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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 (
"fmt"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/errors/linuxerr"
"gvisor.dev/gvisor/pkg/fspath"
"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
"gvisor.dev/gvisor/pkg/sentry/vfs"
)
// filesystemType implements vfs.FilesystemType.
//
// +stateify savable
type filesystemType struct{}
// GetFilesystem implements vfs.FilesystemType.GetFilesystem.
func (fsType filesystemType) GetFilesystem(_ context.Context, vfsObj *vfs.VirtualFilesystem, _ *auth.Credentials, _ string, _ vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
panic("sockfs.filesystemType.GetFilesystem should never be called")
}
// Name implements vfs.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"
}
// Release implements vfs.FilesystemType.Release.
func (filesystemType) Release(ctx context.Context) {}
// +stateify savable
type filesystem struct {
kernfs.Filesystem
devMinor uint32
}
// NewFilesystem sets up and returns 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, error) {
devMinor, err := vfsObj.GetAnonBlockDevMinor()
if err != nil {
return nil, err
}
fs := &filesystem{
devMinor: devMinor,
}
fs.Filesystem.VFSFilesystem().Init(vfsObj, filesystemType{}, fs)
return fs.Filesystem.VFSFilesystem(), nil
}
// Release implements vfs.FilesystemImpl.Release.
func (fs *filesystem) Release(ctx context.Context) {
fs.Filesystem.VFSFilesystem().VirtualFilesystem().PutAnonBlockDevMinor(fs.devMinor)
fs.Filesystem.Release(ctx)
}
// PrependPath implements vfs.FilesystemImpl.PrependPath.
func (fs *filesystem) PrependPath(ctx context.Context, vfsroot, vd vfs.VirtualDentry, b *fspath.Builder) error {
inode := vd.Dentry().Impl().(*kernfs.Dentry).Inode().(*inode)
b.PrependComponent(fmt.Sprintf("socket:[%d]", inode.InodeAttrs.Ino()))
return vfs.PrependPathSyntheticError{}
}
// MountOptions implements vfs.FilesystemImpl.MountOptions.
func (fs *filesystem) MountOptions() string {
return ""
}
// inode implements kernfs.Inode.
//
// +stateify savable
type inode struct {
kernfs.InodeAttrs
kernfs.InodeNoopRefCount
kernfs.InodeNotDirectory
kernfs.InodeNotSymlink
}
// Open implements kernfs.Inode.Open.
func (i *inode) Open(ctx context.Context, rp *vfs.ResolvingPath, d *kernfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
return nil, linuxerr.ENXIO
}
// StatFS implements kernfs.Inode.StatFS.
func (i *inode) StatFS(ctx context.Context, fs *vfs.Filesystem) (linux.Statfs, error) {
return vfs.GenericStatFS(linux.SOCKFS_MAGIC), nil
}
// NewDentry constructs and returns a sockfs dentry.
//
// Preconditions: mnt.Filesystem() must have been returned by NewFilesystem().
func NewDentry(ctx context.Context, mnt *vfs.Mount) *vfs.Dentry {
fs := mnt.Filesystem().Impl().(*filesystem)
// File mode matches net/socket.c:sock_alloc.
filemode := linux.FileMode(linux.S_IFSOCK | 0600)
i := &inode{}
i.InodeAttrs.Init(ctx, auth.CredentialsFromContext(ctx), linux.UNNAMED_MAJOR, fs.devMinor, fs.Filesystem.NextIno(), filemode)
d := &kernfs.Dentry{}
d.Init(&fs.Filesystem, i)
return d.VFSDentry()
}
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