From d001e55ed0c650fc7f1faa80cdcb440ecc2a0a44 Mon Sep 17 00:00:00 2001
From: Xantios Krugor <github@xantios.nl>
Date: Mon, 12 Aug 2024 12:41:54 +0200
Subject: [PATCH] Make UDP connection timeout configurable. (#238)

---
 cmd/chirpstack-gateway-bridge/cmd/configfile.go | 6 ++++++
 cmd/chirpstack-gateway-bridge/cmd/root.go       | 1 +
 internal/backend/semtechudp/backend.go          | 3 ++-
 internal/backend/semtechudp/registry.go         | 9 +++------
 internal/config/config.go                       | 7 ++++---
 5 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/cmd/chirpstack-gateway-bridge/cmd/configfile.go b/cmd/chirpstack-gateway-bridge/cmd/configfile.go
index 94d85a98..0eeb9e9d 100644
--- a/cmd/chirpstack-gateway-bridge/cmd/configfile.go
+++ b/cmd/chirpstack-gateway-bridge/cmd/configfile.go
@@ -88,6 +88,12 @@ type="{{ .Backend.Type }}"
   # the time would otherwise be unset.
   fake_rx_time={{ .Backend.SemtechUDP.FakeRxTime }}
 
+  # Connection timeout duration
+  #
+  # ChirpStack Gateway Bridge keeps a list of connected gateways. If a gateway does not send any
+  # UDP data within the configured timeout, then ChirpStack Gateway Bridge will consider the gateway
+  # disconnected and it will unsubscribe from the gateway MQTT topic and cleanup the UDP docket. 
+  connection_timeout_duration={{ .Backend.SemtechUDP.CleanupDuration }}
 
   # ChirpStack Concentratord backend.
   [backend.concentratord]
diff --git a/cmd/chirpstack-gateway-bridge/cmd/root.go b/cmd/chirpstack-gateway-bridge/cmd/root.go
index 5ad16bde..aa09c2b4 100644
--- a/cmd/chirpstack-gateway-bridge/cmd/root.go
+++ b/cmd/chirpstack-gateway-bridge/cmd/root.go
@@ -39,6 +39,7 @@ func init() {
 	viper.SetDefault("general.log_level", 4)
 	viper.SetDefault("backend.type", "semtech_udp")
 	viper.SetDefault("backend.semtech_udp.udp_bind", "0.0.0.0:1700")
+	viper.SetDefault("backend.semtech_udp.cleanup_duration", time.Minute)
 
 	viper.SetDefault("backend.concentratord.crc_check", true)
 	viper.SetDefault("backend.concentratord.event_url", "ipc:///tmp/concentratord_event")
diff --git a/internal/backend/semtechudp/backend.go b/internal/backend/semtechudp/backend.go
index 14128a68..41bb3b05 100644
--- a/internal/backend/semtechudp/backend.go
+++ b/internal/backend/semtechudp/backend.go
@@ -67,7 +67,8 @@ func NewBackend(conf config.Config) (*Backend, error) {
 		conn:        conn,
 		udpSendChan: make(chan udpPacket),
 		gateways: gateways{
-			gateways: make(map[lorawan.EUI64]gateway),
+			gateways:        make(map[lorawan.EUI64]gateway),
+			cleanupDuration: time.Duration(conf.Backend.SemtechUDP.CleanupDuration),
 		},
 		fakeRxTime:   conf.Backend.SemtechUDP.FakeRxTime,
 		skipCRCCheck: conf.Backend.SemtechUDP.SkipCRCCheck,
diff --git a/internal/backend/semtechudp/registry.go b/internal/backend/semtechudp/registry.go
index d1e91b37..ce483c0e 100644
--- a/internal/backend/semtechudp/registry.go
+++ b/internal/backend/semtechudp/registry.go
@@ -16,10 +16,6 @@ var (
 	errGatewayDoesNotExist = errors.New("gateway does not exist")
 )
 
-// gatewayCleanupDuration contains the duration after which the gateway is
-// cleaned up from the registry after no activity
-var gatewayCleanupDuration = -1 * time.Minute
-
 // gateway contains a connection and meta-data for a gateway connection.
 type gateway struct {
 	stats           *stats.Collector
@@ -31,7 +27,8 @@ type gateway struct {
 // gateways contains the gateways registry.
 type gateways struct {
 	sync.RWMutex
-	gateways map[lorawan.EUI64]gateway
+	gateways        map[lorawan.EUI64]gateway
+	cleanupDuration time.Duration
 
 	subscribeEventFunc func(events.Subscribe)
 }
@@ -82,7 +79,7 @@ func (c *gateways) cleanup() error {
 	defer c.Unlock()
 
 	for gatewayID := range c.gateways {
-		if c.gateways[gatewayID].lastSeen.Before(time.Now().Add(gatewayCleanupDuration)) {
+		if c.gateways[gatewayID].lastSeen.Before(time.Now().Add(c.cleanupDuration)) {
 			disconnectCounter().Inc()
 
 			if c.subscribeEventFunc != nil {
diff --git a/internal/config/config.go b/internal/config/config.go
index 70d42f2a..d201bca4 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -21,9 +21,10 @@ type Config struct {
 		Type string `mapstructure:"type"`
 
 		SemtechUDP struct {
-			UDPBind      string `mapstructure:"udp_bind"`
-			SkipCRCCheck bool   `mapstructure:"skip_crc_check"`
-			FakeRxTime   bool   `mapstructure:"fake_rx_time"`
+			UDPBind         string `mapstructure:"udp_bind"`
+			SkipCRCCheck    bool   `mapstructure:"skip_crc_check"`
+			FakeRxTime      bool   `mapstructure:"fake_rx_time"`
+			CleanupDuration int    `mapstructure:"connection_timeout_duration"`
 		} `mapstructure:"semtech_udp"`
 
 		BasicStation struct {