fix(publicip): rework run loop and fix restarts

- Clearing IP data on VPN disconnection clears file
- More efficient partial updates
- Fix loop exit
- Validate settings before updating

internal/publicip/data.go

@@ -0,0 +1,24 @@
+package publicip
+
+import "github.com/qdm12/gluetun/internal/models"
+
+// GetData returns the public IP data obtained from the last
+// fetch. It is notably used by the HTTP control server.
+func (l *Loop) GetData() (data models.PublicIP) {
+	l.ipDataMutex.RLock()
+	defer l.ipDataMutex.RUnlock()
+	return l.ipData
+}
+
+// ClearData is used when the VPN connection goes down
+// and the public IP is not known anymore.
+func (l *Loop) ClearData() (err error) {
+	l.ipDataMutex.Lock()
+	defer l.ipDataMutex.Unlock()
+	l.ipData = models.PublicIP{}
+
+	l.settingsMutex.RLock()
+	filepath := *l.settings.IPFilepath
+	l.settingsMutex.RUnlock()
+	return persistPublicIP(filepath, "", l.puid, l.pgid)
+}