Add GSO support

tun_linux_flags.go

@@ -0,0 +1,84 @@
+//go:build linux
+
+package tun
+
+import (
+	"os"
+	"syscall"
+	"unsafe"
+
+	E "github.com/sagernet/sing/common/exceptions"
+
+	"golang.org/x/sys/unix"
+)
+
+func checkVNETHDREnabled(fd int, name string) (bool, error) {
+	ifr, err := unix.NewIfreq(name)
+	if err != nil {
+		return false, err
+	}
+	err = unix.IoctlIfreq(fd, unix.TUNGETIFF, ifr)
+	if err != nil {
+		return false, os.NewSyscallError("TUNGETIFF", err)
+	}
+	return ifr.Uint16()&unix.IFF_VNET_HDR != 0, nil
+}
+
+func setTCPOffload(fd int) error {
+	const (
+		// TODO: support TSO with ECN bits
+		tunOffloads = unix.TUN_F_CSUM | unix.TUN_F_TSO4 | unix.TUN_F_TSO6
+	)
+	err := unix.IoctlSetInt(fd, unix.TUNSETOFFLOAD, tunOffloads)
+	if err != nil {
+		return E.Cause(os.NewSyscallError("TUNSETOFFLOAD", err), "enable offload")
+	}
+	return nil
+}
+
+type ifreqData struct {
+	ifrName [unix.IFNAMSIZ]byte
+	ifrData uintptr
+}
+
+type ethtoolValue struct {
+	cmd  uint32
+	data uint32
+}
+
+//go:linkname ioctlPtr golang.org/x/sys/unix.ioctlPtr
+func ioctlPtr(fd int, req uint, arg unsafe.Pointer) (err error)
+
+func checkChecksumOffload(name string, cmd uint32) (bool, error) {
+	fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_IP)
+	if err != nil {
+		return false, err
+	}
+	defer syscall.Close(fd)
+	ifr := ifreqData{}
+	copy(ifr.ifrName[:], name)
+	data := ethtoolValue{cmd: cmd}
+	ifr.ifrData = uintptr(unsafe.Pointer(&data))
+	err = ioctlPtr(fd, unix.SIOCETHTOOL, unsafe.Pointer(&ifr))
+	if err != nil {
+		return false, os.NewSyscallError("SIOCETHTOOL ETHTOOL_GTXCSUM", err)
+	}
+	return data.data == 0, nil
+}
+
+func setChecksumOffload(name string, cmd uint32) error {
+	fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_IP)
+	if err != nil {
+		return err
+	}
+	defer syscall.Close(fd)
+	ifr := ifreqData{}
+	copy(ifr.ifrName[:], name)
+	data := ethtoolValue{cmd: cmd, data: 0}
+	ifr.ifrData = uintptr(unsafe.Pointer(&data))
+	err = ioctlPtr(fd, unix.SIOCETHTOOL, unsafe.Pointer(&ifr))
+	if err != nil {
+		return os.NewSyscallError("SIOCETHTOOL ETHTOOL_STXCSUM", err)
+	}
+	return nil
+}