209 lines
4.7 KiB
Go
209 lines
4.7 KiB
Go
// Copyright 2021 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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package lisafs
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import (
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"io"
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"golang.org/x/sys/unix"
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"gvisor.dev/gvisor/pkg/log"
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"gvisor.dev/gvisor/pkg/unet"
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)
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var (
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sockHeaderLen = uint32((*sockHeader)(nil).SizeBytes())
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)
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// sockHeader is the header present in front of each message received on a UDS.
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//
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// +marshal
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type sockHeader struct {
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payloadLen uint32
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message MID
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_ uint16 // Need to make struct packed.
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}
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// sockCommunicator implements Communicator. This is not thread safe.
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type sockCommunicator struct {
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fdTracker
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sock *unet.Socket
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buf []byte
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}
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var _ Communicator = (*sockCommunicator)(nil)
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func newSockComm(sock *unet.Socket) *sockCommunicator {
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return &sockCommunicator{
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sock: sock,
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buf: make([]byte, sockHeaderLen),
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}
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}
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func (s *sockCommunicator) FD() int {
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return s.sock.FD()
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}
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func (s *sockCommunicator) destroy() {
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s.sock.Close()
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}
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func (s *sockCommunicator) shutdown() {
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if err := s.sock.Shutdown(); err != nil {
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log.Warningf("Socket.Shutdown() failed (FD: %d): %v", s.sock.FD(), err)
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}
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}
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func (s *sockCommunicator) resizeBuf(size uint32) {
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if cap(s.buf) < int(size) {
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s.buf = s.buf[:cap(s.buf)]
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s.buf = append(s.buf, make([]byte, int(size)-cap(s.buf))...)
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} else {
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s.buf = s.buf[:size]
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}
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}
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// PayloadBuf implements Communicator.PayloadBuf.
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func (s *sockCommunicator) PayloadBuf(size uint32) []byte {
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s.resizeBuf(sockHeaderLen + size)
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return s.buf[sockHeaderLen : sockHeaderLen+size]
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}
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// SndRcvMessage implements Communicator.SndRcvMessage.
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func (s *sockCommunicator) SndRcvMessage(m MID, payloadLen uint32, wantFDs uint8) (MID, uint32, error) {
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if err := s.sndPrepopulatedMsg(m, payloadLen, nil); err != nil {
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return 0, 0, err
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}
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return s.rcvMsg(wantFDs)
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}
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// sndPrepopulatedMsg assumes that s.buf has already been populated with
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// `payloadLen` bytes of data.
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func (s *sockCommunicator) sndPrepopulatedMsg(m MID, payloadLen uint32, fds []int) error {
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header := sockHeader{payloadLen: payloadLen, message: m}
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header.MarshalUnsafe(s.buf)
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dataLen := sockHeaderLen + payloadLen
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return writeTo(s.sock, [][]byte{s.buf[:dataLen]}, int(dataLen), fds)
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}
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// writeTo writes the passed iovec to the UDS and donates any passed FDs.
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func writeTo(sock *unet.Socket, iovec [][]byte, dataLen int, fds []int) error {
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w := sock.Writer(true)
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if len(fds) > 0 {
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w.PackFDs(fds...)
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}
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fdsUnpacked := false
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for n := 0; n < dataLen; {
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cur, err := w.WriteVec(iovec)
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if err != nil {
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return err
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}
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n += cur
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// Fast common path.
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if n >= dataLen {
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break
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}
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// Consume iovecs.
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for consumed := 0; consumed < cur; {
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if len(iovec[0]) <= cur-consumed {
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consumed += len(iovec[0])
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iovec = iovec[1:]
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} else {
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iovec[0] = iovec[0][cur-consumed:]
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break
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}
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}
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if n > 0 && !fdsUnpacked {
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// Don't resend any control message.
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fdsUnpacked = true
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w.UnpackFDs()
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}
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}
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return nil
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}
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// rcvMsg reads the message header and payload from the UDS. It also populates
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// fds with any donated FDs.
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func (s *sockCommunicator) rcvMsg(wantFDs uint8) (MID, uint32, error) {
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fds, err := readFrom(s.sock, s.buf[:sockHeaderLen], wantFDs)
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if err != nil {
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return 0, 0, err
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}
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for _, fd := range fds {
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s.TrackFD(fd)
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}
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var header sockHeader
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header.UnmarshalUnsafe(s.buf)
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// No payload? We are done.
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if header.payloadLen == 0 {
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return header.message, 0, nil
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}
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if _, err := readFrom(s.sock, s.PayloadBuf(header.payloadLen), 0); err != nil {
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return 0, 0, err
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}
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return header.message, header.payloadLen, nil
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}
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// readFrom fills the passed buffer with data from the socket. It also returns
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// any donated FDs.
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func readFrom(sock *unet.Socket, buf []byte, wantFDs uint8) ([]int, error) {
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r := sock.Reader(true)
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r.EnableFDs(int(wantFDs))
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var (
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fds []int
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fdInit bool
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)
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n := len(buf)
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for got := 0; got < n; {
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cur, err := r.ReadVec([][]byte{buf[got:]})
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// Ignore EOF if cur > 0.
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if err != nil && (err != io.EOF || cur == 0) {
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r.CloseFDs()
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return nil, err
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}
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if !fdInit && cur > 0 {
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fds, err = r.ExtractFDs()
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if err != nil {
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return nil, err
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}
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fdInit = true
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r.EnableFDs(0)
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}
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got += cur
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}
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return fds, nil
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}
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func closeFDs(fds []int) {
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for _, fd := range fds {
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if fd >= 0 {
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unix.Close(fd)
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}
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}
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}
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