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.

client/internal/proxy/noproxy.go

@@ -0,0 +1,49 @@
+package proxy
+
+import (
+	log "github.com/sirupsen/logrus"
+	"github.com/wiretrustee/wiretrustee/iface"
+	"net"
+)
+
+// NoProxy is used when there is no need for a proxy between ICE and Wireguard.
+// This is possible in either of these cases:
+// - peers are in the same local network
+// - one of the peers has a public static IP (host)
+// NoProxy will just update remote peer with a remote host and fixed Wireguard port (r.g. 51820).
+// In order NoProxy to work, Wireguard port has to be fixed for the time being.
+type NoProxy struct {
+	config Config
+}
+
+func NewNoProxy(config Config) *NoProxy {
+	return &NoProxy{config: config}
+}
+
+func (p *NoProxy) Close() error {
+	// noop
+	return nil
+}
+
+// Start just updates Wireguard peer with the remote IP and default Wireguard port
+func (p *NoProxy) Start(remoteConn net.Conn) error {
+
+	log.Debugf("using NoProxy while connecting to peer %s", p.config.RemoteKey)
+	addr, err := net.ResolveUDPAddr("udp", remoteConn.RemoteAddr().String())
+	if err != nil {
+		return err
+	}
+	addr.Port = iface.DefaultWgPort
+	err = p.config.WgInterface.UpdatePeer(p.config.RemoteKey, p.config.AllowedIps, DefaultWgKeepAlive,
+		addr, p.config.PreSharedKey)
+
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (p *NoProxy) Type() Type {
+	return TypeNoProxy
+}