[client] Refactor/iface pkg (#2646)

Refactor the flat code structure

client/iface/device/address.go

@@ -0,0 +1,29 @@
+package device
+
+import (
+	"fmt"
+	"net"
+)
+
+// WGAddress WireGuard parsed address
+type WGAddress struct {
+	IP      net.IP
+	Network *net.IPNet
+}
+
+// ParseWGAddress parse a string ("1.2.3.4/24") address to WG Address
+func ParseWGAddress(address string) (WGAddress, error) {
+	ip, network, err := net.ParseCIDR(address)
+	if err != nil {
+		return WGAddress{}, err
+	}
+	return WGAddress{
+		IP:      ip,
+		Network: network,
+	}, nil
+}
+
+func (addr WGAddress) String() string {
+	maskSize, _ := addr.Network.Mask.Size()
+	return fmt.Sprintf("%s/%d", addr.IP.String(), maskSize)
+}