add SCTP SerializableLayer support

[GoogleCodeExporter]

What steps will reproduce the problem?
1. The code:
-------------------------
package main

import (
        "fmt"
        "code.google.com/p/gopacket"
        "code.google.com/p/gopacket/layers"
)

func main() {
        sb := gopacket.NewSerializeBuffer()
        gopacket.SerializeLayers(sb, gopacket.SerializeOptions{
                ComputeChecksums:true,
        }, layers.SCTP{})
        fmt.Print(sb.Bytes())
}

-------------------------

What is the expected output? What do you see instead?

expected:

[0 0 0 0 0 0 0 0 93 181 96 43]

instead:

# command-line-arguments
./hoge.go:13: cannot use layers.SCTP literal (type layers.SCTP) as type 
gopacket.SerializableLayer in function argument:
        layers.SCTP does not implement gopacket.SerializableLayer (missing SerializeTo method)

Please provide any additional information below.

diff --git a/layers/sctp.go b/layers/sctp.go
index 1d84506..28436de 100644
--- a/layers/sctp.go
+++ b/layers/sctp.go
@@ -51,6 +51,107 @@ func decodeWithSCTPChunkTypePrefix(data []byte, p 
gopacket.PacketBuilder) error
    return chunkType.Decode(data, p)
 }

+// SerializeTo is for gopacket.SerializableLayer.
+func (s SCTP) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   var payload []byte
+   if opts.ComputeChecksums {
+       payload = b.Bytes()
+   }
+   bytes, err := b.PrependBytes(12)
+   if err != nil {
+       return err
+   }
+   binary.BigEndian.PutUint16(bytes[0:2], uint16(s.SrcPort))
+   binary.BigEndian.PutUint16(bytes[2:4], uint16(s.DstPort))
+   binary.BigEndian.PutUint32(bytes[4:8], s.VerificationTag)
+   if opts.ComputeChecksums {
+       binary.LittleEndian.PutUint32(bytes[8:12], s.computeChecksum(payload))
+   }
+   return nil
+}
+
+func (s SCTP) computeChecksum(payload []byte) uint32 {
+   s.Checksum = 0
+   sb := gopacket.NewSerializeBuffer()
+   s.SerializeTo(sb, gopacket.SerializeOptions{ComputeChecksums: false})
+   // RFC 3309
+   crc_c := [256]uint32{
+       0x00000000, 0xF26B8303, 0xE13B70F7, 0x1350F3F4,
+       0xC79A971F, 0x35F1141C, 0x26A1E7E8, 0xD4CA64EB,
+       0x8AD958CF, 0x78B2DBCC, 0x6BE22838, 0x9989AB3B,
+       0x4D43CFD0, 0xBF284CD3, 0xAC78BF27, 0x5E133C24,
+       0x105EC76F, 0xE235446C, 0xF165B798, 0x030E349B,
+       0xD7C45070, 0x25AFD373, 0x36FF2087, 0xC494A384,
+       0x9A879FA0, 0x68EC1CA3, 0x7BBCEF57, 0x89D76C54,
+       0x5D1D08BF, 0xAF768BBC, 0xBC267848, 0x4E4DFB4B,
+       0x20BD8EDE, 0xD2D60DDD, 0xC186FE29, 0x33ED7D2A,
+       0xE72719C1, 0x154C9AC2, 0x061C6936, 0xF477EA35,
+       0xAA64D611, 0x580F5512, 0x4B5FA6E6, 0xB93425E5,
+       0x6DFE410E, 0x9F95C20D, 0x8CC531F9, 0x7EAEB2FA,
+       0x30E349B1, 0xC288CAB2, 0xD1D83946, 0x23B3BA45,
+       0xF779DEAE, 0x05125DAD, 0x1642AE59, 0xE4292D5A,
+       0xBA3A117E, 0x4851927D, 0x5B016189, 0xA96AE28A,
+       0x7DA08661, 0x8FCB0562, 0x9C9BF696, 0x6EF07595,
+       0x417B1DBC, 0xB3109EBF, 0xA0406D4B, 0x522BEE48,
+       0x86E18AA3, 0x748A09A0, 0x67DAFA54, 0x95B17957,
+       0xCBA24573, 0x39C9C670, 0x2A993584, 0xD8F2B687,
+       0x0C38D26C, 0xFE53516F, 0xED03A29B, 0x1F682198,
+       0x5125DAD3, 0xA34E59D0, 0xB01EAA24, 0x42752927,
+       0x96BF4DCC, 0x64D4CECF, 0x77843D3B, 0x85EFBE38,
+       0xDBFC821C, 0x2997011F, 0x3AC7F2EB, 0xC8AC71E8,
+       0x1C661503, 0xEE0D9600, 0xFD5D65F4, 0x0F36E6F7,
+       0x61C69362, 0x93AD1061, 0x80FDE395, 0x72966096,
+       0xA65C047D, 0x5437877E, 0x4767748A, 0xB50CF789,
+       0xEB1FCBAD, 0x197448AE, 0x0A24BB5A, 0xF84F3859,
+       0x2C855CB2, 0xDEEEDFB1, 0xCDBE2C45, 0x3FD5AF46,
+       0x7198540D, 0x83F3D70E, 0x90A324FA, 0x62C8A7F9,
+       0xB602C312, 0x44694011, 0x5739B3E5, 0xA55230E6,
+       0xFB410CC2, 0x092A8FC1, 0x1A7A7C35, 0xE811FF36,
+       0x3CDB9BDD, 0xCEB018DE, 0xDDE0EB2A, 0x2F8B6829,
+       0x82F63B78, 0x709DB87B, 0x63CD4B8F, 0x91A6C88C,
+       0x456CAC67, 0xB7072F64, 0xA457DC90, 0x563C5F93,
+       0x082F63B7, 0xFA44E0B4, 0xE9141340, 0x1B7F9043,
+       0xCFB5F4A8, 0x3DDE77AB, 0x2E8E845F, 0xDCE5075C,
+       0x92A8FC17, 0x60C37F14, 0x73938CE0, 0x81F80FE3,
+       0x55326B08, 0xA759E80B, 0xB4091BFF, 0x466298FC,
+       0x1871A4D8, 0xEA1A27DB, 0xF94AD42F, 0x0B21572C,
+       0xDFEB33C7, 0x2D80B0C4, 0x3ED04330, 0xCCBBC033,
+       0xA24BB5A6, 0x502036A5, 0x4370C551, 0xB11B4652,
+       0x65D122B9, 0x97BAA1BA, 0x84EA524E, 0x7681D14D,
+       0x2892ED69, 0xDAF96E6A, 0xC9A99D9E, 0x3BC21E9D,
+       0xEF087A76, 0x1D63F975, 0x0E330A81, 0xFC588982,
+       0xB21572C9, 0x407EF1CA, 0x532E023E, 0xA145813D,
+       0x758FE5D6, 0x87E466D5, 0x94B49521, 0x66DF1622,
+       0x38CC2A06, 0xCAA7A905, 0xD9F75AF1, 0x2B9CD9F2,
+       0xFF56BD19, 0x0D3D3E1A, 0x1E6DCDEE, 0xEC064EED,
+       0xC38D26C4, 0x31E6A5C7, 0x22B65633, 0xD0DDD530,
+       0x0417B1DB, 0xF67C32D8, 0xE52CC12C, 0x1747422F,
+       0x49547E0B, 0xBB3FFD08, 0xA86F0EFC, 0x5A048DFF,
+       0x8ECEE914, 0x7CA56A17, 0x6FF599E3, 0x9D9E1AE0,
+       0xD3D3E1AB, 0x21B862A8, 0x32E8915C, 0xC083125F,
+       0x144976B4, 0xE622F5B7, 0xF5720643, 0x07198540,
+       0x590AB964, 0xAB613A67, 0xB831C993, 0x4A5A4A90,
+       0x9E902E7B, 0x6CFBAD78, 0x7FAB5E8C, 0x8DC0DD8F,
+       0xE330A81A, 0x115B2B19, 0x020BD8ED, 0xF0605BEE,
+       0x24AA3F05, 0xD6C1BC06, 0xC5914FF2, 0x37FACCF1,
+       0x69E9F0D5, 0x9B8273D6, 0x88D28022, 0x7AB90321,
+       0xAE7367CA, 0x5C18E4C9, 0x4F48173D, 0xBD23943E,
+       0xF36E6F75, 0x0105EC76, 0x12551F82, 0xE03E9C81,
+       0x34F4F86A, 0xC69F7B69, 0xD5CF889D, 0x27A40B9E,
+       0x79B737BA, 0x8BDCB4B9, 0x988C474D, 0x6AE7C44E,
+       0xBE2DA0A5, 0x4C4623A6, 0x5F16D052, 0xAD7D5351,
+   }
+
+   crc32 := uint32(0xffffffff)
+   for _, b := range sb.Bytes() {
+       crc32 = (crc32 >> 8) ^ crc_c[(byte(crc32)^b)&0xFF]
+   }
+   for _, b := range payload {
+       crc32 = (crc32 >> 8) ^ crc_c[(byte(crc32)^b)&0xFF]
+   }
+   return 0xffffffff &^ crc32
+}
+
 // SCTPChunk contains the common fields in all SCTP chunks.
 type SCTPChunk struct {
    BaseLayer
@@ -102,6 +203,15 @@ func decodeSCTPParameter(data []byte) SCTPParameter {
    }
 }

+func (p SCTPParameter) Bytes() []byte {
+   length := 4 + len(p.Value)
+   data := make([]byte, roundUpToNearest4(length))
+   binary.BigEndian.PutUint16(data[0:2], p.Type)
+   binary.BigEndian.PutUint16(data[2:4], uint16(length))
+   copy(data[4:], p.Value)
+   return data
+}
+
 // SCTPUnknownChunkType is the layer type returned when we don't recognize the
 // chunk type.  Since there's a length in a known location, we can skip over
 // it even if we don't know what it is, and continue parsing the rest of the
@@ -119,6 +229,16 @@ func decodeSCTPChunkTypeUnknown(data []byte, p 
gopacket.PacketBuilder) error {
    return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
 }

+// SerializeTo is for gopacket.SerializableLayer.
+func (s SCTPUnknownChunkType) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   bytes, err := b.PrependBytes(s.ActualLength)
+   if err != nil {
+       return err
+   }
+   copy(bytes, s.bytes)
+   return nil
+}
+
 // LayerType returns gopacket.LayerTypeSCTPUnknownChunkType.
 func (s *SCTPUnknownChunkType) LayerType() gopacket.LayerType { return LayerTypeSCTPUnknownChunkType }

@@ -168,6 +288,34 @@ func decodeSCTPData(data []byte, p gopacket.PacketBuilder) 
error {
    return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
 }

+// SerializeTo is for gopacket.SerializableLayer.
+func (sc SCTPData) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   length := 16 + len(sc.PayloadData)
+   bytes, err := b.PrependBytes(roundUpToNearest4(length))
+   if err != nil {
+       return err
+   }
+   bytes[0] = uint8(sc.Type)
+   flags := uint8(0)
+   if sc.Unordered {
+       flags |= 0x4
+   }
+   if sc.BeginFragment {
+       flags |= 0x2
+   }
+   if sc.EndFragment {
+       flags |= 0x1
+   }
+   bytes[1] = flags
+   binary.BigEndian.PutUint16(bytes[2:4], uint16(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], sc.PayloadProtocol)
+   copy(bytes[16:], sc.PayloadData)
+   return nil
+}
+
 // SCTPInitParameter is a parameter for an SCTP Init or InitAck packet.
 type SCTPInitParameter SCTPParameter

@@ -210,6 +358,30 @@ func decodeSCTPInit(data []byte, p gopacket.PacketBuilder) 
error {
    return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
 }

+// SerializeTo is for gopacket.SerializableLayer.
+func (sc SCTPInit) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   var payload []byte
+   for _, param := range sc.Parameters {
+       payload = append(payload, SCTPParameter(param).Bytes()...)
+   }
+   length := 20 + len(payload)
+
+   bytes, err := b.PrependBytes(roundUpToNearest4(length))
+   if err != nil {
+       return err
+   }
+   bytes[0] = uint8(sc.Type)
+   bytes[1] = sc.Flags
+   binary.BigEndian.PutUint16(bytes[2:4], uint16(length))
+   binary.BigEndian.PutUint32(bytes[4:8], sc.InitiateTag)
+   binary.BigEndian.PutUint32(bytes[8:12], sc.AdvertisedReceiverWindowCredit)
+   binary.BigEndian.PutUint16(bytes[12:14], sc.OutboundStreams)
+   binary.BigEndian.PutUint16(bytes[14:16], sc.InboundStreams)
+   binary.BigEndian.PutUint32(bytes[16:20], sc.InitialTSN)
+   copy(bytes[20:], payload)
+   return nil
+}
+
 // SCTPSack is the SCTP Selective ACK chunk layer.
 type SCTPSack struct {
    SCTPChunk
@@ -262,6 +434,30 @@ func decodeSCTPSack(data []byte, p gopacket.PacketBuilder) 
error {
    return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
 }

+// SerializeTo is for gopacket.SerializableLayer.
+func (sc SCTPSack) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   length := 16 + 2*len(sc.GapACKs) + 4*len(sc.DuplicateTSNs)
+   bytes, err := b.PrependBytes(roundUpToNearest4(length))
+   if err != nil {
+       return err
+   }
+   bytes[0] = uint8(sc.Type)
+   bytes[1] = sc.Flags
+   binary.BigEndian.PutUint16(bytes[2:4], uint16(length))
+   binary.BigEndian.PutUint32(bytes[4:8], sc.CumulativeTSNAck)
+   binary.BigEndian.PutUint32(bytes[8:12], sc.AdvertisedReceiverWindowCredit)
+   binary.BigEndian.PutUint16(bytes[12:14], uint16(len(sc.GapACKs)))
+   binary.BigEndian.PutUint16(bytes[14:16], uint16(len(sc.DuplicateTSNs)))
+   for i, v := range sc.GapACKs {
+       binary.BigEndian.PutUint16(bytes[16+i*2:], v)
+   }
+   offset := 16 + 2*len(sc.GapACKs)
+   for i, v := range sc.DuplicateTSNs {
+       binary.BigEndian.PutUint32(bytes[offset+i*4:], v)
+   }
+   return nil
+}
+
 // SCTPHeartbeatParameter is the parameter type used by SCTP heartbeat and
 // heartbeat ack layers.
 type SCTPHeartbeatParameter SCTPParameter
@@ -295,6 +491,25 @@ func decodeSCTPHeartbeat(data []byte, p 
gopacket.PacketBuilder) error {
    return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
 }

+// SerializeTo is for gopacket.SerializableLayer.
+func (sc SCTPHeartbeat) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   var payload []byte
+   for _, param := range sc.Parameters {
+       payload = append(payload, SCTPParameter(param).Bytes()...)
+   }
+   length := 4 + len(payload)
+
+   bytes, err := b.PrependBytes(roundUpToNearest4(length))
+   if err != nil {
+       return err
+   }
+   bytes[0] = uint8(sc.Type)
+   bytes[1] = sc.Flags
+   binary.BigEndian.PutUint16(bytes[2:4], uint16(length))
+   copy(bytes[4:], payload)
+   return nil
+}
+
 // SCTPErrorParameter is the parameter type used by SCTP Abort and Error layers.
 type SCTPErrorParameter SCTPParameter

@@ -328,6 +543,25 @@ func decodeSCTPError(data []byte, p 
gopacket.PacketBuilder) error {
    return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
 }

+// SerializeTo is for gopacket.SerializableLayer.
+func (sc SCTPError) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   var payload []byte
+   for _, param := range sc.Parameters {
+       payload = append(payload, SCTPParameter(param).Bytes()...)
+   }
+   length := 4 + len(payload)
+
+   bytes, err := b.PrependBytes(roundUpToNearest4(length))
+   if err != nil {
+       return err
+   }
+   bytes[0] = uint8(sc.Type)
+   bytes[1] = sc.Flags
+   binary.BigEndian.PutUint16(bytes[2:4], uint16(length))
+   copy(bytes[4:], payload)
+   return nil
+}
+
 // SCTPShutdown is the SCTP shutdown layer.
 type SCTPShutdown struct {
    SCTPChunk
@@ -346,6 +580,19 @@ func decodeSCTPShutdown(data []byte, p 
gopacket.PacketBuilder) error {
    return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
 }

+// SerializeTo is for gopacket.SerializableLayer.
+func (sc SCTPShutdown) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   bytes, err := b.PrependBytes(8)
+   if err != nil {
+       return err
+   }
+   bytes[0] = uint8(sc.Type)
+   bytes[1] = sc.Flags
+   binary.BigEndian.PutUint16(bytes[2:4], 8)
+   binary.BigEndian.PutUint32(bytes[4:8], sc.CumulativeTSNAck)
+   return nil
+}
+
 // SCTPShutdownAck is the SCTP shutdown layer.
 type SCTPShutdownAck struct {
    SCTPChunk
@@ -362,6 +609,18 @@ func decodeSCTPShutdownAck(data []byte, p 
gopacket.PacketBuilder) error {
    return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
 }

+// SerializeTo is for gopacket.SerializableLayer.
+func (sc SCTPShutdownAck) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   bytes, err := b.PrependBytes(4)
+   if err != nil {
+       return err
+   }
+   bytes[0] = uint8(sc.Type)
+   bytes[1] = sc.Flags
+   binary.BigEndian.PutUint16(bytes[2:4], 4)
+   return nil
+}
+
 // SCTPCookieEcho is the SCTP Cookie Echo layer.
 type SCTPCookieEcho struct {
    SCTPChunk
@@ -380,6 +639,20 @@ func decodeSCTPCookieEcho(data []byte, p 
gopacket.PacketBuilder) error {
    return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
 }

+// SerializeTo is for gopacket.SerializableLayer.
+func (sc SCTPCookieEcho) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   length := 4 + len(sc.Cookie)
+   bytes, err := b.PrependBytes(roundUpToNearest4(length))
+   if err != nil {
+       return err
+   }
+   bytes[0] = uint8(sc.Type)
+   bytes[1] = sc.Flags
+   binary.BigEndian.PutUint16(bytes[2:4], uint16(length))
+   copy(bytes[4:], sc.Cookie)
+   return nil
+}
+
 // This struct is used by all empty SCTP chunks (currently CookieAck and
 // ShutdownComplete).
 type SCTPEmptyLayer struct {
@@ -403,3 +676,15 @@ func decodeSCTPEmptyLayer(data []byte, p 
gopacket.PacketBuilder) error {
    p.AddLayer(sc)
    return p.NextDecoder(gopacket.DecodeFunc(decodeWithSCTPChunkTypePrefix))
 }
+
+// SerializeTo is for gopacket.SerializableLayer.
+func (sc SCTPEmptyLayer) SerializeTo(b gopacket.SerializeBuffer, opts 
gopacket.SerializeOptions) error {
+   bytes, err := b.PrependBytes(4)
+   if err != nil {
+       return err
+   }
+   bytes[0] = uint8(sc.Type)
+   bytes[1] = sc.Flags
+   binary.BigEndian.PutUint16(bytes[2:4], 4)
+   return nil
+}

Original issue reported on code.google.com by Hiroaki.Kawai@gmail.com on 23 Jul 2014 at 5:10

[GoogleCodeExporter]

Hey, thanks for the code, and sorry for the delay.  Just getting back from 
vacation.

This should be integrated into master today.

Original comment by gconnell@google.com on 28 Jul 2014 at 3:13

• Changed state: Accepted
• Added labels: Type-Enhancement
• Removed labels: Type-Defect

[GoogleCodeExporter]

I've added the code to my local branch, and will push by EOD.

BTW, since this is a relatively large contribution, I've added your name to the 
AUTHORS file.

Original comment by gconnell@google.com on 28 Jul 2014 at 4:16

• Changed state: Fixed