RTP-enable MNCC API for LCR + ip.access

Instead of passing TRAU frames down the MNCC API to the call control
application like MNCC, we now decode the TRAU frame into the actual codec
frame.  We do the same with the RTP packets in case of ip.access and
thus have a unified format of passing codec data from the BTS to
an application, independent of the BTS type.

This is only implemented for V1 full-rate at the moment, and needs
to be fixed.

1 files changed, 222 insertions, 5 deletions

diff --git a/openbsc/src/rtp_proxy.c b/openbsc/src/rtp_proxy.c
index bfd494856..f9207d661 100644
--- a/openbsc/src/rtp_proxy.c
+++ b/openbsc/src/rtp_proxy.c
@@ -24,6 +24,10 @@
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
+#include <sys/time.h>    /* gettimeofday() */
+#include <unistd.h>      /* get..() */
+#include <time.h>        /* clock() */
+#include <sys/utsname.h> /* uname() */
 
 #include <openbsc/talloc.h>
 #include <openbsc/gsm_data.h>
@@ -57,6 +61,169 @@ struct rtcp_hdr {
 	
 #define RTCP_IE_CNAME	1
 
+/* according to RFC 3550 */
+struct rtp_hdr {
+	u_int8_t  csrc_count:4,
+		  extension:1,
+		  padding:1,
+		  version:2;
+	u_int8_t  payload_type:7,
+		  marker:1;
+	u_int16_t sequence;
+	u_int32_t timestamp;
+	u_int32_t ssrc;
+} __attribute__((packed));
+
+struct rtp_x_hdr {
+	u_int16_t by_profile;
+	u_int16_t length;
+} __attribute__((packed));
+
+#define RTP_VERSION	2
+
+#define RTP_PT_GSM_FULL	3
+
+/* decode an rtp frame and create a new buffer with payload */
+static int rtp_decode(struct msgb *msg, u_int32_t callref, struct msgb **data)
+{
+	struct msgb *new_msg;
+	struct gsm_data_frame *frame;
+	struct rtp_hdr *rtph = (struct rtp_hdr *)msg->data;
+	struct rtp_x_hdr *rtpxh;
+	u_int8_t *payload;
+	int payload_len;
+	int msg_type;
+	int x_len;
+
+	if (msg->len < 12) {
+		DEBUGPC(DMUX, "received RTP frame too short (len = %d)\n",
+			msg->len);
+		return -EINVAL;
+	}
+	if (rtph->version != RTP_VERSION) {
+		DEBUGPC(DMUX, "received RTP version %d not supported.\n",
+			rtph->version);
+		return -EINVAL;
+	}
+	payload = msg->data + sizeof(struct rtp_hdr) + (rtph->csrc_count << 2);
+	payload_len = msg->len - sizeof(struct rtp_hdr) - (rtph->csrc_count << 2);
+	if (payload_len < 0) {
+		DEBUGPC(DMUX, "received RTP frame too short (len = %d, "
+			"csrc count = %d)\n", msg->len, rtph->csrc_count);
+		return -EINVAL;
+	}
+	if (rtph->extension) {
+		if (payload_len < sizeof(struct rtp_x_hdr)) {
+			DEBUGPC(DMUX, "received RTP frame too short for "
+				"extension header\n");
+			return -EINVAL;
+		}
+		rtpxh = (struct rtp_x_hdr *)payload;
+		x_len = ntohs(rtpxh->length) * 4 + sizeof(struct rtp_x_hdr);
+		payload += x_len;
+		payload_len -= x_len;
+		if (payload_len < 0) {
+			DEBUGPC(DMUX, "received RTP frame too short, "
+				"extension header exceeds frame length\n");
+			return -EINVAL;
+		}
+	}
+	if (rtph->padding) {
+		if (payload_len < 0) {
+			DEBUGPC(DMUX, "received RTP frame too short for "
+				"padding length\n");
+			return -EINVAL;
+		}
+		payload_len -= payload[payload_len - 1];
+		if (payload_len < 0) {
+			DEBUGPC(DMUX, "received RTP frame with padding "
+				"greater than payload\n");
+			return -EINVAL;
+		}
+	}
+
+	switch (rtph->payload_type) {
+	case RTP_PT_GSM_FULL:
+		msg_type = GSM_TCHF_FRAME;
+		if (payload_len != 33) {
+			DEBUGPC(DMUX, "received RTP full rate frame with "
+				"payload length != 32 (len = %d)\n",
+				payload_len);
+			return -EINVAL;
+		}
+		break;
+	default:
+		DEBUGPC(DMUX, "received RTP frame with unknown payload "
+			"type %d\n", rtph->payload_type);
+		return -EINVAL;
+	}
+
+	new_msg = msgb_alloc(sizeof(struct gsm_data_frame) + payload_len,
+				"GSM-DATA");
+	if (!new_msg)
+		return -ENOMEM;
+	frame = (struct gsm_data_frame *)(new_msg->data);
+	frame->msg_type = msg_type;
+	frame->callref = callref;
+	memcpy(frame->data, payload, payload_len);
+	msgb_put(new_msg, sizeof(struct gsm_data_frame) + payload_len);
+
+	*data = new_msg;
+	return 0;
+}
+
+/* encode and send a rtp frame */
+int rtp_send_frame(struct rtp_socket *rs, struct gsm_data_frame *frame)
+{
+	struct rtp_sub_socket *rss = &rs->rtp;
+	struct msgb *msg;
+	struct rtp_hdr *rtph;
+	int payload_type;
+	int payload_len;
+	int duration; /* in samples */
+
+	if (rs->tx_action != RTP_SEND_DOWNSTREAM) {
+		/* initialize sequences */
+		rs->tx_action = RTP_SEND_DOWNSTREAM;
+		rs->transmit.ssrc = rand();
+		rs->transmit.sequence = random();
+		rs->transmit.timestamp = random();
+	}
+
+	switch (frame->msg_type) {
+	case GSM_TCHF_FRAME:
+		payload_type = RTP_PT_GSM_FULL;
+		payload_len = 33;
+		duration = 160;
+		break;
+	default:
+		DEBUGPC(DMUX, "unsupported message type %d\n",
+			frame->msg_type);
+		return -EINVAL;
+	}
+
+	msg = msgb_alloc(sizeof(struct rtp_hdr) + payload_len, "RTP-GSM-FULL");
+	if (!msg)
+		return -ENOMEM;
+	rtph = (struct rtp_hdr *)msg->data;
+	rtph->version = RTP_VERSION;
+	rtph->padding = 0;
+	rtph->extension = 0;
+	rtph->csrc_count = 0;
+	rtph->marker = 0;
+	rtph->payload_type = payload_type;
+	rtph->sequence = htons(rs->transmit.sequence++);
+	rtph->timestamp = htonl(rs->transmit.timestamp);
+	rs->transmit.timestamp += duration;
+	rtph->ssrc = htonl(rs->transmit.ssrc);
+	memcpy(msg->data + sizeof(struct rtp_hdr), frame->data, payload_len);
+	msgb_put(msg, sizeof(struct rtp_hdr) + payload_len);
+	msgb_enqueue(&rss->tx_queue, msg);
+	rss->bfd.when |= BSC_FD_WRITE;
+
+	return 0;
+}
+
 /* iterate over all chunks in one RTCP message, look for CNAME IEs and
  * replace all of those with 'new_cname' */
 static int rtcp_sdes_cname_mangle(struct msgb *msg, struct rtcp_hdr *rh,
@@ -123,10 +290,16 @@ static int rtcp_mangle(struct msgb *msg, struct rtp_socket *rs)
 	if (!mangle_rtcp_cname)
 		return 0;
 
+	printf("RTCP\n");
 	/* iterate over list of RTCP messages */
 	rtph = (struct rtcp_hdr *)msg->data;
-	while ((void *)rtph + sizeof(*rtph) < (void *)msg->data + msg->len) {
+	while ((void *)rtph + sizeof(*rtph) <= (void *)msg->data + msg->len) {
 		old_len = (ntohs(rtph->length) + 1) * 4;
+		if ((void *)rtph + old_len > (void *)msg->data + msg->len) {
+			DEBUGPC(DMUX, "received RTCP packet too short for "
+				"length element\n");
+			return -EINVAL;
+		}
 		if (rtph->type == RTCP_TYPE_SDES) {
 			char new_cname[255];
 			strncpy(new_cname, inet_ntoa(rss->sin_local.sin_addr),
@@ -148,6 +321,7 @@ static int rtp_socket_read(struct rtp_socket *rs, struct rtp_sub_socket *rss)
 {
 	int rc;
 	struct msgb *msg = msgb_alloc(RTP_ALLOC_SIZE, "RTP/RTCP");
+	struct msgb *new_msg;
 	struct rtp_sub_socket *other_rss;
 
 	if (!msg)
@@ -184,13 +358,40 @@ static int rtp_socket_read(struct rtp_socket *rs, struct rtp_sub_socket *rss)
 		break;
 
 	case RTP_RECV_UPSTREAM:
-	case RTP_NONE:
-		/* FIXME: other cases */
-		DEBUGP(DMUX, "unhandled action: %d\n", rs->rx_action);
+		if (!rs->receive.callref || !rs->receive.net) {
+			rc = -EIO;
+			goto out_free;
+		}
+		if (rss->bfd.priv_nr == RTP_PRIV_RTCP) {
+			if (!mangle_rtcp_cname) {
+				msgb_free(msg);
+				break;
+			}
+			/* modify RTCP SDES CNAME */
+			rc = rtcp_mangle(msg, rs);
+			if (rc < 0)
+				goto out_free;
+			msgb_enqueue(&rss->tx_queue, msg);
+			rss->bfd.when |= BSC_FD_WRITE;
+			break;
+		}
+		if (rss->bfd.priv_nr != RTP_PRIV_RTP) {
+			rc = -EINVAL;
+			goto out_free;
+		}
+		rc = rtp_decode(msg, rs->receive.callref, &new_msg);
+		if (rc < 0)
+			goto out_free;
+		msgb_free(msg);
+		msgb_enqueue(&rs->receive.net->upqueue, new_msg);
+		break;
+
+	case RTP_NONE: /* if socket exists, but disabled by app */
+		msgb_free(msg);
 		break;
 	}
 
-	return rc;
+	return 0;
 
 out_free:
 	msgb_free(msg);
@@ -420,6 +621,22 @@ int rtp_socket_proxy(struct rtp_socket *this, struct rtp_socket *other)
 	return 0;
 }
 
+/* bind RTP/RTCP socket to application */
+int rtp_socket_upstream(struct rtp_socket *this, struct gsm_network *net, u_int32_t callref)
+{
+	DEBUGP(DMUX, "rtp_socket_proxy(this=%p, callref=%lu)\n",
+		this, callref);
+
+	if (callref) {
+		this->rx_action = RTP_RECV_UPSTREAM;
+		this->receive.net = net;
+		this->receive.callref = callref;
+	} else
+		this->rx_action = RTP_NONE;
+
+	return 0;
+}
+
 static void free_tx_queue(struct rtp_sub_socket *rss)
 {
 	struct msgb *msg;