From 3c50130c7bfb214bfa45eb44eebf917784e37c96 Mon Sep 17 00:00:00 2001
From: Richard Fuchs <rfuchs@sipwise.com>
Date: Wed, 5 Dec 2018 08:43:13 -0500
Subject: [PATCH] TT#45472 process and retain media ID strings (a=mid)

Change-Id: Icf7219f407ed660c009ffde838c942e13aad40ce
---
 daemon/call.c  | 18 ++++++++++++++++++
 daemon/sdp.c   | 23 +++++++++++++----------
 include/call.h |  2 ++
 3 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/daemon/call.c b/daemon/call.c
index ee92a2d54..df3e4712d 100644
--- a/daemon/call.c
+++ b/daemon/call.c
@@ -1669,6 +1669,23 @@ static void __endpoint_loop_protect(struct stream_params *sp, struct call_media
 	MEDIA_SET(media, LOOP_CHECK);
 }
 
+static void __update_media_id(struct call_media *media, struct call_media *other_media,
+		struct stream_params *sp, const struct sdp_ng_flags *flags)
+{
+	struct call *call = media->call;
+
+	if (!other_media->media_id.s) {
+		// incoming side: we copy what we received
+		if (sp->media_id.s)
+			call_str_cpy(call, &other_media->media_id, &sp->media_id);
+	}
+	if (!media->media_id.s) {
+		// outgoing side: we copy from the other side
+		if (other_media->media_id.s)
+			call_str_cpy(call, &media->media_id, &other_media->media_id);
+	}
+}
+
 /* called with call->master_lock held in W */
 int monologue_offer_answer(struct call_monologue *other_ml, GQueue *streams,
 		const struct sdp_ng_flags *flags)
@@ -1741,6 +1758,7 @@ int monologue_offer_answer(struct call_monologue *other_ml, GQueue *streams,
 				&& other_media->protocol && other_media->protocol->rtp)
 			media->protocol = flags->transport_protocol;
 
+		__update_media_id(media, other_media, sp, flags);
 		__endpoint_loop_protect(sp, other_media);
 
 		if (sp->rtp_endpoint.port) {
diff --git a/daemon/sdp.c b/daemon/sdp.c
index 3d68682b1..43a0c4a59 100644
--- a/daemon/sdp.c
+++ b/daemon/sdp.c
@@ -169,7 +169,7 @@ struct attribute_fmtp {
 	unsigned int payload_type;
 };
 
-struct sdp_attribute {
+struct sdp_attribute {	/* example: a=rtpmap:8 PCMA/8000 */
 	str full_line,	/* including a= and \r\n */
 	    line_value,	/* without a= and without \r\n */
 	    name,	/* just "rtpmap" */
@@ -1323,6 +1323,11 @@ int sdp_streams(const GQueue *sessions, GQueue *streams, struct sdp_ng_flags *fl
 						sp->fingerprint.hash_func->num_bytes);
 			}
 
+			// a=mid
+			attr = attr_get_by_id(&media->attributes, ATTR_MID);
+			if (attr)
+				sp->media_id = attr->value;
+
 			__sdp_ice(sp, media);
 
 			/* determine RTCP endpoint */
@@ -1697,6 +1702,7 @@ static int process_media_attributes(struct sdp_chopper *chop, struct sdp_media *
 			case ATTR_SENDRECV:
 			case ATTR_IGNORE:
 			case ATTR_END_OF_CANDIDATES: // we strip it here and re-insert it later
+			case ATTR_MID:
 				goto strip;
 
 			case ATTR_RTPMAP:
@@ -1714,15 +1720,6 @@ static int process_media_attributes(struct sdp_chopper *chop, struct sdp_media *
 					break;
 				goto strip;
 
-			case ATTR_MID:
-				if (MEDIA_ISSET(media, PASSTHRU))
-					break;
-//				a = attr_get_by_id(&sdp->session->attributes, ATTR_GROUP);
-//				if (a && a->u.group.semantics == GROUP_BUNDLE)
-//					goto strip;
-				goto strip; // hack/workaround: always remove a=mid
-				break;
-
 			default:
 				break;
 		}
@@ -2063,6 +2060,12 @@ int sdp_replace(struct sdp_chopper *chop, GQueue *sessions, struct call_monologu
 
 			copy_up_to_end_of(chop, &sdp_media->s);
 
+			if (call_media->media_id.s) {
+				chopper_append_c(chop, "a=mid:");
+				chopper_append_str(chop, &call_media->media_id);
+				chopper_append_c(chop, "\r\n");
+			}
+
 			insert_codec_parameters(chop, call_media);
 
 			ps_rtcp = NULL;
diff --git a/include/call.h b/include/call.h
index 5db4a16b4..17797b7d0 100644
--- a/include/call.h
+++ b/include/call.h
@@ -242,6 +242,7 @@ struct stream_params {
 	str			ice_ufrag;
 	str			ice_pwd;
 	int			ptime;
+	str			media_id;
 };
 
 struct endpoint_map {
@@ -320,6 +321,7 @@ struct call_media {
 
 	struct ice_agent	*ice_agent;
 
+	str			media_id;
 	GQueue			sdes_in, sdes_out;
 	struct dtls_fingerprint fingerprint; /* as received */