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// Copyright 2021 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 hostinet
import (
"runtime"
"unsafe"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/sentry/inet"
)
func queryInterfaceFeatures(interfaces map[int32]*inet.Interface) error {
fd, err := queryFD()
if err != nil {
return err
}
defer unix.Close(fd)
for idx, nic := range interfaces {
var ifr linux.IFReq
copy(ifr.IFName[:], nic.Name)
var gfeatures linux.EthtoolGFeatures
// Each feature block is sufficient to query 32 features, the linux
// kernel today supports upto 64 features per device. Technically it
// can support more in the future but this is sufficient for our use
// right now.
const (
numFeatureBlocks = 2
ifrDataSz = unsafe.Sizeof(linux.EthtoolGFeatures{}) + numFeatureBlocks*unsafe.Sizeof(linux.EthtoolGetFeaturesBlock{})
)
featureBlocks := make([]linux.EthtoolGetFeaturesBlock, numFeatureBlocks)
b := make([]byte, ifrDataSz)
gfeatures.Cmd = uint32(linux.ETHTOOL_GFEATURES)
gfeatures.Size = numFeatureBlocks
gfeatures.MarshalBytes(b)
next := b[unsafe.Sizeof(linux.EthtoolGFeatures{}):]
for i := 0; i < numFeatureBlocks; i++ {
featureBlocks[i].MarshalBytes(next)
next = next[unsafe.Sizeof(linux.EthtoolGetFeaturesBlock{}):]
}
// Technically the next two lines are not safe as Go GC can technically move
// b to a new location and the pointer value stored in ifr.Data could point
// to random memory. But the reality today is that Go GC is not a moving GC
// so this is essentially safe as of today.
//
// TODO(b/209014118): Use Pin API when available in Go runtime to make this
// safe.
dataPtr := unsafe.Pointer(&b[0])
hostarch.ByteOrder.PutUint64(ifr.Data[:8], uint64(uintptr(dataPtr)))
if _, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), unix.SIOCETHTOOL, uintptr(unsafe.Pointer(&ifr))); errno != 0 {
return errno
}
// Unmarshall the features back.
gfeatures.UnmarshalBytes(b)
next = b[unsafe.Sizeof(linux.EthtoolGFeatures{}):]
for i := 0; i < int(gfeatures.Size); i++ {
featureBlocks[i].UnmarshalBytes(next)
next = next[unsafe.Sizeof(linux.EthtoolGetFeaturesBlock{}):]
}
// Store the queried features.
interfaces[idx].Features = make([]linux.EthtoolGetFeaturesBlock, gfeatures.Size)
copy(interfaces[idx].Features, featureBlocks)
// This ensures b is not garbage collected before this point to ensure that
// the slice is not collected before the syscall returns and we copy out the
// data.
runtime.KeepAlive(b)
}
return nil
}
func queryFD() (int, error) {
// Try both AF_INET and AF_INET6 in case only one is supported.
var fd int
var err error
for _, family := range []int{unix.AF_INET6, unix.AF_INET} {
fd, err = unix.Socket(family, unix.SOCK_STREAM, 0)
if err == nil {
return fd, err
}
}
return fd, err
}
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