osmux: Support local CID != remote CID

So far the implementation only allowed the remote CID being the same as
the one dynamically implemented internally.

Related: SYS#6138
Change-Id: I6b03eabc0305580c9788c529bec7dda9044a008f
diff --git a/include/osmocom/mgcp/mgcp_conn.h b/include/osmocom/mgcp/mgcp_conn.h
index 14ddfbb..9ffa7dc 100644
--- a/include/osmocom/mgcp/mgcp_conn.h
+++ b/include/osmocom/mgcp/mgcp_conn.h
@@ -80,10 +80,14 @@
 	struct {
 		/* Osmux state: disabled, activating, active */
 		enum osmux_state state;
-		/* Is cid holding valid data? is it allocated from pool? */
-		bool cid_allocated;
-		/* Allocated Osmux circuit ID for this conn */
-		uint8_t cid;
+		/* Is local_cid holding valid data? is it allocated from pool? */
+		bool local_cid_allocated;
+		/* Allocated local Osmux circuit ID for this conn */
+		uint8_t local_cid;
+		/* Is remote_cid holding valid data? was it already received from client? */
+		bool remote_cid_present;
+		/* Received remote Osmux circuit ID for this conn */
+		uint8_t remote_cid;
 		/* handle to batch messages, shared (refcounted) among several conns */
 		struct osmux_in_handle *in;
 		/* handle to unbatch messages, one allocated and owned per conn */
diff --git a/include/osmocom/mgcp/osmux.h b/include/osmocom/mgcp/osmux.h
index 26c1bdf..1a99e6d 100644
--- a/include/osmocom/mgcp/osmux.h
+++ b/include/osmocom/mgcp/osmux.h
@@ -17,8 +17,8 @@
 int osmux_enable_conn(struct mgcp_endpoint *endp, struct mgcp_conn_rtp *conn,
 		      const struct osmo_sockaddr *addr);
 void conn_osmux_disable(struct mgcp_conn_rtp *conn);
-int conn_osmux_allocate_cid(struct mgcp_conn_rtp *conn, int osmux_cid);
-void conn_osmux_release_cid(struct mgcp_conn_rtp *conn);
+int conn_osmux_allocate_local_cid(struct mgcp_conn_rtp *conn);
+void conn_osmux_release_local_cid(struct mgcp_conn_rtp *conn);
 int osmux_xfrm_to_osmux(char *buf, int buf_len, struct mgcp_conn_rtp *conn);
 int osmux_send_dummy(struct mgcp_endpoint *endp, struct mgcp_conn_rtp *conn);
 
diff --git a/src/libosmo-mgcp/mgcp_conn.c b/src/libosmo-mgcp/mgcp_conn.c
index d963a56..cc309a3 100644
--- a/src/libosmo-mgcp/mgcp_conn.c
+++ b/src/libosmo-mgcp/mgcp_conn.c
@@ -95,8 +95,10 @@
 	static atomic_uint rate_ctr_index = 0;
 
 	conn_rtp->type = MGCP_RTP_DEFAULT;
-	conn_rtp->osmux.cid_allocated = false;
-	conn_rtp->osmux.cid = 0;
+	conn_rtp->osmux.local_cid_allocated = false;
+	conn_rtp->osmux.local_cid = 0;
+	conn_rtp->osmux.remote_cid_present = false;
+	conn_rtp->osmux.remote_cid = 0;
 
 	/* backpointer to the generic part of the connection */
 	conn->u.rtp.conn = conn;
diff --git a/src/libosmo-mgcp/mgcp_osmux.c b/src/libosmo-mgcp/mgcp_osmux.c
index 83a96fe..72152c7 100644
--- a/src/libosmo-mgcp/mgcp_osmux.c
+++ b/src/libosmo-mgcp/mgcp_osmux.c
@@ -210,7 +210,7 @@
 
 	if (conn->osmux.state != OSMUX_STATE_ENABLED) {
 		LOGPCONN(conn->conn, DOSMUX, LOGL_INFO, "forwarding RTP to Osmux conn not yet enabled, dropping (cid=%d)\n",
-		conn->osmux.cid);
+		conn->osmux.remote_cid);
 		rtpconn_rate_ctr_inc(conn, conn->conn->endp, OSMUX_DROPPED_AMR_PAYLOADS_CTR);
 		return -1;
 	}
@@ -222,7 +222,7 @@
 	memcpy(msg->data, buf, buf_len);
 	msgb_put(msg, buf_len);
 
-	while ((ret = osmux_xfrm_input(conn->osmux.in, msg, conn->osmux.cid)) > 0) {
+	while ((ret = osmux_xfrm_input(conn->osmux.in, msg, conn->osmux.remote_cid)) > 0) {
 		/* batch full, build and deliver it */
 		osmux_xfrm_input_deliver(conn->osmux.in);
 	}
@@ -231,7 +231,7 @@
 
 /* Lookup the endpoint that corresponds to the specified address (port) */
 static struct mgcp_conn_rtp*
-osmux_conn_lookup(struct mgcp_trunk *trunk, uint8_t cid, const struct osmo_sockaddr *rem_addr)
+osmux_conn_lookup(struct mgcp_trunk *trunk, uint8_t local_cid, const struct osmo_sockaddr *rem_addr)
 {
 	struct mgcp_endpoint *endp;
 	struct mgcp_conn *conn = NULL;
@@ -252,13 +252,13 @@
 
 			/* FIXME: Match remote address! */
 
-			if (conn_rtp->osmux.cid == cid)
+			if (conn_rtp->osmux.local_cid == local_cid)
 				return conn_rtp;
 		}
 	}
 
-	LOGP(DOSMUX, LOGL_ERROR, "Cannot find osmux conn with rem_addr=%s cid=%d\n",
-	     osmo_sockaddr_to_str(rem_addr), cid);
+	LOGP(DOSMUX, LOGL_ERROR, "Cannot find osmux conn with rem_addr=%s local_cid=%d\n",
+	     osmo_sockaddr_to_str(rem_addr), local_cid);
 
 	return NULL;
 }
@@ -327,7 +327,8 @@
 		LOGPCONN(conn->conn, DOSMUX, LOGL_INFO,
 			 "Osmux %s CID %u towards %s is now enabled\n",
 			 sending ? "sent" : "received",
-			 conn->osmux.cid, osmo_sockaddr_to_str(&rem_addr));
+			 sending ? conn->osmux.remote_cid : conn->osmux.local_cid,
+			 osmo_sockaddr_to_str(&rem_addr));
 		return 0;
 	case OSMUX_STATE_ENABLED:
 		return 0;
@@ -517,16 +518,16 @@
 			mgcp_conn_dump(conn->conn));
 		return -1;
 	}
-	if (osmux_xfrm_input_open_circuit(conn->osmux.in, conn->osmux.cid, osmux_dummy) < 0) {
+	if (osmux_xfrm_input_open_circuit(conn->osmux.in, conn->osmux.remote_cid, osmux_dummy) < 0) {
 		LOGPCONN(conn->conn, DOSMUX, LOGL_ERROR,
 			"Cannot open osmux circuit %u for conn:%s\n",
-		     conn->osmux.cid, mgcp_conn_dump(conn->conn));
+		     conn->osmux.remote_cid, mgcp_conn_dump(conn->conn));
 		return -1;
 	}
 
 	conn->osmux.out = osmux_xfrm_output_alloc(conn->conn);
 	osmux_xfrm_output_set_rtp_ssrc(conn->osmux.out,
-				       (conn->osmux.cid * rtp_ssrc_winlen) +
+				       (conn->osmux.remote_cid * rtp_ssrc_winlen) +
 				       (random() % rtp_ssrc_winlen));
 	osmux_xfrm_output_set_rtp_pl_type(conn->osmux.out, conn->end.codec->payload_type);
 	osmux_xfrm_output_set_tx_cb(conn->osmux.out,
@@ -547,7 +548,7 @@
 	OSMO_ASSERT(conn->osmux.state != OSMUX_STATE_DISABLED);
 
 	LOGPCONN(conn->conn, DOSMUX, LOGL_INFO,
-		"Releasing connection using Osmux CID %u\n", conn->osmux.cid);
+		"Releasing connection using local Osmux CID %u\n", conn->osmux.local_cid);
 
 	struct rate_ctr_group *all_osmux_stats = conn->conn->endp->trunk->ratectr.all_osmux_conn_stats;
 	rate_ctr_inc(rate_ctr_group_get_ctr(all_osmux_stats, OSMUX_NUM_CONNECTIONS));
@@ -557,53 +558,44 @@
 		osmux_xfrm_output_set_tx_cb(conn->osmux.out, NULL, NULL);
 		TALLOC_FREE(conn->osmux.out);
 
-		osmux_xfrm_input_close_circuit(conn->osmux.in, conn->osmux.cid);
+		osmux_xfrm_input_close_circuit(conn->osmux.in, conn->osmux.remote_cid);
 		conn->osmux.state = OSMUX_STATE_DISABLED;
 		osmux_handle_put(conn->osmux.in);
+		conn->osmux.remote_cid = 0;
+		conn->osmux.remote_cid_present = false;
 
 		rate_ctr_group_free(conn->osmux.ctrg);
 		conn->osmux.ctrg = NULL;
 	}
-	conn_osmux_release_cid(conn);
+	conn_osmux_release_local_cid(conn);
 }
 
 /*! relase OSXMUX cid, that had been allocated to this connection.
  *  \param[in] conn connection with OSMUX cid to release */
-void conn_osmux_release_cid(struct mgcp_conn_rtp *conn)
+void conn_osmux_release_local_cid(struct mgcp_conn_rtp *conn)
 {
-	if (conn->osmux.cid_allocated)
-		osmux_cid_pool_put(conn->osmux.cid);
-	conn->osmux.cid = 0;
-	conn->osmux.cid_allocated = false;
+	if (conn->osmux.local_cid_allocated)
+		osmux_cid_pool_put(conn->osmux.local_cid);
+	conn->osmux.local_cid = 0;
+	conn->osmux.local_cid_allocated = false;
 }
 
-/*! allocate OSXMUX cid to connection.
- *  \param[in] conn connection for which we allocate the OSMUX cid
- * \param[in] osmux_cid OSMUX cid to allocate. -1 Means take next available one.
- * \returns Allocated OSMUX cid, -1 on error (no free  cids avail, or selected one is already taken).
+/*! allocate local OSMUX cid to connection.
+ *  \param[in] conn connection for which we allocate the local OSMUX cid
+ * \returns Allocated OSMUX cid, -1 on error (no free CIDs avail).
  */
-int conn_osmux_allocate_cid(struct mgcp_conn_rtp *conn, int osmux_cid)
+int conn_osmux_allocate_local_cid(struct mgcp_conn_rtp *conn)
 {
-	if (osmux_cid != -1 && osmux_cid_pool_allocated((uint8_t) osmux_cid)) {
+	OSMO_ASSERT(conn->osmux.local_cid_allocated == false);
+	int osmux_cid = osmux_cid_pool_get_next();
+	if (osmux_cid == -1) {
 		LOGPCONN(conn->conn, DOSMUX, LOGL_INFO,
-			 "Osmux CID %d already allocated!\n",
-			 osmux_cid);
+			 "no available local Osmux CID to allocate!\n");
 		return -1;
 	}
 
-	if (osmux_cid == -1) {
-		osmux_cid = osmux_cid_pool_get_next();
-		if (osmux_cid == -1) {
-			LOGPCONN(conn->conn, DOSMUX, LOGL_INFO,
-				 "no available Osmux CID to allocate!\n");
-			return -1;
-		}
-	} else {
-		osmux_cid_pool_get(osmux_cid);
-	}
-
-	conn->osmux.cid = (uint8_t) osmux_cid;
-	conn->osmux.cid_allocated = true;
+	conn->osmux.local_cid = (uint8_t) osmux_cid;
+	conn->osmux.local_cid_allocated = true;
 	conn->type = MGCP_OSMUX_BSC;
 	return osmux_cid;
 }
@@ -640,12 +632,12 @@
 	memset(osmuxh, 0, buf_len);
 	osmuxh->ft = OSMUX_FT_DUMMY;
 	osmuxh->amr_ft = AMR_FT_0;
-	osmuxh->circuit_id = conn->osmux.cid;
+	osmuxh->circuit_id = conn->osmux.remote_cid;
 
 	LOGPCONN(conn->conn, DOSMUX, LOGL_DEBUG,
 		 "sending OSMUX dummy load to %s:%u CID %u\n",
 		 osmo_sockaddr_ntop(&conn->end.addr.u.sa, ipbuf),
-		 ntohs(conn->end.rtp_port), conn->osmux.cid);
+		 ntohs(conn->end.rtp_port), conn->osmux.remote_cid);
 
 	return mgcp_udp_send(osmux_fd.fd, &conn->end.addr,
 			     conn->end.rtp_port, (char*)osmuxh, buf_len);
diff --git a/src/libosmo-mgcp/mgcp_protocol.c b/src/libosmo-mgcp/mgcp_protocol.c
index 7f31cfd..506de34 100644
--- a/src/libosmo-mgcp/mgcp_protocol.c
+++ b/src/libosmo-mgcp/mgcp_protocol.c
@@ -301,7 +301,7 @@
 
 	/* Attach optional OSMUX parameters */
 	if (mgcp_conn_rtp_is_osmux(conn)) {
-		rc = msgb_printf(sdp, MGCP_X_OSMO_OSMUX_HEADER " %u\r\n", conn->osmux.cid);
+		rc = msgb_printf(sdp, MGCP_X_OSMO_OSMUX_HEADER " %u\r\n", conn->osmux.local_cid);
 		if (rc < 0)
 			goto error;
 	}
@@ -846,7 +846,7 @@
 	const char *callid = NULL;
 	const char *mode = NULL;
 	char *line;
-	int have_sdp = 0, osmux_cid = -2;
+	int have_sdp = 0, remote_osmux_cid = -2;
 	struct mgcp_conn_rtp *conn = NULL;
 	struct mgcp_conn *_conn = NULL;
 	char conn_name[512];
@@ -895,7 +895,7 @@
 				/* If osmux is disabled, just skip setting it up */
 				if (rq->endp->trunk->cfg->osmux_use == OSMUX_USAGE_OFF)
 					break;
-				osmux_cid = mgcp_osmux_setup(endp, line);
+				remote_osmux_cid = mgcp_osmux_setup(endp, line);
 				break;
 			}
 
@@ -1001,12 +1001,17 @@
 	/* Annotate Osmux circuit ID and set it to negotiating state until this
 	 * is fully set up from the dummy load. */
 	conn->osmux.state = OSMUX_STATE_DISABLED;
-	if (osmux_cid >= -1) { /* -1 is wilcard, alloc next avail CID */
+	/* If X-Osmux (remote CID) was received (-1 is wilcard), alloc next avail CID as local CID */
+	if (remote_osmux_cid >= -1) {
 		conn->osmux.state = OSMUX_STATE_ACTIVATING;
-		if (conn_osmux_allocate_cid(conn, osmux_cid) == -1) {
+		if (conn_osmux_allocate_local_cid(conn) == -1) {
 			rate_ctr_inc(rate_ctr_group_get_ctr(rate_ctrs, MGCP_CRCX_FAIL_NO_OSMUX));
 			goto error2;
 		}
+		if (remote_osmux_cid >= 0) {
+			conn->osmux.remote_cid_present = true;
+			conn->osmux.remote_cid = remote_osmux_cid;
+		}
 	} else if (endp->trunk->cfg->osmux_use == OSMUX_USAGE_ONLY) {
 		LOGPCONN(_conn, DLMGCP, LOGL_ERROR,
 			 "CRCX: osmux only and no osmux offered\n");
@@ -1118,7 +1123,7 @@
 	const char *mode = NULL;
 	struct mgcp_conn_rtp *conn = NULL;
         const char *conn_id = NULL;
-	int osmux_cid = -2;
+	int remote_osmux_cid = -2;
 	int rc;
 
 	LOGPENDP(endp, DLMGCP, LOGL_NOTICE, "MDCX: modifying existing connection ...\n");
@@ -1176,7 +1181,7 @@
 				/* If osmux is disabled, just skip setting it up */
 				if (endp->trunk->cfg->osmux_use == OSMUX_USAGE_OFF)
 					break;
-				osmux_cid = mgcp_osmux_setup(endp, line);
+				remote_osmux_cid = mgcp_osmux_setup(endp, line);
 				break;
 			}
 			/* Ignore unknown X-headers */
@@ -1253,23 +1258,23 @@
 	}
 
 	if (mgcp_conn_rtp_is_osmux(conn)) {
-		OSMO_ASSERT(conn->osmux.cid_allocated);
-		if (osmux_cid < -1) {
+		OSMO_ASSERT(conn->osmux.local_cid_allocated);
+		if (remote_osmux_cid < -1) {
 			LOGPCONN(conn->conn, DLMGCP, LOGL_ERROR,
 				 "MDCX: Failed to parse Osmux CID!\n");
 			goto error3;
-		} else if (osmux_cid == -1) {
+		} else if (remote_osmux_cid == -1) {
 			LOGPCONN(conn->conn, DLMGCP, LOGL_ERROR,
 				 "MDCX: wilcard in MDCX is not supported!\n");
 			goto error3;
-		} else if (osmux_cid != (int) conn->osmux.cid) {
+		} else if (conn->osmux.remote_cid_present &&
+			   remote_osmux_cid != (int) conn->osmux.remote_cid) {
 			LOGPCONN(conn->conn, DLMGCP, LOGL_ERROR,
 				 "MDCX: changing already allocated CID is not supported!\n");
 			goto error3;
 		}
-		/* TODO: In the future (when we have recvCID!=sendCID), we need to
-		   tell Osmux code that osmux_cid is to be used as sendCID for
-		   that conn. */
+		conn->osmux.remote_cid_present = true;
+		conn->osmux.remote_cid = remote_osmux_cid;
 	}
 
 	/* MDCX may have provided a new remote address, which means we may need