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
+––––––––+
match_dtls is a MatchFunc that accepts packets with the first byte in [20..63]
as defied in RFC7983