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, 10 insertions, 5 deletions

diff --git a/src/osmo-bsc/bsc_subscr_conn_fsm.c b/src/osmo-bsc/bsc_subscr_conn_fsm.c
index 1d3024610..0ed6715be 100644
--- a/src/osmo-bsc/bsc_subscr_conn_fsm.c
+++ b/src/osmo-bsc/bsc_subscr_conn_fsm.c
@@ -182,14 +182,14 @@ static void gscon_release_lchan(struct gsm_subscriber_connection *conn, struct g
 	lchan_release(lchan, do_rr_release, err, cause_rr);
 }
 
-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)
 {
 	if (conn->ho.fi)
 		handover_end(conn, HO_RESULT_CONN_RELEASE);
 
 	assignment_reset(conn);
 
-	gscon_release_lchan(conn, conn->lchan, do_rr_release, false, 0);
+	gscon_release_lchan(conn, conn->lchan, do_rr_release, false, cause_rr);
 }
 
 static void handle_bssap_n_connect(struct osmo_fsm_inst *fi, struct osmo_scu_prim *scu_prim)
@@ -746,17 +746,20 @@ void gscon_forget_mgw_endpoint_ci(struct gsm_subscriber_connection *conn, struct
 static void gscon_fsm_allstate(struct osmo_fsm_inst *fi, uint32_t event, void *data)
 {
 	struct gsm_subscriber_connection *conn = fi->priv;
+	const struct gscon_clear_cmd_data *ccd;
 
 	/* Regular allstate event processing */
 	switch (event) {
 	case GSCON_EV_A_CLEAR_CMD:
+		OSMO_ASSERT(data);
+		ccd = data;
 		if (conn->lchan)
-			conn->lchan->release.is_csfb = *(bool *)data;
+			conn->lchan->release.is_csfb = ccd->is_csfb;
 		/* MSC tells us to cleanly shut down */
 		if (conn->fi->state != ST_CLEARING)
 			osmo_fsm_inst_state_chg(fi, ST_CLEARING, 60, 999);
 		LOGPFSML(fi, LOGL_DEBUG, "Releasing all lchans (if any) after BSSMAP Clear Command\n");
-		gscon_release_lchans(conn, true);
+		gscon_release_lchans(conn, true, bsc_gsm48_rr_cause_from_gsm0808_cause(ccd->cause_0808));
 		/* FIXME: Release all terestrial resources in ST_CLEARING */
 		/* According to 3GPP 48.008 3.1.9.1. "The BSS need not wait for the radio channel
 		 * release to be completed or for the guard timer to expire before returning the
@@ -833,7 +836,9 @@ static void gscon_pre_term(struct osmo_fsm_inst *fi, enum osmo_fsm_term_cause ca
 	}
 
 	LOGPFSML(fi, LOGL_DEBUG, "Releasing all lchans (if any) because this conn is terminating\n");
-	gscon_release_lchans(conn, true);
+	/* when things go smoothly, the lchan should have been released before FSM instance termination. So if this is
+	 * necessary it's probably "abnormal". */
+	gscon_release_lchans(conn, true, GSM48_RR_CAUSE_ABNORMAL_UNSPEC);
 
 	/* drop pending messages */
 	gscon_dtap_queue_flush(conn, 0);