183 lines
4.7 KiB
Go
183 lines
4.7 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build linux
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// Package rawfile contains utilities for using the netstack with raw host
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// files on Linux hosts.
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package rawfile
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import (
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"syscall"
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"unsafe"
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"gvisor.dev/gvisor/pkg/tcpip"
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)
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// GetMTU determines the MTU of a network interface device.
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func GetMTU(name string) (uint32, error) {
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fd, err := syscall.Socket(syscall.AF_UNIX, syscall.SOCK_DGRAM, 0)
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if err != nil {
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return 0, err
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}
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defer syscall.Close(fd)
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var ifreq struct {
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name [16]byte
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mtu int32
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_ [20]byte
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}
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copy(ifreq.name[:], name)
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_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), syscall.SIOCGIFMTU, uintptr(unsafe.Pointer(&ifreq)))
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if errno != 0 {
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return 0, errno
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}
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return uint32(ifreq.mtu), nil
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}
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// NonBlockingWrite writes the given buffer to a file descriptor. It fails if
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// partial data is written.
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func NonBlockingWrite(fd int, buf []byte) *tcpip.Error {
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var ptr unsafe.Pointer
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if len(buf) > 0 {
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ptr = unsafe.Pointer(&buf[0])
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}
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_, _, e := syscall.RawSyscall(syscall.SYS_WRITE, uintptr(fd), uintptr(ptr), uintptr(len(buf)))
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if e != 0 {
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return TranslateErrno(e)
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}
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return nil
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}
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// NonBlockingWrite3 writes up to three byte slices to a file descriptor in a
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// single syscall. It fails if partial data is written.
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func NonBlockingWrite3(fd int, b1, b2, b3 []byte) *tcpip.Error {
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// If the is no second buffer, issue a regular write.
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if len(b2) == 0 {
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return NonBlockingWrite(fd, b1)
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}
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// We have two buffers. Build the iovec that represents them and issue
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// a writev syscall.
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iovec := [3]syscall.Iovec{
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{
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Base: &b1[0],
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Len: uint64(len(b1)),
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},
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{
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Base: &b2[0],
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Len: uint64(len(b2)),
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},
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}
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iovecLen := uintptr(2)
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if len(b3) > 0 {
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iovecLen++
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iovec[2].Base = &b3[0]
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iovec[2].Len = uint64(len(b3))
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}
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_, _, e := syscall.RawSyscall(syscall.SYS_WRITEV, uintptr(fd), uintptr(unsafe.Pointer(&iovec[0])), iovecLen)
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if e != 0 {
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return TranslateErrno(e)
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}
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return nil
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}
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// PollEvent represents the pollfd structure passed to a poll() system call.
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type PollEvent struct {
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FD int32
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Events int16
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Revents int16
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}
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// BlockingRead reads from a file descriptor that is set up as non-blocking. If
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// no data is available, it will block in a poll() syscall until the file
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// descriptor becomes readable.
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func BlockingRead(fd int, b []byte) (int, *tcpip.Error) {
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for {
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n, _, e := syscall.RawSyscall(syscall.SYS_READ, uintptr(fd), uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)))
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if e == 0 {
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return int(n), nil
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}
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event := PollEvent{
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FD: int32(fd),
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Events: 1, // POLLIN
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}
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_, e = BlockingPoll(&event, 1, nil)
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if e != 0 && e != syscall.EINTR {
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return 0, TranslateErrno(e)
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}
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}
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}
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// BlockingReadv reads from a file descriptor that is set up as non-blocking and
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// stores the data in a list of iovecs buffers. If no data is available, it will
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// block in a poll() syscall until the file descriptor becomes readable.
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func BlockingReadv(fd int, iovecs []syscall.Iovec) (int, *tcpip.Error) {
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for {
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n, _, e := syscall.RawSyscall(syscall.SYS_READV, uintptr(fd), uintptr(unsafe.Pointer(&iovecs[0])), uintptr(len(iovecs)))
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if e == 0 {
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return int(n), nil
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}
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event := PollEvent{
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FD: int32(fd),
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Events: 1, // POLLIN
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}
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_, e = BlockingPoll(&event, 1, nil)
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if e != 0 && e != syscall.EINTR {
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return 0, TranslateErrno(e)
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}
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}
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}
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// MMsgHdr represents the mmsg_hdr structure required by recvmmsg() on linux.
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type MMsgHdr struct {
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Msg syscall.Msghdr
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Len uint32
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_ [4]byte
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}
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// BlockingRecvMMsg reads from a file descriptor that is set up as non-blocking
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// and stores the received messages in a slice of MMsgHdr structures. If no data
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// is available, it will block in a poll() syscall until the file descriptor
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// becomes readable.
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func BlockingRecvMMsg(fd int, msgHdrs []MMsgHdr) (int, *tcpip.Error) {
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for {
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n, _, e := syscall.RawSyscall6(syscall.SYS_RECVMMSG, uintptr(fd), uintptr(unsafe.Pointer(&msgHdrs[0])), uintptr(len(msgHdrs)), syscall.MSG_DONTWAIT, 0, 0)
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if e == 0 {
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return int(n), nil
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}
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event := PollEvent{
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FD: int32(fd),
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Events: 1, // POLLIN
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}
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if _, e := BlockingPoll(&event, 1, nil); e != 0 && e != syscall.EINTR {
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return 0, TranslateErrno(e)
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}
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}
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}
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