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

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Date:   Tue, 15 Mar 2022 21:05:53 +0100
From:   Phil Sutter <phil@....cc>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Pablo Neira Ayuso <pablo@...filter.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

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?

Thanks, Phil