From: Evgeniy Polyakov <zbr@ioremap•net>
To: "Paul E. McKenney" <paulmck@linux•vnet.ibm.com>
Cc: Patrick McHardy <kaber@trash•net>,
netdev@vger•kernel.org, David Miller <davem@davemloft•net>,
Netfilter Development Mailinglist
<netfilter-devel@vger•kernel.org>
Subject: Re: Passive OS fingerprint xtables match.
Date: Thu, 12 Feb 2009 20:51:30 +0300 [thread overview]
Message-ID: <20090212175130.GA16318@ioremap.net> (raw)
In-Reply-To: <20090212174253.GF6759@linux.vnet.ibm.com>
Hi.
On Thu, Feb 12, 2009 at 09:42:53AM -0800, Paul E. McKenney (paulmck@linux•vnet.ibm.com) wrote:
> > Passive OS fingerprint homepage (archives, examples):
> > http://www.ioremap.net/projects/osf
>
> I advocate using this to get more accurate censuses of machines
> accessing given web servers, given the tendency of browsers to lie
> about themselves in order to avoid being shut out of certain web sites.
>
> One question about the module-unload sequence below.
>
> Given a reasonable answer to that question, I am OK with this from
> an RCU viewpoint.
Thanks a lot Paul, but are they actually questions? You answered all of them :)
> > +static void __devexit ipt_osf_fini(void)
> > +{
> > + struct ipt_osf_finger *f;
> > + int i;
> > +
> > + cn_del_callback(&cn_osf_id);
> > + xt_unregister_match(&ipt_osf_match);
> > +
> > + rcu_read_lock();
> > + for (i=0; i<ARRAY_SIZE(ipt_osf_fingers); ++i) {
> > + struct ipt_osf_finger_storage *st = &ipt_osf_fingers[i];
> > +
> > + list_for_each_entry_rcu(f, &st->finger_list, finger_entry) {
> > + list_del_rcu(&f->finger_entry);
>
> For the above to be safe:
>
> o Any remaining RCU callbacks cannot reference the list
> (and your callbacks do in fact meet this constraint).
They do not access that list.
> o Any timers have to have fired or been cancelled (but you
> don't seem to have any timers, so not a problem).
No timers, tasklets, work queues or whatever else postponing the work.
> o All pathways to the data structure have to have been
> shut down. This is the tough one -- or is it simply
> a requirement that the guy removing the module has shut
> down all requests?
They can be accessed via connector configuration, but it is stopped
above (and it waits for currently active users to run away);
and netfilter path, which should be prevented after match was also
unregistered above.
--
Evgeniy Polyakov
next prev parent reply other threads:[~2009-02-12 17:51 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-12 17:12 Passive OS fingerprint xtables match Evgeniy Polyakov
2009-02-12 17:42 ` Paul E. McKenney
2009-02-12 17:51 ` Evgeniy Polyakov [this message]
2009-02-12 20:41 ` Paul E. McKenney
2009-02-18 14:55 ` Patrick McHardy
2009-02-12 18:22 ` Jan Engelhardt
2009-02-12 18:57 ` Evgeniy Polyakov
2009-02-12 20:12 ` Jan Engelhardt
2009-02-13 13:03 ` Evgeniy Polyakov
2009-02-13 13:51 ` Jan Engelhardt
2009-02-13 14:22 ` Evgeniy Polyakov
2009-02-13 14:41 ` Jan Engelhardt
2009-02-15 17:32 ` Evgeniy Polyakov
2009-02-18 15:02 ` Patrick McHardy
2009-02-18 15:07 ` Evgeniy Polyakov
2009-02-18 15:30 ` Jan Engelhardt
2009-02-19 11:56 ` Evgeniy Polyakov
2009-02-18 15:00 ` Patrick McHardy
2009-02-18 15:28 ` Jan Engelhardt
2009-02-12 18:26 ` Passive OS fingerprint xtables match (iptables part) Jan Engelhardt
2009-02-12 19:18 ` Evgeniy Polyakov
2009-02-12 20:19 ` Jan Engelhardt
2009-02-13 12:48 ` Evgeniy Polyakov
2009-02-13 12:52 ` Evgeniy Polyakov
2009-02-13 13:03 ` Jan Engelhardt
2009-02-13 13:12 ` Evgeniy Polyakov
2009-02-13 13:54 ` Jan Engelhardt
2009-02-15 17:35 ` Evgeniy Polyakov
2009-02-18 15:14 ` Passive OS fingerprint xtables match Patrick McHardy
-- strict thread matches above, loose matches on Subject: below --
2009-06-07 15:17 Evgeniy Polyakov
2009-06-08 15:06 ` Patrick McHardy
2009-06-08 17:25 ` Evgeniy Polyakov
2009-06-04 16:22 Evgeniy Polyakov
2009-06-05 11:54 ` Patrick McHardy
2009-06-05 13:10 ` Jan Engelhardt
2009-06-05 13:30 ` Patrick McHardy
2009-06-05 13:44 ` Jan Engelhardt
2009-06-07 15:12 ` Evgeniy Polyakov
2009-03-26 14:14 Evgeniy Polyakov
2009-03-26 14:18 ` Patrick McHardy
2009-03-26 14:59 ` Evgeniy Polyakov
2009-03-26 15:08 ` Patrick McHardy
2009-03-26 15:41 ` Evgeniy Polyakov
2009-03-26 15:47 ` Patrick McHardy
2009-03-30 6:20 ` Evgeniy Polyakov
2009-05-01 20:15 ` Evgeniy Polyakov
2009-03-10 15:13 Evgeniy Polyakov
2009-03-10 16:01 ` Evgeniy Polyakov
2009-03-10 16:07 ` Jan Engelhardt
2009-03-11 21:43 ` Evgeniy Polyakov
2009-03-10 21:01 ` Jesper Dangaard Brouer
2009-03-10 21:54 ` Evgeniy Polyakov
2009-03-16 14:40 ` Patrick McHardy
2009-03-11 9:54 ` Pablo Neira Ayuso
2009-03-11 10:00 ` Evgeniy Polyakov
2009-03-16 14:42 ` Patrick McHardy
2009-01-29 17:20 Evgeniy Polyakov
2009-01-30 1:05 ` Paul E. McKenney
2009-02-09 16:09 ` Patrick McHardy
2009-02-13 12:49 ` Evgeniy Polyakov
2009-01-27 22:55 Evgeniy Polyakov
2009-01-29 3:36 ` Paul E. McKenney
2009-01-29 15:03 ` Evgeniy Polyakov
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