make gsup ipa name configurable in osmo-msc.cfg

Add a 'ipa-name' VTY command which overrides the default IPA name
used by the MSC. This is a prerequisite for inter-MSC handover.

Related: OS#3355
Change-Id: I317d6c59f77e92fbb2b875a83dc0ec2fa5cb6006
diff --git a/include/osmocom/msc/gsm_data.h b/include/osmocom/msc/gsm_data.h
index 63af3e7..d2511cb 100644
--- a/include/osmocom/msc/gsm_data.h
+++ b/include/osmocom/msc/gsm_data.h
@@ -212,6 +212,12 @@
 		/* MSISDN to which to route MO emergency calls */
 		char *route_to_msisdn;
 	} emergency;
+
+	/* This is transmitted as IPA Serial Number tag, which is used for GSUP routing (e.g. in OsmoHLR).
+         * For inter-MSC handover, the remote MSC's neighbor configuration requires to match this name.
+	 * If no name is set, the IPA Serial Number will be the same as the Unit Name,
+	 * and will be of the form 'MSC-00-00-00-00-00-00' */
+	char *msc_ipa_name;
 };
 
 struct osmo_esme;