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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.
// Package fdpipe implements common namedpipe opening and accessing logic.
package fdpipe
import (
"os"
"sync"
"syscall"
"gvisor.googlesource.com/gvisor/pkg/fd"
"gvisor.googlesource.com/gvisor/pkg/fdnotifier"
"gvisor.googlesource.com/gvisor/pkg/log"
"gvisor.googlesource.com/gvisor/pkg/secio"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
"gvisor.googlesource.com/gvisor/pkg/sentry/safemem"
"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
"gvisor.googlesource.com/gvisor/pkg/syserror"
"gvisor.googlesource.com/gvisor/pkg/waiter"
)
// pipeOperations are the fs.FileOperations of a host pipe.
//
// +stateify savable
type pipeOperations struct {
fsutil.PipeSeek `state:"nosave"`
fsutil.NotDirReaddir `state:"nosave"`
fsutil.NoFsync `state:"nosave"`
fsutil.NoopFlush `state:"nosave"`
fsutil.NoMMap `state:"nosave"`
fsutil.NoIoctl `state:"nosave"`
waiter.Queue `state:"nosave"`
// flags are the flags used to open the pipe.
flags fs.FileFlags `state:".(fs.FileFlags)"`
// opener is how the pipe was opened.
opener NonBlockingOpener `state:"wait"`
// file represents the host pipe.
file *fd.FD `state:"nosave"`
// mu protects readAheadBuffer access below.
mu sync.Mutex `state:"nosave"`
// readAheadBuffer contains read bytes that have not yet been read
// by the application but need to be buffered for save-restore for correct
// opening semantics. The readAheadBuffer will only be non-empty when the
// is first opened and will be drained by subsequent reads on the pipe.
readAheadBuffer []byte
}
// newPipeOperations returns an implementation of fs.FileOperations for a pipe.
func newPipeOperations(ctx context.Context, opener NonBlockingOpener, flags fs.FileFlags, file *fd.FD, readAheadBuffer []byte) (*pipeOperations, error) {
pipeOps := &pipeOperations{
flags: flags,
opener: opener,
file: file,
readAheadBuffer: readAheadBuffer,
}
if err := pipeOps.init(); err != nil {
return nil, err
}
return pipeOps, nil
}
// init initializes p.file.
func (p *pipeOperations) init() error {
var s syscall.Stat_t
if err := syscall.Fstat(p.file.FD(), &s); err != nil {
log.Warningf("pipe: cannot stat fd %d: %v", p.file.FD(), err)
return syscall.EINVAL
}
if s.Mode&syscall.S_IFIFO != syscall.S_IFIFO {
log.Warningf("pipe: cannot load fd %d as pipe, file type: %o", p.file.FD(), s.Mode)
return syscall.EINVAL
}
if err := syscall.SetNonblock(p.file.FD(), true); err != nil {
return err
}
return fdnotifier.AddFD(int32(p.file.FD()), &p.Queue)
}
// EventRegister implements waiter.Waitable.EventRegister.
func (p *pipeOperations) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
p.Queue.EventRegister(e, mask)
fdnotifier.UpdateFD(int32(p.file.FD()))
}
// EventUnregister implements waiter.Waitable.EventUnregister.
func (p *pipeOperations) EventUnregister(e *waiter.Entry) {
p.Queue.EventUnregister(e)
fdnotifier.UpdateFD(int32(p.file.FD()))
}
// Readiness returns a mask of ready events for stream.
func (p *pipeOperations) Readiness(mask waiter.EventMask) (eventMask waiter.EventMask) {
return fdnotifier.NonBlockingPoll(int32(p.file.FD()), mask)
}
// Release implements fs.FileOperations.Release.
func (p *pipeOperations) Release() {
fdnotifier.RemoveFD(int32(p.file.FD()))
p.file.Close()
p.file = nil
}
// Read implements fs.FileOperations.Read.
func (p *pipeOperations) Read(ctx context.Context, file *fs.File, dst usermem.IOSequence, offset int64) (int64, error) {
// Drain the read ahead buffer, if it contains anything first.
var bufN int
var bufErr error
p.mu.Lock()
if len(p.readAheadBuffer) > 0 {
bufN, bufErr = dst.CopyOut(ctx, p.readAheadBuffer)
p.readAheadBuffer = p.readAheadBuffer[bufN:]
dst = dst.DropFirst(bufN)
}
p.mu.Unlock()
if dst.NumBytes() == 0 || bufErr != nil {
return int64(bufN), bufErr
}
// Pipes expect full reads.
n, err := dst.CopyOutFrom(ctx, safemem.FromIOReader{secio.FullReader{p.file}})
total := int64(bufN) + n
if err != nil && isBlockError(err) {
return total, syserror.ErrWouldBlock
}
return total, err
}
// Write implements fs.FileOperations.Write.
func (p *pipeOperations) Write(ctx context.Context, file *fs.File, src usermem.IOSequence, offset int64) (int64, error) {
n, err := src.CopyInTo(ctx, safemem.FromIOWriter{p.file})
if err != nil && isBlockError(err) {
return n, syserror.ErrWouldBlock
}
return n, err
}
// isBlockError unwraps os errors and checks if they are caused by EAGAIN or
// EWOULDBLOCK. This is so they can be transformed into syserror.ErrWouldBlock.
func isBlockError(err error) bool {
if err == syserror.EAGAIN || err == syserror.EWOULDBLOCK {
return true
}
if pe, ok := err.(*os.PathError); ok {
return isBlockError(pe.Err)
}
return false
}
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