Hello,

I'm using tryit.jssip.net with a SIP-over-Websocket server on the other side. 
What's worth noting is that it really doesn't matter what the caller is using 
(Chrome, another FF, or a plain SIP client), because the receiving FF is only 
seeing the server's ICE candidates in the SDP, no matter what's on the other 
side.

So what's basically happening is this (please correct me if I'm 
misunderstanding something):

1. FF receives an inbound call, and jssip is asking for permissions to access 
media.
2. FF starts sending out "normal" STUN requests to the STUN server configured 
in the javascript app.
3. FF now sends STUN binding requests with the "ICE-CONTROLLED" attribute to 
the candidates in the SDP.
4. FF receives STUN binding responses from these candidates. That way, FF now 
knows it can happily reach some of the candidates.
5. What I would expect from FF now (and this is also what Chrome is doing) is a 
STUN request with a set USE-CANDIDATE attribute being sent to one of the 
candidates, to tell the other side which address to use. However, I don't see 
any such request.
6. So as a consequence, the other side starts sending UDP packets for DTLS 
negotiation to the address defined by FF in the c=/m= lines of the answer, but 
they never reach FF through the NAT.

The reason why outbound calls from FF work is that compared to the inbound 
scenario, FF starts sending UDP packets to the other side, which learns from 
the source address of these packets where to send responses to. In the inbound 
scenario, FF doesn't send any packets but seems to wait for the other side to 
start sending UDP (which it does, but to the wrong address due to the missing 
USE-CANDIDATE, and therefore to the wrong address).

I will open a bug report with a pcap of the STUN traffic attached, but maybe 
someone here knows whether this is intended behavior or whether it might be a 
real issue.

Andreas

On Thursday, March 20, 2014 8:09:28 PM UTC+1, Randell Jesup wrote:
> On 3/20/2014 2:18 PM, Eric Rescorla wrote:
> 
> > On Thu, Mar 20, 2014 at 10:40 AM, <[email protected]> wrote:
> 
> >
> 
> >> Calling from FF 32 (nightly) to Chrome works fine, however calling from
> 
> >> Chrome to FF fails.
> 
> >>
> 
> >> What I can see is FF sending a couple of STUN bind requests to the server,
> 
> >> but it never puts the USE-CANDIDATE into any of them. Any idea why this
> 
> >> could be the case?
> 
> > To the server? Or to Chrome?
> 
> >
> 
> > In any case, please file a bug with supply the about:webrtc logs
> 
> > from Firefox and the Chrome logs (webrtc:internal, perhaps?)
> 
> 
> 
> Also, what webpage/service are you using to set up the call?
> 
> 
> 
> -- 
> 
> Randell Jesup, Mozilla

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