package system import ( "context" "io" "os" "github.com/docker/cli/cli" "github.com/docker/cli/cli/command" "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(dockerCli) }, } return cmd } func runDialStdio(dockerCli command.Cli) error { ctx, cancel := context.WithCancel(context.Background()) 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) conn2stdout := make(chan error) 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() }