148 lines
4.3 KiB
Go
148 lines
4.3 KiB
Go
package sctp
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import (
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"encoding/binary"
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"errors"
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"fmt"
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)
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// This chunk shall be used by the data sender to inform the data
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// receiver to adjust its cumulative received TSN point forward because
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// some missing TSNs are associated with data chunks that SHOULD NOT be
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// transmitted or retransmitted by the sender.
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//
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// 0 1 2 3
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// 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
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | Type = 192 | Flags = 0x00 | Length = Variable |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | New Cumulative TSN |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | Stream-1 | Stream Sequence-1 |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// \ /
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// / \
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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// | Stream-N | Stream Sequence-N |
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// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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type chunkForwardTSN struct {
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chunkHeader
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// This indicates the new cumulative TSN to the data receiver. Upon
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// the reception of this value, the data receiver MUST consider
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// any missing TSNs earlier than or equal to this value as received,
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// and stop reporting them as gaps in any subsequent SACKs.
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newCumulativeTSN uint32
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streams []chunkForwardTSNStream
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}
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const (
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newCumulativeTSNLength = 4
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forwardTSNStreamLength = 4
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)
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var (
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errMarshalStreamFailed = errors.New("failed to marshal stream")
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errChunkTooShort = errors.New("chunk too short")
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)
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func (c *chunkForwardTSN) unmarshal(raw []byte) error {
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if err := c.chunkHeader.unmarshal(raw); err != nil {
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return err
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}
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if len(c.raw) < newCumulativeTSNLength {
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return errChunkTooShort
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}
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c.newCumulativeTSN = binary.BigEndian.Uint32(c.raw[0:])
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offset := newCumulativeTSNLength
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remaining := len(c.raw) - offset
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for remaining > 0 {
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s := chunkForwardTSNStream{}
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if err := s.unmarshal(c.raw[offset:]); err != nil {
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return fmt.Errorf("%w: %v", errMarshalStreamFailed, err)
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}
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c.streams = append(c.streams, s)
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offset += s.length()
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remaining -= s.length()
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}
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return nil
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}
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func (c *chunkForwardTSN) marshal() ([]byte, error) {
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out := make([]byte, newCumulativeTSNLength)
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binary.BigEndian.PutUint32(out[0:], c.newCumulativeTSN)
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for _, s := range c.streams {
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b, err := s.marshal()
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if err != nil {
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return nil, fmt.Errorf("%w: %v", errMarshalStreamFailed, err)
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}
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out = append(out, b...)
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}
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c.typ = ctForwardTSN
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c.raw = out
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return c.chunkHeader.marshal()
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}
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func (c *chunkForwardTSN) check() (abort bool, err error) {
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return true, nil
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}
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// String makes chunkForwardTSN printable
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func (c *chunkForwardTSN) String() string {
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res := fmt.Sprintf("New Cumulative TSN: %d\n", c.newCumulativeTSN)
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for _, s := range c.streams {
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res += fmt.Sprintf(" - si=%d, ssn=%d\n", s.identifier, s.sequence)
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}
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return res
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}
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type chunkForwardTSNStream struct {
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// This field holds a stream number that was skipped by this
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// FWD-TSN.
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identifier uint16
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// This field holds the sequence number associated with the stream
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// that was skipped. The stream sequence field holds the largest
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// stream sequence number in this stream being skipped. The receiver
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// of the FWD-TSN's can use the Stream-N and Stream Sequence-N fields
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// to enable delivery of any stranded TSN's that remain on the stream
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// re-ordering queues. This field MUST NOT report TSN's corresponding
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// to DATA chunks that are marked as unordered. For ordered DATA
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// chunks this field MUST be filled in.
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sequence uint16
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}
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func (s *chunkForwardTSNStream) length() int {
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return forwardTSNStreamLength
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}
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func (s *chunkForwardTSNStream) unmarshal(raw []byte) error {
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if len(raw) < forwardTSNStreamLength {
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return errChunkTooShort
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}
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s.identifier = binary.BigEndian.Uint16(raw[0:])
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s.sequence = binary.BigEndian.Uint16(raw[2:])
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return nil
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}
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func (s *chunkForwardTSNStream) marshal() ([]byte, error) { // nolint:unparam
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out := make([]byte, forwardTSNStreamLength)
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binary.BigEndian.PutUint16(out[0:], s.identifier)
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binary.BigEndian.PutUint16(out[2:], s.sequence)
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return out, nil
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}
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