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// Copyright 2018 Google LLC
//
// 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.
// +build linux
// Package rawfile contains utilities for using the netstack with raw host
// files on Linux hosts.
package rawfile
import (
"syscall"
"unsafe"
"gvisor.googlesource.com/gvisor/pkg/tcpip"
)
// GetMTU determines the MTU of a network interface device.
func GetMTU(name string) (uint32, error) {
fd, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_DGRAM, 0)
if err != nil {
return 0, err
}
defer syscall.Close(fd)
var ifreq struct {
name [16]byte
mtu int32
_ [20]byte
}
copy(ifreq.name[:], name)
_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), syscall.SIOCGIFMTU, uintptr(unsafe.Pointer(&ifreq)))
if errno != 0 {
return 0, errno
}
return uint32(ifreq.mtu), nil
}
// NonBlockingWrite writes the given buffer to a file descriptor. It fails if
// partial data is written.
func NonBlockingWrite(fd int, buf []byte) *tcpip.Error {
var ptr unsafe.Pointer
if len(buf) > 0 {
ptr = unsafe.Pointer(&buf[0])
}
_, _, e := syscall.RawSyscall(syscall.SYS_WRITE, uintptr(fd), uintptr(ptr), uintptr(len(buf)))
if e != 0 {
return TranslateErrno(e)
}
return nil
}
// NonBlockingWrite2 writes up to two byte slices to a file descriptor in a
// single syscall. It fails if partial data is written.
func NonBlockingWrite2(fd int, b1, b2 []byte) *tcpip.Error {
// If the is no second buffer, issue a regular write.
if len(b2) == 0 {
return NonBlockingWrite(fd, b1)
}
// We have two buffers. Build the iovec that represents them and issue
// a writev syscall.
iovec := [...]syscall.Iovec{
{
Base: &b1[0],
Len: uint64(len(b1)),
},
{
Base: &b2[0],
Len: uint64(len(b2)),
},
}
_, _, e := syscall.RawSyscall(syscall.SYS_WRITEV, uintptr(fd), uintptr(unsafe.Pointer(&iovec[0])), uintptr(len(iovec)))
if e != 0 {
return TranslateErrno(e)
}
return nil
}
// PollEvent represents the pollfd structure passed to a poll() system call.
type PollEvent struct {
FD int32
Events int16
Revents int16
}
// BlockingRead reads from a file descriptor that is set up as non-blocking. If
// no data is available, it will block in a poll() syscall until the file
// descirptor becomes readable.
func BlockingRead(fd int, b []byte) (int, *tcpip.Error) {
for {
n, _, e := syscall.RawSyscall(syscall.SYS_READ, uintptr(fd), uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)))
if e == 0 {
return int(n), nil
}
event := PollEvent{
FD: int32(fd),
Events: 1, // POLLIN
}
_, e = BlockingPoll(&event, 1, -1)
if e != 0 && e != syscall.EINTR {
return 0, TranslateErrno(e)
}
}
}
// BlockingReadv reads from a file descriptor that is set up as non-blocking and
// stores the data in a list of iovecs buffers. If no data is available, it will
// block in a poll() syscall until the file descriptor becomes readable.
func BlockingReadv(fd int, iovecs []syscall.Iovec) (int, *tcpip.Error) {
for {
n, _, e := syscall.RawSyscall(syscall.SYS_READV, uintptr(fd), uintptr(unsafe.Pointer(&iovecs[0])), uintptr(len(iovecs)))
if e == 0 {
return int(n), nil
}
event := PollEvent{
FD: int32(fd),
Events: 1, // POLLIN
}
_, e = BlockingPoll(&event, 1, -1)
if e != 0 && e != syscall.EINTR {
return 0, TranslateErrno(e)
}
}
}
// MMsgHdr represents the mmsg_hdr structure required by recvmmsg() on linux.
type MMsgHdr struct {
Msg syscall.Msghdr
Len uint32
_ [4]byte
}
// BlockingRecvMMsg reads from a file descriptor that is set up as non-blocking
// and stores the received messages in a slice of MMsgHdr structures. If no data
// is available, it will block in a poll() syscall until the file descriptor
// becomes readable.
func BlockingRecvMMsg(fd int, msgHdrs []MMsgHdr) (int, *tcpip.Error) {
for {
n, _, e := syscall.RawSyscall6(syscall.SYS_RECVMMSG, uintptr(fd), uintptr(unsafe.Pointer(&msgHdrs[0])), uintptr(len(msgHdrs)), syscall.MSG_DONTWAIT, 0, 0)
if e == 0 {
return int(n), nil
}
event := PollEvent{
FD: int32(fd),
Events: 1, // POLLIN
}
if _, e := BlockingPoll(&event, 1, -1); e != 0 && e != syscall.EINTR {
return 0, TranslateErrno(e)
}
}
}
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