tty: move IO of master pty to be done with epoll

This moves all console code to use github.com/containerd/console library to
handle console I/O. Also move to use EpollConsole by default when user requests
a terminal so we can still cope when the other side temporarily goes away.

Signed-off-by: Daniel Dao <dqminh89@gmail.com>

vendor/github.com/containerd/console/tc_linux.go

@@ -0,0 +1,67 @@
+package console
+
+import (
+	"fmt"
+	"os"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+func tcget(fd uintptr, p *unix.Termios) error {
+	termios, err := unix.IoctlGetTermios(int(fd), unix.TCGETS)
+	if err != nil {
+		return err
+	}
+	*p = *termios
+	return nil
+}
+
+func tcset(fd uintptr, p *unix.Termios) error {
+	return unix.IoctlSetTermios(int(fd), unix.TCSETS, p)
+}
+
+func ioctl(fd, flag, data uintptr) error {
+	if _, _, err := unix.Syscall(unix.SYS_IOCTL, fd, flag, data); err != 0 {
+		return err
+	}
+	return nil
+}
+
+// unlockpt unlocks the slave pseudoterminal device corresponding to the master pseudoterminal referred to by f.
+// unlockpt should be called before opening the slave side of a pty.
+func unlockpt(f *os.File) error {
+	var u int32
+	return ioctl(f.Fd(), unix.TIOCSPTLCK, uintptr(unsafe.Pointer(&u)))
+}
+
+// ptsname retrieves the name of the first available pts for the given master.
+func ptsname(f *os.File) (string, error) {
+	n, err := unix.IoctlGetInt(int(f.Fd()), unix.TIOCGPTN)
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("/dev/pts/%d", n), nil
+}
+
+func saneTerminal(f *os.File) error {
+	var termios unix.Termios
+	if err := tcget(f.Fd(), &termios); err != nil {
+		return err
+	}
+	// Set -onlcr so we don't have to deal with \r.
+	termios.Oflag &^= unix.ONLCR
+	return tcset(f.Fd(), &termios)
+}
+
+func cfmakeraw(t unix.Termios) unix.Termios {
+	t.Iflag = t.Iflag & ^uint32((unix.IGNBRK | unix.BRKINT | unix.PARMRK | unix.ISTRIP | unix.INLCR | unix.IGNCR | unix.ICRNL | unix.IXON))
+	t.Oflag = t.Oflag & ^uint32(unix.OPOST)
+	t.Lflag = t.Lflag & ^(uint32(unix.ECHO | unix.ECHONL | unix.ICANON | unix.ISIG | unix.IEXTEN))
+	t.Cflag = t.Cflag & ^(uint32(unix.CSIZE | unix.PARENB))
+	t.Cflag = t.Cflag | unix.CS8
+	t.Cc[unix.VMIN] = 1
+	t.Cc[unix.VTIME] = 0
+
+	return t
+}