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moby--moby/container/stream/attach.go
Jim Minter 84d6240cfe Resolve race conditions in attach API call
Signed-off-by: Jim Minter <jminter@redhat.com>
2017-02-01 09:01:36 +00:00

235 lines
5.4 KiB
Go

package stream
import (
"io"
"sync"
"golang.org/x/net/context"
"github.com/Sirupsen/logrus"
"github.com/docker/docker/pkg/promise"
)
var defaultEscapeSequence = []byte{16, 17} // ctrl-p, ctrl-q
// DetachError is special error which returned in case of container detach.
type DetachError struct{}
func (DetachError) Error() string {
return "detached from container"
}
// AttachConfig is the config struct used to attach a client to a stream's stdio
type AttachConfig struct {
// Tells the attach copier that the stream's stdin is a TTY and to look for
// escape sequences in stdin to detach from the stream.
// When true the escape sequence is not passed to the underlying stream
TTY bool
// Specifies the detach keys the client will be using
// Only useful when `TTY` is true
DetachKeys []byte
// CloseStdin signals that once done, stdin for the attached stream should be closed
// For example, this would close the attached container's stdin.
CloseStdin bool
// UseStd* indicate whether the client has requested to be connected to the
// given stream or not. These flags are used instead of checking Std* != nil
// at points before the client streams Std* are wired up.
UseStdin, UseStdout, UseStderr bool
// CStd* are the streams directly connected to the container
CStdin io.WriteCloser
CStdout, CStderr io.ReadCloser
// Provide client streams to wire up to
Stdin io.ReadCloser
Stdout, Stderr io.Writer
}
// AttachStreams attaches the container's streams to the AttachConfig
func (c *Config) AttachStreams(cfg *AttachConfig) {
if cfg.UseStdin {
cfg.CStdin = c.StdinPipe()
}
if cfg.UseStdout {
cfg.CStdout = c.StdoutPipe()
}
if cfg.UseStderr {
cfg.CStderr = c.StderrPipe()
}
}
// CopyStreams starts goroutines to copy data in and out to/from the container
func (c *Config) CopyStreams(ctx context.Context, cfg *AttachConfig) chan error {
var (
wg sync.WaitGroup
errors = make(chan error, 3)
)
if cfg.Stdin != nil {
wg.Add(1)
}
if cfg.Stdout != nil {
wg.Add(1)
}
if cfg.Stderr != nil {
wg.Add(1)
}
// Connect stdin of container to the attach stdin stream.
go func() {
if cfg.Stdin == nil {
return
}
logrus.Debug("attach: stdin: begin")
var err error
if cfg.TTY {
_, err = copyEscapable(cfg.CStdin, cfg.Stdin, cfg.DetachKeys)
} else {
_, err = io.Copy(cfg.CStdin, cfg.Stdin)
}
if err == io.ErrClosedPipe {
err = nil
}
if err != nil {
logrus.Errorf("attach: stdin: %s", err)
errors <- err
}
if cfg.CloseStdin && !cfg.TTY {
cfg.CStdin.Close()
} else {
// No matter what, when stdin is closed (io.Copy unblock), close stdout and stderr
if cfg.CStdout != nil {
cfg.CStdout.Close()
}
if cfg.CStderr != nil {
cfg.CStderr.Close()
}
}
logrus.Debug("attach: stdin: end")
wg.Done()
}()
attachStream := func(name string, stream io.Writer, streamPipe io.ReadCloser) {
if stream == nil {
return
}
logrus.Debugf("attach: %s: begin", name)
_, err := io.Copy(stream, streamPipe)
if err == io.ErrClosedPipe {
err = nil
}
if err != nil {
logrus.Errorf("attach: %s: %v", name, err)
errors <- err
}
// Make sure stdin gets closed
if cfg.Stdin != nil {
cfg.Stdin.Close()
}
streamPipe.Close()
logrus.Debugf("attach: %s: end", name)
wg.Done()
}
go attachStream("stdout", cfg.Stdout, cfg.CStdout)
go attachStream("stderr", cfg.Stderr, cfg.CStderr)
return promise.Go(func() error {
done := make(chan struct{})
go func() {
wg.Wait()
close(done)
}()
select {
case <-done:
case <-ctx.Done():
// close all pipes
if cfg.CStdin != nil {
cfg.CStdin.Close()
}
if cfg.CStdout != nil {
cfg.CStdout.Close()
}
if cfg.CStderr != nil {
cfg.CStderr.Close()
}
<-done
}
close(errors)
for err := range errors {
if err != nil {
return err
}
}
return nil
})
}
// ttyProxy is used only for attaches with a TTY. It is used to proxy
// stdin keypresses from the underlying reader and look for the passed in
// escape key sequence to signal a detach.
type ttyProxy struct {
escapeKeys []byte
escapeKeyPos int
r io.Reader
}
func (r *ttyProxy) Read(buf []byte) (int, error) {
nr, err := r.r.Read(buf)
preserve := func() {
// this preserves the original key presses in the passed in buffer
nr += r.escapeKeyPos
preserve := make([]byte, 0, r.escapeKeyPos+len(buf))
preserve = append(preserve, r.escapeKeys[:r.escapeKeyPos]...)
preserve = append(preserve, buf...)
r.escapeKeyPos = 0
copy(buf[0:nr], preserve)
}
if nr != 1 || err != nil {
if r.escapeKeyPos > 0 {
preserve()
}
return nr, err
}
if buf[0] != r.escapeKeys[r.escapeKeyPos] {
if r.escapeKeyPos > 0 {
preserve()
}
return nr, nil
}
if r.escapeKeyPos == len(r.escapeKeys)-1 {
return 0, DetachError{}
}
// Looks like we've got an escape key, but we need to match again on the next
// read.
// Store the current escape key we found so we can look for the next one on
// the next read.
// Since this is an escape key, make sure we don't let the caller read it
// If later on we find that this is not the escape sequence, we'll add the
// keys back
r.escapeKeyPos++
return nr - r.escapeKeyPos, nil
}
func copyEscapable(dst io.Writer, src io.ReadCloser, keys []byte) (written int64, err error) {
if len(keys) == 0 {
keys = defaultEscapeSequence
}
pr := &ttyProxy{escapeKeys: keys, r: src}
defer src.Close()
return io.Copy(dst, pr)
}