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dial_stdio.go
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dial_stdio.go
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package system
import (
"context"
"io"
"os"
"github.com/docker/cli/cli"
"github.com/docker/cli/cli/command"
"github.com/docker/cli/cli/command/completion"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"github.com/spf13/cobra"
)
// newDialStdioCommand creates a new cobra.Command for `docker system dial-stdio`
func newDialStdioCommand(dockerCli command.Cli) *cobra.Command {
cmd := &cobra.Command{
Use: "dial-stdio",
Short: "Proxy the stdio stream to the daemon connection. Should not be invoked manually.",
Args: cli.NoArgs,
Hidden: true,
RunE: func(cmd *cobra.Command, args []string) error {
return runDialStdio(cmd.Context(), dockerCli)
},
ValidArgsFunction: completion.NoComplete,
}
return cmd
}
func runDialStdio(ctx context.Context, dockerCli command.Cli) error {
ctx, cancel := context.WithCancel(ctx)
defer cancel()
dialer := dockerCli.Client().Dialer()
conn, err := dialer(ctx)
if err != nil {
return errors.Wrap(err, "failed to open the raw stream connection")
}
defer conn.Close()
var connHalfCloser halfCloser
switch t := conn.(type) {
case halfCloser:
connHalfCloser = t
case halfReadWriteCloser:
connHalfCloser = &nopCloseReader{t}
default:
return errors.New("the raw stream connection does not implement halfCloser")
}
stdin2conn := make(chan error, 1)
conn2stdout := make(chan error, 1)
go func() {
stdin2conn <- copier(connHalfCloser, &halfReadCloserWrapper{os.Stdin}, "stdin to stream")
}()
go func() {
conn2stdout <- copier(&halfWriteCloserWrapper{os.Stdout}, connHalfCloser, "stream to stdout")
}()
select {
case err = <-stdin2conn:
if err != nil {
return err
}
// wait for stdout
err = <-conn2stdout
case err = <-conn2stdout:
// return immediately without waiting for stdin to be closed.
// (stdin is never closed when tty)
}
return err
}
func copier(to halfWriteCloser, from halfReadCloser, debugDescription string) error {
defer func() {
if err := from.CloseRead(); err != nil {
logrus.Errorf("error while CloseRead (%s): %v", debugDescription, err)
}
if err := to.CloseWrite(); err != nil {
logrus.Errorf("error while CloseWrite (%s): %v", debugDescription, err)
}
}()
if _, err := io.Copy(to, from); err != nil {
return errors.Wrapf(err, "error while Copy (%s)", debugDescription)
}
return nil
}
type halfReadCloser interface {
io.Reader
CloseRead() error
}
type halfWriteCloser interface {
io.Writer
CloseWrite() error
}
type halfCloser interface {
halfReadCloser
halfWriteCloser
}
type halfReadWriteCloser interface {
io.Reader
halfWriteCloser
}
type nopCloseReader struct {
halfReadWriteCloser
}
func (x *nopCloseReader) CloseRead() error {
return nil
}
type halfReadCloserWrapper struct {
io.ReadCloser
}
func (x *halfReadCloserWrapper) CloseRead() error {
return x.Close()
}
type halfWriteCloserWrapper struct {
io.WriteCloser
}
func (x *halfWriteCloserWrapper) CloseWrite() error {
return x.Close()
}