From: Florian Westphal <fw@strlen.de>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Florian Westphal <fw@strlen.de>, netfilter-devel@vger.kernel.org
Subject: Re: [PATCH nf-next 2/6] netfilter: conntrack: get rid of conntrack timer
Date: Mon, 22 Aug 2016 10:53:13 +0200 [thread overview]
Message-ID: <20160822085313.GA6199@breakpoint.cc> (raw)
In-Reply-To: <1471839211.14381.4.camel@edumazet-glaptop3.roam.corp.google.com>
Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Fri, 2016-08-19 at 18:04 +0200, Florian Westphal wrote:
> > Eric Dumazet <eric.dumazet@gmail.com> wrote:
> > > On Fri, 2016-08-19 at 17:16 +0200, Florian Westphal wrote:
> > >
> > > > Hmm, ____nf_conntrack_find caller needs to hold rcu_read_lock,
> > > > in case object is free'd SLAB_DESTROY_BY_RCU should delay actual release
> > > > of the page.
> > >
> > > Well, point is that SLAB_DESTROY_BY_RCU means that we have no grace
> > > period, and object can be immediately reused and recycled.
> > >
> > > @next pointer can definitely be overwritten.
> >
> > I see. Isn't that detected by the nulls magic (to restart
> > lookup if entry was moved to other chain due to overwritten next pointer)?
>
> Well, you did not add the nulls magic in your code ;)
Oh. Right, its indeed mising in the gc code.
> It might be fine, since it should be a rare event, and garbage
> collection is best effort, so you might add a comment in gc_worker() why
> it is probably overkill to restart the loop in this unlikely event.
Seems like a good idea, I will add it.
> BTW, maybe nf_conntrack_tuple_taken() should get the nulls magic check,
> as it is currently missing.
Good point, I will investigate.
Thanks Eric!
next prev parent reply other threads:[~2016-08-22 8:53 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-19 11:36 [PATCH nf-next 0/6] conntrack: get rid of per-object timer Florian Westphal
2016-08-19 11:36 ` [PATCH nf-next 1/6] netfilter: don't rely on DYING bit to detect when destroy event was sent Florian Westphal
2016-08-19 11:36 ` [PATCH nf-next 2/6] netfilter: conntrack: get rid of conntrack timer Florian Westphal
2016-08-19 14:37 ` Eric Dumazet
2016-08-19 15:16 ` Florian Westphal
2016-08-19 15:24 ` Eric Dumazet
2016-08-19 16:04 ` Florian Westphal
2016-08-22 4:13 ` Eric Dumazet
2016-08-22 8:53 ` Florian Westphal [this message]
2016-08-19 11:36 ` [PATCH nf-next 3/6] netfilter: evict stale entries on netlink dumps Florian Westphal
2016-08-19 11:36 ` [PATCH nf-next 4/6] netfilter: conntrack: add gc worker to remove timed-out entries Florian Westphal
2016-08-19 14:41 ` Eric Dumazet
2016-08-19 15:22 ` Florian Westphal
2016-08-19 11:36 ` [PATCH nf-next 5/6] netfilter: conntrack: resched gc again if eviction rate is high Florian Westphal
2016-08-19 11:36 ` [PATCH nf-next 6/6] netfilter: remove __nf_ct_kill_acct helper Florian Westphal
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