Thank you for the advice, @miconda. I believe this may be a bug in PJSIP's header parsing (https://trac.pjsip.org/repos/browser/pjproject/trunk/pjsip/src/pjsip/sip_parser.c#L1128). I'm not a C coder, but I've learned to troll through the code until I find something reasonable. Perhaps you can spot something in there. I have requested to join the PJSIP mailing list to ask about this issue.

I asked originally about the quoting because I noticed Kamailio does quote the "received" parameter in the Contact header when it's sent back to a UAC:

SIP/2.0 200 OK.
v: SIP/2.0/UDP 10.1.1.1:5060;rport=5060;branch=z9hG4bKPjCF9fXKT.TUYCvcI8L4gj70nJMeMYZwXR;received=10.1.1.2.
f: "Test" <sip:test@example.com>;tag=fFfFWPFbM71fqOQLp9biV6jtcZy-M3Ja.
t: "Test" <sip:test@example.com>;tag=ac90c8713242940d16090974f12e49d3.d0ca.
i: ZU0l8HgtMQ80aFG.P6LdNwCTtFiAlTBr.
CSeq: 895 REGISTER.
Contact: <sip:test@10.1.1.1:5060;ob>;expires=900;received="sip:10.1.1.2:5060".
Supported: outbound.
Content-Length: 0.

—
Reply to this email directly or view it on GitHub.