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|
package sctp
import (
"encoding/binary"
"errors"
"fmt"
"time"
)
/*
chunkPayloadData represents an SCTP Chunk of type DATA
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0 | Reserved|U|B|E| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TSN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Stream Identifier S | Stream Sequence Number n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Protocol Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| User Data (seq n of Stream S) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
An unfragmented user message shall have both the B and E bits set to
'1'. Setting both B and E bits to '0' indicates a middle fragment of
a multi-fragment user message, as summarized in the following table:
B E Description
============================================================
| 1 0 | First piece of a fragmented user message |
+----------------------------------------------------------+
| 0 0 | Middle piece of a fragmented user message |
+----------------------------------------------------------+
| 0 1 | Last piece of a fragmented user message |
+----------------------------------------------------------+
| 1 1 | Unfragmented message |
============================================================
| Table 1: Fragment Description Flags |
============================================================
*/
type chunkPayloadData struct {
chunkHeader
unordered bool
beginningFragment bool
endingFragment bool
immediateSack bool
tsn uint32
streamIdentifier uint16
streamSequenceNumber uint16
payloadType PayloadProtocolIdentifier
userData []byte
// Whether this data chunk was acknowledged (received by peer)
acked bool
missIndicator uint32
// Partial-reliability parameters used only by sender
since time.Time
nSent uint32 // number of transmission made for this chunk
_abandoned bool
_allInflight bool // valid only with the first fragment
// Retransmission flag set when T1-RTX timeout occurred and this
// chunk is still in the inflight queue
retransmit bool
head *chunkPayloadData // link to the head of the fragment
}
const (
payloadDataEndingFragmentBitmask = 1
payloadDataBeginingFragmentBitmask = 2
payloadDataUnorderedBitmask = 4
payloadDataImmediateSACK = 8
payloadDataHeaderSize = 12
)
// PayloadProtocolIdentifier is an enum for DataChannel payload types
type PayloadProtocolIdentifier uint32
// PayloadProtocolIdentifier enums
// https://www.iana.org/assignments/sctp-parameters/sctp-parameters.xhtml#sctp-parameters-25
const (
PayloadTypeUnknown PayloadProtocolIdentifier = 0
PayloadTypeWebRTCDCEP PayloadProtocolIdentifier = 50
PayloadTypeWebRTCString PayloadProtocolIdentifier = 51
PayloadTypeWebRTCBinary PayloadProtocolIdentifier = 53
PayloadTypeWebRTCStringEmpty PayloadProtocolIdentifier = 56
PayloadTypeWebRTCBinaryEmpty PayloadProtocolIdentifier = 57
)
// Data chunk errors
var (
ErrChunkPayloadSmall = errors.New("packet is smaller than the header size")
)
func (p PayloadProtocolIdentifier) String() string {
switch p {
case PayloadTypeWebRTCDCEP:
return "WebRTC DCEP"
case PayloadTypeWebRTCString:
return "WebRTC String"
case PayloadTypeWebRTCBinary:
return "WebRTC Binary"
case PayloadTypeWebRTCStringEmpty:
return "WebRTC String (Empty)"
case PayloadTypeWebRTCBinaryEmpty:
return "WebRTC Binary (Empty)"
default:
return fmt.Sprintf("Unknown Payload Protocol Identifier: %d", p)
}
}
func (p *chunkPayloadData) unmarshal(raw []byte) error {
if err := p.chunkHeader.unmarshal(raw); err != nil {
return err
}
p.immediateSack = p.flags&payloadDataImmediateSACK != 0
p.unordered = p.flags&payloadDataUnorderedBitmask != 0
p.beginningFragment = p.flags&payloadDataBeginingFragmentBitmask != 0
p.endingFragment = p.flags&payloadDataEndingFragmentBitmask != 0
if len(raw) < payloadDataHeaderSize {
return ErrChunkPayloadSmall
}
p.tsn = binary.BigEndian.Uint32(p.raw[0:])
p.streamIdentifier = binary.BigEndian.Uint16(p.raw[4:])
p.streamSequenceNumber = binary.BigEndian.Uint16(p.raw[6:])
p.payloadType = PayloadProtocolIdentifier(binary.BigEndian.Uint32(p.raw[8:]))
p.userData = p.raw[payloadDataHeaderSize:]
return nil
}
func (p *chunkPayloadData) marshal() ([]byte, error) {
payRaw := make([]byte, payloadDataHeaderSize+len(p.userData))
binary.BigEndian.PutUint32(payRaw[0:], p.tsn)
binary.BigEndian.PutUint16(payRaw[4:], p.streamIdentifier)
binary.BigEndian.PutUint16(payRaw[6:], p.streamSequenceNumber)
binary.BigEndian.PutUint32(payRaw[8:], uint32(p.payloadType))
copy(payRaw[payloadDataHeaderSize:], p.userData)
flags := uint8(0)
if p.endingFragment {
flags = 1
}
if p.beginningFragment {
flags |= 1 << 1
}
if p.unordered {
flags |= 1 << 2
}
if p.immediateSack {
flags |= 1 << 3
}
p.chunkHeader.flags = flags
p.chunkHeader.typ = ctPayloadData
p.chunkHeader.raw = payRaw
return p.chunkHeader.marshal()
}
func (p *chunkPayloadData) check() (abort bool, err error) {
return false, nil
}
// String makes chunkPayloadData printable
func (p *chunkPayloadData) String() string {
return fmt.Sprintf("%s\n%d", p.chunkHeader, p.tsn)
}
func (p *chunkPayloadData) abandoned() bool {
if p.head != nil {
return p.head._abandoned && p.head._allInflight
}
return p._abandoned && p._allInflight
}
func (p *chunkPayloadData) setAbandoned(abandoned bool) {
if p.head != nil {
p.head._abandoned = abandoned
return
}
p._abandoned = abandoned
}
func (p *chunkPayloadData) setAllInflight() {
if p.endingFragment {
if p.head != nil {
p.head._allInflight = true
} else {
p._allInflight = true
}
}
}
|
