Re: [BProc] BProc & /dev/tty - anything to watch out?

[<ha...@no...>]

> In the mean time you could probably get away with adding a setgpid(0, getpid())
> in to openssh source where it opens the controlling tty, I suspect this will
> fix bash but won't do squat for TIOCSCTTY..
> 
> - Wilton

I recompiled sshd with this change (supposing you ment setpgid(), not
setgpid() ?):

openssh-3.1p1, sshpty.c:

  /* ADDED BY VACLAV HANZL */
  debug("Trying to avoid bproc problems with TIOCSCTTY by setpgid(0, getpid()).");
  if (setpgid(0, getpid()) < 0)
          error("setpgid(0, getpid()): %.100s", strerror(errno));
  /* END OF PART ADDED BY VACLAV HANZL */

  debug("Setting controlling tty using TIOCSCTTY.");
  if (ioctl(*ttyfd, TIOCSCTTY, NULL) < 0)
  	error("ioctl(TIOCSCTTY): %.100s", strerror(errno));

Unfortunately, setpgid() fails as well:

 n1 sshd[19998]: error: setpgid(0, getpid()): Operation not permitted 
 n1 sshd[19998]: error: ioctl(TIOCSCTTY): Operation not permitted 

However now I can easily add any debug prints to sshd. Suggestions for
things to test are welcome.


I guess TIOCSCTTY fails because kernel does not consider the process
to be a session leader:

in kernel, drivers/char/tty_io.c:

  case TIOCSCTTY:
    return tiocsctty(tty, arg);

  int tiocsctty(...)
    ...

  static int tiocsctty(struct tty_struct *tty, int arg)
  {
    if (current->leader &&
        (current->session == tty->session))
            return 0;
    /*
     * The process must be a session leader and
     * not have a controlling tty already.
     */
    if (!current->leader || current->tty)
                return -EPERM;


Any hints welcome, I continue my effort on this...

Best Regards

Vaclav


On Tue, 14 May 2002, ha...@no... wrote:

> Dear BProc users and gurus,
> 
> I am trying to setup occasional master->slave OpenSSH access (just for
> the convenience of environment, pty etc. during service work on slave
> node).
> 
> It works but it cannot use controlling tty. Server process complains:
> 
>  n1 sshd[19675]: error: ioctl(TIOCSCTTY): Operation not permitted 
>  n1 sshd[19675]: error: open /dev/tty failed - could not set controlling tty: No such device or address 
> 
> and client process complains:
> 
>  bash: initialize_job_control: setpgid: Operation not permitted
> 
> Then it works OK, just job control is missing. Server process is able
> to use /dev/ptmx to allocate /dev/pts/0, it opens /dev/tty but then it
> is unable to use it. This seemes strange to me.
> 
> At this moment I am not sure whether I should continue looking for
> missing files, kernel modules etc. on slave node (usual game when you
> insist on running some daemon :-) or delve into kernel sources and
> look for strange interactions of BProc and controlling tty.
> 
> 
> So, my only question is: Is it likely that controlling terminal things
> are a bit broken in BProc patched kernel?
> 
> Just give me some opinions to let me search in more likely
> directions...
> 
> Thanks
> 
> Vaclav Hanzl