Support no-proxy mode connection mode (#245)

When one of the peers has a static public host IP
or both peers are in the same local network
we establish a direct Wireguard connection
bypassing proxy usage.
This helps reduce FD usage and improves
performance.

iface/iface.go

@@ -9,6 +9,7 @@ import (
 
 const (
 	DefaultMTU = 1280
+	DefaultWgPort = 51820
 )
 
 // WGIface represents a interface instance