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// Copyright 2019 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package sandbox
import (
"fmt"
"os"
"unsafe"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
)
type ethtoolValue struct {
cmd uint32
val uint32
}
type ifreq struct {
ifrName [unix.IFNAMSIZ]byte
ifrData *ethtoolValue
}
const (
_ETHTOOL_GGSO = 0x00000023
)
func isGSOEnabled(fd int, intf string) (bool, error) {
val := ethtoolValue{
cmd: _ETHTOOL_GGSO,
}
var name [unix.IFNAMSIZ]byte
copy(name[:], []byte(intf))
ifr := ifreq{
ifrName: name,
ifrData: &val,
}
if _, _, err := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), unix.SIOCETHTOOL, uintptr(unsafe.Pointer(&ifr))); err != 0 {
return false, err
}
return val.val != 0, nil
}
func writeNATBlob() (*os.File, error) {
// Open a socket to use with iptables.
iptSock, err := unix.Socket(unix.AF_INET, unix.SOCK_RAW, unix.IPPROTO_ICMP)
if err != nil {
return nil, fmt.Errorf("failed to open socket for iptables: %v", err)
}
defer unix.Close(iptSock)
// Get the iptables info.
var NATName [linux.XT_TABLE_MAXNAMELEN]byte
copy(NATName[:], []byte("nat\x00"))
natInfo := linux.IPTGetinfo{Name: NATName}
natInfoLen := int32(unsafe.Sizeof(linux.IPTGetinfo{}))
_, _, errno := unix.Syscall6(unix.SYS_GETSOCKOPT,
uintptr(iptSock),
unix.SOL_IP,
linux.IPT_SO_GET_INFO,
uintptr(unsafe.Pointer(&natInfo)),
uintptr(unsafe.Pointer(&natInfoLen)),
0)
if errno != 0 {
return nil, fmt.Errorf("failed to call IPT_SO_GET_INFO: %v", err)
}
// Get the iptables entries.
entries := linux.IPTGetEntries{Name: NATName, Size: natInfo.Size}
entriesBufLen := uint32(unsafe.Sizeof(entries)) + natInfo.Size
entriesBuf := make([]byte, entriesBufLen)
entries.MarshalUnsafe(entriesBuf[:unsafe.Sizeof(entries)])
_, _, errno = unix.Syscall6(unix.SYS_GETSOCKOPT,
uintptr(iptSock),
unix.SOL_IP,
linux.IPT_SO_GET_ENTRIES,
uintptr(unsafe.Pointer(&entriesBuf[0])),
uintptr(unsafe.Pointer(&entriesBufLen)),
0)
if errno != 0 {
return nil, fmt.Errorf("failed to call IPT_SO_GET_ENTRIES: %v", errno)
}
var gotEntries linux.IPTGetEntries
gotEntries.UnmarshalUnsafe(entriesBuf[:unsafe.Sizeof(entries)])
// Construct an IPTReplace that can be used to set rules.
replace := linux.IPTReplace{
Name: NATName,
ValidHooks: natInfo.ValidHooks,
NumEntries: natInfo.NumEntries,
Size: natInfo.Size,
HookEntry: natInfo.HookEntry,
Underflow: natInfo.Underflow,
// We don't implement counters yet.
NumCounters: 0,
Counters: 0,
}
// Marshal into a blob.
replaceBuf := make([]byte, unsafe.Sizeof(replace)+uintptr(natInfo.Size))
replace.MarshalUnsafe(replaceBuf[:unsafe.Sizeof(replace)])
if n := copy(replaceBuf[unsafe.Sizeof(replace):], entriesBuf[unsafe.Sizeof(entries):]); uint32(n) != natInfo.Size {
panic(fmt.Sprintf("failed to populate entry table: copied %d bytes, but wanted to copy %d", n, natInfo.Size))
}
// Write blob to a pipe.
reader, writer, err := os.Pipe()
if err != nil {
return nil, fmt.Errorf("failed to create iptables blob pipe: %v", err)
}
defer writer.Close()
if n, err := writer.Write(replaceBuf); n != len(replaceBuf) || err != nil {
return nil, fmt.Errorf("failed to write iptables blob: wrote %d bytes (%d expected) and got error: %v", n, len(replaceBuf), err)
}
return reader, nil
}
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