sms: Increment the RP Message Reference for each transaction

Each RP-DATA should have a unique msg reference. Currently 42 is
used for all of these. Remember the last reference we used and
increment it on the next SMS. Do not track if the reference is
still in use a clash is a lot less likely now. First unless SMPP
is used only one SMS is delivered at a time, second the transaction
space is a lot smaller than the one for the reference.

openbsc/include/openbsc/gsm_04_11.h

@@ -37,4 +37,6 @@ int gsm411_send_sms_subscr(struct gsm_subscriber *subscr,
 int gsm411_send_sms(struct gsm_subscriber_connection *conn,
 		    struct gsm_sms *sms);
 void gsm411_sapi_n_reject(struct gsm_subscriber_connection *conn);
+
+uint8_t sms_next_rp_msg_ref(struct gsm_subscriber_connection *conn);
 #endif

openbsc/include/openbsc/gsm_data.h

@@ -106,6 +106,8 @@ struct gsm_subscriber_connection {
 
 	/* LU expiration handling */
 	uint8_t expire_timer_stopped;
+	/* SMS helpers for libmsc */
+	uint8_t next_rp_ref;
 
 	/*
 	 * Operations that have a state and might be pending

openbsc/src/libmsc/Makefile.am

@@ -6,7 +6,8 @@ noinst_LIBRARIES = libmsc.a
 
 libmsc_a_SOURCES =	auth.c \
 			db.c \
-			gsm_04_08.c gsm_04_11.c gsm_04_80.c \
+			gsm_04_08.c gsm_04_11.c gsm_04_11_helper.c \
+			gsm_04_80.c \
 			gsm_subscriber.c \
 			mncc.c mncc_builtin.c mncc_sock.c \
 			rrlp.c \

openbsc/src/libmsc/gsm_04_11.c

@@ -450,7 +450,7 @@ static int gsm411_rp_sendmsg(struct gsm411_smr_inst *inst, struct msgb *msg,
 	rp = (struct gsm411_rp_hdr *)msgb_push(msg, sizeof(*rp));
 	rp->len = len + 2;
 	rp->msg_type = rp_msg_type;
-	rp->msg_ref = rp_msg_ref; /* FIXME: Choose randomly */
+	rp->msg_ref = rp_msg_ref;
 
 	return gsm411_smr_send(inst, rl_msg_type, msg);
 }
@@ -836,7 +836,7 @@ int gsm411_send_sms(struct gsm_subscriber_connection *conn, struct gsm_sms *sms)
 	struct msgb *msg = gsm411_msgb_alloc();
 	struct gsm_trans *trans;
 	uint8_t *data, *rp_ud_len;
-	uint8_t msg_ref = 42;
+	uint8_t msg_ref = sms_next_rp_msg_ref(conn);
 	int transaction_id;
 	int rc;
 

openbsc/src/libmsc/gsm_04_11_helper.c

@@ -0,0 +1,37 @@
+/* Helpers for SMS/GSM 04.11 */
+/*
+ * (C) 2014 by Holger Hans Peter Freyther
+ *
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <openbsc/gsm_data.h>
+#include <openbsc/gsm_04_11.h>
+
+uint8_t sms_next_rp_msg_ref(struct gsm_subscriber_connection *conn)
+{
+	const uint8_t rp_msg_ref = conn->next_rp_ref;
+	/*
+	 * This should wrap as the valid range is 0 to 255. We only
+	 * transfer one SMS at a time so we don't need to check if
+	 * the id has been already assigned.
+	 */
+	conn->next_rp_ref += 1;
+
+	return rp_msg_ref;
+}
+

openbsc/tests/gsm0408/gsm0408_test.c

@@ -25,6 +25,7 @@
 #include <arpa/inet.h>
 
 #include <openbsc/gsm_04_08.h>
+#include <openbsc/gsm_04_11.h>
 #include <openbsc/gsm_subscriber.h>
 #include <openbsc/debug.h>
 #include <openbsc/arfcn_range_encode.h>
@@ -448,6 +449,29 @@ static void test_si_range_helpers()
 	VERIFY(f0, ==, 1);
 }
 
+static void test_gsm411_rp_ref_wrap(void)
+{
+	struct gsm_subscriber_connection conn;
+	int res;
+
+	printf("testing RP-Reference wrap\n");
+
+	memset(&conn, 0, sizeof(conn));
+	conn.next_rp_ref = 255;
+
+	res = sms_next_rp_msg_ref(&conn);
+	printf("Allocated reference: %d\n", res);
+	OSMO_ASSERT(res == 255);
+
+	res = sms_next_rp_msg_ref(&conn);
+	printf("Allocated reference: %d\n", res);
+	OSMO_ASSERT(res == 0);
+
+	res = sms_next_rp_msg_ref(&conn);
+	printf("Allocated reference: %d\n", res);
+	OSMO_ASSERT(res == 1);
+}
+
 int main(int argc, char **argv)
 {
 	osmo_init_logging(&log_info);
@@ -460,6 +484,7 @@ int main(int argc, char **argv)
 	test_arfcn_filter();
 	test_print_encoding();
 	test_range_encoding();
+	test_gsm411_rp_ref_wrap();
 
 	printf("Done.\n");
 	return EXIT_SUCCESS;

openbsc/tests/gsm0408/gsm0408_test.ok

@@ -58,4 +58,8 @@ Random range test: range 127, max num ARFCNs 29
 Random range test: range 255, max num ARFCNs 22
 Random range test: range 511, max num ARFCNs 18
 Random range test: range 1023, max num ARFCNs 16
+testing RP-Reference wrap
+Allocated reference: 255
+Allocated reference: 0
+Allocated reference: 1
 Done.