gbproxy: Add new VTY-managed timer: link-list clean-stale-timer

This timer allows periodically cleaning up stale links in link-list of
each gbproxy_peer. Previous to this patch, this kind of cleanup
(gbproxy_remove_stale_link_infos) was being done only as a consequence
of external events being triggered, such as a message from that peer
being received.
It was found in a production network agreggating several BSS that some
of them were offline for a longtime but gbproxy was still caching big
amounts of really old link_info for the NSEI assigned to those BSS,
because since they were probably turned off abruptely, no new messages
were received from it which would trigger the cleanup.
As a consequence, it has been observed that a timer to periodically
clean up old entries (link-list max-age) is requird in case w don't
receive messages from that NSEI periodically.

Related: SYS#4431
Change-Id: Ic777016f6d4f0e30fb736484774ca46878f17b7a

3 files changed, 67 insertions, 2 deletions

diff --git a/include/osmocom/sgsn/gb_proxy.h b/include/osmocom/sgsn/gb_proxy.h
index 16082fcde..7e2ae42fb 100644
--- a/include/osmocom/sgsn/gb_proxy.h
+++ b/include/osmocom/sgsn/gb_proxy.h
@@ -105,6 +105,8 @@ struct gbproxy_config {
 	struct osmo_plmn_id core_plmn;
 	uint8_t* core_apn;
 	size_t core_apn_size;
+	/* Frequency (sec) at which timer to clean stale links is fired (0 disabled) */
+	unsigned int clean_stale_timer_freq;
 	/* If !0, Max age to consider a struct gbproxy_link_info as stale */
 	int tlli_max_age;
 	/* If !0, Max len of gbproxy_peer->list (list of struct gbproxy_link_info) */
@@ -151,6 +153,9 @@ struct gbproxy_peer {
 	struct rate_ctr_group *ctrg;
 
 	struct gbproxy_patch_state patch_state;
+
+	/* Fired periodically to clean up stale links from list */
+	struct osmo_timer_list clean_stale_timer;
 };
 
 struct gbproxy_tlli_state {
diff --git a/src/gprs/gb_proxy_peer.c b/src/gprs/gb_proxy_peer.c
index f2cdd9388..8e28fc4bc 100644
--- a/src/gprs/gb_proxy_peer.c
+++ b/src/gprs/gb_proxy_peer.c
@@ -167,6 +167,19 @@ struct gbproxy_peer *gbproxy_peer_by_bssgp_tlv(struct gbproxy_config *cfg,
 	return NULL;
 }
 
+static void clean_stale_timer_cb(void *data)
+{
+	time_t now;
+	struct timespec ts = {0,};
+	struct gbproxy_peer *peer = (struct gbproxy_peer *) data;
+
+	osmo_clock_gettime(CLOCK_MONOTONIC, &ts);
+	now = ts.tv_sec;
+	gbproxy_remove_stale_link_infos(peer, now);
+	if (peer->cfg->clean_stale_timer_freq != 0)
+		osmo_timer_schedule(&peer->clean_stale_timer,
+					peer->cfg->clean_stale_timer_freq, 0);
+}
 
 struct gbproxy_peer *gbproxy_peer_alloc(struct gbproxy_config *cfg, uint16_t bvci)
 {
@@ -188,13 +201,18 @@ struct gbproxy_peer *gbproxy_peer_alloc(struct gbproxy_config *cfg, uint16_t bvc
 
 	INIT_LLIST_HEAD(&peer->patch_state.logical_links);
 
+	osmo_timer_setup(&peer->clean_stale_timer, clean_stale_timer_cb, peer);
+	if (peer->cfg->clean_stale_timer_freq != 0)
+		osmo_timer_schedule(&peer->clean_stale_timer,
+					peer->cfg->clean_stale_timer_freq, 0);
+
 	return peer;
 }
 
 void gbproxy_peer_free(struct gbproxy_peer *peer)
 {
 	llist_del(&peer->list);
-
+	osmo_timer_del(&peer->clean_stale_timer);
 	gbproxy_delete_link_infos(peer);
 
 	rate_ctr_group_free(peer->ctrg);
@@ -220,4 +238,3 @@ int gbproxy_cleanup_peers(struct gbproxy_config *cfg, uint16_t nsei, uint16_t bv
 
 	return counter;
 }
-
diff --git a/src/gprs/gb_proxy_vty.c b/src/gprs/gb_proxy_vty.c
index d74335556..52c39fdcd 100644
--- a/src/gprs/gb_proxy_vty.c
+++ b/src/gprs/gb_proxy_vty.c
@@ -120,6 +120,9 @@ static int config_write_gbproxy(struct vty *vty)
 		vty_out(vty, " secondary-sgsn nsei %u%s", g_cfg->nsip_sgsn2_nsei,
 			VTY_NEWLINE);
 
+	if (g_cfg->clean_stale_timer_freq > 0)
+		vty_out(vty, " link-list clean-stale-timer %u%s",
+			g_cfg->clean_stale_timer_freq, VTY_NEWLINE);
 	if (g_cfg->tlli_max_age > 0)
 		vty_out(vty, " link-list max-age %d%s",
 			g_cfg->tlli_max_age, VTY_NEWLINE);
@@ -407,6 +410,44 @@ DEFUN(cfg_gbproxy_no_secondary_sgsn,
 
 #define GBPROXY_LINK_LIST_STR "Set TLLI list parameters\n"
 #define GBPROXY_LINK_STR "Set TLLI parameters\n"
+
+#define GBPROXY_CLEAN_STALE_TIMER_STR "Periodic timer to clean stale links\n"
+
+DEFUN(cfg_gbproxy_link_list_clean_stale_timer,
+      cfg_gbproxy_link_list_clean_stale_timer_cmd,
+      "link-list clean-stale-timer <1-999999>",
+      GBPROXY_LINK_LIST_STR GBPROXY_CLEAN_STALE_TIMER_STR
+      "Frequency at which the periodic timer is fired (in seconds)\n")
+{
+	struct gbproxy_peer *peer;
+	g_cfg->clean_stale_timer_freq = (unsigned int) atoi(argv[0]);
+
+	/* Re-schedule running timers soon in case prev frequency was really big
+	   and new frequency is desired to be lower. After initial run, periodic
+	   time is used. Use random() to avoid firing timers for all peers at
+	   the same time */
+	llist_for_each_entry(peer, &g_cfg->bts_peers, list)
+		osmo_timer_schedule(&peer->clean_stale_timer,
+					random() % 5, random() % 1000000);
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_gbproxy_link_list_no_clean_stale_timer,
+      cfg_gbproxy_link_list_no_clean_stale_timer_cmd,
+      "no link-list clean-stale-timer",
+      NO_STR GBPROXY_LINK_LIST_STR GBPROXY_CLEAN_STALE_TIMER_STR)
+
+{
+	struct gbproxy_peer *peer;
+	g_cfg->clean_stale_timer_freq = 0;
+
+	llist_for_each_entry(peer, &g_cfg->bts_peers, list)
+		osmo_timer_del(&peer->clean_stale_timer);
+
+	return CMD_SUCCESS;
+}
+
 #define GBPROXY_MAX_AGE_STR "Limit maximum age\n"
 
 DEFUN(cfg_gbproxy_link_list_max_age,
@@ -846,6 +887,7 @@ int gbproxy_vty_init(void)
 	install_element(GBPROXY_NODE, &cfg_gbproxy_secondary_sgsn_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_patch_ptmsi_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_acquire_imsi_cmd);
+	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_clean_stale_timer_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_max_age_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_max_len_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_keep_mode_cmd);
@@ -857,6 +899,7 @@ int gbproxy_vty_init(void)
 	install_element(GBPROXY_NODE, &cfg_gbproxy_no_secondary_sgsn_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_no_patch_ptmsi_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_no_acquire_imsi_cmd);
+	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_no_clean_stale_timer_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_no_max_age_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_no_max_len_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_no_stored_msgs_max_len_cmd);