[pjsip] via header and TLS on a Freeswitch PBX

[Pierre-Luc Bacon]

I am implementing TLS transport from the PJSIP library and ran over a
via header problem while trying to register to Freeswitch server. 

>From the debug output on the freeswitch box I see: 
"nta: Via check: invalid transport "SIP/2.0/tls" from
192.168.1.12:37842"

Where 192.168.1.12 is from the the softphone that is implementing
PJSIP. 

Digging into the freeswitch source code, I saw that this message was
coming from 

libs/sofia-sip/libsofia-sip-ua/nta/nta.c

where they do "[...]!su_strmatch(v->v_protocol, tpv->v_protocol)", and
su_strmatch is a wrapper over strcmp.

It turns out that "SIP/2.0/tls" (pjsip) is compared with
"SIP/2.0/TLS" (sofia) and strcmp being case sensitive, the match fails. 


I tried to look in RFC3261 to see what was said about that but I
couldn't find it exactly. I'm pretty sure that PJSIP is doing it right
and that the via header should be processed in a case-insensitive way.