osmo-bsc: make sure only default SSNs are used

The VTY technically allows setting custom values for the
SSN. However, SSN values and their purposes are well
standardized.

If the user has configured an SSN, check that is compliant
to the standard. If not, warn and ignore the setting by
using the stanard SSN.

If the user left out the SSN, automatically use the standard
SSN.

2 files changed, 21 insertions, 2 deletions

diff --git a/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c b/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c
index 0646a69a2..b40177eb8 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c
@@ -427,7 +427,7 @@ int osmo_bsc_sigtran_init(struct llist_head *mscs)
 		    osmo_sccp_simple_client(NULL, msc_name, msc->a.g_calling_addr.pc,
 					    OSMO_SS7_ASP_PROT_M3UA, 0, NULL, M3UA_PORT, "127.0.0.1");
 		msc->a.sccp_user =
-		    osmo_sccp_user_bind(msc->a.sccp, msc_name, sccp_sap_up, SCCP_SSN_BSSAP);
+		    osmo_sccp_user_bind(msc->a.sccp, msc_name, sccp_sap_up, msc->a.g_calling_addr.ssn);
 
 		/* Start MSC reset procedure */
 		msc->a.reset = a_reset_alloc(msc, msc_name, osmo_bsc_sigtran_reset_cb, msc);
diff --git a/openbsc/src/osmo-bsc/osmo_bsc_vty.c b/openbsc/src/osmo-bsc/osmo_bsc_vty.c
index 5d6491047..17764e85b 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_vty.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_vty.c
@@ -28,6 +28,7 @@
 
 #include <osmocom/core/talloc.h>
 #include <osmocom/vty/logging.h>
+#include <osmocom/sccp/sccp_types.h>
 
 #include <time.h>
 
@@ -717,6 +718,21 @@ DEFUN(cfg_msc_cs7_instance,
 	return CMD_SUCCESS;
 }
 
+/* Make sure only standard SSN numbers are used. If no ssn number is
+ * configured, silently apply the default SSN */
+static void enforce_standard_ssn(struct vty *vty, struct osmo_sccp_addr *addr)
+{
+	if (addr->presence & OSMO_SCCP_ADDR_T_SSN) {
+		if (addr->ssn != SCCP_SSN_BSSAP)
+			vty_out(vty,
+				"setting ssn different from the standard (%u) is not allowd!%s",
+				SCCP_SSN_BSSAP, VTY_NEWLINE);
+	}
+
+	addr->presence |= OSMO_SCCP_ADDR_T_SSN;
+	addr->ssn = SCCP_SSN_BSSAP;
+}
+
 DEFUN(cfg_msc_cs7_calling_addr,
       cfg_msc_cs7_calling_addr_cmd,
       "calling-addr NAME",
@@ -739,8 +755,9 @@ DEFUN(cfg_msc_cs7_calling_addr,
 		return CMD_WARNING;
 	}
 
-	memcpy(&msc->a.g_calling_addr, calling_addr, sizeof(*calling_addr));
+	enforce_standard_ssn(vty, calling_addr);
 
+	memcpy(&msc->a.g_calling_addr, calling_addr, sizeof(*calling_addr));
 	return CMD_SUCCESS;
 }
 
@@ -766,6 +783,8 @@ DEFUN(cfg_msc_cs7_called_addr,
 		return CMD_WARNING;
 	}
 
+	enforce_standard_ssn(vty, called_addr);
+
 	memcpy(&msc->a.g_called_addr, called_addr, sizeof(*called_addr));
 
 	return CMD_SUCCESS;