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

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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@xxxxxxxxx>
---
  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.




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