chan_sip.c Session timers get removed on UPDATE

If Asterisk receives a SIP REFER with Session-Timers UAC
maintain Session-Timers when sending UPDATE"

ASTERISK-29843

Change-Id: I8e9a21c13bf757fa34d778f49ba3cf859b29ae5c

channels/chan_sip.c

@@ -12507,11 +12507,9 @@ static int reqprep(struct sip_request *req, struct sip_pvt *p, int sipmethod, ui
 	   An exception to this behavior is the ACK request. Since Asterisk never requires
 	   session-timers support from a remote end-point (UAS) in an INVITE, it must
 	   not send 'Require: timer' header in the ACK request.
-	   This should only be added in the INVITE transactions, not MESSAGE or REFER or other
-	   in-dialog messages.
 	*/
 	if (p->stimer && p->stimer->st_active == TRUE && p->stimer->st_active_peer_ua == TRUE
-	    && sipmethod == SIP_INVITE) {
+	    && (sipmethod == SIP_INVITE || sipmethod == SIP_UPDATE)) {
 		char se_hdr[256];
 		snprintf(se_hdr, sizeof(se_hdr), "%d;refresher=%s", p->stimer->st_interval,
 			p->stimer->st_ref == SESSION_TIMER_REFRESHER_US ? "uac" : "uas");

doc/CHANGES-staging/chan_sip_session-timer_on_update.txt

@@ -0,0 +1,6 @@
+Subject: chan_sip
+
+Session timers get removed on UPDATE
+Fix if Asterisk receives a SIP REFER with Session-Timers UAC
+that Asterisk maintains Session-Timers when sending UPDATE request
+