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// Copyright 2018 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 host
import (
"fmt"
"syscall"
"gvisor.dev/gvisor/pkg/fdnotifier"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/waiter"
)
// descriptor wraps a host fd.
//
// +stateify savable
type descriptor struct {
// If origFD >= 0, it is the host fd that this file was originally created
// from, which must be available at time of restore. The FD can be closed
// after descriptor is created.
origFD int
// wouldBlock is true if value (below) points to a file that can
// return EWOULDBLOCK for operations that would block.
wouldBlock bool
// value is the wrapped host fd. It is never saved or restored
// directly.
value int `state:"nosave"`
}
// newDescriptor returns a wrapped host file descriptor. On success,
// the descriptor is registered for event notifications with queue.
func newDescriptor(fd int, saveable bool, wouldBlock bool, queue *waiter.Queue) (*descriptor, error) {
ownedFD := fd
origFD := -1
if saveable {
var err error
ownedFD, err = syscall.Dup(fd)
if err != nil {
return nil, err
}
origFD = fd
}
if wouldBlock {
if err := syscall.SetNonblock(ownedFD, true); err != nil {
return nil, err
}
if err := fdnotifier.AddFD(int32(ownedFD), queue); err != nil {
return nil, err
}
}
return &descriptor{
origFD: origFD,
wouldBlock: wouldBlock,
value: ownedFD,
}, nil
}
// initAfterLoad initializes the value of the descriptor after Load.
func (d *descriptor) initAfterLoad(id uint64, queue *waiter.Queue) error {
var err error
d.value, err = syscall.Dup(d.origFD)
if err != nil {
return fmt.Errorf("failed to dup restored fd %d: %v", d.origFD, err)
}
if d.wouldBlock {
if err := syscall.SetNonblock(d.value, true); err != nil {
return err
}
if err := fdnotifier.AddFD(int32(d.value), queue); err != nil {
return err
}
}
return nil
}
// Release releases all resources held by descriptor.
func (d *descriptor) Release() {
if d.wouldBlock {
fdnotifier.RemoveFD(int32(d.value))
}
if err := syscall.Close(d.value); err != nil {
log.Warningf("error closing fd %d: %v", d.value, err)
}
d.value = -1
}
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