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// Copyright 2020 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 sockfs provides a filesystem implementation for anonymous sockets.
package sockfs
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
)
// NewFilesystem creates a new sockfs filesystem.
//
// Note that there should only ever be one instance of sockfs.Filesystem,
// backing a global socket mount.
func NewFilesystem(vfsObj *vfs.VirtualFilesystem) *vfs.Filesystem {
fs, _, err := filesystemType{}.GetFilesystem(nil, vfsObj, nil, "", vfs.GetFilesystemOptions{})
if err != nil {
panic("failed to create sockfs filesystem")
}
return fs
}
// filesystemType implements vfs.FilesystemType.
type filesystemType struct{}
// GetFilesystem implements FilesystemType.GetFilesystem.
func (fsType filesystemType) GetFilesystem(_ context.Context, vfsObj *vfs.VirtualFilesystem, _ *auth.Credentials, _ string, _ vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
fs := &filesystem{}
fs.Init(vfsObj, fsType)
return fs.VFSFilesystem(), nil, nil
}
// Name implements FilesystemType.Name.
//
// Note that registering sockfs is unnecessary, except for the fact that it
// will not show up under /proc/filesystems as a result. This is a very minor
// discrepancy from Linux.
func (filesystemType) Name() string {
return "sockfs"
}
// filesystem implements vfs.FilesystemImpl.
type filesystem struct {
kernfs.Filesystem
}
// inode implements kernfs.Inode.
//
// TODO(gvisor.dev/issue/1476): Add device numbers to this inode (which are
// not included in InodeAttrs) to store the numbers of the appropriate
// socket device. Override InodeAttrs.Stat() accordingly.
type inode struct {
kernfs.InodeNotDirectory
kernfs.InodeNotSymlink
kernfs.InodeAttrs
kernfs.InodeNoopRefCount
}
// Open implements kernfs.Inode.Open.
func (i *inode) Open(rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
return nil, syserror.ENXIO
}
// InitSocket initializes a socket FileDescription, with a corresponding
// Dentry in mnt.
//
// fd should be the FileDescription associated with socketImpl, i.e. its first
// field. mnt should be the global socket mount, Kernel.socketMount.
func InitSocket(socketImpl vfs.FileDescriptionImpl, fd *vfs.FileDescription, mnt *vfs.Mount, creds *auth.Credentials) error {
fsimpl := mnt.Filesystem().Impl()
fs := fsimpl.(*kernfs.Filesystem)
// File mode matches net/socket.c:sock_alloc.
filemode := linux.FileMode(linux.S_IFSOCK | 0600)
i := &inode{}
i.Init(creds, fs.NextIno(), filemode)
d := &kernfs.Dentry{}
d.Init(i)
opts := &vfs.FileDescriptionOptions{UseDentryMetadata: true}
if err := fd.Init(socketImpl, linux.O_RDWR, mnt, d.VFSDentry(), opts); err != nil {
return err
}
return nil
}
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