core / pjsip: Add support for grouping streams together.

In WebRTC streams (or media tracks in their world) can be grouped
together using the mslabel. This informs the browser that each
should be synchronized with each other.

This change extends the stream API so this information can
be stored with streams. The PJSIP support has been extended
to use the mslabel to determine grouped streams and store
this association on the streams. Finally when creating the
SDP the group information is used to cause each media stream
to use the same mslabel.

ASTERISK-27379

Change-Id: Id6299aa031efe46254edbdc7973c534d54d641ad

1 files changed, 67 insertions, 0 deletions

diff --git a/res/res_pjsip_session.c b/res/res_pjsip_session.c
index 37ff53105..4724d46ce 100644
--- a/res/res_pjsip_session.c
+++ b/res/res_pjsip_session.c
@@ -399,6 +399,7 @@ static void session_media_dtor(void *obj)
 	}
 
 	ast_free(session_media->mid);
+	ast_free(session_media->remote_mslabel);
 }
 
 struct ast_sip_session_media *ast_sip_session_media_state_add(struct ast_sip_session *session,
@@ -553,6 +554,70 @@ static int set_mid_and_bundle_group(struct ast_sip_session *session,
 	return 0;
 }
 
+static void set_remote_mslabel_and_stream_group(struct ast_sip_session *session,
+	struct ast_sip_session_media *session_media,
+	const pjmedia_sdp_session *sdp,
+	const struct pjmedia_sdp_media *stream,
+	struct ast_stream *asterisk_stream)
+{
+	int index;
+
+	ast_free(session_media->remote_mslabel);
+	session_media->remote_mslabel = NULL;
+
+	for (index = 0; index < stream->attr_count; ++index) {
+		pjmedia_sdp_attr *attr = stream->attr[index];
+		char attr_value[pj_strlen(&attr->value) + 1];
+		char *ssrc_attribute_name, *ssrc_attribute_value = NULL;
+		char *msid, *tmp = attr_value;
+		static const pj_str_t STR_msid = { "msid", 4 };
+		static const pj_str_t STR_ssrc = { "ssrc", 4 };
+
+		if (!pj_strcmp(&attr->name, &STR_msid)) {
+			ast_copy_pj_str(attr_value, &attr->value, sizeof(attr_value));
+			msid = strsep(&tmp, " ");
+			session_media->remote_mslabel = ast_strdup(msid);
+			break;
+		} else if (!pj_strcmp(&attr->name, &STR_ssrc)) {
+			ast_copy_pj_str(attr_value, &attr->value, sizeof(attr_value));
+
+			if ((ssrc_attribute_name = strchr(attr_value, ' '))) {
+				/* This has an actual attribute */
+				*ssrc_attribute_name++ = '\0';
+				ssrc_attribute_value = strchr(ssrc_attribute_name, ':');
+				if (ssrc_attribute_value) {
+					/* Values are actually optional according to the spec */
+					*ssrc_attribute_value++ = '\0';
+				}
+
+				if (!strcasecmp(ssrc_attribute_name, "mslabel") && !ast_strlen_zero(ssrc_attribute_value)) {
+					session_media->remote_mslabel = ast_strdup(ssrc_attribute_value);
+					break;
+				}
+			}
+		}
+	}
+
+	if (ast_strlen_zero(session_media->remote_mslabel)) {
+		return;
+	}
+
+	/* Iterate through the existing streams looking for a match and if so then group this with it */
+	for (index = 0; index < AST_VECTOR_SIZE(&session->pending_media_state->sessions); ++index) {
+		struct ast_sip_session_media *group_session_media;
+
+		group_session_media = AST_VECTOR_GET(&session->pending_media_state->sessions, index);
+
+		if (ast_strlen_zero(group_session_media->remote_mslabel) ||
+			strcmp(group_session_media->remote_mslabel, session_media->remote_mslabel)) {
+			continue;
+		}
+
+		ast_stream_set_group(asterisk_stream, index);
+		break;
+	}
+}
+
 static void remove_stream_from_bundle(struct ast_sip_session_media *session_media,
 	struct ast_stream *stream)
 {
@@ -630,6 +695,7 @@ static int handle_incoming_sdp(struct ast_sip_session *session, const pjmedia_sd
 		}
 
 		set_mid_and_bundle_group(session, session_media, sdp, remote_stream);
+		set_remote_mslabel_and_stream_group(session, session_media, sdp, remote_stream, stream);
 
 		if (session_media->handler) {
 			handler = session_media->handler;
@@ -730,6 +796,7 @@ static int handle_negotiated_sdp_session_media(struct ast_sip_session_media *ses
 	ast_copy_pj_str(media, &local->media[index]->desc.media, sizeof(media));
 
 	set_mid_and_bundle_group(session, session_media, remote, remote->media[index]);
+	set_remote_mslabel_and_stream_group(session, session_media, remote, remote->media[index], asterisk_stream);
 
 	handler = session_media->handler;
 	if (handler) {