Change in ...osmo-bsc[master]: bsc_subscr_conn_fsm: Cleanly clear BSSAP conn if associated channel c...

[pespin]

pespin has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-bsc/+/15408


Change subject: bsc_subscr_conn_fsm: Cleanly clear BSSAP conn if associated channel closed during WAIT_CC
......................................................................

bsc_subscr_conn_fsm: Cleanly clear BSSAP conn if associated channel closed during WAIT_CC

TTCN3 BSC_Tests.TC_ms_rel_ind_does_not_cause_bssmap_reset seems to
sometimes run into a race condition on the order of messages received by
osmo-bsc comming from MSC and BTS.

Usual (expected) scenario):
BTS->BSC      EST IND
     BSC->MSC CL3 Info
     BSC<-MSC CC
BTS->BSC      REL IND
BTS<-BSC      DEACT SACCH
     BSC->MSC ClearRequest
     BSC<-MSC ClearCommand
     BSC->MSC ClearComplete
BTS<-BSC      RF Chan Release
BTS->BSC      RF Chan Release ACK

Sometimes CC message and REL IND message are received swapped (because they
are sent by different components asynchronously in TTCN3).

As a result, osmo-bsc was failing to go into CLEARING state and was
unable to send the ClearRequest because CC was still not received.
So the idea is to stay in WAIT_CC until CC is received, then check if
the lchan was dropped and in that case go into clearing state.

Change-Id: Id1abf5ee44c60925b478123409f26bd29006202b
---
M src/osmo-bsc/bsc_subscr_conn_fsm.c
1 file changed, 24 insertions(+), 8 deletions(-)



  git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/08/15408/1

diff --git a/src/osmo-bsc/bsc_subscr_conn_fsm.c b/src/osmo-bsc/bsc_subscr_conn_fsm.c
index f8784f9..b5edeb8 100644
--- a/src/osmo-bsc/bsc_subscr_conn_fsm.c
+++ b/src/osmo-bsc/bsc_subscr_conn_fsm.c
@@ -99,6 +99,12 @@
 				     conn->network->T_defs, \
 				     -1)
 
+static bool gscon_is_active(struct gsm_subscriber_connection *conn)
+{
+	enum gscon_fsm_states st = conn->fi->state;
+	return st == ST_ACTIVE || st == ST_ASSIGNMENT || st == ST_HANDOVER;
+}
+
 /* forward MT DTAP from BSSAP side to RSL side */
 static inline void submit_dtap(struct gsm_subscriber_connection *conn, struct msgb *msg)
 {
@@ -333,10 +339,19 @@
 	switch (event) {
 	case GSCON_EV_A_CONN_CFM:
 		/* MSC has confirmed the connection, we now change into the
-		 * active state and wait there for further operations */
-		conn_fsm_state_chg(ST_ACTIVE);
-		/* if there's user payload, forward it just like EV_MT_DTAP */
-		/* FIXME: Question: if there's user payload attached to the CC, forward it like EV_MT_DTAP? */
+		 * active state and wait there for further operations. */
+		if (conn->lchan) {
+			conn_fsm_state_chg(ST_ACTIVE);
+			/* if there's user payload, forward it just like EV_MT_DTAP */
+			/* FIXME: Question: if there's user payload attached to the CC, forward it like EV_MT_DTAP? */
+		} else {
+			/* If associated lchan was released while we were
+			 * waiting for the confirmed connection, then instead
+			 * simply drop the connection */
+			LOGPFSML(fi, LOGL_INFO, "Connection confirmed but lchan was dropped before, clearing conn\n");
+			osmo_fsm_inst_state_chg(conn->fi, ST_CLEARING, 60, 999);
+			gscon_bssmap_clear(conn, GSM0808_CAUSE_EQUIPMENT_FAILURE);
+		}
 		break;
 	default:
 		OSMO_ASSERT(false);
@@ -589,7 +604,7 @@
 	[ST_WAIT_CC] = {
 		.name = "WAIT_CC",
 		.in_event_mask = S(GSCON_EV_A_CONN_CFM),
-		.out_state_mask = S(ST_ACTIVE),
+		.out_state_mask = S(ST_ACTIVE) | S(ST_CLEARING),
 		.action = gscon_fsm_wait_cc,
 	},
 	[ST_ACTIVE] = {
@@ -651,9 +666,10 @@
 		lchan_forget_conn(conn->lchan);
 		conn->lchan = NULL;
 	}
-	if (!conn->lchan) {
-		if (conn->fi->state != ST_CLEARING)
-			osmo_fsm_inst_state_chg(conn->fi, ST_CLEARING, 60, 999);
+	/* if conn is not active we cannot send bssap. If on WAIT_CC, then let's
+	 * wait until CC is received to tear down */
+	if (!conn->lchan && gscon_is_active(conn)) {
+		osmo_fsm_inst_state_chg(conn->fi, ST_CLEARING, 60, 999);
 		gscon_bssmap_clear(conn, GSM0808_CAUSE_EQUIPMENT_FAILURE);
 	}
 }

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Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-Change-Id: Id1abf5ee44c60925b478123409f26bd29006202b
Gerrit-Change-Number: 15408
Gerrit-PatchSet: 1
Gerrit-Owner: pespin <pespin at sysmocom.de>
Gerrit-MessageType: newchange
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