Add initial 3GPP LCLS support to OsmoBSC

This code contains the following code:
* receive/parse/interpret LCLS specific BSSMAP IEs and PDUs
* osmo_fsm handling the various states and their transitions
* call leg correlation (finding the other subscr_conn with same GCR)
* communication between the two call-leg LCLS FSMs
* detection of supported / unsupported LCLS configurations
* display of GCR / LCLS information in "show conns"
* switch the media streams locally using MDCX to the MGW

Closes: OS#1602
Change-Id: I614fade62834def5cafc94c4d2578cd747a3f9f7

5 files changed, 59 insertions, 0 deletions

diff --git a/include/osmocom/bsc/Makefile.am b/include/osmocom/bsc/Makefile.am
index bae13f0cb..0987be9dd 100644
--- a/include/osmocom/bsc/Makefile.am
+++ b/include/osmocom/bsc/Makefile.am
@@ -47,4 +47,5 @@ noinst_HEADERS = \
 	vty.h \
 	bsc_api.h \
 	penalty_timers.h \
+	osmo_bsc_lcls.h \
 	$(NULL)
diff --git a/include/osmocom/bsc/bsc_subscr_conn_fsm.h b/include/osmocom/bsc/bsc_subscr_conn_fsm.h
index 9498d9f2e..e8226f443 100644
--- a/include/osmocom/bsc/bsc_subscr_conn_fsm.h
+++ b/include/osmocom/bsc/bsc_subscr_conn_fsm.h
@@ -48,6 +48,8 @@ enum gscon_fsm_event {
 	GSCON_EV_MGW_MDCX_RESP_BTS,
 	/* CRCX response received (MSC) */
 	GSCON_EV_MGW_CRCX_RESP_MSC,
+	/* MDCX response received (MSC) - triggered by LCLS */
+	GSCON_EV_MGW_MDCX_RESP_MSC,
 
 	/* Internal handover request (intra-BSC handover) */
 	GSCON_EV_HO_START,
@@ -57,6 +59,9 @@ enum gscon_fsm_event {
 	GSCON_EV_HO_FAIL,
 	/* Handover completed successfully (handover_logic.c) */
 	GSCON_EV_HO_COMPL,
+
+	/* LCLS child FSM has terminated due to hard failure */
+	GSCON_EV_LCLS_FAIL,
 };
 
 struct gsm_subscriber_connection;
diff --git a/include/osmocom/bsc/debug.h b/include/osmocom/bsc/debug.h
index 37f102c7a..006b91873 100644
--- a/include/osmocom/bsc/debug.h
+++ b/include/osmocom/bsc/debug.h
@@ -25,5 +25,6 @@ enum {
 	DCTRL,
 	DFILTER,
 	DPCU,
+	DLCLS,
 	Debug_LastEntry,
 };
diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h
index 1cf79a53d..b1fceb3ea 100644
--- a/include/osmocom/bsc/gsm_data.h
+++ b/include/osmocom/bsc/gsm_data.h
@@ -188,6 +188,18 @@ struct gsm_subscriber_connection {
 		enum gsm48_chan_mode chan_mode;
 
 	} user_plane;
+
+	/* LCLS (local call, local switch) related state */
+	struct {
+		uint8_t global_call_ref[15];
+		uint8_t global_call_ref_len; /* length of global_call_ref */
+		uint8_t config;	/* TS 48.008 3.2.2.116 */
+		uint8_t control;/* TS 48.008 3.2.2.117 */
+		/* LCLS FSM */
+		struct osmo_fsm_inst *fi;
+		/* pointer to "other" connection, if Call Leg Relocation was successful */
+		struct gsm_subscriber_connection *other;
+	} lcls;
 };
 
 
diff --git a/include/osmocom/bsc/osmo_bsc_lcls.h b/include/osmocom/bsc/osmo_bsc_lcls.h
new file mode 100644
index 000000000..2e6023404
--- /dev/null
+++ b/include/osmocom/bsc/osmo_bsc_lcls.h
@@ -0,0 +1,40 @@
+#pragma once
+#include <osmocom/core/fsm.h>
+
+enum lcls_fsm_state {
+	ST_NO_LCLS,
+	ST_NOT_YET_LS,
+	ST_NOT_POSSIBLE_LS,
+	ST_NO_LONGER_LS,
+	ST_REQ_LCLS_NOT_SUPP,
+	ST_LOCALLY_SWITCHED,
+	/* locally switched; received remote break; wait for "local" break */
+	ST_LOCALLY_SWITCHED_WAIT_BREAK,
+	/* locally switched; received break; wait for "other" break */
+	ST_LOCALLY_SWITCHED_WAIT_OTHER_BREAK,
+};
+
+enum lcls_event {
+	/* update LCLS config/control based on some BSSMAP signaling */
+	LCLS_EV_UPDATE_CFG_CSC,
+	/* apply LCLS config/control */
+	LCLS_EV_APPLY_CFG_CSC,
+	/* we have been identified as the correlation peer of another conn */
+	LCLS_EV_CORRELATED,
+	/* "other" LCLS connection has enabled local switching */
+	LCLS_EV_OTHER_ENABLED,
+	/* "other" LCLS connection is breaking local switch */
+	LCLS_EV_OTHER_BREAK,
+	/* "other" LCLS connection is dying */
+	LCLS_EV_OTHER_DEAD,
+};
+
+enum gsm0808_lcls_status lcls_get_status(struct gsm_subscriber_connection *conn);
+
+void lcls_update_config(struct gsm_subscriber_connection *conn,
+			const uint8_t *config, const uint8_t *control);
+
+void lcls_apply_config(struct gsm_subscriber_connection *conn);
+
+extern struct osmo_fsm lcls_fsm;
+