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package mux
import (
"bytes"
"encoding/binary"
)
// MatchFunc allows custom logic for mapping packets to an Endpoint
type MatchFunc func([]byte) bool
// MatchAll always returns true
func MatchAll(b []byte) bool {
return true
}
// MatchNone always returns false
func MatchNone(b []byte) bool {
return false
}
// MatchRange is a MatchFunc that accepts packets with the first byte in [lower..upper]
func MatchRange(lower, upper byte) MatchFunc {
return func(buf []byte) bool {
if len(buf) < 1 {
return false
}
b := buf[0]
return b >= lower && b <= upper
}
}
// MatchFuncs as described in RFC7983
// https://tools.ietf.org/html/rfc7983
// +----------------+
// | [0..3] -+--> forward to STUN
// | |
// | [16..19] -+--> forward to ZRTP
// | |
// packet --> | [20..63] -+--> forward to DTLS
// | |
// | [64..79] -+--> forward to TURN Channel
// | |
// | [128..191] -+--> forward to RTP/RTCP
// +----------------+
// MatchSTUN is a MatchFunc that accepts packets with the first byte in [0..3]
// as defied in RFC7983
func MatchSTUN(b []byte) bool {
return MatchRange(0, 3)(b)
}
// MatchZRTP is a MatchFunc that accepts packets with the first byte in [16..19]
// as defied in RFC7983
func MatchZRTP(b []byte) bool {
return MatchRange(16, 19)(b)
}
// MatchDTLS is a MatchFunc that accepts packets with the first byte in [20..63]
// as defied in RFC7983
func MatchDTLS(b []byte) bool {
return MatchRange(20, 63)(b)
}
// MatchTURN is a MatchFunc that accepts packets with the first byte in [64..79]
// as defied in RFC7983
func MatchTURN(b []byte) bool {
return MatchRange(64, 79)(b)
}
// MatchSRTPOrSRTCP is a MatchFunc that accepts packets with the first byte in [128..191]
// as defied in RFC7983
func MatchSRTPOrSRTCP(b []byte) bool {
return MatchRange(128, 191)(b)
}
func isRTCP(buf []byte) bool {
// Not long enough to determine RTP/RTCP
if len(buf) < 4 {
return false
}
var rtcpPacketType uint8
r := bytes.NewReader([]byte{buf[1]})
if err := binary.Read(r, binary.BigEndian, &rtcpPacketType); err != nil {
return false
} else if rtcpPacketType >= 192 && rtcpPacketType <= 223 {
return true
}
return false
}
// MatchSRTP is a MatchFunc that only matches SRTP and not SRTCP
func MatchSRTP(buf []byte) bool {
return MatchSRTPOrSRTCP(buf) && !isRTCP(buf)
}
// MatchSRTCP is a MatchFunc that only matches SRTCP and not SRTP
func MatchSRTCP(buf []byte) bool {
return MatchSRTPOrSRTCP(buf) && isRTCP(buf)
}
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