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