chan_sip: Better ICE handling for RTCP-MUX

If we are offered or are offering RTCP-MUX, don't consider RTCP ICE
candidates. This confuses certain browsers (current Firefox for
example) and causes intial audio setup delays.

ASTERISK-26982 #close

Change-Id: Ifeaf47e83972fe8dbe58b7fb3d6d1823400cfb91

1 files changed, 36 insertions, 8 deletions

diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index ff2e5ba3f..5affee6eb 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -1211,7 +1211,7 @@ static int process_sdp(struct sip_pvt *p, struct sip_request *req, int t38action
 static int process_sdp_o(const char *o, struct sip_pvt *p);
 static int process_sdp_c(const char *c, struct ast_sockaddr *addr);
 static int process_sdp_a_sendonly(const char *a, int *sendonly);
-static int process_sdp_a_ice(const char *a, struct sip_pvt *p, struct ast_rtp_instance *instance);
+static int process_sdp_a_ice(const char *a, struct sip_pvt *p, struct ast_rtp_instance *instance, int rtcp_mux);
 static int process_sdp_a_rtcp_mux(const char *a, struct sip_pvt *p, int *requested);
 static int process_sdp_a_dtls(const char *a, struct sip_pvt *p, struct ast_rtp_instance *instance);
 static int process_sdp_a_audio(const char *a, struct sip_pvt *p, struct ast_rtp_codecs *newaudiortp, int *last_rtpmap_codec);
@@ -10135,6 +10135,24 @@ static void set_ice_components(struct sip_pvt *p, struct ast_rtp_instance *insta
 	}
 }
 
+static int has_media_level_attribute(int start, struct sip_request *req, const char *attr)
+{
+	int next = start;
+	char type;
+	const char *value;
+
+	/* We don't care about the return result here */
+	get_sdp_iterate(&next, req, "m");
+
+	while ((type = get_sdp_line(&start, next, req, &value)) != '\0') {
+		if (type == 'a' && !strcasecmp(value, attr)) {
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
 /*! \brief Process SIP SDP offer, select formats and activate media channels
 	If offer is rejected, we will not change any properties of the call
  	Return 0 on success, a negative value on errors.
@@ -10277,13 +10295,13 @@ static int process_sdp(struct sip_pvt *p, struct sip_request *req, int t38action
 			else if (process_sdp_a_image(value, p))
 				processed = TRUE;
 
-			if (process_sdp_a_ice(value, p, p->rtp)) {
+			if (process_sdp_a_ice(value, p, p->rtp, 0)) {
 				processed = TRUE;
 			}
-			if (process_sdp_a_ice(value, p, p->vrtp)) {
+			if (process_sdp_a_ice(value, p, p->vrtp, 0)) {
 				processed = TRUE;
 			}
-			if (process_sdp_a_ice(value, p, p->trtp)) {
+			if (process_sdp_a_ice(value, p, p->trtp, 0)) {
 				processed = TRUE;
 			}
 
@@ -10323,6 +10341,7 @@ static int process_sdp(struct sip_pvt *p, struct sip_request *req, int t38action
 		int image = FALSE;
 		int text = FALSE;
 		int processed_crypto = FALSE;
+		int rtcp_mux_offered = 0;
 		char protocol[18] = {0,};
 		unsigned int x;
 		struct ast_rtp_engine_dtls *dtls;
@@ -10342,6 +10361,9 @@ static int process_sdp(struct sip_pvt *p, struct sip_request *req, int t38action
 		AST_LIST_INSERT_TAIL(&p->offered_media, offer, next);
 		offer->type = SDP_UNKNOWN;
 
+		/* We need to check for this ahead of time */
+		rtcp_mux_offered = has_media_level_attribute(iterator, req, "rtcp-mux");
+
 		/* Check for 'audio' media offer */
 		if (strncmp(m, "audio ", 6) == 0) {
 			if ((sscanf(m, "audio %30u/%30u %17s %n", &x, &numberofports, protocol, &len) == 3 && len > 0) ||
@@ -10708,7 +10730,7 @@ static int process_sdp(struct sip_pvt *p, struct sip_request *req, int t38action
 			case 'a':
 				/* Audio specific scanning */
 				if (audio) {
-					if (process_sdp_a_ice(value, p, p->rtp)) {
+					if (process_sdp_a_ice(value, p, p->rtp, rtcp_mux_offered)) {
 						processed = TRUE;
 					} else if (process_sdp_a_dtls(value, p, p->rtp)) {
 						processed_crypto = TRUE;
@@ -10729,7 +10751,7 @@ static int process_sdp(struct sip_pvt *p, struct sip_request *req, int t38action
 				}
 				/* Video specific scanning */
 				else if (video) {
-					if (process_sdp_a_ice(value, p, p->vrtp)) {
+					if (process_sdp_a_ice(value, p, p->vrtp, rtcp_mux_offered)) {
 						processed = TRUE;
 					} else if (process_sdp_a_dtls(value, p, p->vrtp)) {
 						processed_crypto = TRUE;
@@ -10748,7 +10770,7 @@ static int process_sdp(struct sip_pvt *p, struct sip_request *req, int t38action
 				}
 				/* Text (T.140) specific scanning */
 				else if (text) {
-					if (process_sdp_a_ice(value, p, p->trtp)) {
+					if (process_sdp_a_ice(value, p, p->trtp, rtcp_mux_offered)) {
 						processed = TRUE;
 					} else if (process_sdp_a_text(value, p, &newtextrtp, red_fmtp, &red_num_gen, red_data_pt, &last_rtpmap_codec)) {
 						processed = TRUE;
@@ -11270,7 +11292,7 @@ static int process_sdp_a_sendonly(const char *a, int *sendonly)
 	return found;
 }
 
-static int process_sdp_a_ice(const char *a, struct sip_pvt *p, struct ast_rtp_instance *instance)
+static int process_sdp_a_ice(const char *a, struct sip_pvt *p, struct ast_rtp_instance *instance, int rtcp_mux_offered)
 {
 	struct ast_rtp_engine_ice *ice;
 	int found = FALSE;
@@ -11290,6 +11312,12 @@ static int process_sdp_a_ice(const char *a, struct sip_pvt *p, struct ast_rtp_in
 		found = TRUE;
 	} else if (sscanf(a, "candidate: %31s %30u %3s %30u %23s %30u typ %5s %*s %23s %*s %30u", foundation, &candidate.id, transport, (unsigned *)&candidate.priority,
 			  address, &port, cand_type, relay_address, &relay_port) >= 7) {
+
+		if (rtcp_mux_offered && ast_test_flag(&p->flags[2], SIP_PAGE3_RTCP_MUX) && candidate.id > 1) {
+			/* If we support RTCP-MUX and they offered it, don't consider RTCP candidates */
+			return TRUE;
+		}
+
 		candidate.foundation = foundation;
 		candidate.transport = transport;