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Recently I upgraded to Wireshark 1.12.2 and it started decode some RTP packets as STU packets. Why? Upgrade to 1.12.4 showed the same behavior.

Now, according to STUN RFC5389, the UDP payload bits 0 and 1 are both 0 and the RTP packets are version 2 so there is no way to misinterpret the two.

asked 24 Apr '15, 14:20

prorad's gravatar image

accept rate: 0%

edited 25 Apr '15, 04:18

Bill%20Meier's gravatar image

Bill Meier ♦♦

Do you have the "Try to decode RTP outside of conversations" preference for RTP set?

According to RFC 3489, the UDP payload bits 0 and 1 are not necessarily both 0; Wireshark dissects both "classic STUN" (RFC 3489) and "current" STUN (RFC 5389).

(24 Apr '15, 16:15) Guy Harris ♦♦

Yes I do have this set.

(24 Apr '15, 17:41) prorad

So are those packets showing up as "ChannelData TURN Message" packets? Those are described in section 11.4 of RFC 5766.

(24 Apr '15, 17:48) Guy Harris ♦♦

According to rfc3489, all supported STUN message types have both bits 0 and 1 equal zero.

That's why these two bits would be nailed to zero. As such, there should be no collision between the STUN protocol and the RTP version 2.

That's my understanding.

(24 Apr '15, 17:50) prorad

I was going say "that's why rfc5389 could nail the bits 0 and 1 to zero."

(24 Apr '15, 17:52) prorad

...and RFC 5766 says that ChannelData messages don't necessarily have both bits 0 and 1 equal zero, so they're not nailed to zero, and there is a risk of collision between TURN and RTP version 2.

(24 Apr '15, 18:07) Guy Harris ♦♦

Correct, those packets are showing up as "ChannelData TURN Message" packets.

(25 Apr '15, 09:59) prorad
showing 5 of 7 show 2 more comments

Wireshark's STUN/TURN dissector is, as indicated, dissecting the RTP packets as TURN packets.

This would either require a stronger TURN heuristic or a way to disable the TURN heuristic. Please file a bug at the Wireshark Bugzilla, and attach a capture file containing the mis-dissected packets.

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answered 25 Apr '15, 11:36

Guy%20Harris's gravatar image

Guy Harris ♦♦
accept rate: 19%

Thank you. Will do.

(25 Apr '15, 11:43) prorad

Created a bugzilla but report "Bug 11152"

(27 Apr '15, 08:33) prorad
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question asked: 24 Apr '15, 14:20

question was seen: 4,517 times

last updated: 27 Apr '15, 08:43

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