Introduce support for libosmo-mgcp-client MGW pooling

Large RAN installations may benefit from distributing the RTP voice
stream load over multiple media gateways.

libosmo-mgcp-client supports MGW pooling since version 1.8.0 (more than
one year ago). OsmoBSC has already been making use of it since then (see
osmo-bsc.git 8d22e6870637ed6d392a8a77aeaebc51b23a8a50); lets use this
feature in osmo-msc too.

This commit is also part of a series of patches cleaning up
libosmo-mgcp-client and slowly getting rid of the old non-mgw-pooled VTY
configuration, in order to keep only 1 way to configure
libosmo-mgcp-client through VTY.

Related: SYS#5091
Related: SYS#5987
Change-Id: I7670ba56fe989706579224a364595fdd4b4708ff

4 files changed, 28 insertions, 13 deletions

diff --git a/doc/examples/osmo-msc/osmo-msc.cfg b/doc/examples/osmo-msc/osmo-msc.cfg
index 83b2c6fec..2b0d98d80 100644
--- a/doc/examples/osmo-msc/osmo-msc.cfg
+++ b/doc/examples/osmo-msc/osmo-msc.cfg
@@ -12,10 +12,11 @@ network
  encryption a5 0
  rrlp mode none
  mm info 1
+ mgw 0
+  mgw remote-ip 127.0.0.1
+  mgw remote-port 2427
+  mgw local-port 2728
 msc
- mgw remote-ip 127.0.0.1
- mgw remote-port 2427
- mgw local-port 2728
  assign-tmsi
  auth-tuple-max-reuse-count 3
  auth-tuple-reuse-on-error 1
diff --git a/doc/examples/osmo-msc/osmo-msc_custom-sccp.cfg b/doc/examples/osmo-msc/osmo-msc_custom-sccp.cfg
index d949ef9a0..d014eddcb 100644
--- a/doc/examples/osmo-msc/osmo-msc_custom-sccp.cfg
+++ b/doc/examples/osmo-msc/osmo-msc_custom-sccp.cfg
@@ -12,6 +12,10 @@ network
  encryption a5 0
  rrlp mode none
  mm info 1
+ mgw 0
+  mgw remote-ip 127.0.0.1
+  mgw remote-port 2427
+  mgw local-port 2728
 cs7 instance 0
  point-code 0.23.1
  asp asp-clnt-OsmoMSC-A-Iu 2905 0 m3ua
@@ -21,7 +25,4 @@ cs7 instance 0
 msc
  cs7-instance-a 0
  cs7-instance-iu 0
- mgw remote-ip 127.0.0.1
- mgw remote-port 2427
- mgw local-port 2728
  assign-tmsi
diff --git a/doc/examples/osmo-msc/osmo-msc_multi-cs7.cfg b/doc/examples/osmo-msc/osmo-msc_multi-cs7.cfg
index cb1157db3..62c927095 100644
--- a/doc/examples/osmo-msc/osmo-msc_multi-cs7.cfg
+++ b/doc/examples/osmo-msc/osmo-msc_multi-cs7.cfg
@@ -12,6 +12,10 @@ network
  encryption a5 0
  rrlp mode none
  mm info 1
+ mgw 0
+  mgw remote-ip 127.0.0.1
+  mgw remote-port 2427
+  mgw local-port 2728
 cs7 instance 0
  point-code 0.23.1
  asp asp-clnt-OsmoMSC-A 2905 0 m3ua
@@ -23,7 +27,4 @@ cs7 instance 1
 msc
  cs7-instance-a 0
  cs7-instance-iu 1
- mgw remote-ip 127.0.0.1
- mgw remote-port 2427
- mgw local-port 2728
  assign-tmsi
diff --git a/doc/manuals/chapters/running.adoc b/doc/manuals/chapters/running.adoc
index 86653954e..4556e0143 100644
--- a/doc/manuals/chapters/running.adoc
+++ b/doc/manuals/chapters/running.adoc
@@ -149,11 +149,23 @@ default port for MGCP (2427) on local host (127.0.0.1).
 Here is an example configuration for a remote MGW:
 
 ----
-msc
- mgw remote-ip 10.9.8.7
- mgw remote-port 2427
- mgw reset-endpoint rtpbridge/* <1>
+network
+ mgw 0
+  mgw remote-ip 10.9.8.7
+  mgw remote-port 2427
+  mgw reset-endpoint rtpbridge/* <1>
 ----
 <1> The 'reset-endpoint' setting instructs the OsmoMGW to send a wildcarded
 DLCX to the media gateway. This helps to clear lingering calls from the
 media gateway when the OsmoMSC is restarted.
+
+[NOTE]
+====
+Previous versions of OsmoMSC (1.9.0 and below) didn't have the 'mgw' VTY node and
+hence didn't support the MGW pooling feature. Therefore, historically the MGW
+related commands where placed under the `msc` VTY node. The MGW related commands
+under the  `msc` VTY are still parsed and used but its use is deprecated and
+hence discouraged in favour of the new `mgw` node. Writing the config to a file
+from within OsmoMSC will automatically convert the config to use the new `mgw`
+node.
+====