Maint: rework publicip package

- Use loopstate package
- Loop interface composition
- Return concrete struct from constructors
- Split into more files
- Add publicip/state package

internal/publicip/state/publicip.go

@@ -0,0 +1,29 @@
+package state
+
+import (
+	"net"
+)
+
+type PublicIPGetSetter interface {
+	PublicIPGetter
+	SetPublicIP(publicIP net.IP)
+}
+
+type PublicIPGetter interface {
+	GetPublicIP() (publicIP net.IP)
+}
+
+func (s *State) GetPublicIP() (publicIP net.IP) {
+	s.publicIPMu.RLock()
+	defer s.publicIPMu.RUnlock()
+	publicIP = make(net.IP, len(s.publicIP))
+	copy(publicIP, s.publicIP)
+	return publicIP
+}
+
+func (s *State) SetPublicIP(publicIP net.IP) {
+	s.settingsMu.Lock()
+	defer s.settingsMu.Unlock()
+	s.publicIP = make(net.IP, len(publicIP))
+	copy(s.publicIP, publicIP)
+}