From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Ansis Atteka <aatteka@nicira.com>
Cc: netfilter-devel@vger.kernel.org
Subject: Re: [PATCH] conntrackd: claim lockfile ownership properly
Date: Tue, 25 Mar 2014 22:05:28 +0100 [thread overview]
Message-ID: <20140325210528.GA3780@localhost> (raw)
In-Reply-To: <20140325205831.GA3681@localhost>
On Tue, Mar 25, 2014 at 09:58:31PM +0100, Pablo Neira Ayuso wrote:
> On Tue, Mar 11, 2014 at 06:31:13PM -0700, Ansis Atteka wrote:
> > Before this patch, if conntrackd died in an abrupt manner (either
> > by SIGKILL, SIGSEGV or abrupt shutdown), then it would have left
> > a stale lock file that would have prevented any new conntrackd
> > instances from running.
>
> SIGKILL and SIGSEGV need a closer look from the admin, since things
> are not going right. Sudden (abrupt) shutdown is indeed a problem.
>
> > Contrary to abrupt termination, this same bug was not present when
> > conntrackd was terminated with a graceful signal (e.g. SIGTERM).
> > This was because then the lock file would have been removed from
> > the signal handler as expected.
> >
> > This patch fixes this bug by using POSIX File Locking API instead
> > of opening file in O_EXCL mode. File Locking API ensures that file
> > lock will be released once the process holding it terminates (either
> > gracefully or abruptly).
> >
> > One side effect of this patch is that daemonization has to happen
> > before the lock file is locked (due to the fact that child processes
> > do not inherit file locks from the parent process). This means that
> > some error messages have to be logged in log file instead of STDOUT.
>
> Can you rework this to avoid converting all those message from stdout
> to the log file? I like that this daemon bails out to stdout if early
> problems are found, I find it quite annoying when you launch things
> and then you have to check ps and log file to see the reason for an
> early configuration problem. And I don't find a good reason why we
> need an early daemonization that this patch introduces.
Now I noticed after reading my own words, this can be problematic if
someone just types 'conntrackd' by mistake instead of 'conntrackd -e'
to dump the external cache.
What about using two locks? I mean, one that is grabbed when the
process is in non-daemon stage, then another one once one it enters
daemon stage. I think that should help to workaround the posix file
locking limitation which doesn't allow us to inherit lock file?
prev parent reply other threads:[~2014-03-25 21:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-12 1:31 [PATCH] conntrackd: claim lockfile ownership properly Ansis Atteka
2014-03-24 17:37 ` Ansis Atteka
2014-03-25 20:58 ` Pablo Neira Ayuso
2014-03-25 21:05 ` Pablo Neira Ayuso [this message]
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