sgsn_rim: Add routing for (GERAN) BSSGP RIM messages

The SGSN currently does not forward BSSGP RIM messages.

Related: SYS#5103
Depends: libosmocore Icd667f41d5735de56cd9fb257670337c679dd258
Change-Id: I6fde8ab8955660b48000ca1b650cfc7c7b2e24ba

include/osmocom/sgsn/Makefile.am

@@ -24,6 +24,7 @@ noinst_HEADERS = \
 	gprs_utils.h \
 	gtphub.h \
 	sgsn.h \
+	sgsn_rim.h \
 	signal.h \
 	slhc.h \
 	v42bis.h \

include/osmocom/sgsn/debug.h

@@ -27,6 +27,7 @@ enum {
 	DSIGTRAN,
 	DGTP,
 	DOBJ,
+	DRIM,
 	Debug_LastEntry,
 };
 

include/osmocom/sgsn/sgsn_rim.h

@@ -0,0 +1,3 @@
+#pragma once
+
+int sgsn_rim_rx(struct osmo_bssgp_prim *bp, struct msgb *msg);

src/sgsn/Makefile.am

@@ -62,6 +62,7 @@ osmo_sgsn_SOURCES = \
 	sgsn_auth.c \
 	gprs_subscriber.c \
 	sgsn_cdr.c \
+	sgsn_rim.c \
 	slhc.c \
 	gprs_llc_xid.c \
 	v42bis.c \

src/sgsn/sgsn_main.c

@@ -67,6 +67,7 @@
 #include <osmocom/ctrl/ports.h>
 
 #include <gtp.h>
+#include <osmocom/sgsn/sgsn_rim.h>
 
 #include "../../bscconfig.h"
 
@@ -120,6 +121,8 @@ int bssgp_prim_cb(struct osmo_prim_hdr *oph, void *ctx)
 		break;
 	case SAP_BSSGP_NM:
 		break;
+	case SAP_BSSGP_RIM:
+		return sgsn_rim_rx(bp, oph->msg);
 	}
 	return 0;
 }
@@ -311,6 +314,11 @@ static struct log_info_cat gprs_categories[] = {
 		.description = "GPRS Tunnelling Protocol (GTP)",
 		.enabled = 1, .loglevel = LOGL_NOTICE,
 	},
+	[DRIM] = {
+		.name = "DRIM",
+		.description = "RAN Information Management (RIM)",
+		.enabled = 1, .loglevel = LOGL_NOTICE,
+	},
 };
 
 static const struct log_info gprs_log_info = {

src/sgsn/sgsn_rim.c

@@ -0,0 +1,67 @@
+
+#include <stdio.h>
+
+#include <errno.h>
+#include <stdint.h>
+
+#include <osmocom/core/msgb.h>
+#include <osmocom/gsm/tlv.h>
+#include <osmocom/vty/logging.h>
+#include <osmocom/gprs/gprs_ns.h>
+#include <osmocom/gprs/gprs_bssgp.h>
+#include <osmocom/gprs/gprs_bssgp_rim.h>
+#include <osmocom/sgsn/sgsn_rim.h>
+#include <osmocom/sgsn/debug.h>
+
+/* Find an NSEI for the destination cell, this function works only for GERAN! */
+static int find_dest_nsei_geran(struct bssgp_rim_routing_info *dest_rim_ri, uint16_t nsei)
+{
+	struct bssgp_bvc_ctx *bvc_ctx;
+
+	OSMO_ASSERT(dest_rim_ri->discr == BSSGP_RIM_ROUTING_INFO_GERAN);
+
+	bvc_ctx = btsctx_by_raid_cid(&dest_rim_ri->geran.raid, dest_rim_ri->geran.cid);
+	if (!bvc_ctx) {
+		LOGP(DRIM, LOGL_ERROR, "BSSGP RIM (NSEI=%u) cannot find NSEI for destination cell\n", nsei);
+		return -EINVAL;
+	}
+
+	return bvc_ctx->nsei;
+}
+
+int sgsn_rim_rx(struct osmo_bssgp_prim *bp, struct msgb *msg)
+{
+	struct bssgp_ran_information_pdu *pdu = &bp->u.rim_pdu;
+	int d_nsei;
+	uint16_t nsei = msgb_nsei(msg);
+
+	/* At the moment we only support GERAN, so we block all other network
+	 * types here. */
+	if (pdu->routing_info_dest.discr != BSSGP_RIM_ROUTING_INFO_GERAN) {
+		LOGP(DRIM, LOGL_ERROR,
+		     "BSSGP RIM (NSEI=%u) only GERAN supported, destination cell is not a GERAN cell -- rejected.\n",
+		     nsei);
+		/* At the moment we can only handle GERAN addresses, any other
+		 * type of address will be consideres as an invalid address.
+		 * see also: 3GPP TS 48.018, section 8c.3.1.3 */
+		return bssgp_tx_status(BSSGP_CAUSE_UNKN_RIM_AI, NULL, msg);
+	}
+	if (pdu->routing_info_src.discr != BSSGP_RIM_ROUTING_INFO_GERAN) {
+		LOGP(DRIM, LOGL_ERROR,
+		     "BSSGP RIM (NSEI=%u) only GERAN supported, source cell is not a GERAN cell -- rejected.\n", nsei);
+		/* See comment above */
+		return bssgp_tx_status(BSSGP_CAUSE_UNKN_RIM_AI, NULL, msg);
+	}
+
+	d_nsei = find_dest_nsei_geran(&pdu->routing_info_dest, nsei);
+	if (d_nsei < 0) {
+		LOGP(DRIM, LOGL_NOTICE, "BSSGP RIM (NSEI=%u) Cell %s unknown to this sgsn\n",
+		     nsei, bssgp_rim_ri_name(&pdu->routing_info_dest));
+		/* In case of an invalid destination address we respond with
+		 * a BSSGP STATUS PDU, see also: 3GPP TS 48.018, section 8c.3.1.3 */
+		return bssgp_tx_status(BSSGP_CAUSE_UNKN_RIM_AI, NULL, msg);
+	}
+
+	/* Forward PDU as it is to the correct interface */
+	return bssgp_tx_rim(pdu, (uint16_t) d_nsei);
+}