TT#92250 add `single codec` flag

Change-Id: I7c84e1f906fec93ed624d2fb4a4d9e9bfc9b4109

README.md

@@ -774,6 +774,12 @@ Optionally included keys are:
 		PCMA. With this flag however, *rtpengine* honours the single accepted codec from the
 		answer and so is able to eliminate PCMA from its own answer as it's not needed.
 
+	- `single codec`
+
+		Using this flag in an `answer` message will leave only the first listed codec in place
+		and will remove all others from the list. Useful for RTP clients which get confused if
+		more than one codec is listed in an answer.
+
 	- `all`
 
 		Only relevant to the `unblock media` message. Instructs *rtpengine* to remove not only a

daemon/call_interfaces.c

@@ -816,6 +816,9 @@ static void call_ng_flags_flags(struct sdp_ng_flags *out, str *s, void *dummy) {
 		case CSH_LOOKUP("symmetric-codecs"):
 			out->symmetric_codecs = 1;
 			break;
+		case CSH_LOOKUP("single-codec"):
+			out->single_codec = 1;
+			break;
 		case CSH_LOOKUP("inject-DTMF"):
 			out->inject_dtmf = 1;
 			break;

daemon/codec.c

@@ -2572,6 +2572,25 @@ void codec_rtp_payload_types(struct call_media *media, struct call_media *other_
 		}
 	}
 
+	if (flags->opmode == OP_ANSWER && flags->single_codec) {
+		int have_codec = 0;
+		for (GList *l = media->codecs_prefs_recv.head; l;) {
+			struct rtp_payload_type *pt = l->data;
+			ensure_codec_def(pt, media);
+			if (pt->codec_def && pt->codec_def->supplemental) {
+				// leave these alone
+				l = l->next;
+				continue;
+			}
+			if (!have_codec) {
+				have_codec = 1;
+				l = l->next;
+				continue;
+			}
+			l = __delete_receiver_codec(media, l);
+		}
+	}
+
 #ifdef WITH_TRANSCODING
 	// add transcode codecs
 	for (GList *l = flags->codec_transcode.head; l; l = l->next) {

include/call_interfaces.h

@@ -80,6 +80,7 @@ struct sdp_ng_flags {
 	    always_transcode:1,
 	    asymmetric_codecs:1,
 	    symmetric_codecs:1,
+	    single_codec:1,
 	    inject_dtmf:1,
 	    t38_decode:1,
 	    t38_force:1,

t/auto-daemon-tests.pl

@@ -1045,6 +1045,108 @@ rcv($sock_a, $port_b, rtpm(96, 1004, 4200, $ssrc, "\xf0\x14\x41\x00\x30\x44\x41\
 
 
 
+new_call;
+
+offer('multi codec offer/answer', {
+		ICE => 'remove',
+		flags => [],
+	}, <<SDP);
+v=0
+o=Z 58440449 0 IN IP4 89.225.243.254
+s=Z
+c=IN IP4 89.225.243.254
+t=0 0
+m=audio 8000 RTP/AVP 0 8
+a=sendrecv
+--------------------------------------
+v=0
+o=Z 58440449 0 IN IP4 89.225.243.254
+s=Z
+c=IN IP4 203.0.113.1
+t=0 0
+m=audio PORT RTP/AVP 0 8
+a=rtpmap:0 PCMU/8000
+a=rtpmap:8 PCMA/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+answer('multi codec offer/answer', {
+		ICE => 'remove',
+		flags => [],
+	}, <<SDP);
+v=0
+o=Z 58440449 0 IN IP4 89.225.243.254
+s=Z
+c=IN IP4 89.225.243.254
+t=0 0
+m=audio 8000 RTP/AVP 0 8
+a=sendrecv
+--------------------------------------
+v=0
+o=Z 58440449 0 IN IP4 89.225.243.254
+s=Z
+c=IN IP4 203.0.113.1
+t=0 0
+m=audio PORT RTP/AVP 0 8
+a=rtpmap:0 PCMU/8000
+a=rtpmap:8 PCMA/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+new_call;
+
+offer('multi codec offer/answer w single-codec', {
+		ICE => 'remove',
+		flags => [],
+	}, <<SDP);
+v=0
+o=Z 58440449 0 IN IP4 89.225.243.254
+s=Z
+c=IN IP4 89.225.243.254
+t=0 0
+m=audio 8000 RTP/AVP 0 8
+a=sendrecv
+--------------------------------------
+v=0
+o=Z 58440449 0 IN IP4 89.225.243.254
+s=Z
+c=IN IP4 203.0.113.1
+t=0 0
+m=audio PORT RTP/AVP 0 8
+a=rtpmap:0 PCMU/8000
+a=rtpmap:8 PCMA/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+answer('multi codec offer/answer', {
+		ICE => 'remove',
+		flags => ['single codec'],
+	}, <<SDP);
+v=0
+o=Z 58440449 0 IN IP4 89.225.243.254
+s=Z
+c=IN IP4 89.225.243.254
+t=0 0
+m=audio 8000 RTP/AVP 0 8
+a=sendrecv
+--------------------------------------
+v=0
+o=Z 58440449 0 IN IP4 89.225.243.254
+s=Z
+c=IN IP4 203.0.113.1
+t=0 0
+m=audio PORT RTP/AVP 0
+a=rtpmap:0 PCMU/8000
+a=sendrecv
+a=rtcp:PORT
+SDP
+
+
+
+
 new_call;
 
 offer('add transcode w supp codec', {