mgcp: add voice muxer support

This patch adds the voice muxer. You can use this to batch RTP
traffic to reduce bandwidth comsuption. Basically, osmux transforms
RTP flows to a compact batch format, that is later on decompacted
to its original form. Port UDP/1984 is used for the muxer traffic
between osmo-bsc_nat and osmo-bsc_mgcp (in the BSC side). This
feature depends on libosmo-netif, which contains the osmux core
support.

Osmux is requested on-demand via the MGCP CRCX/MDCX messages (using
the vendor-specific extension X-Osmux: on) coming from the BSC-NAT,
so you can selectively enable osmux per BSC from one the bsc-nat.cfg
file, so we have a centralized point to enable/disable osmux.

First thing you need to do is to accept requests to use Osmux,
this can be done from VTY interface of osmo-bsc_nat and
osmo-bsc_mgcp by adding the following line:

mgcp
  ...
  osmux on
  osmux batch-factor 4

This just initializes the osmux engine. You still have to specify
what BSC uses osmux from osmo-bsc_nat configuration file:

...
 bsc 1
  osmux on
 bsc 2
  ...
 bsc 3
  osmux on

In this case, bsc 1 and 3 should use osmux if possible, bsc 2 does
not have osmux enabled.

Thus, you can selectively enable osmux depending on the BSC, and
we have a centralized point for configuration from the bsc-nat to
enable osmux on demand, as suggested by Holger.

At this moment, this patch contains heavy debug logging for each
RTP packet that can be removed later to save cycles.

The RTP ssrc/seqnum/timestamp is randomly allocated for each MDCX that
is received to configure an endpoint.

5 files changed, 53 insertions, 2 deletions

diff --git a/openbsc/include/openbsc/Makefile.am b/openbsc/include/openbsc/Makefile.am
index 8f7c1c423..d902315b5 100644
--- a/openbsc/include/openbsc/Makefile.am
+++ b/openbsc/include/openbsc/Makefile.am
@@ -13,7 +13,8 @@ noinst_HEADERS = abis_nm.h abis_rsl.h db.h gsm_04_08.h gsm_data.h \
 		osmo_bsc_rf.h osmo_bsc.h network_listen.h bsc_nat_sccp.h \
 		osmo_msc_data.h osmo_bsc_grace.h sms_queue.h abis_om2000.h \
 		bss.h gsm_data_shared.h control_cmd.h ipaccess.h mncc_int.h \
-		arfcn_range_encode.h nat_rewrite_trie.h bsc_nat_callstats.h
+		arfcn_range_encode.h nat_rewrite_trie.h bsc_nat_callstats.h \
+		osmux.h
 
 openbsc_HEADERS = gsm_04_08.h meas_rep.h bsc_api.h
 openbscdir = $(includedir)/openbsc
diff --git a/openbsc/include/openbsc/bsc_nat.h b/openbsc/include/openbsc/bsc_nat.h
index 7bd582cf6..7a161ff27 100644
--- a/openbsc/include/openbsc/bsc_nat.h
+++ b/openbsc/include/openbsc/bsc_nat.h
@@ -176,6 +176,9 @@ struct bsc_config {
 	struct bsc_config_stats stats;
 
 	struct llist_head lac_list;
+
+	/* Osmux is enabled/disabled per BSC */
+	int osmux;
 };
 
 struct bsc_lac_entry {
@@ -418,7 +421,7 @@ int bsc_mgcp_nat_init(struct bsc_nat *nat);
 
 struct nat_sccp_connection *bsc_mgcp_find_con(struct bsc_nat *, int endpoint_number);
 struct msgb *bsc_mgcp_rewrite(char *input, int length, int endp, const char *ip,
-			      int port, int *payload_type);
+			      int port, int osmux, int *payload_type);
 void bsc_mgcp_forward(struct bsc_connection *bsc, struct msgb *msg);
 
 void bsc_mgcp_clear_endpoints_for(struct bsc_connection *bsc);
diff --git a/openbsc/include/openbsc/mgcp.h b/openbsc/include/openbsc/mgcp.h
index 1d7407820..939e7eed1 100644
--- a/openbsc/include/openbsc/mgcp.h
+++ b/openbsc/include/openbsc/mgcp.h
@@ -181,6 +181,15 @@ struct mgcp_config {
 	int last_bts_port;
 
 	enum mgcp_role role;
+
+	/* osmux translator: 0 means disabled, 1 means enabled */
+	int osmux;
+	/* The BSC-NAT may ask for enabling osmux on demand. This tells us if
+	 * the osmux socket is already initialized.
+	 */
+	int osmux_init;
+	/* osmux batch factor: from 1 to 4 maximum */
+	int osmux_batch;
 };
 
 /* config management */
@@ -222,4 +231,8 @@ int mgcp_send_reset_ep(struct mgcp_endpoint *endp, int endpoint);
 int mgcp_send_reset_all(struct mgcp_config *cfg);
 
 
+int mgcp_create_bind(const char *source_addr, struct osmo_fd *fd, int port);
+int mgcp_send(struct mgcp_endpoint *endp, int dest, int is_rtp, struct sockaddr_in *addr, char *buf, int rc);
+int mgcp_udp_send(int fd, struct in_addr *addr, int port, char *buf, int len);
+
 #endif
diff --git a/openbsc/include/openbsc/mgcp_internal.h b/openbsc/include/openbsc/mgcp_internal.h
index 9b9716539..8fe9f8182 100644
--- a/openbsc/include/openbsc/mgcp_internal.h
+++ b/openbsc/include/openbsc/mgcp_internal.h
@@ -126,8 +126,12 @@ struct mgcp_lco {
 enum mgcp_type {
 	MGCP_RTP_DEFAULT	= 0,
 	MGCP_RTP_TRANSCODED,
+	MGCP_OSMUX_BSC,
+	MGCP_OSMUX_BSC_NAT,
 };
 
+#include <openbsc/osmux.h>
+
 struct mgcp_endpoint {
 	int allocated;
 	uint32_t ci;
@@ -163,6 +167,11 @@ struct mgcp_endpoint {
 
 	/* tap for the endpoint */
 	struct mgcp_rtp_tap taps[MGCP_TAP_COUNT];
+
+	/* osmux is enabled/disabled */
+	int osmux;
+	/* osmux internal to unbatch messages for this endpoint */
+	struct osmux_out_handle osmux_out;
 };
 
 #define ENDPOINT_NUMBER(endp) abs(endp - endp->tcfg->endpoints)
@@ -197,5 +206,11 @@ void mgcp_state_calc_loss(struct mgcp_rtp_state *s, struct mgcp_rtp_end *,
 			uint32_t *expected, int *loss);
 uint32_t mgcp_state_calc_jitter(struct mgcp_rtp_state *);
 
+enum {
+	MGCP_DEST_NET = 0,
+	MGCP_DEST_BTS,
+};
+
+#define MGCP_DUMMY_LOAD 0x23
 
 #endif
diff --git a/openbsc/include/openbsc/osmux.h b/openbsc/include/openbsc/osmux.h
new file mode 100644
index 000000000..33456b76d
--- /dev/null
+++ b/openbsc/include/openbsc/osmux.h
@@ -0,0 +1,19 @@
+#ifndef _OPENBSC_OSMUX_H_
+#define _OPENBSC_OSMUX_H_
+
+#include <osmocom/netif/osmux.h>
+
+enum {
+	OSMUX_ROLE_BSC = 0,
+	OSMUX_ROLE_BSC_NAT,
+};
+
+int osmux_init(int role, struct mgcp_config *cfg);
+int osmux_enable_endpoint(struct mgcp_endpoint *endp, int role);
+
+int osmux_xfrm_to_rtp(struct mgcp_endpoint *endp, int type, char *buf, int rc);
+int osmux_xfrm_to_osmux(int type, char *buf, int rc, struct mgcp_endpoint *endp);
+
+int osmux_send_dummy(struct mgcp_endpoint *endp);
+
+#endif