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

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Date:   Tue, 17 Nov 2020 19:09:16 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Jakub Kicinski <kuba@...nel.org>, 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 11/17/20 5:07 PM, Jakub Kicinski wrote:
> 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

Digging up ancient history. ;)

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

Notify the maintainer!

-- 
~Randy