The problem that you're facing is that RTP doesn't define a very
"unique" way to determine that this UDP data actually is RTP. So, as
far as I know, the only way you can automagically dissect UDP data as
RTP is by capturing the control packets as well (i.e. SIP/SDP, IPDC,
MGCP, RTCP, etc).
I haven't worked with RTP in about a year, so I'm a little rusty, but as
I recall, you can determine the IP:Port information from the session
control packets (if they're captured as well) in the form of SIP/SDP
packets for example. I wrote some code a while back to decode define
the conversation from an SDP packet, but I don't think it ever got
checked in (as I recall, it had a bunch of memory leaks and general "not
good code" problems).
Here's my original post:
http://marc.theaimsgroup.com/?l=ethereal-dev&m=99184276504320&w=2
And here was Guy Harris's response. I never took the patch any further
than my original post because I didn't have time:
http://marc.theaimsgroup.com/?l=ethereal-dev&m=99292667406710&w=2
Hope it helps!
Marco Molteni wrote:
Hi,
first of all, I would like to say a big THANK YOU to all the people
involved in Ethereal :-)
The following comes from a MPEG-4 streaming dump but the question is
more generic.
Real Time Protocol (RTP) has a dynamic range of payload types, from 96 to 127.
Ethereal shows (obviously) such RTP packets as payload type=Unknown.
One way to know the payload type is from a RTSP/SD packet.
Now, let's say I know the payload type, how do I tell ethereal to use
that payload type to dissect the RTP packet? Do I just write the
dissector and then use "Tools|Decode Packet As" to map the RTP protocol
type to my dissector?
Also, it seems to me that the "Decode Packet As" doesn't have the
granularity that I want, because it allows me to map, for example, UDP
plus a source/destination port to a protocol, while what I would like to
do is to map the RTP (contained in UDP) type field to a protocol. Any
suggestions?
thanks for your help
Marco
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