[asterisk-dev] Wrong IP-address in SDP when on NAT in challenged Invite

[Joshua C. Colp]

On Thu, May 6, 2021 at 7:12 PM Michael Maier <m1278468 at mailbox.org> wrote:

<snip>

Another question follows now, which is firewall related: At which point
> exactly starts asterisk to send outgoing RTP?
>
> Why am I asking? Given is an outbound call e.g. Portfilter opens
> incoming port as soon as it has seen an outgoing packet. If there is no
> outgoing RTP, the incoming RTP packages will be dropped because
> portfilter doesn't know what to do with them (no conntrack information
> there).
>
> After applying a DNAT-rule, things are working fine - but that's not a
> good solution.
>
> Now I'm wondering why asterisk doesn't always start sending RTP after a
> 200 OK sdp (or an any other arbitrary SDP) containing a=sendrecv and
> correct media and dest port.
>
> Sometimes asterisk begins to send RTP not until it receives RTP from
> Callee - though the Caller already sends RTP - therefore there is no
> reason to not send anything. I'm quite puzzled.
>
> This behavior is 100% reproducible for certain numbers.
>
>
> Do you by chance have any idea?
>

As soon as Asterisk has received media and the media has gotten past strict
RTP protection, it should then forward that media outward to the target in
the SDP. RTP debug and core debug shows when this is happening.

--
Joshua C. Colp
Asterisk Technical Lead
Sangoma Technologies
Check us out at www.sangoma.com and www.asterisk.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.digium.com/pipermail/asterisk-dev/attachments/20210507/f55d09f6/attachment-0001.html>