handle_linux.go

Documentation: github.com/containerd/fifo

     1  //go:build linux
     2  
     3  /*
     4     Copyright The containerd Authors.
     5  
     6     Licensed under the Apache License, Version 2.0 (the "License");
     7     you may not use this file except in compliance with the License.
     8     You may obtain a copy of the License at
     9  
    10         http://www.apache.org/licenses/LICENSE-2.0
    11  
    12     Unless required by applicable law or agreed to in writing, software
    13     distributed under the License is distributed on an "AS IS" BASIS,
    14     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    15     See the License for the specific language governing permissions and
    16     limitations under the License.
    17  */
    18  
    19  package fifo
    20  
    21  import (
    22  	"fmt"
    23  	"os"
    24  	"sync"
    25  	"syscall"
    26  )
    27  
    28  //nolint:revive
    29  const O_PATH = 010000000
    30  
    31  type handle struct {
    32  	f         *os.File
    33  	fd        uintptr
    34  	dev       uint64
    35  	ino       uint64
    36  	closeOnce sync.Once
    37  	name      string
    38  }
    39  
    40  func getHandle(fn string) (*handle, error) {
    41  	f, err := os.OpenFile(fn, O_PATH, 0)
    42  	if err != nil {
    43  		return nil, fmt.Errorf("failed to open %v with O_PATH: %w", fn, err)
    44  	}
    45  
    46  	var (
    47  		stat syscall.Stat_t
    48  		fd   = f.Fd()
    49  	)
    50  	if err := syscall.Fstat(int(fd), &stat); err != nil {
    51  		f.Close()
    52  		return nil, fmt.Errorf("failed to stat handle %v: %w", fd, err)
    53  	}
    54  
    55  	h := &handle{
    56  		f:    f,
    57  		name: fn,
    58  		//nolint:unconvert
    59  		dev: uint64(stat.Dev),
    60  		ino: stat.Ino,
    61  		fd:  fd,
    62  	}
    63  
    64  	// check /proc just in case
    65  	if _, err := os.Stat(h.procPath()); err != nil {
    66  		f.Close()
    67  		return nil, fmt.Errorf("couldn't stat %v: %w", h.procPath(), err)
    68  	}
    69  
    70  	return h, nil
    71  }
    72  
    73  func (h *handle) procPath() string {
    74  	return fmt.Sprintf("/proc/self/fd/%d", h.fd)
    75  }
    76  
    77  func (h *handle) Name() string {
    78  	return h.name
    79  }
    80  
    81  func (h *handle) Path() (string, error) {
    82  	var stat syscall.Stat_t
    83  	if err := syscall.Stat(h.procPath(), &stat); err != nil {
    84  		return "", fmt.Errorf("path %v could not be statted: %w", h.procPath(), err)
    85  	}
    86  	//nolint:unconvert
    87  	if uint64(stat.Dev) != h.dev || stat.Ino != h.ino {
    88  		return "", fmt.Errorf("failed to verify handle %v/%v %v/%v", stat.Dev, h.dev, stat.Ino, h.ino)
    89  	}
    90  	return h.procPath(), nil
    91  }
    92  
    93  func (h *handle) Close() error {
    94  	h.closeOnce.Do(func() {
    95  		h.f.Close()
    96  	})
    97  	return nil
    98  }
    99
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