res_rtp_asterisk / res_pjsip: Add support for BUNDLE.

BUNDLE is a specification used in WebRTC to allow multiple streams to use the same underlying transport. This reduces the number of ICE and DTLS negotiations that has to occur to 1 normally. This change implements this by adding support for it to the RTP SDP module in PJSIP. BUNDLE can be turned on using the "bundle" option and on an offer we will offer to bundle streams together. On an answer we will accept any bundle groups provided. Once accepted each stream is bundled to another RTP instance for transport. For the res_rtp_asterisk changes the ability to bundle an RTP instance to another based on the SSRC received from the remote side has been added. For outgoing traffic if an RTP instance is bundled to another we will use the other RTP instance for any transport related things. For incoming traffic received from the transport instance we look up the correct instance based on the SSRC and use it for any non-transport related data. ASTERISK-27118 Change-Id: I96c0920b9f9aca7382256484765a239017973c11
2025-10-13 00:04:53 +00:00 · 2017-06-30 18:55:57 +00:00
parent e1c0e14fac
commit 065c3005ad
11 changed files with 1170 additions and 393 deletions
--- a/res/res_pjsip_session.c
+++ b/res/res_pjsip_session.c
@@ -324,6 +324,28 @@ int ast_sip_session_media_set_write_callback(struct ast_sip_session *session, st
 	return 0;
 }

+struct ast_sip_session_media *ast_sip_session_media_get_transport(struct ast_sip_session *session, struct ast_sip_session_media *session_media)
+{
+	int index;
+
+	if (!session->endpoint->media.bundle || ast_strlen_zero(session_media->mid)) {
+		return session_media;
+	}
+
+	for (index = 0; index < AST_VECTOR_SIZE(&session->pending_media_state->sessions); ++index) {
+		struct ast_sip_session_media *bundle_group_session_media;
+
+		bundle_group_session_media = AST_VECTOR_GET(&session->pending_media_state->sessions, index);
+
+		/* The first session which is in the bundle group is considered the authoritative session for transport */
+		if (bundle_group_session_media->bundle_group == session_media->bundle_group) {
+			return bundle_group_session_media;
+		}
+	}
+
+	return session_media;
+}
+
 /*!
 * \brief Set an SDP stream handler for a corresponding session media.
 *
@@ -371,6 +393,8 @@ static void session_media_dtor(void *obj)
 	if (session_media->srtp) {
 		ast_sdp_srtp_destroy(session_media->srtp);
 	}
+
+	ast_free(session_media->mid);
 }

 struct ast_sip_session_media *ast_sip_session_media_state_add(struct ast_sip_session *session,
@@ -408,13 +432,25 @@ struct ast_sip_session_media *ast_sip_session_media_state_add(struct ast_sip_ses
 		session_media->timeout_sched_id = -1;
 		session_media->type = type;
 		session_media->stream_num = position;
+
+		if (session->endpoint->media.bundle) {
+			/* This is a new stream so create a new mid based on media type and position, which makes it unique.
+			 * If this is the result of an offer the mid will just end up getting replaced.
+			 */
+			if (ast_asprintf(&session_media->mid, "%s-%d", ast_codec_media_type2str(type), position) < 0) {
+				ao2_ref(session_media, -1);
+				return NULL;
+			}
+			session_media->bundle_group = 0;
+		} else {
+			session_media->bundle_group = -1;
+		}
 	}

 	AST_VECTOR_REPLACE(&media_state->sessions, position, session_media);

 	/* If this stream will be active in some way and it is the first of this type then consider this the default media session to match */
-	if (!media_state->default_session[type] &&
-		ast_stream_get_state(ast_stream_topology_get_stream(media_state->topology, position)) != AST_STREAM_STATE_REMOVED) {
+	if (!media_state->default_session[type] && ast_stream_get_state(ast_stream_topology_get_stream(media_state->topology, position)) != AST_STREAM_STATE_REMOVED) {
 		media_state->default_session[type] = session_media;
 	}

@@ -441,6 +477,78 @@ static int is_stream_limitation_reached(enum ast_media_type type, const struct a
 	}
 }

+static int get_mid_bundle_group(const pjmedia_sdp_session *sdp, const char *mid)
+{
+	int bundle_group = 0;
+	int index;
+
+	for (index = 0; index < sdp->attr_count; ++index) {
+		pjmedia_sdp_attr *attr = sdp->attr[index];
+		char value[pj_strlen(&attr->value) + 1], *mids = value, *attr_mid;
+
+		if (pj_strcmp2(&attr->name, "group") || pj_strncmp2(&attr->value, "BUNDLE", 6)) {
+			continue;
+		}
+
+		ast_copy_pj_str(value, &attr->value, sizeof(value));
+
+		/* Skip the BUNDLE at the front */
+		mids += 7;
+
+		while ((attr_mid = strsep(&mids, " "))) {
+			if (!strcmp(attr_mid, mid)) {
+				/* The ordering of attributes determines our internal identification of the bundle group based on number,
+				 * with -1 being not in a bundle group. Since this is only exposed internally for response purposes it's
+				 * actually even fine if things move around.
+				 */
+				return bundle_group;
+			}
+		}
+
+		bundle_group++;
+	}
+
+	return -1;
+}
+
+static int set_mid_and_bundle_group(struct ast_sip_session *session,
+	struct ast_sip_session_media *session_media,
+	const pjmedia_sdp_session *sdp,
+	const struct pjmedia_sdp_media *stream)
+{
+	pjmedia_sdp_attr *attr;
+
+	if (!session->endpoint->media.bundle) {
+		return 0;
+	}
+
+	/* By default on an incoming negotiation we assume no mid and bundle group is present */
+	ast_free(session_media->mid);
+	session_media->mid = NULL;
+	session_media->bundle_group = -1;
+	session_media->bundled = 0;
+
+	/* Grab the media identifier for the stream */
+	attr = pjmedia_sdp_media_find_attr2(stream, "mid", NULL);
+	if (!attr) {
+		return 0;
+	}
+
+	session_media->mid = ast_calloc(1, attr->value.slen + 1);
+	if (!session_media->mid) {
+		return 0;
+	}
+	ast_copy_pj_str(session_media->mid, &attr->value, attr->value.slen + 1);
+
+	/* Determine what bundle group this is part of */
+	session_media->bundle_group = get_mid_bundle_group(sdp, session_media->mid);
+
+	/* If this is actually part of a bundle group then the other side requested or accepted the bundle request */
+	session_media->bundled = session_media->bundle_group != -1;
+
+	return 0;
+}
+
 static int handle_incoming_sdp(struct ast_sip_session *session, const pjmedia_sdp_session *sdp)
 {
 	int i;
@@ -497,9 +605,13 @@ static int handle_incoming_sdp(struct ast_sip_session *session, const pjmedia_sd
 			ast_debug(1, "Declining incoming SDP media stream '%s' at position '%d'\n",
 				ast_codec_media_type2str(type), i);
 			ast_stream_set_state(stream, AST_STREAM_STATE_REMOVED);
+			session_media->bundle_group = -1;
+			session_media->bundled = 0;
 			continue;
 		}

+		set_mid_and_bundle_group(session, session_media, sdp, remote_stream);
+
 		if (session_media->handler) {
 			handler = session_media->handler;
 			ast_debug(1, "Negotiating incoming SDP media stream '%s' using %s SDP handler\n",
@@ -589,6 +701,8 @@ static int handle_negotiated_sdp_session_media(struct ast_sip_session_media *ses
 	/* We need a null-terminated version of the media string */
 	ast_copy_pj_str(media, &local->media[index]->desc.media, sizeof(media));

+	set_mid_and_bundle_group(session, session_media, remote, remote->media[index]);
+
 	handler = session_media->handler;
 	if (handler) {
 		ast_debug(1, "Applying negotiated SDP media stream '%s' using %s SDP handler\n",
@@ -3443,6 +3557,82 @@ static int add_sdp_streams(struct ast_sip_session_media *session_media,
 	return 0;
 }

+/*! \brief Bundle group building structure */
+struct sip_session_media_bundle_group {
+	/*! \brief The media identifiers in this bundle group */
+	char *mids[PJMEDIA_MAX_SDP_MEDIA];
+	/*! \brief SDP attribute string */
+	struct ast_str *attr_string;
+};
+
+static int add_bundle_groups(struct ast_sip_session *session, pj_pool_t *pool, pjmedia_sdp_session *answer)
+{
+	pj_str_t stmp;
+	pjmedia_sdp_attr *attr;
+	struct sip_session_media_bundle_group bundle_groups[PJMEDIA_MAX_SDP_MEDIA];
+	int index, mid_id;
+	struct sip_session_media_bundle_group *bundle_group;
+
+	if (!session->endpoint->media.bundle) {
+		return 0;
+	}
+
+	memset(bundle_groups, 0, sizeof(bundle_groups));
+
+	attr = pjmedia_sdp_attr_create(pool, "msid-semantic", pj_cstr(&stmp, "WMS *"));
+	pjmedia_sdp_attr_add(&answer->attr_count, answer->attr, attr);
+
+	/* Build the bundle group layout so we can then add it to the SDP */
+	for (index = 0; index < AST_VECTOR_SIZE(&session->pending_media_state->sessions); ++index) {
+		struct ast_sip_session_media *session_media = AST_VECTOR_GET(&session->pending_media_state->sessions, index);
+
+		/* If this stream is not part of a bundle group we can't add it */
+		if (session_media->bundle_group == -1) {
+			continue;
+		}
+
+		bundle_group = &bundle_groups[session_media->bundle_group];
+
+		/* If this is the first mid then we need to allocate the attribute string and place BUNDLE in front */
+		if (!bundle_group->mids[0]) {
+			bundle_group->mids[0] = session_media->mid;
+			bundle_group->attr_string = ast_str_create(64);
+			if (!bundle_group->attr_string) {
+				continue;
+			}
+
+			ast_str_set(&bundle_group->attr_string, -1, "BUNDLE %s", session_media->mid);
+			continue;
+		}
+
+		for (mid_id = 1; mid_id < PJMEDIA_MAX_SDP_MEDIA; ++mid_id) {
+			if (!bundle_group->mids[mid_id]) {
+				bundle_group->mids[mid_id] = session_media->mid;
+				ast_str_append(&bundle_group->attr_string, -1, " %s", session_media->mid);
+				break;
+			} else if (!strcmp(bundle_group->mids[mid_id], session_media->mid)) {
+				break;
+			}
+		}
+	}
+
+	/* Add all bundle groups that have mids to the SDP */
+	for (index = 0; index < PJMEDIA_MAX_SDP_MEDIA; ++index) {
+		bundle_group = &bundle_groups[index];
+
+		if (!bundle_group->attr_string) {
+			continue;
+		}
+
+		attr = pjmedia_sdp_attr_create(pool, "group", pj_cstr(&stmp, ast_str_buffer(bundle_group->attr_string)));
+		pjmedia_sdp_attr_add(&answer->attr_count, answer->attr, attr);
+
+		ast_free(bundle_group->attr_string);
+	}
+
+	return 0;
+}
+
 static struct pjmedia_sdp_session *create_local_sdp(pjsip_inv_session *inv, struct ast_sip_session *session, const pjmedia_sdp_session *offer)
 {
 	static const pj_str_t STR_IN = { "IN", 2 };
@@ -3485,6 +3675,7 @@ static struct pjmedia_sdp_session *create_local_sdp(pjsip_inv_session *inv, stru
 	for (i = 0; i < ast_stream_topology_get_count(session->pending_media_state->topology); ++i) {
 		struct ast_sip_session_media *session_media;
 		struct ast_stream *stream;
+		unsigned int streams = local->media_count;

 		/* This code does not enforce any maximum stream count limitations as that is done on either
 		 * the handling of an incoming SDP offer or on the handling of a session refresh.
@@ -3501,12 +3692,30 @@ static struct pjmedia_sdp_session *create_local_sdp(pjsip_inv_session *inv, stru
 			return NULL;
 		}

+		/* If a stream was actually added then add any additional details */
+		if (streams != local->media_count) {
+			pjmedia_sdp_media *media = local->media[streams];
+			pj_str_t stmp;
+			pjmedia_sdp_attr *attr;
+
+			/* Add the media identifier if present */
+			if (!ast_strlen_zero(session_media->mid)) {
+				attr = pjmedia_sdp_attr_create(inv->pool_prov, "mid", pj_cstr(&stmp, session_media->mid));
+				pjmedia_sdp_attr_add(&media->attr_count, media->attr, attr);
+			}
+		}
+
 		/* Ensure that we never exceed the maximum number of streams PJMEDIA will allow. */
 		if (local->media_count == PJMEDIA_MAX_SDP_MEDIA) {
 			break;
 		}
 	}

+	/* Add any bundle groups that are present on the media state */
+	if (add_bundle_groups(session, inv->pool_prov, local)) {
+		return NULL;
+	}
+
 	/* Use the connection details of an available media if possible for SDP level */
 	for (stream = 0; stream < local->media_count; stream++) {
 		if (!local->media[stream]->conn) {