Add tun inbound for linux

common/tun/gvisor_nonlinux.go

@@ -0,0 +1,9 @@
+//go:build !linux
+
+package tun
+
+import "gvisor.dev/gvisor/pkg/tcpip/stack"
+
+func NewEndpoint(tunFd uintptr, tunMtu uint32) (stack.LinkEndpoint, error) {
+	return NewPosixEndpoint(tunFd, tunMtu)
+}