[asterisk-dev] Segfault because RTP frame datalen negative

Mohit Dhiman mohitdhiman736 at gmail.com
Fri Jan 31 06:35:56 CST 2020

I'm using Asterisk-13.21.
I'll check out the code in ast_rtp_interpret but the problem is that I do
not have the access to the production environment to recreate this issue.

can anybody suggest any tool to create dummy RTP payloads or some SIP
client that can generate real-time text over RTP?

On Fri, 31 Jan 2020 at 16:51, Joshua C. Colp <jcolp at sangoma.com> wrote:

> On Fri, Jan 31, 2020 at 3:06 AM Mohit Dhiman <mohitdhiman736 at gmail.com>
> wrote:
>> Hi,
>> I'm trying to debug a segfault in ast_frdup which happened because of
>> the negative datalen of the ast_frame for frame type AST_FRAME_TEXT.
>> My question is that how an RTP frame in categorized as of type TEXT
>> because I can only see two types of RTP payload in network capture (not of
>> the time of segfault)
>> one is G-711 ulaw and the other is Payload Type 106 (not defined in SDP).
>> This Payload 106 is received at the start of the RTP stream and is
>> received only once in an RTP stream.
>> My other question is how the datalen gets calculated for an RTP frame
>> and what could be the possible reason for this to come out negative for it
>> should never be negative as confirmed by Joshua on Asterisk Community Forum.
>> It would be a great help if anybody could help me figure this out.
> What version of Asterisk is in use?
> Otherwise the code itself that interprets RTP packets is
> ast_rtp_interpret[1] in res_rtp_asterisk.c. Adding log messages or reading
> that would probably yield information.
> [1]
> https://github.com/asterisk/asterisk/blob/master/res/res_rtp_asterisk.c#L6932
> --
> Joshua C. Colp
> Asterisk Technical Lead
> Sangoma Technologies
> Check us out at www.sangoma.com and www.asterisk.org
> --
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