From e808724a4fc7bf02532caa24a7ea17d54e6bbd9d Mon Sep 17 00:00:00 2001
From: Neels Hofmeyr <nhofmeyr@sysmocom.de>
Date: Tue, 20 Sep 2022 14:10:37 +0200
Subject: add X27 timeout: release lchan that lacks L1 Info

To lchan_fsm ESTABLISHED, add a timeout: if MEAS REP lack L1 Info for a
time defined by timer net X27, release the lchan.

Related: OS#5530
Related: If7c76445373d5d0e915a3e8910d3eb991216f768 (osmo-ttcn3-hacks)
Change-Id: I6fb29315568554c8490ee999fcfd1b77d8245389
---
 src/osmo-bsc/abis_rsl.c  |  5 +++++
 src/osmo-bsc/lchan_fsm.c | 11 +++++++++++
 src/osmo-bsc/net_init.c  |  1 +
 3 files changed, 17 insertions(+)

(limited to 'src/osmo-bsc')

diff --git a/src/osmo-bsc/abis_rsl.c b/src/osmo-bsc/abis_rsl.c
index 1c60405c4..8f94c05d6 100644
--- a/src/osmo-bsc/abis_rsl.c
+++ b/src/osmo-bsc/abis_rsl.c
@@ -1450,6 +1450,11 @@ static int rsl_rx_meas_res(struct msgb *msg)
 
 	lchan_ms_pwr_ctrl(msg->lchan, mr);
 
+	if ((mr->flags & MEAS_REP_F_MS_L1)) {
+		/* Notify lchan_fsm that L1 is still alive */
+		osmo_fsm_inst_dispatch(mr->lchan->fi, LCHAN_EV_RX_MEAS_RES_L1_INFO, mr);
+	}
+
 	send_lchan_signal(S_LCHAN_MEAS_REP, msg->lchan, mr);
 
 	return 0;
diff --git a/src/osmo-bsc/lchan_fsm.c b/src/osmo-bsc/lchan_fsm.c
index 21e145bdd..1c7e9c9c3 100644
--- a/src/osmo-bsc/lchan_fsm.c
+++ b/src/osmo-bsc/lchan_fsm.c
@@ -285,6 +285,7 @@ struct osmo_tdef_state_timeout lchan_fsm_timeouts[32] = {
 	[LCHAN_ST_WAIT_TS_READY]	= { .T=-5 },
 	[LCHAN_ST_WAIT_ACTIV_ACK]	= { .T=-6 },
 	[LCHAN_ST_WAIT_RLL_RTP_ESTABLISH]	= { .T=3101 },
+	[LCHAN_ST_ESTABLISHED]	= { .T = -27 },
 	[LCHAN_ST_WAIT_RLL_RTP_RELEASED]	= { .T=3109 },
 	[LCHAN_ST_WAIT_BEFORE_RF_RELEASE]	= { .T=3111 },
 	[LCHAN_ST_WAIT_RF_RELEASE_ACK]	= { .T=3111 },
@@ -1666,6 +1667,7 @@ static const struct osmo_fsm_state lchan_fsm_states[] = {
 			| S(LCHAN_EV_REQUEST_MODE_MODIFY)
 			,
 		.out_state_mask = 0
+			| S(LCHAN_ST_ESTABLISHED)
 			| S(LCHAN_ST_UNUSED)
 			| S(LCHAN_ST_WAIT_RLL_RTP_RELEASED)
 			| S(LCHAN_ST_WAIT_BEFORE_RF_RELEASE)
@@ -1764,6 +1766,7 @@ static const struct value_string lchan_fsm_event_names[] = {
 	OSMO_VALUE_STRING(LCHAN_EV_RSL_CHAN_MODE_MODIFY_ACK),
 	OSMO_VALUE_STRING(LCHAN_EV_RSL_CHAN_MODE_MODIFY_NACK),
 	OSMO_VALUE_STRING(LCHAN_EV_REQUEST_MODE_MODIFY),
+	OSMO_VALUE_STRING(LCHAN_EV_RX_MEAS_RES_L1_INFO),
 	{}
 };
 
@@ -1789,6 +1792,13 @@ static void lchan_fsm_allstate_action(struct osmo_fsm_inst *fi, uint32_t event,
 		 * radio link layer failed */
 		return;
 
+	case LCHAN_EV_RX_MEAS_RES_L1_INFO:
+		if (fi->state != LCHAN_ST_ESTABLISHED)
+			return;
+		/* Re-enter ESTABLISHED state to refresh "L1 alive" timeout */
+		lchan_fsm_state_chg(LCHAN_ST_ESTABLISHED);
+		return;
+
 	default:
 		return;
 	}
@@ -1937,6 +1947,7 @@ static struct osmo_fsm lchan_fsm = {
 	.allstate_event_mask = 0
 		| S(LCHAN_EV_TS_ERROR)
 		| S(LCHAN_EV_RLL_ERR_IND)
+		| S(LCHAN_EV_RX_MEAS_RES_L1_INFO)
 		,
 	.timer_cb = lchan_fsm_timer_cb,
 	.cleanup = lchan_fsm_cleanup,
diff --git a/src/osmo-bsc/net_init.c b/src/osmo-bsc/net_init.c
index 8a8c0a674..23a93cc4b 100644
--- a/src/osmo-bsc/net_init.c
+++ b/src/osmo-bsc/net_init.c
@@ -72,6 +72,7 @@ static struct osmo_tdef gsm_network_T_defs[] = {
 			" after this amount of idle time, forget internally cumulated time remainders. Zero to always"
 			" keep remainders. See also X16, X17." },
 	{ .T=-25, .default_val=5, .desc="Timeout for initial user data after an MSC initiated an SCCP connection to the BSS" },
+	{ .T=-27, .default_val = 30, .desc = "Time after which to release an lchan when not receiving L1 Info in MEAS RES" },
 	{ .T=-3111, .default_val=4, .desc="Wait time after lchan was released in error (should be T3111 + 2s)" },
 	{ .T=-3210, .default_val=20, .desc="After L3 Complete, wait for MSC to confirm" },
 	{}
-- 
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