libcontainer/console_linux.go: Make SaneTerminal public

And use it only in local tooling that is forwarding the pseudoterminal
master.  That way runC no longer has an opinion on the onlcr setting
for folks who are creating a terminal and detaching.  They'll use
--console-socket and can setup the pseudoterminal however they like
without runC having an opinion.  With this commit, the only cases
where runC still has applies SaneTerminal is when *it* is the process
consuming the master descriptor.

Signed-off-by: W. Trevor King <wking@tremily.us>

contrib/cmd/recvtty/recvtty.go

@@ -24,6 +24,7 @@ import (
 	"os"
 	"strings"
 
+	"github.com/opencontainers/runc/libcontainer"
 	"github.com/opencontainers/runc/libcontainer/utils"
 	"github.com/urfave/cli"
 )
@@ -100,6 +101,9 @@ func handleSingle(path string) error {
 	if err != nil {
 		return err
 	}
+	if err = libcontainer.SaneTerminal(master); err != nil {
+		return err
+	}
 
 	// Copy from our stdio to the master fd.
 	quitChan := make(chan struct{})

libcontainer/console_linux.go

@@ -21,9 +21,6 @@ func newConsole() (Console, 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
@@ -133,12 +130,12 @@ func ptsname(f *os.File) (string, error) {
 	return fmt.Sprintf("/dev/pts/%d", n), nil
 }
 
-// saneTerminal sets the necessary tty_ioctl(4)s to ensure that a pty pair
+// 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 {
+func SaneTerminal(terminal *os.File) error {
 	// Go doesn't have a wrapper for any of the termios ioctls.
 	var termios unix.Termios
 

libcontainer/integration/execin_test.go

@@ -300,6 +300,7 @@ func TestExecInTTY(t *testing.T) {
 				err: err,
 			}
 		}
+		libcontainer.SaneTerminal(f)
 		dc <- &cdata{
 			c: libcontainer.ConsoleFromFile(f),
 		}

tty.go

@@ -74,6 +74,9 @@ func (t *tty) recvtty(process *libcontainer.Process, socket *os.File) error {
 	if err != nil {
 		return err
 	}
+	if err = libcontainer.SaneTerminal(f); err != nil {
+		return err
+	}
 	console := libcontainer.ConsoleFromFile(f)
 	go io.Copy(console, os.Stdin)
 	t.wg.Add(1)