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Date:   Wed, 19 Jun 2019 19:46:42 +0200
From:   Pablo Neira Ayuso <pablo@netfilter.org>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Jozsef Kadlecsik <kadlec@netfilter.org>,
        Florian Westphal <fw@strlen.de>,
        "David S. Miller" <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Fernando Fernandez Mancera <ffmancera@riseup.net>,
        wenxu <wenxu@ucloud.cn>, netfilter-devel@vger.kernel.org,
        coreteam@netfilter.org, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org
Subject: Re: [PATCH] netfilter: synproxy: fix building syncookie calls
Message-ID: <20190619174642.hvjvmfaptfdkmbpk@salvia>
References: <20190619125500.1054426-1-arnd@arndb.de>
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On Wed, Jun 19, 2019 at 02:54:36PM +0200, Arnd Bergmann wrote:
> When either CONFIG_IPV6 or CONFIG_SYN_COOKIES are disabled, the kernel
> fails to build:
> 
> include/linux/netfilter_ipv6.h:180:9: error: implicit declaration of function '__cookie_v6_init_sequence'
>       [-Werror,-Wimplicit-function-declaration]
>         return __cookie_v6_init_sequence(iph, th, mssp);
> include/linux/netfilter_ipv6.h:194:9: error: implicit declaration of function '__cookie_v6_check'
>       [-Werror,-Wimplicit-function-declaration]
>         return __cookie_v6_check(iph, th, cookie);
> net/ipv6/netfilter.c:237:26: error: use of undeclared identifier '__cookie_v6_init_sequence'; did you mean 'cookie_init_sequence'?
> net/ipv6/netfilter.c:238:21: error: use of undeclared identifier '__cookie_v6_check'; did you mean '__cookie_v4_check'?
> 
> Fix the IS_ENABLED() checks to match the function declaration
> and definitions for these.

I made this:

https://patchwork.ozlabs.org/patch/1117735/

Basically it does:

+#endif
+#if IS_MODULE(CONFIG_IPV6) && defined(CONFIG_SYN_COOKIES)
        .cookie_init_sequence   = __cookie_v6_init_sequence,
        .cookie_v6_check        = __cookie_v6_check,
 #endif

If CONFIG_IPV6=n, then net/ipv6/netfilter.c is never compiled.

Unless I'm missing anything, I'd prefer my patch because it's a bit
less of ifdefs 8-)

Thanks!