Fix crash when a prefix family was empty

config-example.yaml

@@ -137,6 +137,12 @@ disable_check_updates: false
 # Time before an inactive ephemeral node is deleted?
 ephemeral_node_inactivity_timeout: 30m
 
+# Period to check for node updates within the tailnet. A value too low will severely affect
+# CPU consumption of Headscale. A value too high (over 60s) will cause problems
+# for the nodes, as they won't get updates or keep alive messages frequently enough.
+# In case of doubts, do not touch the default 10s.
+node_update_check_interval: 10s
+
 database:
   type: sqlite
 

hscontrol/types/config.go

@@ -46,6 +46,7 @@ type Config struct {
 	GRPCAddr                       string
 	GRPCAllowInsecure              bool
 	EphemeralNodeInactivityTimeout time.Duration
+	NodeUpdateCheckInterval        time.Duration
 	PrefixV4                       *netip.Prefix
 	PrefixV6                       *netip.Prefix
 	IPAllocation                   IPAllocationStrategy
@@ -232,6 +233,8 @@ func LoadConfig(path string, isFile bool) error {
 
 	viper.SetDefault("ephemeral_node_inactivity_timeout", "120s")
 
+	viper.SetDefault("node_update_check_interval", "10s")
+
 	viper.SetDefault("tuning.batch_change_delay", "800ms")
 	viper.SetDefault("tuning.node_mapsession_buffered_chan_size", 30)
 
@@ -287,6 +290,15 @@ func LoadConfig(path string, isFile bool) error {
 		)
 	}
 
+	maxNodeUpdateCheckInterval, _ := time.ParseDuration("60s")
+	if viper.GetDuration("node_update_check_interval") > maxNodeUpdateCheckInterval {
+		errorText += fmt.Sprintf(
+			"Fatal config error: node_update_check_interval (%s) is set too high, must be less than %s",
+			viper.GetString("node_update_check_interval"),
+			maxNodeUpdateCheckInterval,
+		)
+	}
+
 	if errorText != "" {
 		// nolint
 		return errors.New(strings.TrimSuffix(errorText, "\n"))
@@ -702,6 +714,10 @@ func GetHeadscaleConfig() (*Config, error) {
 			"ephemeral_node_inactivity_timeout",
 		),
 
+		NodeUpdateCheckInterval: viper.GetDuration(
+			"node_update_check_interval",
+		),
+
 		Database: GetDatabaseConfig(),
 
 		TLS: GetTLSConfig(),

integration/hsic/config.go

@@ -73,6 +73,7 @@ database:
   type: sqlite3
   sqlite.path: /tmp/integration_test_db.sqlite3
 ephemeral_node_inactivity_timeout: 30m
+node_update_check_interval: 10s
 prefixes:
   v6: fd7a:115c:a1e0::/48
   v4: 100.64.0.0/10
@@ -115,6 +116,7 @@ func DefaultConfigEnv() map[string]string {
 		"HEADSCALE_DATABASE_TYPE":                     "sqlite",
 		"HEADSCALE_DATABASE_SQLITE_PATH":              "/tmp/integration_test_db.sqlite3",
 		"HEADSCALE_EPHEMERAL_NODE_INACTIVITY_TIMEOUT": "30m",
+		"HEADSCALE_NODE_UPDATE_CHECK_INTERVAL":        "10s",
 		"HEADSCALE_PREFIXES_V4":                       "100.64.0.0/10",
 		"HEADSCALE_PREFIXES_V6":                       "fd7a:115c:a1e0::/48",
 		"HEADSCALE_DNS_CONFIG_BASE_DOMAIN":            "headscale.net",