[asterisk-dev] Issue with PJSIP contacts being "unavailable"

[asterisk at phreaknet.org]

On 6/27/2023 6:22 PM, Joshua C. Colp wrote:
> On Tue, Jun 27, 2023 at 7:18 PM <asterisk at phreaknet.org 
> <mailto:asterisk at phreaknet.org>> wrote:
>
>     On 6/27/2023 6:07 PM, Joshua C. Colp wrote:
>     >
>     > I'm not sure what exactly you are referring to with "using the
>     > transport used for registration". If "rewrite_contact" is set to
>     yes
>     > then the existing active connection should get used. If you are
>     > referring to Asterisk establishing a new outgoing connection to the
>     > registered Contact, then as long as it is optional and doesn't
>     break
>     > other behavior fine.
>
>     Basically, suppose a device registers on a port, associated with some
>     configured transport.
>
>     The reason I'm doing this now is that initially, calls out *to*
>     devices
>     would just use the default transport (the first one configured, or
>     something like that). Specifying a transport= in the endpoint
>     explicitly
>     ensured they'd only use the appropriate one. The problem still
>     remains
>     though that we don't necessarily know what transport a device is
>     going
>     to use in advance, and it could also change at any time.
>
>       I don't know if this would be a "new" outgoing connection to the
>     contact or not... I was noticing this issue with outbound calls to
>     devices using the wrong transport (e.g. an ATA registered using
>     TLS, and
>     Asterisk would call the device using UDP, on a different port). The
>     description for "rewrite_contact" says "Allow Contact header to be
>     rewritten with the source IP address-port" which doesn't really
>     clarify
>     that, but if that means it'll always use the same transport out to
>     the
>     device that the device initiated a connection on, no matter what,
>     then I
>     think that will do the trick. I just want Asterisk to go along with
>     whatever the device wants to do. If there's a gap with
>     "rewrite_contact"
>     then I guess a new option is still needed to do the other half.
>
>
> The source IP address, port, and transport type become the Contact. 
> The Contact target is used for requests, and PJSIP looks for an 
> existing active connection meeting that criteria. If such a connection 
> is found then it is reused.

Thanks - just to clarify, if such a connection *isn't* found, this won't 
help me right now? It would still use the default transport even with 
rewrite_contact=yes?

In that case, I'm thinking the new option would add on to this by 
extending that behavior to if there isn't an active connection and it 
needs to set up a new one. Basically "use the contact to determine the 
transport, unconditionally" is essentially what it would do.

I guess for devices that don't register, you wouldn't necessarily have a 
contact so maybe that's why this isn't done all the time? But those are 
probably the cases where specifying a transport explicitly would 
probably make more sense anyways, and I'm not concerned about those, 
only things that register and as such a contact would always be available.