io.go

/*
   Copyright The containerd 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 runc

import (
	"io"
	"os"
	"os/exec"
)

// IO is the terminal IO interface
type IO interface {
	io.Closer
	Stdin() io.WriteCloser
	Stdout() io.ReadCloser
	Stderr() io.ReadCloser
	Set(*exec.Cmd)
}

// StartCloser is an interface to handle IO closure after start
type StartCloser interface {
	CloseAfterStart() error
}

// IOOpt sets I/O creation options
type IOOpt func(*IOOption)

// IOOption holds I/O creation options
type IOOption struct {
	OpenStdin  bool
	OpenStdout bool
	OpenStderr bool
}

func defaultIOOption() *IOOption {
	return &IOOption{
		OpenStdin:  true,
		OpenStdout: true,
		OpenStderr: true,
	}
}

func newPipe() (*pipe, error) {
	r, w, err := os.Pipe()
	if err != nil {
		return nil, err
	}
	return &pipe{
		r: r,
		w: w,
	}, nil
}

type pipe struct {
	r *os.File
	w *os.File
}

func (p *pipe) Close() error {
	err := p.w.Close()
	if rerr := p.r.Close(); err == nil {
		err = rerr
	}
	return err
}

// NewPipeIO creates pipe pairs to be used with runc. It is not implemented
// on Windows.
func NewPipeIO(uid, gid int, opts ...IOOpt) (i IO, err error) {
	return newPipeIO(uid, gid, opts...)
}

type pipeIO struct {
	in  *pipe
	out *pipe
	err *pipe
}

func (i *pipeIO) Stdin() io.WriteCloser {
	if i.in == nil {
		return nil
	}
	return i.in.w
}

func (i *pipeIO) Stdout() io.ReadCloser {
	if i.out == nil {
		return nil
	}
	return i.out.r
}

func (i *pipeIO) Stderr() io.ReadCloser {
	if i.err == nil {
		return nil
	}
	return i.err.r
}

func (i *pipeIO) Close() error {
	var err error
	for _, v := range []*pipe{
		i.in,
		i.out,
		i.err,
	} {
		if v != nil {
			if cerr := v.Close(); err == nil {
				err = cerr
			}
		}
	}
	return err
}

func (i *pipeIO) CloseAfterStart() error {
	for _, f := range []*pipe{
		i.out,
		i.err,
	} {
		if f != nil {
			f.w.Close()
		}
	}
	return nil
}

// Set sets the io to the exec.Cmd
func (i *pipeIO) Set(cmd *exec.Cmd) {
	if i.in != nil {
		cmd.Stdin = i.in.r
	}
	if i.out != nil {
		cmd.Stdout = i.out.w
	}
	if i.err != nil {
		cmd.Stderr = i.err.w
	}
}

// NewSTDIO returns I/O setup for standard OS in/out/err usage
func NewSTDIO() (IO, error) {
	return &stdio{}, nil
}

type stdio struct{}

func (s *stdio) Close() error {
	return nil
}

func (s *stdio) Set(cmd *exec.Cmd) {
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
}

func (s *stdio) Stdin() io.WriteCloser {
	return os.Stdin
}

func (s *stdio) Stdout() io.ReadCloser {
	return os.Stdout
}

func (s *stdio) Stderr() io.ReadCloser {
	return os.Stderr
}

// NewNullIO returns IO setup for /dev/null use with runc
func NewNullIO() (IO, error) {
	f, err := os.Open(os.DevNull)
	if err != nil {
		return nil, err
	}
	return &nullIO{
		devNull: f,
	}, nil
}

type nullIO struct {
	devNull *os.File
}

func (n *nullIO) Close() error {
	// this should be closed after start but if not
	// make sure we close the file but don't return the error
	n.devNull.Close()
	return nil
}

func (n *nullIO) Stdin() io.WriteCloser {
	return nil
}

func (n *nullIO) Stdout() io.ReadCloser {
	return nil
}

func (n *nullIO) Stderr() io.ReadCloser {
	return nil
}

func (n *nullIO) Set(c *exec.Cmd) {
	// don't set STDIN here
	c.Stdout = n.devNull
	c.Stderr = n.devNull
}

func (n *nullIO) CloseAfterStart() error {
	return n.devNull.Close()
}