Add L3 routing support

transport/wireguard/device.go

@@ -1,13 +1,23 @@
 package wireguard
 
 import (
+	"net/netip"
+
+	"github.com/sagernet/sing-tun"
 	N "github.com/sagernet/sing/common/network"
-	"github.com/sagernet/wireguard-go/tun"
+	wgTun "github.com/sagernet/wireguard-go/tun"
 )
 
 type Device interface {
-	tun.Device
+	wgTun.Device
 	N.Dialer
 	Start() error
+	Inet4Address() netip.Addr
+	Inet6Address() netip.Addr
 	// NewEndpoint() (stack.LinkEndpoint, error)
 }
+
+type NatDevice interface {
+	Device
+	CreateDestination(session tun.RouteSession, conn tun.RouteContext) tun.DirectDestination
+}