External trigger for CoA

[Alan DeKok]

On Sep 27, 2020, at 1:34 AM, Vadim via Freeradius-Users <freeradius-users at lists.freeradius.org> wrote:
> I have been able to implement this approach with coa-relay and it mostly working, but there are a couple of issues with that.

  That's good.

> Here are my observations (note I am talking about FR 3.0.x branch):
> 
> 1) We may specify Packet-DST-IP-Address/Packet-Dst-IPv6-Address or Home-Server-Pool to be able to forward CoA request to the particular NAS.
> 
> 2) If Packet-DST-IP-Address is specified then FR searches the home_server by port type UDP and this is hardcoded. Of course, if I have configured the home_server with RADSEC/TCP FR cannot find it. But at this step that would not be such a big issue if I would be able to specify the NAS via Home-Server-Pool.

  Yeah, that should be configurable.  But you can also use Home-Server-Name = "name" to avoid IP / port / protocol issues.

> 3) If Home-Server-Pool is used, FR still cannot find the home_server. Moreover, it is crashed with SIGSEGV. The reason for this is:
> 
> 	a) listener is set to null in request_coa_originate in process.c
> 	   coa->listener = NULL; /* copied here by request_alloc_fake(), but not needed */
> 	   here is the git ref: https://github.com/FreeRADIUS/freeradius-server/commit/d9dd706503897a4c271b0424221d651115fab446
> 
> 
> 	b) listener type is checked in home_server_ldb in realms.c
> 
>                if ((request->listener->type == RAD_LISTEN_DETAIL) &&
>                    (request->packet->code == PW_CODE_ACCOUNTING_REQUEST) &&
>                    (fr_ipaddr_cmp(&home->ipaddr, &request->packet->src_ipaddr) == 0)) {
>                        continue;
>                }
> 	   Here the listener is NULL and hence the SIGSEGV.

  That's wrong.

> Once I deleted the "coa->listener = NULL;" The flow started to be working as expected.
> 
> Also, if I check if the listener is NULL before checking its type in home_server_ldb - that also worked.
> 
> 
> The questions are:
> 
> 	1) May you recall the reason for "coa->listener = NULL;" in request_coa_originate?

  I don't recall exactly, but it's the correct thing to do.  The CoA packet wasn't received from a socket, so it shouldn't have a listener.

> 	2) Is it safe to remove that line, essentially to revert the commit referenced above?
> 	3) Alternatively, will that be better to check for the listener is NULL just to avoid the crash in home_server_ldb?

  I pushed a fix in home_server_ldb().

  Alan DeKok.