netdev - Re: [PATCH 07/31] netfilter: ctnetlink: Support L3 protocol-filter on flush

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Message-ID: <fbafb8db-4a07-9836-5765-afd9ca683cb8@6wind.com>
Date:   Mon, 29 Apr 2019 17:39:44 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     netfilter-devel@...r.kernel.org,
        Kristian Evensen <kristian.evensen@...il.com>,
        davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH 07/31] netfilter: ctnetlink: Support L3 protocol-filter on
 flush

Le 29/04/2019 à 17:23, Pablo Neira Ayuso a écrit :
> On Mon, Apr 29, 2019 at 04:53:38PM +0200, Nicolas Dichtel wrote:
>> Le 26/04/2019 à 21:25, Pablo Neira Ayuso a écrit :
>>> On Thu, Apr 25, 2019 at 05:41:45PM +0200, Nicolas Dichtel wrote:
>>>> Le 25/04/2019 à 12:07, Nicolas Dichtel a écrit :
>>>> [snip]
>>>>> In fact, the conntrack tool set by default the family to AF_INET and forbid to
>>>>> set the family to something else (the '-f' option is not allowed for the command
>>>>> 'flush').
>>>>
>>>> 'conntrack -D -f ipv6' will do the job, but this is still a regression.
>>>
>>> You mean, before this patch, flush was ignoring the family, and after
>>> Kristian's patch, it forces you to use NFPROTO_UNSPEC to achieve the
>>> same thing, right?
>>>
>> Before the patch, flush was ignoring the family, and after the patch, the flush
>> takes care of the family.
>> The conntrack tool has always set the family to AF_INET by default, thus, since
>> this patch, only ipv4 conntracks are flushed with 'conntrack -F':
>> https://git.netfilter.org/conntrack-tools/tree/src/conntrack.c#n2565
>> https://git.netfilter.org/conntrack-tools/tree/src/conntrack.c#n2796
> 
> Thanks for explaining, what fix would you propose for this?
> 
The least bad fix I see is adding a new attribute, something like
CTA_FLUSH_FAMILY, to be used by the flush filter (and ignoring struct
nfgenmsg->nfgen_family in this flush filter).
The drawback is that it will break the (relatively new) users of this feature
(the patch has been pushed in v4.20).


Regards,
Nicolas