Fix: revert to classic TUN creation (#254)

core/device/tun/tun_wireguard.go

@@ -48,7 +48,7 @@ func Open(name string, mtu uint32) (_ device.Device, err error) {
 		forcedMTU = int(t.mtu)
 	}
 
-	nt, err := tun.CreateTUN(t.name, forcedMTU)
+	nt, err := createTUN(t.name, forcedMTU)
 	if err != nil {
 		return nil, fmt.Errorf("create tun: %w", err)
 	}

core/device/tun/tun_wireguard_linux.go

@@ -3,22 +3,24 @@
 package tun
 
 import (
-	"unsafe"
+	"fmt"
+	"os"
+
+	"golang.zx2c4.com/wireguard/tun"
+	gun "gvisor.dev/gvisor/pkg/tcpip/link/tun"
 )
 
 const (
-	virtioNetHdrLen = int(unsafe.Sizeof(virtioNetHdr{}))
-	offset          = virtioNetHdrLen + 0 /* NO_PI */
+	offset     = 0 /* IFF_NO_PI */
 	defaultMTU = 1500
 )
 
-// virtioNetHdr is defined in the kernel in include/uapi/linux/virtio_net.h. The
-// kernel symbol is virtio_net_hdr.
-type virtioNetHdr struct {
-	flags      uint8
-	gsoType    uint8
-	hdrLen     uint16
-	gsoSize    uint16
-	csumStart  uint16
-	csumOffset uint16
+func createTUN(name string, mtu int) (tun.Device, error) {
+	nfd, err := gun.Open(name)
+	if err != nil {
+		return nil, fmt.Errorf("create tun: %w", err)
+	}
+
+	fd := os.NewFile(uintptr(nfd), "/dev/net/tun")
+	return tun.CreateTUNFromFile(fd, mtu)
 }

core/device/tun/tun_wireguard_unix.go

@@ -2,7 +2,15 @@
 
 package tun
 
+import (
+	"golang.zx2c4.com/wireguard/tun"
+)
+
 const (
 	offset     = 4 /* 4 bytes TUN_PI */
 	defaultMTU = 1500
 )
+
+func createTUN(name string, mtu int) (tun.Device, error) {
+	return tun.CreateTUN(name, mtu)
+}

core/device/tun/tun_wireguard_windows.go

@@ -1,6 +1,14 @@
 package tun
 
+import (
+	"golang.zx2c4.com/wireguard/tun"
+)
+
 const (
 	offset     = 0
 	defaultMTU = 0 /* auto */
 )
+
+func createTUN(name string, mtu int) (tun.Device, error) {
+	return tun.CreateTUN(name, mtu)
+}