netdev - Re: [PATCH net-next 1/3] netfilter: nf_defrag_ipv4: Add nf_ct_frag

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Date:   Mon, 6 Jul 2020 18:29:15 +0200
From:   Florian Westphal <fw@...len.de>
To:     wenxu <wenxu@...oud.cn>
Cc:     Florian Westphal <fw@...len.de>, davem@...emloft.net,
        pablo@...filter.org, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org
Subject: Re: [PATCH net-next 1/3] netfilter: nf_defrag_ipv4: Add
 nf_ct_frag_gather support

wenxu <wenxu@...oud.cn> wrote:
> 
> 在 2020/7/6 22:38, Florian Westphal 写道:
> > wenxu@...oud.cn <wenxu@...oud.cn> wrote:
> >> From: wenxu <wenxu@...oud.cn>
> >>
> >> Add nf_ct_frag_gather for conntrack defrag and it will
> >> elide the CB clear when packets are defragmented by
> >> connection tracking
> > Why is this patch required?
> > Can't you rework ip_defrag to avoid the cb clear if you need that?
> 
> The ip_defrag used by ip stack and can work with the cb setting.

Yes, but does it have to?

If yes, why does nf_ct_frag not need it whereas ip_defrag has to?

> Defragment case only for conntrack maybe need to avoid the cb
> 
> clear. So it is more clear to nf_ct_frag_gather for conntrack like the
> 
> function nf_ct_frag6_gather for ipv6.

nf_ct_frag6_gather() is only re-using less code from ipv6 for historical
reasons.  If anything, ipv6 conntrack defrag should re-use more code from
ipv6 defrag, rather than making ipv4 conntrack defrag look more like
ipv6 conntrack defrag.