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io: stop screwing with \n in console output

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The default terminal setting for a new pty on Linux (unix98) has +ONLCR,
resulting in '\n' writes by a container process to be converted to
'\r\n' reads by the managing process. This is quite unexpected, To fix it, make
the terminal sane after opening it by setting -ONLCR.

this patch fix method comes from: eea28f480d
thanks @cyphar Aleksa Sarai <asarai@suse.de>

Signed-off-by: Wang Long <long.wanglong@huawei.com>
This commit is contained in:
Wang Long 2017-01-14 06:43:57 +00:00
parent e6f6261bae
commit 7c473041a0
1 changed files with 26 additions and 0 deletions
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26
cmd/containerd-shim/console.go
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@ -16,6 +16,9 @@ func newConsole(uid, gid int) (*os.File, string, error) {
if err != nil {
return nil, "", err
}
if err = saneTerminal(master); err != nil {
return nil, "", err
}
console, err := ptsname(master)
if err != nil {
return nil, "", err
@ -32,6 +35,29 @@ func newConsole(uid, gid int) (*os.File, string, error) {
return master, console, nil
}
// saneTerminal sets the necessary tty_ioctl(4)s to ensure that a pty pair
// created by us acts normally. In particular, a not-very-well-known default of
// Linux unix98 ptys is that they have +onlcr by default. While this isn't a
// problem for terminal emulators, because we relay data from the terminal we
// also relay that funky line discipline.
func saneTerminal(terminal *os.File) error {
// Go doesn't have a wrapper for any of the termios ioctls.
var termios syscall.Termios
if err := ioctl(terminal.Fd(), syscall.TCGETS, uintptr(unsafe.Pointer(&termios))); err != nil {
return fmt.Errorf("ioctl(tty, tcgets): %s", err.Error())
}
// Set -onlcr so we don't have to deal with \r.
termios.Oflag &^= syscall.ONLCR
if err := ioctl(terminal.Fd(), syscall.TCSETS, uintptr(unsafe.Pointer(&termios))); err != nil {
return fmt.Errorf("ioctl(tty, tcsets): %s", err.Error())
}
return nil
}
func ioctl(fd uintptr, flag, data uintptr) error {
if _, _, err := syscall.Syscall(syscall.SYS_IOCTL, fd, flag, data); err != 0 {
return err