[asterisk-dev] Segfault because RTP frame datalen negative

Mohit Dhiman mohitdhiman736 at gmail.com
Fri Jan 31 06:40:18 CST 2020

turns out Asterisk-13.21 does not have the ast_rtp_interpret is there a
similar entry point to interpret RTP packets?

On Fri, 31 Jan 2020 at 18:05, Mohit Dhiman <mohitdhiman736 at gmail.com> wrote:

> 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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