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<title>Re: OpenSSH 3.6.1p1 on NCR MP-RAS v4.3, several weird terminal problems</title>
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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Hi Darren –</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Cc: list –</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>There's not much that I can tell you about
NCR MP-RAS, other than that it is a SysV r4.3 derivative, and the hardest UNIX
to port to that I've encountered since my Xenix 286 days.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Here is an excerpt from the setsid()
manual page:</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> WARNING</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
If the calling process is the last member of a
pipeline</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
started by a job control shell, the shell
may make the</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
calling process a process group leader. The other processes</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
of the pipeline become members of that process group.
In</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
this case, the call to setsid will fail. For this reason, a</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
process that calls setsid and expects
to be part of a</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
pipeline should always first fork; the parent should exit</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
and the child should call setsid, thereby insuring that the</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
process will work reliably when started by both job control</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
shells and non-job control shells.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I noticed in sshpty.c that the call to setsid()
follows a section which will call ioctl(fd, TIOCNOTTY, NULL) #ifdef TIOCNOTTY.
Looking in /usr/include/sys/*.h I find that termios.h and ttold.h #define
TIOCNOTTY.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>termios.h will only #define TIOCNOTTY if all
three of _<i><span style='font-style:italic'>SYS_TTOLD</span></i>_H, _<i><span
style='font-style:italic'>POSIX</span></i>_SOURCE, and _<i><span
style='font-style:italic'>XOPEN</span></i>_SOURCE are not defined.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>ttold.h will only #define TIOCNOTTY if _<i><span
style='font-style:italic'>SYS_TERMIOS</span></i>_H is not defined.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I do see termios.h included in the compile
on this platform. I do not see ttold.h included. Therefore, I assume that the
section in sshpty.c which would call ioctl() with TIOCNOTTY is NOT being executed.
I did a test by commenting out the #ifdef TIOCNOTTY to ensure that the ioctl()
call does happen, and took out the #define STREAMS_PUSH_ACQUIRES_CTTY. It did
not fix the problem, so calling or not calling the ioctl() with TIOCNOTTY
doesn't affect this problem. (Just casting about here).</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Regarding O_NOCTTY, the man page for open()
describes O_NOCTTY as:</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
O_NOCTTY If set and the
file is a terminal, the</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
terminal will not be allocated as the calling</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>
process's controlling terminal.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>If you have any specific questions
regarding the platform, I'm happy to dig in manual pages, run tests, and report
back.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>-Jay</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=2 face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma'>-----Original Message-----<br>
<b><span style='font-weight:bold'>From:</span></b> Darren Tucker
[mailto:dtucker@zip.com.au] <br>
<b><span style='font-weight:bold'>Sent:</span></b> Wednesday, April 09, 2003
20:18<br>
<b><span style='font-weight:bold'>To:</span></b> Jay Libove<br>
<b><span style='font-weight:bold'>Cc:</span></b> openssh-unix-dev@mindrot.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: OpenSSH 3.6.1p1 on
NCR MP-RAS v4.3, several weird terminal problems</span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font></p>
<p style='margin-left:.5in'><font size=2 face="Times New Roman"><span
style='font-size:10.0pt'>Jay Libove wrote:</span></font> <br>
<font size=2><span style='font-size:10.0pt'>> I tried the suggested config.h
modification of</span></font> <br>
<font size=2><span style='font-size:10.0pt'>> </span></font><br>
<font size=2><span style='font-size:10.0pt'>> #define
STREAMS_PUSH_ACQUIRES_CTTY 1</span></font> <br>
<font size=2><span style='font-size:10.0pt'>> </span></font><br>
<font size=2><span style='font-size:10.0pt'>> .. and it seems to have
fixed all of the problems that I reported below</span></font> <br>
<font size=2><span style='font-size:10.0pt'>> (^C killing the session,
logging out not fully closing the connection,</span></font> <br>
<font size=2><span style='font-size:10.0pt'>> lack of job control, and
command line pipes being broken).</span></font> </p>
<p style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font><font
size=2><span style='font-size:10.0pt'>This means that MP-RAS somehow
re-acquires a controlling terminal after</span></font> <br>
<font size=2><span style='font-size:10.0pt'>forking and calling setsid() the
first time. In the Solaris case, a bug</span></font> <br>
<font size=2><span style='font-size:10.0pt'>in the pty driver caused it to
happen when pushing a STREAMS module</span></font> <br>
<font size=2><span style='font-size:10.0pt'>(hence the #define name).
Linux/glibc5 has the same symptoms but it</span></font> <br>
<font size=2><span style='font-size:10.0pt'>doesn't have STREAMS so it must be
acquiring it some other way (not</span></font> <br>
<font size=2><span style='font-size:10.0pt'>honouring O_NOCTTY maybe?)</span></font>
</p>
<p style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font><font
size=2><span style='font-size:10.0pt'>What can you tell us about MP-RAS?
Is it a SysV derivative?</span></font> </p>
<p style='margin-left:.5in'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'> </span></font><font
size=2><span style='font-size:10.0pt'>Should we just change the define to
HAVE_BROKEN_O_NOCTTY. We could</span></font> <br>
<font size=2><span style='font-size:10.0pt'>have configure do a run-tine test
for it but it'd need a lot of the code</span></font> <br>
<font size=2><span style='font-size:10.0pt'>from pty_allocate().</span></font> </p>
<p style='margin-left:.5in'><font size=2 face="Times New Roman"><span
style='font-size:10.0pt'>-- </span></font><br>
<font size=2><span style='font-size:10.0pt'>Darren Tucker (dtucker at
zip.com.au)</span></font> <br>
<font size=2><span style='font-size:10.0pt'>GPG key 8FF4FA69 / D9A3 86E9 7EEE
AF4B B2D4 37C9 C982 80C7 8FF4 FA69</span></font> <br>
<font size=2><span style='font-size:10.0pt'> Good judgement
comes with experience. Unfortunately, the experience</span></font> <br>
<font size=2><span style='font-size:10.0pt'>usually comes from bad judgement.</span></font>
</p>
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