I changed login_tty() to only work when the application is not a session
leader yet. This works fine for applications in the base system, but it
turns out various applications call this function after daemonizing,
which means they already use their own session.
If setsid() fails, just call tcsetsid() on the current session.
tcsetsid() will already perform proper security checks.
Reported by: Oliver Lehmann
MFC after: 1 week
The entire world seems to use the non-standard TIOCSCTTY ioctl to make a
TTY a controlling terminal of a session. Even though tcsetsid(3) is also
non-standard, I think it's a lot better to use in our own source code,
mainly because it's similar to tcsetpgrp(), tcgetpgrp() and tcgetsid().
I stole the idea from QNX. They do it the other way around; their
TIOCSCTTY is just a wrapper around tcsetsid(). tcsetsid() then calls
into an IPC framework.
Install (optional) libutil.h with prototypes for the functions and
document this in the man page.
minor cleanups to the various routines, include the prototype file, declare
return codes etc.
