destroy hnb context by sending a zero-len msgb after rejecting a HNB

These are the osmo-iuh changes corresponding to the libosmo-netif
branch 'destroy_conn_with_zero_msg'.

Change-Id: I15f90a2e899789320e9329e33b3d294a65cc16b6

include/osmocom/iuh/hnbgw.h

@@ -161,7 +161,7 @@ struct ue_context *ue_context_alloc(struct hnb_context *hnb, const char *imsi,
 void ue_context_free(struct ue_context *ue);
 
 struct hnb_context *hnb_context_alloc(struct hnb_gw *gw, struct osmo_stream_srv_link *link, int new_fd);
-void hnb_context_release(struct hnb_context *ctx);
+void hnb_context_release(struct hnb_context *ctx, bool destroy_conn);
 
 void hnbgw_vty_init(struct hnb_gw *gw, void *tall_ctx);
 int hnbgw_vty_go_parent(struct vty *vty);

src/hnbgw.c

@@ -204,6 +204,11 @@ void ue_context_free(struct ue_context *ue)
 }
 static int hnb_close_cb(struct osmo_stream_srv *conn)
 {
+	struct hnb_context *hnb = osmo_stream_srv_get_data(conn);
+
+	if (hnb)
+		hnb_context_release(hnb, false);
+
 	return 0;
 }
 
@@ -228,10 +233,10 @@ static int hnb_read_cb(struct osmo_stream_srv *conn)
 	} else if (rc < 0) {
 		LOGP(DMAIN, LOGL_ERROR, "Error during sctp_recvmsg()\n");
 		/* FIXME: clean up after disappeared HNB */
-		hnb_context_release(hnb);
+		hnb_context_release(hnb, true);
 		goto out;
 	} else if (rc == 0) {
-		hnb_context_release(hnb);
+		hnb_context_release(hnb, true);
 		rc = -1;
 
 		goto out;
@@ -288,7 +293,7 @@ struct hnb_context *hnb_context_alloc(struct hnb_gw *gw, struct osmo_stream_srv_
 	return ctx;
 }
 
-void hnb_context_release(struct hnb_context *ctx)
+void hnb_context_release(struct hnb_context *ctx, bool destroy_conn)
 {
 	struct hnbgw_context_map *map, *map2;
 
@@ -305,7 +310,9 @@ void hnb_context_release(struct hnb_context *ctx)
 		context_map_deactivate(map);
 	}
 	ue_context_free_by_hnb(ctx->gw, ctx);
-	osmo_stream_srv_destroy(ctx->conn);
+
+	if (destroy_conn)
+		osmo_stream_srv_destroy(ctx->conn);
 
 	talloc_free(ctx);
 }

src/hnbgw_hnbap.c

@@ -53,7 +53,7 @@ static int hnbgw_tx_hnb_register_rej(struct hnb_context *ctx)
 {
 	HNBRegisterReject_t reject_out;
 	HNBRegisterRejectIEs_t reject;
-	struct msgb *msg;
+	struct msgb *msg, *msg0;
 	int rc;
 
 	reject.presenceMask = 0,
@@ -69,6 +69,10 @@ static int hnbgw_tx_hnb_register_rej(struct hnb_context *ctx)
 		return rc;
 	}
 
+	msg0 = msgb_alloc(0, "zero-length terminating message");
+	if (msg0 == NULL)
+		return -ENOMEM;
+
 	/* generate a successfull outcome PDU */
 	msg = hnbap_generate_unsuccessful_outcome(ProcedureCode_id_HNBRegister,
 						  Criticality_reject,
@@ -77,7 +81,17 @@ static int hnbgw_tx_hnb_register_rej(struct hnb_context *ctx)
 
 	ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_HNBRegisterReject, &reject_out);
 
-	return hnbgw_hnbap_tx(ctx, msg);
+	rc = hnbgw_hnbap_tx(ctx, msg);
+	if (rc == 0) {
+		/* Enqueue a zero-length message to destroy the connection
+		 * after sending HNB-REGISTER-REJECT. */
+		if (hnbgw_hnbap_tx(ctx, msg0) != 0)
+			LOGP(DHNBAP, LOGL_ERROR, "Failure to send zero-length message after "
+			     "HNB-REGISTER-REJECT to %s: rc=%d; the connection won't be closed "
+			     "from our side\n", ctx->identity_info, rc);
+	}
+
+	return rc;
 }
 
 static int hnbgw_tx_hnb_register_acc(struct hnb_context *ctx)
@@ -393,7 +407,7 @@ static int hnbgw_rx_hnb_deregister(struct hnb_context *ctx, ANY_t *in)
 		hnbap_cause_str(&ies.cause));
 
 	hnbap_free_hnbde_registeries(&ies);
-	hnb_context_release(ctx);
+	hnb_context_release(ctx, true);
 
 	return 0;
 }