HO: Add option to allow immediate retry of assignment/handover if failed

If a number of retries is configured, the retry is allowed. If it fails
more than the number of retries, the penalty timer is started to prevent
subsequent retries for the given time.

Add test case that will test that handover is blocked after the exact
number of handover retries are performed.

6 files changed, 74 insertions, 6 deletions

diff --git a/openbsc/include/openbsc/gsm_data.h b/openbsc/include/openbsc/gsm_data.h
index 0928d0262..c966e0506 100644
--- a/openbsc/include/openbsc/gsm_data.h
+++ b/openbsc/include/openbsc/gsm_data.h
@@ -142,7 +142,8 @@ struct gsm_subscriber_connection {
 	struct gsm_lchan *secondary_lchan;
 	struct llist_head assignment_queue;
 
-	/* penalty timers for handover */
+	/* failure count and penalty timers for handover */
+	int ho_failure;
 	struct llist_head ho_penalty_timers;
 
 	/* phone's bearer capabilities */
diff --git a/openbsc/include/openbsc/gsm_data_shared.h b/openbsc/include/openbsc/gsm_data_shared.h
index 5ef3ef4ea..36cf6f7b0 100644
--- a/openbsc/include/openbsc/gsm_data_shared.h
+++ b/openbsc/include/openbsc/gsm_data_shared.h
@@ -767,6 +767,8 @@ struct gsm_bts {
 		unsigned int penalty_ho_fail;	/* seconds */
 		/* penalty time for a cell after assignment failure */
 		unsigned int penalty_as_fail;	/* seconds */
+		/* number of retries, before starting penality timer */
+		unsigned int retries;
 	} handover;
 #endif /* ROLE_BSC */
 	void *role;
diff --git a/openbsc/src/libbsc/handover_logic.c b/openbsc/src/libbsc/handover_logic.c
index 06f968c2b..2a7733f6e 100644
--- a/openbsc/src/libbsc/handover_logic.c
+++ b/openbsc/src/libbsc/handover_logic.c
@@ -371,6 +371,7 @@ static int ho_gsm48_ho_compl(struct gsm_lchan *new_lchan)
 
 	log_handover(DHO, LOGL_INFO, ho);
 	LOGPC(DHO, LOGL_INFO, "Handover/Assignment completed\n");
+	new_lchan->conn->ho_failure = 0;
 
 	net = new_lchan->ts->trx->bts->network;
 	osmo_counter_inc(net->stats.handover.completed);
@@ -414,11 +415,16 @@ static int ho_gsm48_ho_fail(struct gsm_lchan *old_lchan)
 	new_bts = ho->new_lchan->ts->trx->bts;
 
 	log_handover(DHO, LOGL_NOTICE, ho);
-	LOGPC(DHO, LOGL_NOTICE, "Handover/Assignment failed, start penalty timer\n");
-
-	add_penalty_timer(old_lchan->conn, new_bts,
-		(ho->do_ass) ? old_bts->handover.penalty_as_fail
-			     : old_bts->handover.penalty_ho_fail);
+	if (old_lchan->conn->ho_failure == old_bts->handover.retries) {
+		LOGPC(DHO, LOGL_NOTICE, "Handover/Assignment failed, start penalty timer\n");
+		old_lchan->conn->ho_failure = 0;
+		add_penalty_timer(old_lchan->conn, new_bts,
+			(ho->do_ass) ? old_bts->handover.penalty_as_fail
+				     : old_bts->handover.penalty_ho_fail);
+	} else {
+		LOGPC(DHO, LOGL_NOTICE, "Handover/Assignment failed, trying again.\n");
+		old_lchan->conn->ho_failure++;
+	}
 
 	osmo_counter_inc(net->stats.handover.failed);
 
diff --git a/openbsc/src/libbsc/handover_vty.c b/openbsc/src/libbsc/handover_vty.c
index ee449e9f3..69509a6de 100644
--- a/openbsc/src/libbsc/handover_vty.c
+++ b/openbsc/src/libbsc/handover_vty.c
@@ -95,6 +95,8 @@ void config_write_bts_handover(struct vty *vty, struct gsm_bts *bts)
 			bts->handover.penalty_ho_fail, VTY_NEWLINE);
 		vty_out(vty, "  handover penalty assignment failure %u%s",
 			bts->handover.penalty_as_fail, VTY_NEWLINE);
+		vty_out(vty, "  handover retries %u%s",
+			bts->handover.retries, VTY_NEWLINE);
 	}
 }
 
@@ -484,6 +486,20 @@ DEFUN(cfg_bts_ho_penalty_as_fail, cfg_bts_ho_penalty_as_fail_cmd,
 	return CMD_SUCCESS;
 }
 
+DEFUN(cfg_bts_ho_retries, cfg_bts_ho_retries_cmd,
+      "handover retries <0-9>",
+	HANDOVER_STR
+	"Number of immediate retries, if handover/assignment fails\n"
+	"Retries\n")
+{
+	struct gsm_bts *bts = vty->index;
+
+	if (is_cmd_for_algorithm(vty, 0, 1))
+		return CMD_WARNING;
+	bts->handover.retries = atoi(argv[0]);
+	return CMD_SUCCESS;
+}
+
 void bsc_vty_init_handover(void)
 {
 	install_element(GSMNET_NODE, &cfg_net_ho_algorithm_cmd);
@@ -507,5 +523,6 @@ void bsc_vty_init_handover(void)
 	install_element(BTS_NODE, &cfg_bts_ho_penalty_max_dist_cmd);
 	install_element(BTS_NODE, &cfg_bts_ho_penalty_ho_fail_cmd);
 	install_element(BTS_NODE, &cfg_bts_ho_penalty_as_fail_cmd);
+	install_element(BTS_NODE, &cfg_bts_ho_retries_cmd);
 }
 
diff --git a/openbsc/tests/handover/handover_test.c b/openbsc/tests/handover/handover_test.c
index 1e0d998a5..4557b6500 100644
--- a/openbsc/tests/handover/handover_test.c
+++ b/openbsc/tests/handover/handover_test.c
@@ -1121,6 +1121,33 @@ static char *test_case_26[] = {
 	NULL
 };
 
+static char *test_case_27[] = {
+	"2",
+
+	"Only after maximum allowed retries, start penalty timer\n\n"
+	"The MS will try to handover to a better cell, but this will fail.\n"
+	"The handover is performed again and fails again. After this retry,\n"
+	"the handover is not performed again, because penalty timer is\n"
+	"running.\n",
+
+	"create-bts", "2",
+	"ho-retries", "0", "1",
+	"create-ms", "0", "TCH/F", "AMR",
+	"meas-rep", "0", "20","0", "1","0","30",
+	"expect-chan", "1", "1",
+	"ack-chan",
+	"expect-ho", "0", "1",
+	"ho-failed",
+	"meas-rep", "0", "20","0", "1","0","30",
+	"expect-chan", "1", "1",
+	"ack-chan",
+	"expect-ho", "0", "1",
+	"ho-failed",
+	"meas-rep", "0", "20","0", "1","0","30",
+	"expect-no-chan",
+	NULL
+};
+
 static char **test_cases[] =  {
 	test_case_0,
 	test_case_1,
@@ -1149,6 +1176,7 @@ static char **test_cases[] =  {
 	test_case_24,
 	test_case_25,
 	test_case_26,
+	test_case_27,
 	NULL
 };
 
@@ -1240,6 +1268,14 @@ int main(int argc, char **argv)
 				atoi(test_case[2]);
 			test_case += 3;
 		} else
+		if (!strcmp(*test_case, "ho-retries")) {
+			fprintf(stderr, "- Set number of handover/assignment "
+				"retries at BTS %s to %s\n", test_case[1],
+				test_case[2]);
+			bts[atoi(test_case[1])]->handover.retries =
+				atoi(test_case[2]);
+			test_case += 3;
+		} else
 		if (!strcmp(*test_case, "afs-rxlev-improve")) {
 			fprintf(stderr, "- Set afs RX level improvement at "
 				"BTS %s to %s\n", test_case[1], test_case[2]);
diff --git a/openbsc/tests/testsuite.at b/openbsc/tests/testsuite.at
index 12a648767..2d5dd98bf 100644
--- a/openbsc/tests/testsuite.at
+++ b/openbsc/tests/testsuite.at
@@ -222,3 +222,9 @@ cat $abs_srcdir/handover/handover_test.ok > expout
 AT_CHECK([$abs_top_builddir/tests/handover/handover_test 26], [], [expout], [ignore])
 AT_CLEANUP
 
+AT_SETUP([handover test 27])
+AT_KEYWORDS([handover])
+cat $abs_srcdir/handover/handover_test.ok > expout
+AT_CHECK([$abs_top_builddir/tests/handover/handover_test 27], [], [expout], [ignore])
+AT_CLEANUP
+