linux-kernel - Re: [PATCH v5 2/2] netfilter: save the hash of the tuple in the original direction for latter use

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Date:	Mon, 20 Sep 2010 23:04:33 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	akpm@...ux-foundation.org, netfilter-devel@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/2] netfilter: save the hash of the tuple in the
 original direction for latter use

On Thu, Sep 16, 2010 at 2:18 PM, Patrick McHardy <kaber@...sh.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.

>> __hash_conntrack() is split into two steps: ____hash_conntrack() is used
>> to get the raw hash, and __hash_bucket() is used to get the bucket id.
>
> This patch uses underscores a bit excessively, how about renaming:
>
> - ____hash_conntrack() => hash_conntrack_raw()
> - __hash variables => hash
> - hash variables => bucket

OK. Thanks.

>
>> @@ -408,7 +438,8 @@ __nf_conntrack_confirm(struct sk_buff *skb)
>>               return NF_ACCEPT;
>>
>>       zone = nf_ct_zone(ct);
>> -     hash = hash_conntrack(net, zone, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
>> +     /* reuse the __hash saved before */
>> +     hash = hash_bucket(*(unsigned long *)&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev, net);
>
> Please try to stay at least close to the 80 characters limit.
>

OK. Thanks.

-- 
Regards,
Changli Gao(xiaosuo@...il.com)
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