ASCI: Support conference briding with 1..n connections

For each RTP packet that is received from a connection, the mode is
checked whether receiving is allowed or not. If not it is discarded.

In case of "confecho" mode, the RTP is also sent by the receiving
connection.

Then a loop is used to send RTP to all sending endpoints except the one
that received the packet.

Because we have a loop that allows to have 1..n connections, we have no
maximum number of allowed connections anymore.

Change-Id: Ic99a55ab5a3a6170e940403fadd52697e99f2f3a

include/osmocom/mgcp/mgcp_common.h

@@ -47,6 +47,7 @@ enum mgcp_connection_mode {
 	MGCP_CONN_SEND_ONLY = 2,
 	MGCP_CONN_RECV_SEND = MGCP_CONN_RECV_ONLY | MGCP_CONN_SEND_ONLY,
 	MGCP_CONN_LOOPBACK  = 4 | MGCP_CONN_RECV_SEND,
+	MGCP_CONN_CONFECHO  = 8 | MGCP_CONN_RECV_SEND,
 };
 
 #define MGCP_X_OSMO_IGN_HEADER "X-Osmo-IGN:"

src/libosmo-mgcp-client/mgcp_client.c

@@ -1548,6 +1548,7 @@ const struct value_string mgcp_client_connection_mode_strs[] = {
 	{ MGCP_CONN_RECV_SEND, "sendrecv" },
 	{ MGCP_CONN_SEND_ONLY, "sendonly" },
 	{ MGCP_CONN_RECV_ONLY, "recvonly" },
+	{ MGCP_CONN_CONFECHO, "confecho" },
 	{ MGCP_CONN_LOOPBACK, "loopback" },
 	{ 0, NULL }
 };

src/libosmo-mgcp/mgcp_conn.c

@@ -173,8 +173,8 @@ struct mgcp_conn *mgcp_conn_alloc(void *ctx, struct mgcp_endpoint *endp,
 	struct mgcp_conn *conn;
 	int rc;
 
-	/* Do not allow more then two connections */
-	if (llist_count(&endp->conns) >= endp->type->max_conns)
+	/* Do not allow more then the maximum number of connections */
+	if (endp->type->max_conns && llist_count(&endp->conns) >= endp->type->max_conns)
 		return NULL;
 
 	/* Create new connection and add it to the list */

src/libosmo-mgcp/mgcp_endp.c

@@ -38,7 +38,6 @@
 const struct mgcp_endpoint_typeset ep_typeset = {
 	/* Specify endpoint properties for RTP endpoint */
 	.rtp = {
-		.max_conns = 2,
 		.dispatch_rtp_cb = mgcp_dispatch_rtp_bridge_cb,
 		.cleanup_cb = mgcp_cleanup_rtp_bridge_cb,
 	},

src/libosmo-mgcp/mgcp_msg.c

@@ -75,7 +75,7 @@ void mgcp_disp_msg(unsigned char *message, unsigned int len, char *preamble)
 }
 
 /*! Parse connection mode.
- *  \param[in] mode as string (recvonly, sendrecv, sendonly or loopback)
+ *  \param[in] mode as string (recvonly, sendrecv, sendonly confecho or loopback)
  *  \param[in] endp pointer to endpoint (only used for log output)
  *  \param[out] associated connection to be modified accordingly
  *  \returns 0 on success, -1 on error */
@@ -100,6 +100,8 @@ int mgcp_parse_conn_mode(const char *mode, struct mgcp_endpoint *endp,
 		conn->mode = MGCP_CONN_RECV_SEND;
 	else if (strcasecmp(mode, "sendonly") == 0)
 		conn->mode = MGCP_CONN_SEND_ONLY;
+	else if (strcasecmp(mode, "confecho") == 0)
+		conn->mode = MGCP_CONN_CONFECHO;
 	else if (strcasecmp(mode, "loopback") == 0)
 		conn->mode = MGCP_CONN_LOOPBACK;
 	else {

src/libosmo-mgcp/mgcp_network.c

@@ -1290,8 +1290,10 @@ int mgcp_dispatch_rtp_bridge_cb(struct msgb *msg)
 	struct mgcp_conn_rtp *conn_src = mc->conn_src;
 	struct mgcp_conn *conn = conn_src->conn;
 	struct mgcp_conn *conn_dst;
+	struct mgcp_endpoint *endp = conn->endp;
 	struct osmo_sockaddr *from_addr = mc->from_addr;
 	char ipbuf[INET6_ADDRSTRLEN];
+	int rc = 0;
 
 	/*! NOTE: This callback function implements the endpoint specific
 	 *  dispatch behaviour of an rtp bridge/proxy endpoint. It is assumed
@@ -1323,36 +1325,26 @@ int mgcp_dispatch_rtp_bridge_cb(struct msgb *msg)
 		return mgcp_conn_rtp_dispatch_rtp(conn_src, msg);
 	}
 
-	/* Find a destination connection. */
-	/* NOTE: This code path runs every time an RTP packet is received. The
-	 * function mgcp_find_dst_conn() we use to determine the detination
-	 * connection will iterate the connection list inside the endpoint.
-	 * Since list iterations are quite costly, we will figure out the
-	 * destination only once and use the optional private data pointer of
-	 * the connection to cache the destination connection pointer. */
-	if (!conn->priv) {
-		conn_dst = mgcp_find_dst_conn(conn);
-		conn->priv = conn_dst;
-	} else {
-		conn_dst = (struct mgcp_conn *)conn->priv;
-	}
+	/* If the mode does not allow receiving RTP, we are done. */
+	if (conn->mode != MGCP_CONN_RECV_ONLY &&
+	    conn->mode != MGCP_CONN_RECV_SEND &&
+	    conn->mode != MGCP_CONN_CONFECHO)
+		return rc;
 
-	/* There is no destination conn, stop here */
-	if (!conn_dst) {
-		LOGPCONN(conn, DRTP, LOGL_DEBUG,
-			 "no connection to forward an incoming RTP packet to\n");
-		return -1;
-	}
+	/* If the mode is "confecho", send RTP back to the sender. */
+	if (conn->mode == MGCP_CONN_CONFECHO)
+		rc = mgcp_conn_rtp_dispatch_rtp(conn_src, msg);
 
-	/* The destination conn is not an RTP connection */
-	if (conn_dst->type != MGCP_CONN_TYPE_RTP) {
-		LOGPCONN(conn, DRTP, LOGL_ERROR,
-			 "unable to find suitable destination conn\n");
-		return -1;
+	/* Dispatch RTP packet to all other connection(s) that send audio. */
+	llist_for_each_entry(conn_dst, &endp->conns, entry) {
+		if (conn_dst == conn)
+			continue;
+		if (conn_dst->mode == MGCP_CONN_SEND_ONLY ||
+		    conn_dst->mode == MGCP_CONN_RECV_SEND ||
+		    conn_dst->mode == MGCP_CONN_CONFECHO)
+		rc = mgcp_conn_rtp_dispatch_rtp(&conn_dst->u.rtp, msg);
 	}
-
-	/* Dispatch RTP packet to destination RTP connection */
-	return mgcp_conn_rtp_dispatch_rtp(&conn_dst->u.rtp, msg);
+	return rc;
 }
 
 /*! dispatch incoming RTP packet to E1 subslot, handle RTCP packets locally.

src/libosmo-mgcp/mgcp_protocol.c

@@ -967,7 +967,7 @@ mgcp_header_done:
 	}
 
 	/* Check if we are able to accept the creation of another connection */
-	if (llist_count(&endp->conns) >= endp->type->max_conns) {
+	if (endp->type->max_conns && llist_count(&endp->conns) >= endp->type->max_conns) {
 		LOGPENDP(endp, DLMGCP, LOGL_ERROR,
 			"CRCX: endpoint full, max. %i connections allowed!\n",
 			endp->type->max_conns);