add VTY commands: mncc internal / external (== -M)

So far the only way to use external MNCC is to pass the -M cmdline arg:

  osmo-msc -M /path/to/socket

However, the osmo-msc.service file for systemd is installed by 'make install',
and hence it is quite impractical to depend on such a config item to be
required in the service file:

- It defies any scheme an operator may have in place to compose the
  osmo-msc.cfg file -- this option doesn't go in the .cfg file but needs
  separate action to add to the installed service file.

- After a make install or package upgrades / re-installations, this option will
  be plain overwritten silently, or lead to the need for resolving file
  conflicts.

The initial spark for this came from configuring the 35c3 GSM from cfg
templates.

Change-Id: I2ec59d5eba407f83295528b51b93678d446b9cee

1 files changed, 11 insertions, 2 deletions

diff --git a/src/osmo-msc/msc_main.c b/src/osmo-msc/msc_main.c
index 157d5ae56..8500b9722 100644
--- a/src/osmo-msc/msc_main.c
+++ b/src/osmo-msc/msc_main.c
@@ -573,11 +573,20 @@ int main(int argc, char **argv)
 		return 1;
 	}
 
-	/* Initialize MNCC socket if appropriate */
+	/* Initialize MNCC socket if appropriate. If the cmdline option -M is present, it overrides the .cfg file
+	 * setting 'msc' / 'mncc external MNCC_SOCKET_PATH'. Note that when -M is given, it "bleeds" back into the vty
+	 * 'write' command and is reflected in the written out 'mncc external' cfg. */
 	if (msc_cmdline_config.mncc_sock_path) {
+		LOGP(DMNCC, LOGL_NOTICE,
+		     "MNCC socket path is configured from commandline argument -M."
+		     " This affects a written-back config file. Instead consider using the config file directly"
+		     " ('msc' / 'mncc external MNCC_SOCKET_PATH').\n");
+		gsm_network_set_mncc_sock_path(msc_network, msc_cmdline_config.mncc_sock_path);
+	}
+	if (msc_network->mncc_sock_path) {
 		msc_network->mncc_recv = mncc_sock_from_cc;
 		rc = mncc_sock_init(msc_network,
-				    msc_cmdline_config.mncc_sock_path);
+				    msc_network->mncc_sock_path);
 		if (rc) {
 			fprintf(stderr, "MNCC socket initialization failed. exiting.\n");
 			exit(1);