res_pjsip_session.c: Send 100 Trying out earlier to prevent retransmissions.

If ICE is enabled and a STUN server does not respond then we will block
until we give up on the STUN response.  This will take nine seconds.  In
the mean time the peer that sent the INVITE will send retransmissions.

* Restructure res_pjsip_session.c:new_invite() to send a 100 Trying out
earlier to prevent these retransmissions.

ASTERISK-26890

Change-Id: Ie3fc611e53a0eff6586ad55e4aacad81cf6319a8

res/res_pjsip_session.c

@@ -2148,12 +2148,29 @@ static int new_invite(void *data)
 		goto end;
 	};
 
-	if ((sdp_info = pjsip_rdata_get_sdp_info(invite->rdata)) && (sdp_info->sdp_err == PJ_SUCCESS) && sdp_info->sdp) {
+	pjsip_timer_setting_default(&timer);
+	timer.min_se = invite->session->endpoint->extensions.timer.min_se;
+	timer.sess_expires = invite->session->endpoint->extensions.timer.sess_expires;
+	pjsip_timer_init_session(invite->session->inv_session, &timer);
+
+	/*
+	 * At this point, we've verified what we can that won't take awhile,
+	 * so let's go ahead and send a 100 Trying out to stop any
+	 * retransmissions.
+	 */
+	if (pjsip_inv_initial_answer(invite->session->inv_session, invite->rdata, 100, NULL, NULL, &tdata) != PJ_SUCCESS) {
+		pjsip_inv_terminate(invite->session->inv_session, 500, PJ_TRUE);
+		goto end;
+	}
+	ast_sip_session_send_response(invite->session, tdata);
+
+	sdp_info = pjsip_rdata_get_sdp_info(invite->rdata);
+	if (sdp_info && (sdp_info->sdp_err == PJ_SUCCESS) && sdp_info->sdp) {
 		if (handle_incoming_sdp(invite->session, sdp_info->sdp)) {
-			if (pjsip_inv_initial_answer(invite->session->inv_session, invite->rdata, 488, NULL, NULL, &tdata) == PJ_SUCCESS) {
+			tdata = NULL;
+			if (pjsip_inv_end_session(invite->session->inv_session, 488, NULL, &tdata) == PJ_SUCCESS
+				&& tdata) {
 				ast_sip_session_send_response(invite->session, tdata);
-			} else  {
-				pjsip_inv_terminate(invite->session->inv_session, 488, PJ_TRUE);
 			}
 			goto end;
 		}
@@ -2166,31 +2183,19 @@ static int new_invite(void *data)
 
 	/* If we were unable to create a local SDP terminate the session early, it won't go anywhere */
 	if (!local) {
-		if (pjsip_inv_initial_answer(invite->session->inv_session, invite->rdata, 500, NULL, NULL, &tdata) == PJ_SUCCESS) {
+		tdata = NULL;
+		if (pjsip_inv_end_session(invite->session->inv_session, 500, NULL, &tdata) == PJ_SUCCESS
+			&& tdata) {
 			ast_sip_session_send_response(invite->session, tdata);
-		} else  {
-			pjsip_inv_terminate(invite->session->inv_session, 500, PJ_TRUE);
 		}
 		goto end;
-	} else {
-		pjsip_inv_set_local_sdp(invite->session->inv_session, local);
-		pjmedia_sdp_neg_set_prefer_remote_codec_order(invite->session->inv_session->neg, PJ_FALSE);
-#ifdef PJMEDIA_SDP_NEG_ANSWER_MULTIPLE_CODECS
-		pjmedia_sdp_neg_set_answer_multiple_codecs(invite->session->inv_session->neg, PJ_TRUE);
-#endif
 	}
 
-	pjsip_timer_setting_default(&timer);
-	timer.min_se = invite->session->endpoint->extensions.timer.min_se;
-	timer.sess_expires = invite->session->endpoint->extensions.timer.sess_expires;
-	pjsip_timer_init_session(invite->session->inv_session, &timer);
-
-	/* At this point, we've verified what we can, so let's go ahead and send a 100 Trying out */
-	if (pjsip_inv_initial_answer(invite->session->inv_session, invite->rdata, 100, NULL, NULL, &tdata) != PJ_SUCCESS) {
-		pjsip_inv_terminate(invite->session->inv_session, 500, PJ_TRUE);
-		goto end;
-	}
-	ast_sip_session_send_response(invite->session, tdata);
+	pjsip_inv_set_local_sdp(invite->session->inv_session, local);
+	pjmedia_sdp_neg_set_prefer_remote_codec_order(invite->session->inv_session->neg, PJ_FALSE);
+#ifdef PJMEDIA_SDP_NEG_ANSWER_MULTIPLE_CODECS
+	pjmedia_sdp_neg_set_answer_multiple_codecs(invite->session->inv_session->neg, PJ_TRUE);
+#endif
 
 	handle_incoming_request(invite->session, invite->rdata);