mirror of
https://github.com/netbirdio/gvisor.git
synced 2026-05-22 17:12:49 -07:00
Andrei Vagin
97 lines
2.5 KiB
Go
97 lines
2.5 KiB
Go
// Copyright 2021 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 control
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import (
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"fmt"
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"io"
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"os"
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"gvisor.dev/gvisor/pkg/abi/linux"
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"gvisor.dev/gvisor/pkg/context"
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"gvisor.dev/gvisor/pkg/fspath"
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"gvisor.dev/gvisor/pkg/sentry/kernel"
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"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
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"gvisor.dev/gvisor/pkg/sentry/vfs"
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"gvisor.dev/gvisor/pkg/urpc"
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"gvisor.dev/gvisor/pkg/usermem"
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)
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// CatOpts contains options for the Cat RPC call.
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type CatOpts struct {
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// Files are the filesystem paths for the files to cat.
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Files []string `json:"files"`
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// FilePayload contains the destination for output.
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urpc.FilePayload
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}
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// Fs includes fs-related functions.
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type Fs struct {
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Kernel *kernel.Kernel
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}
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// Cat is a RPC stub which prints out and returns the content of the files.
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func (f *Fs) Cat(o *CatOpts, _ *struct{}) error {
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// Create an output stream.
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if len(o.FilePayload.Files) != 1 {
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return ErrInvalidFiles
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}
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output := o.FilePayload.Files[0]
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for _, file := range o.Files {
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if err := cat(f.Kernel, file, output); err != nil {
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return fmt.Errorf("cannot read from file %s: %v", file, err)
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}
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}
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return nil
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}
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// fdReader provides an io.Reader interface for a vfs.FileDescription.
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type fdReader struct {
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ctx context.Context
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fd *vfs.FileDescription
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}
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// Read implements io.Reader.Read.
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func (f *fdReader) Read(p []byte) (int, error) {
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n, err := f.fd.Read(f.ctx, usermem.BytesIOSequence(p), vfs.ReadOptions{})
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return int(n), err
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}
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func cat(k *kernel.Kernel, path string, output *os.File) error {
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ctx := k.SupervisorContext()
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creds := auth.NewRootCredentials(k.RootUserNamespace())
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mns := k.GlobalInit().Leader().MountNamespace()
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root := mns.Root(ctx)
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defer root.DecRef(ctx)
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fd, err := k.VFS().OpenAt(ctx, creds, &vfs.PathOperation{
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Root: root,
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Start: root,
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Path: fspath.Parse(path),
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}, &vfs.OpenOptions{
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Flags: linux.O_RDONLY,
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})
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if err != nil {
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return fmt.Errorf("failed to open file %s: %v", path, err)
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}
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defer fd.DecRef(ctx)
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_, err = io.Copy(output, &fdReader{ctx: ctx, fd: fd})
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return err
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}
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