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.

1 files changed, 4 insertions, 1 deletions

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);