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Merged
mosajjal merged 1 commit into from
Nov 9, 2024
Merged

Add support for bundled SCTP chunks #72

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4 changes: 2 additions & 2 deletions layers/decode_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -657,9 +657,9 @@ func TestDecodeSCTPPackets(t *testing.T) {
wantLayers := [][]gopacket.LayerType{
[]gopacket.LayerType{LayerTypeSCTPInit},
[]gopacket.LayerType{LayerTypeSCTPInitAck},
[]gopacket.LayerType{LayerTypeSCTPCookieEcho, LayerTypeSCTPData, gopacket.LayerTypePayload},
[]gopacket.LayerType{LayerTypeSCTPCookieEcho, LayerTypeSCTPData},
[]gopacket.LayerType{LayerTypeSCTPCookieAck, LayerTypeSCTPSack},
[]gopacket.LayerType{LayerTypeSCTPData, gopacket.LayerTypePayload},
[]gopacket.LayerType{LayerTypeSCTPData},
[]gopacket.LayerType{LayerTypeSCTPSack},
[]gopacket.LayerType{LayerTypeSCTPShutdown},
[]gopacket.LayerType{LayerTypeSCTPShutdownAck},
Expand Down
40 changes: 32 additions & 8 deletions layers/sctp.go
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,23 @@ func decodeSCTPChunk(data []byte) (SCTPChunk, error) {
}, nil
}

func decodeSCTPDataChunk(data []byte) (SCTPChunk, error) {
length := binary.BigEndian.Uint16(data[2:4])
if length < 4 {
return SCTPChunk{}, errors.New("invalid SCTP chunk length")
}
actual := roundUpToNearest4(int(length))
ct := SCTPChunkType(data[0])

return SCTPChunk{
Type: ct,
Flags: data[1],
Length: length,
ActualLength: actual,
BaseLayer: BaseLayer{data[:actual], data[actual:]},
}, nil
}

// SCTPParameter is a TLV parameter inside a SCTPChunk.
type SCTPParameter struct {
Type uint16
Expand Down Expand Up @@ -214,6 +231,7 @@ type SCTPData struct {
StreamId uint16
StreamSequence uint16
PayloadProtocol SCTPPayloadProtocol
Payload []byte
}

// LayerType returns gopacket.LayerTypeSCTPData.
Expand Down Expand Up @@ -290,10 +308,11 @@ func (p SCTPPayloadProtocol) String() string {
}

func decodeSCTPData(data []byte, p gopacket.PacketBuilder) error {
chunk, err := decodeSCTPChunk(data)
chunk, err := decodeSCTPDataChunk(data)
if err != nil {
return err
}
l := chunk.ActualLength
sc := &SCTPData{
SCTPChunk: chunk,
Unordered: data[1]&0x4 != 0,
Expand All @@ -303,20 +322,24 @@ func decodeSCTPData(data []byte, p gopacket.PacketBuilder) error {
StreamId: binary.BigEndian.Uint16(data[8:10]),
StreamSequence: binary.BigEndian.Uint16(data[10:12]),
PayloadProtocol: SCTPPayloadProtocol(binary.BigEndian.Uint32(data[12:16])),
Payload: []byte{},
}
if l >= 16 {
sc.Payload = data[16:l]
}
// Length is the length in bytes of the data, INCLUDING the 16-byte header.
p.AddLayer(sc)
return p.NextDecoder(gopacket.LayerTypePayload)
return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
}

// SerializeTo is for gopacket.SerializableLayer.
func (sc SCTPData) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.SerializeOptions) error {
payload := b.Bytes()
// Pad the payload to a 32 bit boundary
if rem := len(payload) % 4; rem != 0 {
b.AppendBytes(4 - rem)
payload := sc.Payload
length := len(payload) + 16

if rem := length % 4; rem != 0 {
length += 4 - rem
}
length := 16
bytes, err := b.PrependBytes(length)
if err != nil {
return err
Expand All @@ -333,11 +356,12 @@ func (sc SCTPData) SerializeTo(b gopacket.SerializeBuffer, opts gopacket.Seriali
flags |= 0x1
}
bytes[1] = flags
binary.BigEndian.PutUint16(bytes[2:4], uint16(length+len(payload)))
binary.BigEndian.PutUint16(bytes[2:4], sc.Length)
binary.BigEndian.PutUint32(bytes[4:8], sc.TSN)
binary.BigEndian.PutUint16(bytes[8:10], sc.StreamId)
binary.BigEndian.PutUint16(bytes[10:12], sc.StreamSequence)
binary.BigEndian.PutUint32(bytes[12:16], uint32(sc.PayloadProtocol))
copy(bytes[16:], payload)
return nil
}

Expand Down