SDP API: Add SSRC-level attributes

RFC 5576 defines how SSRC-level attributes may be added to SDP media
descriptions. In general, this is useful for grouping related SSRCes,
indicating SSRC-level format attributes, and resolving collisions in RTP
SSRC values. These attributes are used widely by browsers during WebRTC
communications, including attributes defined by documents outside of RFC
5576.

This commit introduces the addition of SSRC-level attributes into SDPs
generated by Asterisk. Since Asterisk does not tend to use multiple
SSRCs on a media stream, the initial support is minimal. Asterisk
includes an SSRC-level CNAME attribute if configured to do so. This at
least gives browsers (and possibly others) the ability to resolve SSRC
collisions at offer-answer time.

In order to facilitate this, the RTP engine API has been enhanced to be
able to retrieve the SSRC and CNAME on a given RTP instance.

res_rtp_asterisk currently does not provide meaningful CNAME values in
its RTCP SDES items, and therefore it currently will always return an
empty string as the CNAME value. A task in the near future will result
in res_rtp_asterisk generating more meaningful CNAMEs.

Change-Id: I29e7f23e7db77524f82a3b6e8531b1195ff57789

1 files changed, 152 insertions, 14 deletions

diff --git a/tests/test_sdp.c b/tests/test_sdp.c
index 33a6a2892..a5d3710d8 100644
--- a/tests/test_sdp.c
+++ b/tests/test_sdp.c
@@ -29,6 +29,7 @@
 #include "asterisk/format.h"
 #include "asterisk/format_cache.h"
 #include "asterisk/format_cap.h"
+#include "asterisk/rtp_engine.h"
 
 static int validate_o_line(struct ast_test *test, const struct ast_sdp_o_line *o_line,
 	const char *sdpowner, const char *address_type, const char *address)
@@ -353,26 +354,56 @@ end:
 	return res;
 }
 
+static struct ast_sdp_options *sdp_options_common(void)
+{
+	struct ast_sdp_options *options;
+
+	options = ast_sdp_options_alloc();
+	if (!options) {
+		return NULL;
+	}
+	ast_sdp_options_set_media_address(options, "127.0.0.1");
+	ast_sdp_options_set_sdpowner(options, "me");
+	ast_sdp_options_set_rtp_engine(options, "asterisk");
+	ast_sdp_options_set_impl(options, AST_SDP_IMPL_PJMEDIA);
+
+	return options;
+}
+
 struct sdp_format {
 	enum ast_media_type type;
 	const char *formats;
 };
 
-static struct ast_sdp_state *build_sdp_state(int num_streams, const struct sdp_format *formats)
+/*!
+ * \brief Common method to build an SDP state for a test.
+ *
+ * This uses the passed-in formats to create a stream topology, which is then used to create the SDP
+ * state.
+ *
+ * There is an optional test_options field you can use if your test has specific options you need to
+ * set. If your test does not require anything special, it can just pass NULL for this parameter. If
+ * you do pass in test_options, this function steals ownership of those options.
+ *
+ * \param num_streams The number of elements in the formats array.
+ * \param formats Array of media types and formats that will be in the state.
+ * \param test_options Optional SDP options.
+ */
+static struct ast_sdp_state *build_sdp_state(int num_streams, const struct sdp_format *formats, struct ast_sdp_options *test_options)
 {
 	struct ast_stream_topology *topology = NULL;
 	struct ast_sdp_state *state = NULL;
 	struct ast_sdp_options *options;
 	int i;
 
-	options = ast_sdp_options_alloc();
-	if (!options) {
-		goto end;
+	if (!test_options) {
+		options = sdp_options_common();
+		if (!options) {
+			goto end;
+		}
+	} else {
+		options = test_options;
 	}
-	ast_sdp_options_set_media_address(options, "127.0.0.1");
-	ast_sdp_options_set_sdpowner(options, "me");
-	ast_sdp_options_set_rtp_engine(options, "asterisk");
-	ast_sdp_options_set_impl(options, AST_SDP_IMPL_PJMEDIA);
 
 	topology = ast_stream_topology_alloc();
 	if (!topology) {
@@ -436,7 +467,7 @@ AST_TEST_DEFINE(topology_to_sdp)
 		break;
 	}
 
-	sdp_state = build_sdp_state(ARRAY_LEN(formats), formats);
+	sdp_state = build_sdp_state(ARRAY_LEN(formats), formats, NULL);
 	if (!sdp_state) {
 		goto end;
 	}
@@ -580,7 +611,7 @@ AST_TEST_DEFINE(sdp_to_topology)
 		break;
 	}
 
-	sdp_state = build_sdp_state(ARRAY_LEN(sdp_formats), sdp_formats);
+	sdp_state = build_sdp_state(ARRAY_LEN(sdp_formats), sdp_formats, NULL);
 	if (!sdp_state) {
 		res = AST_TEST_FAIL;
 		goto end;
@@ -704,13 +735,13 @@ AST_TEST_DEFINE(sdp_merge_symmetric)
 		break;
 	}
 
-	sdp_state_offerer = build_sdp_state(ARRAY_LEN(offerer_formats), offerer_formats);
+	sdp_state_offerer = build_sdp_state(ARRAY_LEN(offerer_formats), offerer_formats, NULL);
 	if (!sdp_state_offerer) {
 		res = AST_TEST_FAIL;
 		goto end;
 	}
 
-	sdp_state_answerer = build_sdp_state(ARRAY_LEN(answerer_formats), answerer_formats);
+	sdp_state_answerer = build_sdp_state(ARRAY_LEN(answerer_formats), answerer_formats, NULL);
 	if (!sdp_state_answerer) {
 		res = AST_TEST_FAIL;
 		goto end;
@@ -782,13 +813,13 @@ AST_TEST_DEFINE(sdp_merge_crisscross)
 		break;
 	}
 
-	sdp_state_offerer = build_sdp_state(ARRAY_LEN(offerer_formats), offerer_formats);
+	sdp_state_offerer = build_sdp_state(ARRAY_LEN(offerer_formats), offerer_formats, NULL);
 	if (!sdp_state_offerer) {
 		res = AST_TEST_FAIL;
 		goto end;
 	}
 
-	sdp_state_answerer = build_sdp_state(ARRAY_LEN(answerer_formats), answerer_formats);
+	sdp_state_answerer = build_sdp_state(ARRAY_LEN(answerer_formats), answerer_formats, NULL);
 	if (!sdp_state_answerer) {
 		res = AST_TEST_FAIL;
 		goto end;
@@ -827,6 +858,111 @@ end:
 	return res;
 }
 
+static int validate_ssrc(struct ast_test *test, struct ast_sdp_m_line *m_line,
+	struct ast_rtp_instance *rtp)
+{
+	unsigned int ssrc;
+	const char *cname;
+	struct ast_sdp_a_line *a_line;
+	char attr_value[128];
+
+	ssrc = ast_rtp_instance_get_ssrc(rtp);
+	cname = ast_rtp_instance_get_cname(rtp);
+
+	snprintf(attr_value, sizeof(attr_value), "%u cname:%s", ssrc, cname);
+
+	a_line = ast_sdp_m_find_attribute(m_line, "ssrc", -1);
+	if (!a_line) {
+		ast_test_status_update(test, "Could not find 'ssrc' attribute\n");
+		return -1;
+	}
+
+	if (strcmp(a_line->value, attr_value)) {
+		ast_test_status_update(test, "SDP attribute '%s' did not match expected attribute '%s'\n",
+			a_line->value, attr_value);
+		return -1;
+	}
+
+	return 0;
+}
+
+AST_TEST_DEFINE(sdp_ssrc_attributes)
+{
+	enum ast_test_result_state res;
+	struct ast_sdp_state *test_state = NULL;
+	struct ast_sdp_options *options;
+	struct sdp_format formats[] = {
+		{ AST_MEDIA_TYPE_AUDIO, "ulaw,alaw,g722,opus" },
+	};
+	const struct ast_sdp *sdp;
+	struct ast_sdp_m_line *m_line;
+	struct ast_rtp_instance *rtp;
+
+	switch(cmd) {
+	case TEST_INIT:
+		info->name = "sdp_ssrc_attributes";
+		info->category = "/main/sdp/";
+		info->summary = "Ensure SSRC-level attributes are added to local SDPs";
+		info->description =
+			"An SDP is created and is instructed to include SSRC-level attributes.\n"
+			"This test ensures that the CNAME SSRC-level attribute is present and\n"
+			"that the values match what the RTP instance reports";
+		return AST_TEST_NOT_RUN;
+	case TEST_EXECUTE:
+		break;
+	}
+
+	res = AST_TEST_FAIL;
+
+	options = sdp_options_common();
+	if (!options) {
+		ast_test_status_update(test, "Failed to allocate SDP options\n");
+		goto end;
+	}
+	ast_sdp_options_set_ssrc(options, 1);
+
+	test_state = build_sdp_state(ARRAY_LEN(formats), formats, options);
+	if (!test_state) {
+		ast_test_status_update(test, "Failed to create SDP state\n");
+		goto end;
+	}
+
+	sdp = ast_sdp_state_get_local_sdp(test_state);
+	if (!sdp) {
+		ast_test_status_update(test, "Failed to get local SDP\n");
+		goto end;
+	}
+
+	/* Need a couple of sanity checks */
+	if (ast_sdp_get_m_count(sdp) != ARRAY_LEN(formats)) {
+		ast_test_status_update(test, "SDP m count is %d instead of %zu\n",
+			ast_sdp_get_m_count(sdp), ARRAY_LEN(formats));
+		goto end;
+	}
+
+	m_line = ast_sdp_get_m(sdp, 0);
+	if (!m_line) {
+		ast_test_status_update(test, "Failed to get SDP m-line\n");
+		goto end;
+	}
+
+	rtp = ast_sdp_state_get_rtp_instance(test_state, 0);
+	if (!rtp) {
+		ast_test_status_update(test, "Failed to get the RTP instance\n");
+		goto end;
+	}
+
+	if (validate_ssrc(test, m_line, rtp)) {
+		goto end;
+	}
+
+	res = AST_TEST_PASS;
+
+end:
+	ast_sdp_state_free(test_state);
+	return res;
+}
+
 static int unload_module(void)
 {
 	AST_TEST_UNREGISTER(invalid_rtpmap);
@@ -836,6 +972,7 @@ static int unload_module(void)
 	AST_TEST_UNREGISTER(sdp_to_topology);
 	AST_TEST_UNREGISTER(sdp_merge_symmetric);
 	AST_TEST_UNREGISTER(sdp_merge_crisscross);
+	AST_TEST_UNREGISTER(sdp_ssrc_attributes);
 
 	return 0;
 }
@@ -849,6 +986,7 @@ static int load_module(void)
 	AST_TEST_REGISTER(sdp_to_topology);
 	AST_TEST_REGISTER(sdp_merge_symmetric);
 	AST_TEST_REGISTER(sdp_merge_crisscross);
+	AST_TEST_REGISTER(sdp_ssrc_attributes);
 
 	return AST_MODULE_LOAD_SUCCESS;
 }