Re: [PATCH bpf-next] bpf: Move nf_conn extern declarations to filter.h

Martin KaFai Lau
2022-09-16T20:21:01Z

On 9/11/22 11:19 AM, Daniel Xu wrote:
> We're seeing the following new warnings on netdev/build_32bit and
> netdev/build_allmodconfig_warn CI jobs:
>
> ../net/core/filter.c:8608:1: warning: symbol
> 'nf_conn_btf_access_lock' was not declared. Should it be static?
> ../net/core/filter.c:8611:5: warning: symbol 'nfct_bsa' was not
> declared. Should it be static?
>
> Fix by ensuring extern declaration is present while compiling filter.o.
>
> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
> ---
> include/linux/filter.h | 6 ++++++
> include/net/netfilter/nf_conntrack_bpf.h | 7 +------
> 2 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index 527ae1d64e27..96de256b2c8d 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -567,6 +567,12 @@ struct sk_filter {
>
> DECLARE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
>
> +extern struct mutex nf_conn_btf_access_lock;
> +extern int (*nfct_bsa)(struct bpf_verifier_log *log, const struct btf *btf,
> + const struct btf_type *t, int off, int size,
> + enum bpf_access_type atype, u32 *next_btf_id,
> + enum bpf_type_flag *flag);

Can it avoid leaking the nfct specific details like
'nf_conn_btf_access_lock' and the null checking on 'nfct_bsa' to
filter.c? In particular, this code snippet in filter.c:

mutex_lock(&nf_conn_btf_access_lock);
if (nfct_bsa)
ret = nfct_bsa(log, btf, ....);
mutex_unlock(&nf_conn_btf_access_lock);

Can the lock and null check be done as one function (eg.
nfct_btf_struct_access()) in nf_conntrack_bpf.c and use it in filter.c
instead?

btw, 'bsa' stands for btf_struct_access? It is a bit too short to guess ;)

Also, please add a Fixes tag.