| Re: [chrony-dev] Feedback for libchrony API |
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- To: chrony-dev@xxxxxxxxxxxxxxxxxxxx
- Subject: Re: [chrony-dev] Feedback for libchrony API
- From: Miroslav Lichvar <mlichvar@xxxxxxxxxx>
- Date: Thu, 24 Aug 2023 14:33:41 +0200
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On Thu, Aug 24, 2023 at 01:00:02PM +0200, Reinhard Max wrote:
> On Thu, 24 Aug 2023 at 10:09, Miroslav Lichvar wrote:
>
> > Is there a portable way to detect when a Unix socket is no longer
> > referenced by anything?
>
> how about just trying to connect to the socket when the respective file
> exists? If the connection succeeds the socket is in use and if it fails with
> ECONNREFUSED it is unused and can be deleted and reused.
Ok, thanks.
On Linux it seems to be failing with EPERM when the socket is already
connected (as would be expected for libchrony applications).
If the process doesn't have write permissions to the socket, it seems
to be failing with EACCES no matter the socket is unused, only bound,
or also connected. Normally I think there will be only a limited
number of users with write access to /var/run/chrony, so I guess
that's not a problem. On Solaris/illumos the socket permissions are
ignored, so that might work better there.
The race condition due to the clients connecting after binding
doesn't seem to be a problem here.
Is it reasonable to expect this split between ECONNREFUSED and
success/EPERM/EACCESS will work on all POSIX systems?
--
Miroslav Lichvar
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