TT#94201 add ICE=default option

Change-Id: If10e0aa284cc7cc5c1e69855733835bd5b52da31

README.md

@@ -873,18 +873,26 @@ Optionally included keys are:
 
 * `ICE`
 
-	Contains a string, valid values are `remove`, `force` or `force-relay`.
-	With `remove`, any ICE attributes are
-	stripped from the SDP body. With `force`, ICE attributes are first stripped, then new attributes are
-	generated and inserted, which leaves the media proxy as the only ICE candidate. The default behavior
-	(no `ICE` key present at all) is: if no ICE attributes are present, a new set is generated and the
-	media proxy lists itself as ICE candidate; otherwise, the media proxy inserts itself as a
-	low-priority candidate.
+	Contains a string which must be one of the following values:
+
+	With `remove`, any ICE attributes are stripped from the SDP body.
+
+	With `force`, ICE attributes are first stripped, then new attributes are
+	generated and inserted, which leaves the media proxy as the only ICE candidate.
+
+	With `default`, the behaviour will be the same as with `force` if the incoming SDP already
+	had ICE attributes listed. If the incoming SDP did not contain ICE attributes, then no
+	ICE attributes are added.
 
 	With `force-relay`, existing ICE candidates are left in place except `relay`
 	type candidates, and *rtpengine* inserts itself as a `relay` candidate. It will also leave SDP
 	c= and m= lines unchanged.
 
+	The default behavior
+	(no `ICE` key present at all) is: if no ICE attributes are present, a new set is generated and the
+	media proxy lists itself as ICE candidate; otherwise, the media proxy inserts itself as a
+	low-priority candidate.
+
 	This flag operates independently of the `replace` flags.
 
 * `transport protocol`

daemon/call.c

@@ -1242,7 +1242,12 @@ static void __ice_offer(const struct sdp_ng_flags *flags, struct call_media *thi
 	/* we offer ICE by default */
 	if (!MEDIA_ISSET(this, INITIALIZED))
 		MEDIA_SET(this, ICE);
-	if (flags->ice_remove)
+	// unless instructed not to
+	if (flags->ice_default) {
+		if (!MEDIA_ISSET(other, ICE))
+			MEDIA_CLEAR(this, ICE);
+	}
+	else if (flags->ice_remove)
 		MEDIA_CLEAR(this, ICE);
 
 	if (flags->passthrough_on) {

daemon/call_interfaces.c

@@ -932,6 +932,11 @@ static void call_ng_process_flags(struct sdp_ng_flags *out, bencode_item_t *inpu
 			case CSH_LOOKUP("force"):
 				out->ice_force = 1;
 				break;
+			case CSH_LOOKUP("default"):
+				out->ice_default = 1;
+				out->ice_force = 1;
+				out->ice_remove = 1;
+				break;
 			case CSH_LOOKUP("force_relay"):
 			case CSH_LOOKUP("force-relay"):
 			case CSH_LOOKUP("force relay"):

include/call_interfaces.h

@@ -58,6 +58,7 @@ struct sdp_ng_flags {
 	    ice_remove:1,
 	    ice_force:1,
 	    ice_force_relay:1,
+	    ice_default:1,
 	    rtcp_mux_offer:1,
 	    rtcp_mux_require:1,
 	    rtcp_mux_demux:1,