol,
HopLimit: icmpPacket.TTL,
}
require.NoError(t, icmpv6.SetNetworkLayerForChecksum(&ipLayer))
// SerializeTo sets the checksum in icmpv4
require.NoError(t, icmpv6.SerializeTo(buf, serializeOpts))
require.Equal(t, icmpv6.Checksum, uint16(icmpPacket.Checksum))
}
}
func serializeICMPAsPayload(message *icmp.Message, buf gopacket.SerializeBuffer) error {
serializedBody, err := message.Body.Marshal(message.Type.Protocol())
if err != nil {
return err
}
payload := gopacket.Payload(serializedBody)
return payload.SerializeTo(buf, serializeOpts)
}
func TestChecksum(t *testing.T) {
data := []byte{0x63, 0x2c, 0x49, 0xd6, 0x00, 0x0d, 0xc1, 0xda}
pk := ICMP{
IP: &IP{
Src: netip.MustParseAddr("2606:4700:110:89c1:c63a:861:e08c:b049"),
Dst: netip.MustParseAddr("fde8:b693:d420:109b::2"),
Protocol: layers.IPProtocolICMPv6,
TTL: 3,
},
Message: &icmp.Message{
Type: ipv6.ICMPTypeEchoRequest,
Code: 0,
Body: &icmp.Echo{
ID: 0x20a7,
Seq: 8,
Data: data,
},
},
}
encoder := NewEncoder()
encoded, err := encoder.Encode(&pk)
require.NoError(t, err)
decoder := NewICMPDecoder()
decoded, err := decoder.Decode(encoded)
require.Equal(t, 0xff96, decoded.Checksum)
}

1
packet/router_test.go
View File

@ -96,6 +96,7 @@ func assertTTLExceed(t *testing.T, originalPacket *ICMP, expectedSrc netip.Addr,
require.Equal(t, ipv6.ICMPTypeTimeExceeded, decoded.Type)
}
require.Equal(t, 0, decoded.Code)
assertICMPChecksum(t, decoded)
timeExceed, ok := decoded.Body.(*icmp.TimeExceeded)
require.True(t, ok)
require.True(t, bytes.Equal(rawPacket.Data, timeExceed.Data))