sdp: Add support for T.38

This change adds a T.38 format which can be used in a stream
topology to specify that a UDPTL stream needs to be created.
The SDP API has been changed to understand T.38 and create
the UDPTL session, add the attributes, and parse the attributes.

This change does not change the boundary of the T.38 state
machine. It is still up to the channel driver to implement and
act on it (such as queueing control frames or reacting to them).

ASTERISK-26949

Change-Id: If28956762ccb8ead562ac6c03d162d3d6014f2c7

1 files changed, 42 insertions, 19 deletions

diff --git a/main/sdp.c b/main/sdp.c
index 75a9da94d..dc6afe7d8 100644
--- a/main/sdp.c
+++ b/main/sdp.c
@@ -23,6 +23,7 @@
 #include "asterisk/codec.h"
 #include "asterisk/format.h"
 #include "asterisk/format_cap.h"
+#include "asterisk/format_cache.h"
 #include "asterisk/rtp_engine.h"
 #include "asterisk/sdp_state.h"
 #include "asterisk/sdp_options.h"
@@ -712,34 +713,56 @@ static struct ast_stream *get_stream_from_m(const struct ast_sdp_m_line *m_line)
 		ao2_ref(caps, -1);
 		return NULL;
 	}
-	ast_rtp_codecs_payloads_initialize(&codecs);
 
-	for (i = 0; i < ast_sdp_m_get_payload_count(m_line); ++i) {
-		struct ast_sdp_payload *payload_s;
-		struct ast_sdp_rtpmap *rtpmap;
-		int payload;
+	switch (ast_stream_get_type(stream)) {
+	case AST_MEDIA_TYPE_AUDIO:
+	case AST_MEDIA_TYPE_VIDEO:
+		ast_rtp_codecs_payloads_initialize(&codecs);
 
-		payload_s = ast_sdp_m_get_payload(m_line, i);
-		sscanf(payload_s->fmt, "%30d", &payload);
-		ast_rtp_codecs_payloads_set_m_type(&codecs, NULL, payload);
+		for (i = 0; i < ast_sdp_m_get_payload_count(m_line); ++i) {
+			struct ast_sdp_payload *payload_s;
+			struct ast_sdp_rtpmap *rtpmap;
+			int payload;
 
-		rtpmap = sdp_payload_get_rtpmap(m_line, payload);
-		if (!rtpmap) {
-			continue;
+			payload_s = ast_sdp_m_get_payload(m_line, i);
+			sscanf(payload_s->fmt, "%30d", &payload);
+			ast_rtp_codecs_payloads_set_m_type(&codecs, NULL, payload);
+
+			rtpmap = sdp_payload_get_rtpmap(m_line, payload);
+			if (!rtpmap) {
+				continue;
+			}
+			ast_rtp_codecs_payloads_set_rtpmap_type_rate(&codecs, NULL,
+				payload, m_line->type, rtpmap->encoding_name, 0,
+				rtpmap->clock_rate);
+			ast_sdp_rtpmap_free(rtpmap);
+
+			process_fmtp(m_line, payload, &codecs);
 		}
-		ast_rtp_codecs_payloads_set_rtpmap_type_rate(&codecs, NULL,
-			payload, m_line->type, rtpmap->encoding_name, 0,
-			rtpmap->clock_rate);
-		ast_sdp_rtpmap_free(rtpmap);
 
-		process_fmtp(m_line, payload, &codecs);
+		ast_rtp_codecs_payload_formats(&codecs, caps, &non_ast_fmts);
+		ast_rtp_codecs_payloads_destroy(&codecs);
+		break;
+	case AST_MEDIA_TYPE_IMAGE:
+		for (i = 0; i < ast_sdp_m_get_payload_count(m_line); ++i) {
+			struct ast_sdp_payload *payload;
+
+			/* As we don't carry T.38 over RTP we do our own format check */
+			payload = ast_sdp_m_get_payload(m_line, i);
+			if (!strcasecmp(payload->fmt, "t38")) {
+				ast_format_cap_append(caps, ast_format_t38, 0);
+			}
+		}
+		break;
+	case AST_MEDIA_TYPE_UNKNOWN:
+	case AST_MEDIA_TYPE_TEXT:
+	case AST_MEDIA_TYPE_END:
+		break;
 	}
 
-	ast_rtp_codecs_payload_formats(&codecs, caps, &non_ast_fmts);
 	ast_stream_set_formats(stream, caps);
-
 	ao2_ref(caps, -1);
-	ast_rtp_codecs_payloads_destroy(&codecs);
+
 	return stream;
 }