netdev - Re: [PATCH] tun: Persistent devices can get stuck in xoff state

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <48752B60.4050106@qualcomm.com>
Date:	Wed, 09 Jul 2008 14:19:28 -0700
From:	Max Krasnyansky <maxk@...lcomm.com>
To:	Christian Borntraeger <borntraeger@...ibm.com>
CC:	davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH] tun: Persistent devices can get stuck in xoff state

Christian Borntraeger wrote:
> Am Mittwoch, 9. Juli 2008 schrieb Max Krasnyansky:
>> The scenario goes like this. App stops reading from tun/tap.
>> TX queue gets full and driver does netif_stop_queue().
>> App closes fd and TX queue gets flushed as part of the cleanup.
>> Next time the app opens tun/tap and starts reading from it but
>> the xoff state is not cleared. We're stuck.
>> Normally xoff state is cleared when netdev is brought up. But
>> in the case of persistent devices this happens only during
>> initial setup.
> 
> I was able to reproduce the problem. The patch seems to fix it.
> 
> Tested-by: Christian Borntraeger <borntraeger@...ibm.com>

Oh it definitely fixes that problem. It's very easy to reproduce by just 
suspending (ctrl-z) an app that is ready from the tun, waiting a bit for 
the queue to fill up and then killing the app. I have a simple test app 
that simulates this. It's just that in real life that does not happen 
very often. ie Applications either constantly read from tun or they 
close it.

Thanks a lot for testing and confirming.

Max
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html