101 lines
3.3 KiB
Go
101 lines
3.3 KiB
Go
// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
|
|
// SPDX-License-Identifier: MIT
|
|
|
|
package sctp
|
|
|
|
import (
|
|
"encoding/binary"
|
|
"errors"
|
|
"fmt"
|
|
)
|
|
|
|
/*
|
|
chunkHeader represents a SCTP Chunk header, defined in https://tools.ietf.org/html/rfc4960#section-3.2
|
|
The figure below illustrates the field format for the chunks to be
|
|
transmitted in the SCTP packet. Each chunk is formatted with a Chunk
|
|
Type field, a chunk-specific Flag field, a Chunk Length field, and a
|
|
Value field.
|
|
|
|
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
|
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
| Chunk Type | Chunk Flags | Chunk Length |
|
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
| |
|
|
| Chunk Value |
|
|
| |
|
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
*/
|
|
type chunkHeader struct {
|
|
typ chunkType
|
|
flags byte
|
|
raw []byte
|
|
}
|
|
|
|
const (
|
|
chunkHeaderSize = 4
|
|
)
|
|
|
|
// SCTP chunk header errors
|
|
var (
|
|
ErrChunkHeaderTooSmall = errors.New("raw is too small for a SCTP chunk")
|
|
ErrChunkHeaderNotEnoughSpace = errors.New("not enough data left in SCTP packet to satisfy requested length")
|
|
ErrChunkHeaderPaddingNonZero = errors.New("chunk padding is non-zero at offset")
|
|
)
|
|
|
|
func (c *chunkHeader) unmarshal(raw []byte) error {
|
|
if len(raw) < chunkHeaderSize {
|
|
return fmt.Errorf("%w: raw only %d bytes, %d is the minimum length", ErrChunkHeaderTooSmall, len(raw), chunkHeaderSize)
|
|
}
|
|
|
|
c.typ = chunkType(raw[0])
|
|
c.flags = raw[1]
|
|
length := binary.BigEndian.Uint16(raw[2:])
|
|
|
|
// Length includes Chunk header
|
|
valueLength := int(length - chunkHeaderSize)
|
|
lengthAfterValue := len(raw) - (chunkHeaderSize + valueLength)
|
|
|
|
if lengthAfterValue < 0 {
|
|
return fmt.Errorf("%w: remain %d req %d ", ErrChunkHeaderNotEnoughSpace, valueLength, len(raw)-chunkHeaderSize)
|
|
} else if lengthAfterValue < 4 {
|
|
// https://tools.ietf.org/html/rfc4960#section-3.2
|
|
// The Chunk Length field does not count any chunk padding.
|
|
// 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.
|
|
for i := lengthAfterValue; i > 0; i-- {
|
|
paddingOffset := chunkHeaderSize + valueLength + (i - 1)
|
|
if raw[paddingOffset] != 0 {
|
|
return fmt.Errorf("%w: %d ", ErrChunkHeaderPaddingNonZero, paddingOffset)
|
|
}
|
|
}
|
|
}
|
|
|
|
c.raw = raw[chunkHeaderSize : chunkHeaderSize+valueLength]
|
|
return nil
|
|
}
|
|
|
|
func (c *chunkHeader) marshal() ([]byte, error) {
|
|
raw := make([]byte, 4+len(c.raw))
|
|
|
|
raw[0] = uint8(c.typ)
|
|
raw[1] = c.flags
|
|
binary.BigEndian.PutUint16(raw[2:], uint16(len(c.raw)+chunkHeaderSize))
|
|
copy(raw[4:], c.raw)
|
|
return raw, nil
|
|
}
|
|
|
|
func (c *chunkHeader) valueLength() int {
|
|
return len(c.raw)
|
|
}
|
|
|
|
// String makes chunkHeader printable
|
|
func (c chunkHeader) String() string {
|
|
return c.typ.String()
|
|
}
|