Add libbox wrapper

experimental/libbox/tun_gvisor.go

@@ -0,0 +1,19 @@
+//go:build with_gvisor && linux
+
+package libbox
+
+import (
+	"github.com/sagernet/sing-tun"
+
+	"gvisor.dev/gvisor/pkg/tcpip/link/fdbased"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+)
+
+var _ tun.GVisorTun = (*nativeTun)(nil)
+
+func (t *nativeTun) NewEndpoint() (stack.LinkEndpoint, error) {
+	return fdbased.New(&fdbased.Options{
+		FDs: []int{t.tunFd},
+		MTU: t.tunMTU,
+	})
+}