github.com/SagerNet/gvisor@v0.0.0-20210707092255-7731c139d75c/pkg/sentry/fs/host/control.go (about)

     1  // Copyright 2018 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package host
    16  
    17  import (
    18  	"golang.org/x/sys/unix"
    19  	"github.com/SagerNet/gvisor/pkg/context"
    20  	"github.com/SagerNet/gvisor/pkg/sentry/fs"
    21  	"github.com/SagerNet/gvisor/pkg/sentry/socket/control"
    22  	"github.com/SagerNet/gvisor/pkg/sentry/socket/unix/transport"
    23  )
    24  
    25  // LINT.IfChange
    26  
    27  type scmRights struct {
    28  	fds []int
    29  }
    30  
    31  func newSCMRights(fds []int) control.SCMRights {
    32  	return &scmRights{fds}
    33  }
    34  
    35  // Files implements control.SCMRights.Files.
    36  func (c *scmRights) Files(ctx context.Context, max int) (control.RightsFiles, bool) {
    37  	n := max
    38  	var trunc bool
    39  	if l := len(c.fds); n > l {
    40  		n = l
    41  	} else if n < l {
    42  		trunc = true
    43  	}
    44  
    45  	rf := control.RightsFiles(fdsToFiles(ctx, c.fds[:n]))
    46  
    47  	// Only consume converted FDs (fdsToFiles may convert fewer than n FDs).
    48  	c.fds = c.fds[len(rf):]
    49  	return rf, trunc
    50  }
    51  
    52  // Clone implements transport.RightsControlMessage.Clone.
    53  func (c *scmRights) Clone() transport.RightsControlMessage {
    54  	// Host rights never need to be cloned.
    55  	return nil
    56  }
    57  
    58  // Release implements transport.RightsControlMessage.Release.
    59  func (c *scmRights) Release(ctx context.Context) {
    60  	for _, fd := range c.fds {
    61  		unix.Close(fd)
    62  	}
    63  	c.fds = nil
    64  }
    65  
    66  // If an error is encountered, only files created before the error will be
    67  // returned. This is what Linux does.
    68  func fdsToFiles(ctx context.Context, fds []int) []*fs.File {
    69  	files := make([]*fs.File, 0, len(fds))
    70  	for _, fd := range fds {
    71  		// Get flags. We do it here because they may be modified
    72  		// by subsequent functions.
    73  		fileFlags, _, errno := unix.Syscall(unix.SYS_FCNTL, uintptr(fd), unix.F_GETFL, 0)
    74  		if errno != 0 {
    75  			ctx.Warningf("Error retrieving host FD flags: %v", error(errno))
    76  			break
    77  		}
    78  
    79  		// Create the file backed by hostFD.
    80  		file, err := NewFile(ctx, fd)
    81  		if err != nil {
    82  			ctx.Warningf("Error creating file from host FD: %v", err)
    83  			break
    84  		}
    85  
    86  		// Set known flags.
    87  		file.SetFlags(fs.SettableFileFlags{
    88  			NonBlocking: fileFlags&unix.O_NONBLOCK != 0,
    89  		})
    90  
    91  		files = append(files, file)
    92  	}
    93  	return files
    94  }
    95  
    96  // LINT.ThenChange(../../fsimpl/host/control.go)