1 files changed, 127 insertions, 0 deletions
diff --git a/src/sgsn/sgsn_rim.c b/src/sgsn/sgsn_rim.c
new file mode 100644
index 000000000..40e1f9033
--- /dev/null
+++ b/src/sgsn/sgsn_rim.c
@@ -0,0 +1,127 @@
+
+#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/gtp_mme.h>
+#include <osmocom/sgsn/gtp.h>
+#include <osmocom/sgsn/debug.h>
+#include <osmocom/sgsn/sgsn.h>
+
+static int sgsn_bssgp_fwd_rim_to_geran(const struct bssgp_ran_information_pdu *pdu)
+{
+	struct bssgp_bvc_ctx *bvc_ctx;
+	OSMO_ASSERT(pdu->routing_info_dest.discr == BSSGP_RIM_ROUTING_INFO_GERAN);
+
+	/* Resolve RIM ROUTING ADDRESS to a BVC context */
+	bvc_ctx = btsctx_by_raid_cid(&pdu->routing_info_dest.geran.raid, pdu->routing_info_dest.geran.cid);
+	if (!bvc_ctx) {
+		LOGP(DRIM, LOGL_ERROR, "Unable to find NSEI for destination cell %s\n",
+		       bssgp_rim_ri_name(&pdu->routing_info_dest));
+		return -EINVAL;
+	}
+
+	/* Forward PDU to the NSEI of the resolved BVC context */
+	return bssgp_tx_rim(pdu, bvc_ctx->nsei);
+}
+
+static int sgsn_bssgp_fwd_rim_to_geran_encoded(struct msgb *msg, struct bssgp_rim_routing_info *rim_routing_address)
+{
+	struct bssgp_bvc_ctx *bvc_ctx;
+	OSMO_ASSERT(rim_routing_address->discr == BSSGP_RIM_ROUTING_INFO_GERAN);
+
+	/* Resolve RIM ROUTING ADDRESS to a BVC context */
+	bvc_ctx = btsctx_by_raid_cid(&rim_routing_address->geran.raid, rim_routing_address->geran.cid);
+	if (!bvc_ctx) {
+		LOGP(DRIM, LOGL_ERROR, "Unable to find NSEI for destination cell %s\n",
+		       bssgp_rim_ri_name(rim_routing_address));
+		return -EINVAL;
+	}
+
+	/* Forward PDU to the NSEI of the resolved BVC context */
+	return bssgp_tx_rim_encoded(msg, bvc_ctx->nsei);
+}
+
+static int sgsn_bssgp_fwd_rim_to_eutran(const struct bssgp_ran_information_pdu *pdu)
+{
+	struct sgsn_mme_ctx *mme;
+	OSMO_ASSERT(pdu->routing_info_dest.discr == BSSGP_RIM_ROUTING_INFO_EUTRAN);
+
+	mme = sgsn_mme_ctx_by_route(sgsn, &pdu->routing_info_dest.eutran.tai);
+	if (!mme) { /* See if we have a default route configured */
+		mme = sgsn_mme_ctx_by_default_route(sgsn);
+		if (!mme) {
+			LOGP(DRIM, LOGL_ERROR, "Unable to find MME for destination cell %s\n",
+			       bssgp_rim_ri_name(&pdu->routing_info_dest));
+			return -EINVAL;
+		}
+	}
+
+	return sgsn_mme_ran_info_req(mme, pdu);
+}
+
+/* Receive a RIM PDU from BSSGP (GERAN) */
+int sgsn_rim_rx_from_gb(struct osmo_bssgp_prim *bp, struct msgb *msg)
+{
+	uint16_t nsei = msgb_nsei(msg);
+	struct bssgp_ran_information_pdu *pdu = &bp->u.rim_pdu;
+
+	if (pdu->routing_info_src.discr != BSSGP_RIM_ROUTING_INFO_GERAN) {
+		LOGP(DRIM, LOGL_ERROR,
+		     "Rx BSSGP RIM (NSEI=%u): Expected src %s, got %s\n", nsei,
+		     bssgp_rim_routing_info_discr_str(BSSGP_RIM_ROUTING_INFO_GERAN),
+		     bssgp_rim_routing_info_discr_str(pdu->routing_info_src.discr));
+		goto err;
+	}
+
+	switch (pdu->routing_info_dest.discr) {
+	case BSSGP_RIM_ROUTING_INFO_GERAN:
+		return sgsn_bssgp_fwd_rim_to_geran(pdu);
+	case BSSGP_RIM_ROUTING_INFO_EUTRAN:
+		return sgsn_bssgp_fwd_rim_to_eutran(pdu);
+	default:
+		/* At the moment we can only handle GERAN/EUTRAN addresses, any
+		 * other type of address will be considered as an invalid
+		 * address. see also: 3GPP TS 48.018, section 8c.3.1.3
+		 */
+		LOGP(DRIM, LOGL_ERROR,
+		     "Rx BSSGP RIM (NSEI=%u): Unsupported dst %s\n", nsei,
+		     bssgp_rim_routing_info_discr_str(pdu->routing_info_dest.discr));
+	}
+
+	LOGP(DRIM, LOGL_INFO, "Rx BSSGP RIM (NSEI=%u): for dest cell %s\n", nsei,
+	     bssgp_rim_ri_name(&pdu->routing_info_dest));
+
+err:
+	/* 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 */
+	bssgp_tx_status(BSSGP_CAUSE_UNKN_RIM_AI, NULL, msg);
+	return -1;
+}
+
+/* Receive a RIM PDU from GTPv1C (EUTRAN) */
+int sgsn_rim_rx_from_gtp(struct msgb *msg, struct bssgp_rim_routing_info *rim_routing_address)
+{
+	/* TODO: In this code path, we currently only support RIM message forwarding to GERAN (BSSGP). However, it
+	 * technically also be possible to route a message back to GTP (BSSGP_RIM_ROUTING_INFO_EUTRAN) or to
+	 * IuPS (BSSGP_RIM_ROUTING_INFO_UTRAN) */
+	if (rim_routing_address->discr != BSSGP_RIM_ROUTING_INFO_GERAN) {
+		LOGP(DRIM, LOGL_ERROR, "Rx GTP RAN Information Relay: Expected dst %s, got %s\n",
+		     bssgp_rim_routing_info_discr_str(BSSGP_RIM_ROUTING_INFO_GERAN),
+		     bssgp_rim_routing_info_discr_str(rim_routing_address->discr));
+		return -EINVAL;
+	}
+
+	LOGP(DRIM, LOGL_INFO, "Rx GTP RAN Information Relay for dest cell %s\n",
+	     bssgp_rim_ri_name(rim_routing_address));
+
+	return sgsn_bssgp_fwd_rim_to_geran_encoded(msg, rim_routing_address);
+}