netdev - Re: [PATCH nf-next 2/6] netfilter: nf_tables: Reject tables of unsupported family

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Date:   Tue, 15 Mar 2022 21:10:33 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Phil Sutter <phil@....cc>, Jakub Kicinski <kuba@...nel.org>,
        netfilter-devel@...r.kernel.org, davem@...emloft.net,
        netdev@...r.kernel.org
Subject: Re: [PATCH nf-next 2/6] netfilter: nf_tables: Reject tables of
 unsupported family

On Tue, Mar 15, 2022 at 09:05:53PM +0100, Phil Sutter wrote:
> Hi Jakub,
> 
> On Tue, Mar 15, 2022 at 11:56:44AM -0700, Jakub Kicinski wrote:
> > On Tue, 15 Mar 2022 10:15:09 +0100 Pablo Neira Ayuso wrote:
> > > +	return false
> > > +#ifdef CONFIG_NF_TABLES_INET
> > > +		|| family == NFPROTO_INET
> > > +#endif
> > > +#ifdef CONFIG_NF_TABLES_IPV4
> > > +		|| family == NFPROTO_IPV4
> > > +#endif
> > > +#ifdef CONFIG_NF_TABLES_ARP
> > > +		|| family == NFPROTO_ARP
> > > +#endif
> > > +#ifdef CONFIG_NF_TABLES_NETDEV
> > > +		|| family == NFPROTO_NETDEV
> > > +#endif
> > > +#if IS_ENABLED(CONFIG_NF_TABLES_BRIDGE)
> > 
> > is there a reason this one is IS_ENABLED() and everything else is ifdef?
> 
> I based my patch on the existing ifdefs in nft_chain_filter.c where
> these config symbols are checked exactly like above. Looking at git
> history, the check was changed from a simple ifdef in commit
> dfee0e99bcff7 ("netfilter: bridge: make NF_TABLES_BRIDGE tristate").
> 
> > > +		|| family == NFPROTO_BRIDGE
> > > +#endif
> > > +#ifdef CONFIG_NF_TABLES_IPV6
> > > +		|| family == NFPROTO_IPV6
> > > +#endif
> > > +		;
> > 
> > 	return (IS_ENABLED(CONFIG_NF_TABLES_INET) && family == NFPROTO_INET)) ||
> > 	       (IS_ENABLED(CONFIG_NF_TABLES_IPV4) && family == NFPROTO_IPV4)) ||
> > 		...
> > 
> > would have also been an option, for future reference.
> 
> Yes, that is indeed much cleaner. I wasn't aware of this possibility
> using IS_ENABLED. What do you think, worth a follow-up?

CONFIG_NF_TABLES_INET and CONFIG_NF_TABLES_IPV4 are never modules, I
think IS_ENABLED is misleading there to the reader.