netdev - Re: [PATCH] ipv4: use IS_ENABLED instead of ifdef

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Message-ID: <20201117170712.0e5a8b23@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net>
Date:   Tue, 17 Nov 2020 17:07:12 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     David Ahern <dsahern@...il.com>
Cc:     Florian Klink <flokli@...kli.de>, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Kim Phillips <kim.phillips@....com>
Subject: Re: [PATCH] ipv4: use IS_ENABLED instead of ifdef

On Tue, 17 Nov 2020 17:55:54 -0700 David Ahern wrote:
> On 11/17/20 5:01 PM, Jakub Kicinski wrote:
> > On Sun, 15 Nov 2020 23:45:09 +0100 Florian Klink wrote:  
> >> Checking for ifdef CONFIG_x fails if CONFIG_x=m.
> >>
> >> Use IS_ENABLED instead, which is true for both built-ins and modules.
> >>
> >> Otherwise, a  
> >>> ip -4 route add 1.2.3.4/32 via inet6 fe80::2 dev eth1    
> >> fails with the message "Error: IPv6 support not enabled in kernel." if
> >> CONFIG_IPV6 is `m`.
> >>
> >> In the spirit of b8127113d01e53adba15b41aefd37b90ed83d631.
> >>
> >> Cc: Kim Phillips <kim.phillips@....com>
> >> Signed-off-by: Florian Klink <flokli@...kli.de>  
> > 
> > LGTM, this is the fixes tag right?
> > 
> > Fixes: d15662682db2 ("ipv4: Allow ipv6 gateway with ipv4 routes")  
> 
> yep.
> 
> > 
> > CCing David to give him a chance to ack.  
> 
> Reviewed-by: David Ahern <dsahern@...nel.org>

Great, applied, thanks!

> I looked at this yesterday and got distracted diving into the generated
> file to see the difference:
> 
> #define CONFIG_IPV6 1
> 
> vs
> 
> #define CONFIG_IPV6_MODULE 1

Interesting.

drivers/net/ethernet/netronome/nfp/flower/action.c:#ifdef CONFIG_IPV6

Oops.