Fix(core): update gVisor (#82, #95)

core/device/tun/tun_netstack.go

@@ -0,0 +1,112 @@
+//go:build linux
+
+package tun
+
+import (
+	"fmt"
+	"unsafe"
+
+	"github.com/xjasonlyu/tun2socks/v2/core/device"
+
+	"golang.org/x/sys/unix"
+	"gvisor.dev/gvisor/pkg/tcpip/link/fdbased"
+	"gvisor.dev/gvisor/pkg/tcpip/link/rawfile"
+	"gvisor.dev/gvisor/pkg/tcpip/link/tun"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+)
+
+type TUN struct {
+	stack.LinkEndpoint
+
+	fd   int
+	mtu  uint32
+	name string
+}
+
+func Open(name string, mtu uint32) (device.Device, error) {
+	t := &TUN{name: name, mtu: mtu}
+
+	if len(t.name) >= unix.IFNAMSIZ {
+		return nil, fmt.Errorf("interface name too long: %s", t.name)
+	}
+
+	fd, err := tun.Open(t.name)
+	if err != nil {
+		return nil, fmt.Errorf("create tun: %w", err)
+	}
+	t.fd = fd
+
+	if t.mtu > 0 {
+		if err := setMTU(t.name, t.mtu); err != nil {
+			return nil, fmt.Errorf("set mtu: %w", err)
+		}
+	}
+
+	_mtu, err := rawfile.GetMTU(t.name)
+	if err != nil {
+		return nil, fmt.Errorf("get mtu: %w", err)
+	}
+	t.mtu = _mtu
+
+	ep, err := fdbased.New(&fdbased.Options{
+		FDs: []int{fd},
+		MTU: t.mtu,
+		// TUN only, ignore ethernet header.
+		EthernetHeader: false,
+		// SYS_READV support only for TUN fd.
+		PacketDispatchMode: fdbased.Readv,
+		// TODO: set this field to zero in the future.
+		// it's a only temporary hack to avoid `socket operation
+		// on non-socket` error caused by SYS_SENDMMSG syscall.
+		//
+		// Ref: https://github.com/google/gvisor/issues/7125
+		MaxSyscallHeaderBytes: 0x40,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("create endpoint: %w", err)
+	}
+	t.LinkEndpoint = ep
+
+	return t, nil
+}
+
+func (t *TUN) Name() string {
+	return t.name
+}
+
+func (t *TUN) Close() error {
+	return unix.Close(t.fd)
+}
+
+func setMTU(name string, n uint32) error {
+	// open datagram socket
+	fd, err := unix.Socket(
+		unix.AF_INET,
+		unix.SOCK_DGRAM,
+		0,
+	)
+	if err != nil {
+		return err
+	}
+
+	defer unix.Close(fd)
+
+	const ifReqSize = unix.IFNAMSIZ + 64
+
+	// do ioctl call
+	var ifr [ifReqSize]byte
+	copy(ifr[:], name)
+	*(*uint32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = n
+	_, _, errno := unix.Syscall(
+		unix.SYS_IOCTL,
+		uintptr(fd),
+		uintptr(unix.SIOCSIFMTU),
+		uintptr(unsafe.Pointer(&ifr[0])),
+	)
+
+	if errno != 0 {
+		return fmt.Errorf("failed to set MTU: %w", errno)
+	}
+
+	return nil
+}