netdev - Re: [PATCH bpf-next] bpf, netns: Fix build without CONFIG

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Message-ID: <1140c2d9-f0a4-97da-5f3f-23190e6bc6b9@infradead.org>
Date:   Tue, 21 Jul 2020 07:00:58 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Jakub Sitnicki <jakub@...udflare.com>, bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org, kernel-team@...udflare.com,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [PATCH bpf-next] bpf, netns: Fix build without CONFIG_INET

On 7/21/20 3:07 AM, Jakub Sitnicki wrote:
> When CONFIG_NET is set but CONFIG_INET isn't, build fails with:
> 
>   ld: kernel/bpf/net_namespace.o: in function `netns_bpf_attach_type_unneed':
>   kernel/bpf/net_namespace.c:32: undefined reference to `bpf_sk_lookup_enabled'
>   ld: kernel/bpf/net_namespace.o: in function `netns_bpf_attach_type_need':
>   kernel/bpf/net_namespace.c:43: undefined reference to `bpf_sk_lookup_enabled'
> 
> This is because without CONFIG_INET bpf_sk_lookup_enabled symbol is not
> available. Wrap references to bpf_sk_lookup_enabled with preprocessor
> conditionals.
> 
> Fixes: 1559b4aa1db4 ("inet: Run SK_LOOKUP BPF program on socket lookup")
> Reported-by: Randy Dunlap <rdunlap@...radead.org>
> Reported-by: Stephen Rothwell <sfr@...b.auug.org.au>
> Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>

Acked-by: Randy Dunlap <rdunlap@...radead.org> # build-tested

Thanks.

> ---
>  kernel/bpf/net_namespace.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/kernel/bpf/net_namespace.c b/kernel/bpf/net_namespace.c
> index 4e1bcaa2c3cb..71405edd667c 100644
> --- a/kernel/bpf/net_namespace.c
> +++ b/kernel/bpf/net_namespace.c
> @@ -28,9 +28,11 @@ DEFINE_MUTEX(netns_bpf_mutex);
>  static void netns_bpf_attach_type_unneed(enum netns_bpf_attach_type type)
>  {
>  	switch (type) {
> +#ifdef CONFIG_INET
>  	case NETNS_BPF_SK_LOOKUP:
>  		static_branch_dec(&bpf_sk_lookup_enabled);
>  		break;
> +#endif
>  	default:
>  		break;
>  	}
> @@ -39,9 +41,11 @@ static void netns_bpf_attach_type_unneed(enum netns_bpf_attach_type type)
>  static void netns_bpf_attach_type_need(enum netns_bpf_attach_type type)
>  {
>  	switch (type) {
> +#ifdef CONFIG_INET
>  	case NETNS_BPF_SK_LOOKUP:
>  		static_branch_inc(&bpf_sk_lookup_enabled);
>  		break;
> +#endif
>  	default:
>  		break;
>  	}
> 


-- 
~Randy