neels submitted this change.

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emerg call: send BSSMAP Clear Req cause as preemption

After the lchan release, the gscon would go into the Clear dance with an
arbitrary cause value. Instead, explicitly ask for a Clear upon
pre-emption, with the proper cause value.

Related: OS#5535
Change-Id: I20108f7b4769400b89b7b0d65c8dab883bf87c46
---
M include/osmocom/bsc/bsc_subscr_conn_fsm.h
M src/osmo-bsc/abis_rsl.c
M src/osmo-bsc/bsc_subscr_conn_fsm.c
3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/osmocom/bsc/bsc_subscr_conn_fsm.h b/include/osmocom/bsc/bsc_subscr_conn_fsm.h
index 0e495aa..0ab4843 100644
--- a/include/osmocom/bsc/bsc_subscr_conn_fsm.h
+++ b/include/osmocom/bsc/bsc_subscr_conn_fsm.h
@@ -66,6 +66,7 @@
 void gscon_submit_rsl_dtap(struct gsm_subscriber_connection *conn,
 			   struct msgb *msg, int link_id, int allow_sacch);
 int gscon_sigtran_send(struct gsm_subscriber_connection *conn, struct msgb *msg);
+void gscon_bssmap_clear(struct gsm_subscriber_connection *conn, enum gsm0808_cause cause);
 
 struct osmo_mgcpc_ep *gscon_ensure_mgw_endpoint(struct gsm_subscriber_connection *conn,
 						uint16_t msc_assigned_cic, struct gsm_lchan *for_lchan);
diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c
index c50cfeb..627af11 100644
--- a/src/osmo-bsc/abis_rsl.c
+++ b/src/osmo-bsc/abis_rsl.c
@@ -2058,6 +2058,11 @@
 			"CHAN RQD/EMERGENCY-PRIORITY: inducing termination of lchan %s (state:%s) in favor of incoming EMERGENCY CALL!\n",
 			gsm_lchan_name(release_lchan), osmo_fsm_inst_state_name(release_lchan->fi));
 
+		/* Make sure the Clear Request to the MSC has the proper cause */
+		if (release_lchan->conn)
+			gscon_bssmap_clear(release_lchan->conn, GSM0808_CAUSE_PREEMPTION);
+		/* The gscon FSM would only release the lchan after the MSC responds with a Clear Command.
+		 * But we need it released right now. Also with the right RR cause. */
 		lchan_release(release_lchan, !!(release_lchan->conn), true, GSM48_RR_CAUSE_PREMPTIVE_REL,
 			      gscon_last_eutran_plmn(release_lchan->conn));
 
diff --git a/src/osmo-bsc/bsc_subscr_conn_fsm.c b/src/osmo-bsc/bsc_subscr_conn_fsm.c
index bb96aeb..428d200 100644
--- a/src/osmo-bsc/bsc_subscr_conn_fsm.c
+++ b/src/osmo-bsc/bsc_subscr_conn_fsm.c
@@ -144,8 +144,7 @@
 	return rc;
 }
 
-static void gscon_bssmap_clear(struct gsm_subscriber_connection *conn,
-			       enum gsm0808_cause cause)
+void gscon_bssmap_clear(struct gsm_subscriber_connection *conn, enum gsm0808_cause cause)
 {
 	/* already clearing? */
 	switch (conn->fi->state) {

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