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

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Message-ID: <627088b3-7134-2b9a-8be4-7c96d51a3b94@6wind.com>
Date:   Thu, 2 May 2019 14:56:42 +0200
From:   Nicolas Dichtel <nicolas.dichtel@...nd.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>,
        Florian Westphal <fw@...len.de>
Cc:     Kristian Evensen <kristian.evensen@...il.com>,
        Netfilter Development Mailing list 
        <netfilter-devel@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH 07/31] netfilter: ctnetlink: Support L3 protocol-filter on
 flush

Le 02/05/2019 à 13:31, Pablo Neira Ayuso a écrit :
> On Thu, May 02, 2019 at 09:46:42AM +0200, Florian Westphal wrote:
>> Nicolas Dichtel <nicolas.dichtel@...nd.com> wrote:
>>> I understand your point, but this is a regression. Ignoring a field/attribute of
>>> a netlink message is part of the uAPI. This field exists for more than a decade
>>> (probably two), so you cannot just use it because nobody was using it. Just see
>>> all discussions about strict validation of netlink messages.
>>> Moreover, the conntrack tool exists also for ages and is an official tool.
>>
>> FWIW I agree with Nicolas, we should restore old behaviour and flush
>> everything when AF_INET is given.  We can add new netlink attr to
>> restrict this.
> 
> Let's use nfgenmsg->version for this. This is so far set to zero. We
> can just update userspace to set it to 1, so family is used.
> 
> The version field in the kernel size is ignored so far, so this should
> be enough. So we avoid that extract netlink attribute.
Why making such a hack? If any userspace app set this field (simply because it's
not initialized), it will show up a new regression.
What is the problem of adding another attribute?