From: Patrick McHardy <kaber@trash.net>
To: Changli Gao <xiaosuo@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <eric.dumazet@gmail.com>,
Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>,
akpm@linux-foundation.org, netfilter-devel@vger.kernel.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 2/2] netfilter: save the hash of the tuple in the original direction for latter use
Date: Mon, 20 Sep 2010 19:08:37 +0200 [thread overview]
Message-ID: <4C979515.4060908@trash.net> (raw)
In-Reply-To: <AANLkTikZeFrS9pj6jxmOxqY6dsaAf1U+FAXe5jNwQ-nV@mail.gmail.com>
On 20.09.2010 17:04, Changli Gao wrote:
> On Thu, Sep 16, 2010 at 2:18 PM, Patrick McHardy <kaber@trash.net> wrote:
>> On 21.08.2010 00:49, Changli Gao wrote:
>>> Since we don't change the tuple in the original direction, we can save it
>>> in ct->tuplehash[IP_CT_DIR_REPLY].hnode.pprev for __nf_conntrack_confirm()
>>> use.
>>
>> I like this idea. We could actually do the same for the reply tuple
>> and invalidate the saved hash in case the reply tuple is changed
>> (nf_conntrack_alter_reply()), which only happens when NAT is used.
>>
>
> We can't do that, as the unconfirmed ct owned maybe dropped, and
> pre-computing will wast CPU cycles in this case.
Sure we can, dropping unconfirmed conntracks is a rare exception,
not a common case. Even under DoS we usually drop *unassured*
conntracks, which have already enterered the hash. If we're unable
to do that, we won't even allocate a new conntrack.
next prev parent reply other threads:[~2010-09-20 17:08 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-20 22:49 [PATCH v5 2/2] netfilter: save the hash of the tuple in the original direction for latter use Changli Gao
2010-09-16 6:18 ` Patrick McHardy
2010-09-20 15:04 ` Changli Gao
2010-09-20 17:08 ` Patrick McHardy [this message]
2010-09-21 0:02 ` Changli Gao
2010-09-21 15:32 ` Patrick McHardy
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