ensure unique CellIDs in HNB-GW

If we receive a HNB-REGISTER-REQ with a cell ID which is already used
by another registered NNB, log an error and send HNB-REGISTER-REJECT.

Tested manually by running two 'hnb-test' programs concurrently (they
need to listen on different telnet ports; this port is hard-coded so
I compiled two different hnb-test binaries).
Then I issued the 'hnbap hnb register' command on the telnet interface
of each, and verified that the correct action is logged by osmo-hnbgw.
Both hnb-test programs can connect, but only one of them can register
at a time. Killing a registered 'hnb-test' program terminates its
connection and allows the previously rejected one to register.

The new rejection log message looks like this:
 hnbgw_hnbap.c:429 rejecting HNB-REGISTER-REQ with duplicate cell
 identity MCC=901,MNC=99,LAC=49406,RAC=66,SAC=43947,CID=182250155
 from (r=127.0.0.1:42828<->l=127.0.0.1:29169)

Change-Id: Iffd441eb2b6b75dfbe001b49b01bea015ca6e11c
Related: OS#2789

2 files changed, 51 insertions, 0 deletions

diff --git a/include/osmocom/iuh/hnbgw.h b/include/osmocom/iuh/hnbgw.h
index 094f31f..db49dc1 100644
--- a/include/osmocom/iuh/hnbgw.h
+++ b/include/osmocom/iuh/hnbgw.h
@@ -97,6 +97,10 @@ struct hnb_context {
 	/*! SCTP stream ID for RUA */
 	uint16_t rua_stream;
 
+	/*! True if a HNB-REGISTER-REQ from this HNB has been accepted. Note that
+	 * this entire data structure is freed if the HNB sends HNB-DE-REGISTER-REQ. */
+	bool hnb_registered;
+
 	/* linked list of hnbgw_context_map */
 	struct llist_head map_list;
 };
diff --git a/src/hnbgw_hnbap.c b/src/hnbgw_hnbap.c
index 8fba13c..c9a8807 100644
--- a/src/hnbgw_hnbap.c
+++ b/src/hnbgw_hnbap.c
@@ -20,6 +20,7 @@
 
 #include <osmocom/core/msgb.h>
 #include <osmocom/core/utils.h>
+#include <osmocom/core/socket.h>
 #include <osmocom/gsm/gsm48.h>
 #include <osmocom/netif/stream.h>
 
@@ -48,6 +49,37 @@ static int hnbgw_hnbap_tx(struct hnb_context *ctx, struct msgb *msg)
 	return 0;
 }
 
+static int hnbgw_tx_hnb_register_rej(struct hnb_context *ctx)
+{
+	HNBRegisterReject_t reject_out;
+	HNBRegisterRejectIEs_t reject;
+	struct msgb *msg;
+	int rc;
+
+	reject.presenceMask = 0,
+	reject.cause.present = Cause_PR_radioNetwork;
+	reject.cause.choice.radioNetwork = CauseRadioNetwork_unspecified;
+
+	/* encode the Information Elements */
+	memset(&reject_out, 0, sizeof(reject_out));
+	rc = hnbap_encode_hnbregisterrejecties(&reject_out,  &reject);
+	if (rc < 0) {
+		LOGP(DHNBAP, LOGL_ERROR, "Failure to encode HNB-REGISTER-REJECT to %s: rc=%d\n",
+		     ctx->identity_info, rc);
+		return rc;
+	}
+
+	/* generate a successfull outcome PDU */
+	msg = hnbap_generate_unsuccessful_outcome(ProcedureCode_id_HNBRegister,
+						  Criticality_reject,
+						  &asn_DEF_HNBRegisterReject,
+						  &reject_out);
+
+	ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_HNBRegisterReject, &reject_out);
+
+	return hnbgw_hnbap_tx(ctx, msg);
+}
+
 static int hnbgw_tx_hnb_register_acc(struct hnb_context *ctx)
 {
 	HNBRegisterAccept_t accept_out;
@@ -368,6 +400,7 @@ static int hnbgw_rx_hnb_deregister(struct hnb_context *ctx, ANY_t *in)
 
 static int hnbgw_rx_hnb_register_req(struct hnb_context *ctx, ANY_t *in)
 {
+	struct hnb_context *hnb;
 	HNBRegisterRequestIEs_t ies;
 	int rc;
 
@@ -387,6 +420,20 @@ static int hnbgw_rx_hnb_register_req(struct hnb_context *ctx, ANY_t *in)
 	ctx->id.cid = asn1bitstr_to_u28(&ies.cellIdentity);
 	gsm48_mcc_mnc_from_bcd(ies.plmNidentity.buf, &ctx->id.mcc, &ctx->id.mnc);
 
+	llist_for_each_entry(hnb, &ctx->gw->hnb_list, list) {
+		if (hnb->hnb_registered && ctx != hnb && memcmp(&ctx->id, &hnb->id, sizeof(ctx->id)) == 0) {
+			struct osmo_fd *ofd = osmo_stream_srv_get_ofd(ctx->conn);
+			char *name = osmo_sock_get_name(ctx, ofd->fd);
+			LOGP(DHNBAP, LOGL_ERROR, "rejecting HNB-REGISTER-REQ with duplicate cell identity "
+			     "MCC=%u,MNC=%u,LAC=%u,RAC=%u,SAC=%u,CID=%u from %s\n",
+			     ctx->id.mcc, ctx->id.mnc, ctx->id.lac, ctx->id.rac, ctx->id.sac, ctx->id.cid, name);
+			talloc_free(name);
+			return hnbgw_tx_hnb_register_rej(ctx);
+		}
+	}
+
+	ctx->hnb_registered = true;
+
 	DEBUGP(DHNBAP, "HNB-REGISTER-REQ from %s\n", ctx->identity_info);
 
 	/* Send HNBRegisterAccept */