Subject: Re: [PATCH 01/17] netfilter: add struct nf_proto_net for register l4proto sysctl

From: Gao feng <[email-masked]>
Date: Fri, 25 May 2012 09:05:34 +0800

于 2012年05月24日 22:38, Pablo Neira Ayuso 写道:
> On Thu, May 24, 2012 at 06:54:42PM +0800, Gao feng wrote:
> [...]
>>>>> I don't see why we need this new field.
>>>>>
>>>>> It seems to be set to 1 in each structure that has set:
>>>>>
>>>>> .ctl_compat_table
>>>>>
>>>>> to non-NULL. So, it's redundant.
>>>>>
>>>>> Moreover, you already know from the protocol tracker itself if you
>>>>> have to allocate the compat ctl table or not.
>>>>>
>>>>> In other words: You set compat to 1 for nf_conntrack_l4proto_generic.
>>>>> Then, you pass that compat value to generic_init_net via ->inet_net
>>>>> again, but this information (that determines if the compat has to be
>>>>> done or not) is already in the scope of the protocol tracker.
>>>>>
>>>>
>>>> because some protocols such l4proto_tcp6 and l4proto_tcp use the same init_net
>>>> function. the l4proto_tcp6 doesn't need compat sysctl, so we should use this new
>>>> field to identify if we should kmemdup compat_sysctl_table.
>>>
>>> Then, could you use two init_net functions? one for TCP for IPv4 and another
>>> for TCP for IPv6?
>>
>> Of cause, if you prefer to impletment it in this way.
> 
> If this removes the .compat field that you added, then use two
> init_net functions, yes.

Sorry I miss something.

nf_ct_l4proto_unregister_sysctl also uses .compat to identify if we
can unregister the compat sysctl.

if we register l4proto_tcp and l4proto_tcp6 both. without .compat,
when unregister l4proto_tcp6, the compat sysctl will be unregister too.

So maybe we have to use .compat.
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