mgcp: Set net_end audio params in recvonly mode

Currently, if there is no SDP data in the MGCP message received from
the net, the fields containing audio encoding information are not set
in net_end. So in recvonly mode transcoding would not be set up
correctly.

This patch changes the implementation of the code handling CRCX and
MDCX to use the codec signalled in the MGCP local connection options
(field 'a:') if there isn't any SDP data. This is only halfway
negotiation, because the codec is used blindly and not matched
against the supported ones.

Sponsored-by: On-Waves ehf

1 files changed, 38 insertions, 3 deletions

diff --git a/openbsc/src/libmgcp/mgcp_protocol.c b/openbsc/src/libmgcp/mgcp_protocol.c
index 21b9ff0f8..f0457d1aa 100644
--- a/openbsc/src/libmgcp/mgcp_protocol.c
+++ b/openbsc/src/libmgcp/mgcp_protocol.c
@@ -80,6 +80,8 @@ char *strline_r(char *str, char **saveptr)
 #define DEFAULT_RTP_AUDIO_DEFAULT_RATE  8000
 #define DEFAULT_RTP_AUDIO_DEFAULT_CHANNELS 1
 
+#define PTYPE_UNDEFINED (-1)
+
 static void mgcp_rtp_end_reset(struct mgcp_rtp_end *end);
 
 struct mgcp_parse_data {
@@ -598,7 +600,8 @@ static int set_audio_info(void *ctx, struct mgcp_rtp_end *rtp,
 	talloc_free(rtp->audio_name);
 	rtp->audio_name = NULL;
 
-	rtp->payload_type = payload_type;
+	if (payload_type != PTYPE_UNDEFINED)
+		rtp->payload_type = payload_type;
 
 	if (!audio_name) {
 		switch (payload_type) {
@@ -614,7 +617,7 @@ static int set_audio_info(void *ctx, struct mgcp_rtp_end *rtp,
 	}
 
 	if (sscanf(audio_name, "%63[^/]/%d/%d",
-		   audio_codec, &rate, &channels) < 2)
+		   audio_codec, &rate, &channels) < 1)
 		return -EINVAL;
 
 	rtp->rate = rate;
@@ -630,6 +633,20 @@ static int set_audio_info(void *ctx, struct mgcp_rtp_end *rtp,
 		rtp->frame_duration_den = DEFAULT_RTP_AUDIO_FRAME_DUR_DEN;
 	}
 
+	if (payload_type < 0) {
+		payload_type = 96;
+		if (rate == 8000 && channels == 1) {
+			if (!strcmp(audio_codec, "GSM"))
+				payload_type = 3;
+			else if (!strcmp(audio_codec, "PCMA"))
+				payload_type = 8;
+			else if (!strcmp(audio_codec, "G729"))
+				payload_type = 18;
+		}
+
+		rtp->payload_type = payload_type;
+	}
+
 	if (channels != 1)
 		LOGP(DMGCP, LOGL_NOTICE,
 		     "Channels != 1 in SDP: '%s'\n", audio_name);
@@ -801,9 +818,12 @@ static int parse_sdp_data(struct mgcp_rtp_end *rtp, struct mgcp_parse_data *p)
 static void set_local_cx_options(void *ctx, struct mgcp_lco *lco,
 				 const char *options)
 {
-	char *p_opt;
+	char *p_opt, *a_opt;
+	char codec[9];
 
 	talloc_free(lco->string);
+	talloc_free(lco->codec);
+	lco->codec = NULL;
 	lco->pkt_period_min = lco->pkt_period_max = 0;
 	lco->string = talloc_strdup(ctx, options ? options : "");
 
@@ -811,6 +831,10 @@ static void set_local_cx_options(void *ctx, struct mgcp_lco *lco,
 	if (p_opt && sscanf(p_opt, "p:%d-%d",
 			    &lco->pkt_period_min, &lco->pkt_period_max) == 1)
 		lco->pkt_period_max = lco->pkt_period_min;
+
+	a_opt = strstr(lco->string, "a:");
+	if (a_opt && sscanf(a_opt, "a:%8[^,]", codec) == 1)
+		lco->codec = talloc_strdup(ctx, codec);
 }
 
 void mgcp_rtp_end_config(struct mgcp_endpoint *endp, int expect_ssrc_change,
@@ -955,6 +979,9 @@ mgcp_header_done:
 						tcfg->audio_fmtp_extra);
 	if (have_sdp)
 		parse_sdp_data(&endp->net_end, p);
+	else if (endp->local_options.codec)
+		set_audio_info(p->cfg, &endp->net_end,
+			       PTYPE_UNDEFINED, endp->local_options.codec);
 
 	if (p->cfg->bts_force_ptime) {
 		endp->bts_end.packet_duration_ms = p->cfg->bts_force_ptime;
@@ -1012,6 +1039,7 @@ static struct msgb *handle_modify_con(struct mgcp_parse_data *p)
 	struct mgcp_endpoint *endp = p->endp;
 	int error_code = 500;
 	int silent = 0, osmux = 0;
+	int have_sdp = 0;
 	char *line;
 	const char *local_options = NULL;
 
@@ -1058,6 +1086,7 @@ static struct msgb *handle_modify_con(struct mgcp_parse_data *p)
 			break;
 		case '\0':
 			/* SDP file begins */
+			have_sdp = 1;
 			parse_sdp_data(&endp->net_end, p);
 			/* This will exhaust p->save, so the loop will
 			 * terminate next time.
@@ -1088,6 +1117,10 @@ static struct msgb *handle_modify_con(struct mgcp_parse_data *p)
 	set_local_cx_options(endp->tcfg->endpoints, &endp->local_options,
 			     local_options);
 
+	if (!have_sdp && endp->local_options.codec)
+		set_audio_info(p->cfg, &endp->net_end,
+			       PTYPE_UNDEFINED, endp->local_options.codec);
+
 	setup_rtp_processing(endp);
 
 	/* policy CB */
@@ -1462,6 +1495,8 @@ void mgcp_free_endp(struct mgcp_endpoint *endp)
 
 	talloc_free(endp->local_options.string);
 	endp->local_options.string = NULL;
+	talloc_free(endp->local_options.codec);
+	endp->local_options.codec = NULL;
 
 	mgcp_rtp_end_reset(&endp->bts_end);
 	mgcp_rtp_end_reset(&endp->net_end);