osmo-bsc: full auto configuration for SS7/CS7

If invalid addresses, or a missing CS7 instance is detected
during startup, the BSC will assume safe defaults. The defaults
picked are complementary to osmo-msc, so in case the user just
wants to run the osmo-msc and osmo-bsc + the STP on one machine,
no CS7 configuration is needed at all.

1 files changed, 44 insertions, 20 deletions

diff --git a/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c b/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c
index 3d8aecd6f..de9416df8 100644
--- a/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c
+++ b/openbsc/src/osmo-bsc/osmo_bsc_sigtran.c
@@ -40,6 +40,7 @@ static struct llist_head *msc_list;
 
 #define RESET_INTERVAL 1	/* sek */
 #define SCCP_MSG_MAXSIZE 1024
+#define CS7_POINTCODE_DEFAULT_OFFSET 2
 
 /* Internal list with connections we currently maintain. This
  * list is of type struct osmo_bsc_sccp_con */
@@ -410,18 +411,25 @@ static void osmo_bsc_sigtran_reset_cb(const void *priv)
 	osmo_bsc_sigtran_tx_reset(msc);
 }
 
-
 /* Initalize osmo sigtran backhaul */
 int osmo_bsc_sigtran_init(struct llist_head *mscs)
 {
 	/* FIXME: Remove hardcoded IP-Addresses */
 	struct bsc_msc_data *msc;
 	char msc_name[256];
+	uint32_t bsc_default_pc = CS7_POINTCODE_DEFAULT_OFFSET;
+	uint8_t cs7_default_inst = 0;
 
-	OSMO_ASSERT(mscs);
+	/* FIXME: The way this code derives the default parameters is not safe when
+	 * mixing proper configuration with incomplete configuration. When multiple
+	 * MSCs are connected, the autogenerated pointcodes may colide with the
+	 * ones that are properly set. However, this is a very unlikely situation.
+	 * in most cases it will be exactly one MSC<->BSC connection and either no
+	 * configuration done by the user or the user knows how to properly set
+	 * up the configuration */
 
+	OSMO_ASSERT(mscs);
 	msc_list = mscs;
-
 	conn_id_counter = 0;
 
 	llist_for_each_entry(msc, msc_list, entry) {
@@ -431,40 +439,56 @@ int osmo_bsc_sigtran_init(struct llist_head *mscs)
 
 		/* Check if the VTY could determine a valid CS7 instance */
 		if (msc->a.cs7_instance_valid == false) {
-			LOGP(DMSC, LOGL_ERROR, "A-interface: Invalid CS7 instance\n");
-			return -EINVAL;
+			LOGP(DMSC, LOGL_NOTICE,
+			     "A-interface: Unable to detect CS7 instance, assuming instance ID: %u\n",
+			     cs7_default_inst);
+			msc->a.cs7_instance = cs7_default_inst;
 		}
+		cs7_default_inst++;
+
+		/* SS7 Protocol stack */
+		msc->a.sccp =
+		    osmo_sccp_simple_client_on_ss7_id(msc, msc->a.cs7_instance, msc_name, bsc_default_pc,
+						      OSMO_SS7_ASP_PROT_M3UA, 0, NULL, M3UA_PORT, "127.0.0.1");
+		if (!msc->a.sccp)
+			return -EINVAL;
+		bsc_default_pc++;
 
-		/* Check if the sccp-address fullfill minimum requirements (SSN+PC is present) */
+		/* Check if the sccp-address fullfill minimum requirements (SSN+PC is present,
+		 * automatically recover addresses if the addresses are not set up properly) */
 		if (!osmo_sccp_check_addr(&msc->a.bsc_addr, OSMO_SCCP_ADDR_T_SSN | OSMO_SCCP_ADDR_T_PC)) {
-			LOGP(DMSC, LOGL_ERROR,
-			     "A-interface: invalid local SCCP address (a.bsc_addr=%s)\n",
+			/* In case a valid address is not set, derive the address from the SCCP
+			 * instance that has just been created */
+			LOGP(DMSC, LOGL_NOTICE,
+			     "A-interface: invalid or missing local SCCP address (a.bsc_addr=%s)\n",
+			     osmo_sccp_addr_dump(&msc->a.bsc_addr));
+			osmo_sccp_local_addr_by_instance(&msc->a.bsc_addr, msc->a.sccp, SCCP_SSN_BSSAP);
+			LOGP(DMSC, LOGL_NOTICE,
+			     "A-interface: using automatically generated SCCP address (a.bsc_addr=%s)\n",
 			     osmo_sccp_addr_dump(&msc->a.bsc_addr));
-			return -EINVAL;
 		}
 		if (!osmo_sccp_check_addr(&msc->a.msc_addr, OSMO_SCCP_ADDR_T_SSN | OSMO_SCCP_ADDR_T_PC)) {
+			/* In case a valid address is not set, use the SCCP instance to query a local
+			 * address and subtract one from the pointcode */
 			LOGP(DMSC, LOGL_ERROR,
-			     "A-interface: invalid remote SCCP address for the MSC (a.msc_addr=%s)\n",
+			     "A-interface: invalid or missing remote SCCP address for the MSC (a.msc_addr=%s)\n",
+			     osmo_sccp_addr_dump(&msc->a.msc_addr));
+			osmo_sccp_local_addr_by_instance(&msc->a.msc_addr, msc->a.sccp, SCCP_SSN_BSSAP);
+			msc->a.msc_addr.pc -= 1;
+			LOGP(DMSC, LOGL_NOTICE,
+			     "A-interface: using automatically generated SCCP address (a.msc_addr=%s)\n",
 			     osmo_sccp_addr_dump(&msc->a.msc_addr));
-			return -EINVAL;
 		}
 
-		/* SS7 Protocol stack */
-		msc->a.sccp =
-		    osmo_sccp_simple_client_on_ss7_id(msc, msc->a.cs7_instance, msc_name, msc->a.bsc_addr.pc,
-						      OSMO_SS7_ASP_PROT_M3UA, 0, NULL, M3UA_PORT, "127.0.0.1");
-		if (!msc->a.sccp)
-			return -EINVAL;
-
+		/* Bind SCCP user */
 		msc->a.sccp_user = osmo_sccp_user_bind(msc->a.sccp, msc_name, sccp_sap_up, msc->a.bsc_addr.ssn);
 		if (!msc->a.sccp_user)
 			return -EINVAL;
 
-		/* Start MSC reset procedure */
+		/* Start MSC-Reset procedure */
 		msc->a.reset = a_reset_alloc(msc, msc_name, osmo_bsc_sigtran_reset_cb, msc);
 		if (!msc->a.reset)
 			return -EINVAL;
-
 	}
 
 	return 0;