linux-kernel - Re: [PATCH bpf-next 3/7] netfilter: defrag: Add glue hooks for enabling/disabling defrag

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Message-ID: <20230627110400.GG3207@breakpoint.cc>
Date:   Tue, 27 Jun 2023 13:04:00 +0200
From:   Florian Westphal <fw@...len.de>
To:     Daniel Xu <dxu@...uu.xyz>
Cc:     edumazet@...gle.com, dsahern@...nel.org, kuba@...nel.org,
        fw@...len.de, pabeni@...hat.com, pablo@...filter.org,
        davem@...emloft.net, kadlec@...filter.org, daniel@...earbox.net,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next 3/7] netfilter: defrag: Add glue hooks for
 enabling/disabling defrag

Daniel Xu <dxu@...uu.xyz> wrote:
> diff --git a/net/ipv4/netfilter/nf_defrag_ipv4.c b/net/ipv4/netfilter/nf_defrag_ipv4.c
> index e61ea428ea18..436e629b0969 100644
> --- a/net/ipv4/netfilter/nf_defrag_ipv4.c
> +++ b/net/ipv4/netfilter/nf_defrag_ipv4.c
> @@ -7,6 +7,7 @@
>  #include <linux/ip.h>
>  #include <linux/netfilter.h>
>  #include <linux/module.h>
> +#include <linux/rcupdate.h>
>  #include <linux/skbuff.h>
>  #include <net/netns/generic.h>
>  #include <net/route.h>
> @@ -113,17 +114,24 @@ static void __net_exit defrag4_net_exit(struct net *net)
>  	}
>  }
>  
> +static struct nf_defrag_v4_hook defrag_hook = {
> +	.enable = nf_defrag_ipv4_enable,
> +	.disable = nf_defrag_ipv4_disable,
> +};

Nit: static const, same for v6.

>  static struct pernet_operations defrag4_net_ops = {
>  	.exit = defrag4_net_exit,
>  };
>  
>  static int __init nf_defrag_init(void)
>  {
> +	rcu_assign_pointer(nf_defrag_v4_hook, &defrag_hook);
>  	return register_pernet_subsys(&defrag4_net_ops);

register_pernet failure results in nf_defrag_v4_hook pointing to
garbage.