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

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Date:   Tue, 17 Nov 2020 16:01:10 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Florian Klink <flokli@...kli.de>
Cc:     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>,
        David Ahern <dsahern@...il.com>
Subject: Re: [PATCH] ipv4: use IS_ENABLED instead of ifdef

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")

CCing David to give him a chance to ack.

> diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
> index 86a23e4a6a50..b87140a1fa28 100644
> --- a/net/ipv4/fib_frontend.c
> +++ b/net/ipv4/fib_frontend.c
> @@ -696,7 +696,7 @@ int fib_gw_from_via(struct fib_config *cfg, struct nlattr *nla,
>  		cfg->fc_gw4 = *((__be32 *)via->rtvia_addr);
>  		break;
>  	case AF_INET6:
> -#ifdef CONFIG_IPV6
> +#if IS_ENABLED(CONFIG_IPV6)
>  		if (alen != sizeof(struct in6_addr)) {
>  			NL_SET_ERR_MSG(extack, "Invalid IPv6 address in RTA_VIA");
>  			return -EINVAL;