openssh unix dev - Dec 2000 - OpenSSH 2.3.0p1: Broken pipe / SIGPIPE

Dear OpenSSH gurus! ;-)

I recently upgraded from "OpenSSH 2.1.1p4" to "OpenSSH
2.3.0p1"
on my Linux 2.2.17 box with OpenSSL 0.9.5a (RedHat 7.0).

According to the "ChangeLog", there was a change in SIGPIPE
handling:

 | 20000930
 |  [...]
 |  - (djm) Ignore SIGPIPEs from serverloop to child. Fixes crashes with
 |    very short lived X connections. Bug report from Tobias Oetiker 
 |    <oetiker at ee.ethz.ch>. Fix from Markus Friedl <markus at
cvs.openbsd.org>

I don't know what it fixes for X, but it breaks pipe handling in
some other ways.

While "yes | head -1" worked okay with OpenSSH 2.1.1p4, it hangs
with tcsh 6.10.00 and OpenSSH 2.3.0p1 due to the ignored SIGPIPE
in the serverloop. With bash 2.04.11 and OpenSSH 2.3.0p1,
"yes | head -1" says "Broken pipe".

It works okay with OpenSSH 2.3.0p1 if I disable the two signal()
calls (in serverloop.c) that ignore SIGPIPE.

Another example is to call something like "grep foobar file | less"
on a file with thousands of occurences of "foobar". After
"less"
has displayed the first page, if I then hit "q" (for quit), I get
thousands of lines saying:

	grep: writing output: Broken pipe

With OpenSSH 2.1.1p4, everything was fine.

Well, I don't say, that OpenSSH is broken... although the bad behaviour
obviously came from a change to OpenSSH (see ChangeLog). But even if
it's not OpenSSH's fault, maybe you have an idea what's wrong with
the
other applications like tcsh, bash, head, less etc.

Any help is welcome! ;-)

	Greetings, Andreas

I believe this is normal behavior. Try it without using SSH, and it will
happen.

Basically it happens if the command on the right hand side of the pipe
exits (normally or abnormally) before the command on the left of the
pipe finishes writing its output. The fd will be closed and thus the
process on the left will get a SIGPIPE (or pipe write error if its
masked out).

-rchit
> "yes | head -1" says "Broken pipe".
> Another example is to call something like "grep foobar file |
less"
> on a file with thousands of occurences of "foobar". After
"less"
> has displayed the first page, if I then hit "q" (for quit), I get
> thousands of lines saying:
> 
>         grep: writing output: Broken pipe
>