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|
package sctp
import (
"encoding/binary"
"errors"
"fmt"
)
/*
chunkInitCommon represents an SCTP Chunk body of type INIT and INIT ACK
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 = 1 | Chunk Flags | Chunk Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Initiate Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertised Receiver Window Credit (a_rwnd) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Outbound Streams | Number of Inbound Streams |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Initial TSN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Optional/Variable-Length Parameters |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The INIT chunk contains the following parameters. Unless otherwise
noted, each parameter MUST only be included once in the INIT chunk.
Fixed Parameters Status
----------------------------------------------
Initiate Tag Mandatory
Advertised Receiver Window Credit Mandatory
Number of Outbound Streams Mandatory
Number of Inbound Streams Mandatory
Initial TSN Mandatory
*/
type chunkInitCommon struct {
initiateTag uint32
advertisedReceiverWindowCredit uint32
numOutboundStreams uint16
numInboundStreams uint16
initialTSN uint32
params []param
}
const (
initChunkMinLength = 16
initOptionalVarHeaderLength = 4
)
// Init chunk errors
var (
ErrInitChunkParseParamTypeFailed = errors.New("failed to parse param type")
ErrInitChunkUnmarshalParam = errors.New("failed unmarshalling param in Init Chunk")
ErrInitAckMarshalParam = errors.New("unable to marshal parameter for INIT/INITACK")
)
func (i *chunkInitCommon) unmarshal(raw []byte) error {
i.initiateTag = binary.BigEndian.Uint32(raw[0:])
i.advertisedReceiverWindowCredit = binary.BigEndian.Uint32(raw[4:])
i.numOutboundStreams = binary.BigEndian.Uint16(raw[8:])
i.numInboundStreams = binary.BigEndian.Uint16(raw[10:])
i.initialTSN = binary.BigEndian.Uint32(raw[12:])
// https://tools.ietf.org/html/rfc4960#section-3.2.1
//
// Chunk values of SCTP control chunks consist of a chunk-type-specific
// header of required fields, followed by zero or more parameters. The
// optional and variable-length parameters contained in a chunk are
// defined in a Type-Length-Value format as shown below.
//
// 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
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | Parameter Type | Parameter Length |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | |
// | Parameter Value |
// | |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
offset := initChunkMinLength
remaining := len(raw) - offset
for remaining > 0 {
if remaining > initOptionalVarHeaderLength {
pType, err := parseParamType(raw[offset:])
if err != nil {
return fmt.Errorf("%w: %v", ErrInitChunkParseParamTypeFailed, err)
}
p, err := buildParam(pType, raw[offset:])
if err != nil {
return fmt.Errorf("%w: %v", ErrInitChunkUnmarshalParam, err)
}
i.params = append(i.params, p)
padding := getPadding(p.length())
offset += p.length() + padding
remaining -= p.length() + padding
} else {
break
}
}
return nil
}
func (i *chunkInitCommon) marshal() ([]byte, error) {
out := make([]byte, initChunkMinLength)
binary.BigEndian.PutUint32(out[0:], i.initiateTag)
binary.BigEndian.PutUint32(out[4:], i.advertisedReceiverWindowCredit)
binary.BigEndian.PutUint16(out[8:], i.numOutboundStreams)
binary.BigEndian.PutUint16(out[10:], i.numInboundStreams)
binary.BigEndian.PutUint32(out[12:], i.initialTSN)
for idx, p := range i.params {
pp, err := p.marshal()
if err != nil {
return nil, fmt.Errorf("%w: %v", ErrInitAckMarshalParam, err)
}
out = append(out, pp...)
// Chunks (including Type, Length, and Value fields) are padded out
// by the sender with all zero bytes to be a multiple of 4 bytes
// long. This padding MUST NOT be more than 3 bytes in total. The
// Chunk Length value does not include terminating padding of the
// chunk. *However, it does include padding of any variable-length
// parameter except the last parameter in the chunk.* The receiver
// MUST ignore the padding.
if idx != len(i.params)-1 {
out = padByte(out, getPadding(len(pp)))
}
}
return out, nil
}
// String makes chunkInitCommon printable
func (i chunkInitCommon) String() string {
format := `initiateTag: %d
advertisedReceiverWindowCredit: %d
numOutboundStreams: %d
numInboundStreams: %d
initialTSN: %d`
res := fmt.Sprintf(format,
i.initiateTag,
i.advertisedReceiverWindowCredit,
i.numOutboundStreams,
i.numInboundStreams,
i.initialTSN,
)
for i, param := range i.params {
res += fmt.Sprintf("Param %d:\n %s", i, param)
}
return res
}
|
