netdev - Re: xt_recent broken in kernel 3.19.0 + PATCH

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Date:	Thu, 12 Feb 2015 10:54:17 +0000
From:	Chris Vine <chris@...ne.freeserve.co.uk>
To:	Florian Westphal <fw@...len.de>
Cc:	Cong Wang <xiyou.wangcong@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	netfilter-devel@...r.kernel.org,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: xt_recent broken in kernel 3.19.0 + PATCH

On Thu, 12 Feb 2015 10:26:16 +0000
Chris Vine <chris@...ne.freeserve.co.uk> wrote:
> On Thu, 12 Feb 2015 09:35:33 +0100
> Florian Westphal <fw@...len.de> wrote:
> > Cong Wang <xiyou.wangcong@...il.com> wrote:
> > > (Cc'ing netdev and netfilter-devel lists)
> > 
> > Thanks for forwarding.
> > 
> > > > Chris Vine <chris@...ne.freeserve.co.uk> wrote:
> > > >>   iptables -D SSH_CHAIN -m conntrack --ctstate NEW \
> > > >>     -m recent --update --seconds $SSH_LOGIN_PERIOD --hitcount
> > > >> $SSH_TRIES -j DROP
> > > > --- linux-3.19.0/net/netfilter/xt_recent.c~     2015-02-10
> > > > 09:18:44.657376355 +0000 +++
> > > > linux-3.19.0/net/netfilter/xt_recent.c      2015-02-11
> > > > 17:58:33.311608835 +0000 @@ -378,7 +378,7 @@
> > > > mutex_lock(&recent_mutex); t = recent_table_lookup(recent_net,
> > > > info->name); if (t != NULL) {
> > > > -               if (info->hit_count > t->nstamps_max_mask) {
> > > > +               if (info->hit_count > t->nstamps_max_mask + 1) {
> > 
> > Looks good. Chris, could you formally submit this patch to
> > netfilter-devel@...r.kernel.org?
> > 
> > Thanks!
> 
> Done.

On further testing I see that that patch only solves the problem if
SSH_TRIES is set to a power of two boundary.  You still get an error
loading the rule if it is anything else.  I think there is something
wrong with the nstamp_mask heuristic which is used here.

Chris
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