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

From: Pablo Neira Ayuso <[email-masked]>
Date: Fri, 25 May 2012 04:54:51 +0200

On Fri, May 25, 2012 at 09:05:34AM +0800, Gao feng wrote:
> 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.

Could you resolve this by checking pn->ctl_compat_header != NULL ?
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