RR Channel Release: pass Cause code from BSSMAP Clear to the BTS

In lchan.release, add 'cause_rr', and set RR Channel Release message's cause
value to lchan.release.cause_rr.

In lchan_release(), do not set lchan.release.rsl_error_cause to the RR cause
value, these are unrelated. Store in new lchan.release.cause_rr instead. The
rsl_error_cause is apparently only used for logging, except for one place in
lchan_fsm_wait_activ_ack() that compares it to RSL_ERR_RCH_ALR_ACTV_ALLOC, so
there should not be a functional difference by this fix.

Propagate the BSSMAP Clear Command cause to the RR Channel Release:

Add struct gscon_clear_cmd_data as event data for GSCON_EV_A_CLEAR_CMD -- so
far it sent the is_csfb flag, add the gsm0808_cause; invoking the event happens
in bssmap_handle_clear_cmd().

Adjust event handling in gscon_fsm_allstate(); there, pass the cause to
gscon_release_lchans(). In gscon_release_lchans(), pass the cause to
gscon_release_lchan(), and then lchan_release(), which sets the new
lchan.release.cause_rr to the passed cause value.

As soon as the lchan FSM enters the proper state, it calls
gsm48_send_rr_release(). There, set the cause value in the encoded message to
lchan.release.cause_rr.

Interworking with osmo-msc: so far, osmo-msc fails to set the Clear Command
cause code for normal release, it just passes 0 which amounts to
GSM0808_CAUSE_RADIO_INTERFACE_MESSAGE_FAILURE. Before this patch, osmo-bsc
always sent GSM48_RR_CAUSE_NORMAL in the RR Channel Release, and after this
patch it will receive 0 == GSM0808_CAUSE_RADIO_INTERFACE_MESSAGE_FAILURE from
osmo-msc and more accurately translate that to GSM48_RR_CAUSE_PROT_ERROR_UNSPC.
This means in practice that we will now see an error cause in RR Channel
Release instead of GSM48_RR_CAUSE_NORMAL when working with osmo-msc. For
changing osmo-msc to send GSM0808_CAUSE_CALL_CONTROL instead (which translates
to GSM48_RR_CAUSE_NORMAL), see OS#4664 and change-id
I1347ed72ae7d7ea73a557b866e764819c5ef8c42 (osmo-msc).

A test for this is in Ie6c99f28b610a67f2d59ec00b3541940e882251b
(osmo-ttcn3-hacks).

Related: SYS#4872
Change-Id: I734cc55c501d61bbdadee81a223b26f9df57f959

1 files changed, 8 insertions, 1 deletions

diff --git a/include/osmocom/bsc/bsc_subscr_conn_fsm.h b/include/osmocom/bsc/bsc_subscr_conn_fsm.h
index 5475272b0..1a827d95c 100644
--- a/include/osmocom/bsc/bsc_subscr_conn_fsm.h
+++ b/include/osmocom/bsc/bsc_subscr_conn_fsm.h
@@ -1,4 +1,6 @@
 #pragma once
+#include <osmocom/gsm/protocol/gsm_08_08.h>
+#include <osmocom/gsm/protocol/gsm_04_08.h>
 #include <osmocom/core/fsm.h>
 
 enum gscon_fsm_event {
@@ -40,6 +42,11 @@ enum gscon_fsm_event {
 	GSCON_EV_FORGET_MGW_ENDPOINT,
 };
 
+struct gscon_clear_cmd_data {
+	enum gsm0808_cause cause_0808;
+	bool is_csfb;
+};
+
 struct gsm_subscriber_connection;
 struct gsm_network;
 struct msgb;
@@ -71,7 +78,7 @@ void gscon_start_assignment(struct gsm_subscriber_connection *conn,
 			    struct assignment_request *req);
 
 void gscon_change_primary_lchan(struct gsm_subscriber_connection *conn, struct gsm_lchan *new_lchan);
-void gscon_release_lchans(struct gsm_subscriber_connection *conn, bool do_rr_release);
+void gscon_release_lchans(struct gsm_subscriber_connection *conn, bool do_rr_release, enum gsm48_rr_cause cause_rr);
 
 void gscon_lchan_releasing(struct gsm_subscriber_connection *conn, struct gsm_lchan *lchan);
 void gscon_forget_lchan(struct gsm_subscriber_connection *conn, struct gsm_lchan *lchan);