Before, we were getting this warning:

  net/netfilter/nf_bpf_link.c:32:1: warning: 'get_proto_defrag_hook' defined but not used [-Wunused-function]

Guard the definition with CONFIG_NF_DEFRAG_IPV[4|6].

Fixes: 91721c2d02d3 ("netfilter: bpf: Support BPF_F_NETFILTER_IP_DEFRAG in netfilter link")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202307291213.fZ0zDmoG-lkp@intel.com/
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
---
 net/netfilter/nf_bpf_link.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/netfilter/nf_bpf_link.c b/net/netfilter/nf_bpf_link.c
index 8fe594bbc7e2..e502ec00b2fe 100644
--- a/net/netfilter/nf_bpf_link.c
+++ b/net/netfilter/nf_bpf_link.c
@@ -28,6 +28,7 @@ struct bpf_nf_link {
 	const struct nf_defrag_hook *defrag_hook;
 };
 
+#if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4) || IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
 static const struct nf_defrag_hook *
 get_proto_defrag_hook(struct bpf_nf_link *link,
 		      const struct nf_defrag_hook __rcu *global_hook,
@@ -68,6 +69,7 @@ get_proto_defrag_hook(struct bpf_nf_link *link,
 
 	return hook;
 }
+#endif
 
 static int bpf_nf_enable_defrag(struct bpf_nf_link *link)
 {
-- 
2.41.0

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Mon, 31 Jul 2023 15:55:00 -0600 you wrote:
> Before, we were getting this warning:
> 
>   net/netfilter/nf_bpf_link.c:32:1: warning: 'get_proto_defrag_hook' defined but not used [-Wunused-function]
> 
> Guard the definition with CONFIG_NF_DEFRAG_IPV[4|6].
> 
> Fixes: 91721c2d02d3 ("netfilter: bpf: Support BPF_F_NETFILTER_IP_DEFRAG in netfilter link")
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202307291213.fZ0zDmoG-lkp@intel.com/
> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
> 
> [...]

Here is the summary with links:
  - netfilter: bpf: Only define get_proto_defrag_hook() if necessary
    https://git.kernel.org/bpf/bpf-next/c/81584c23f249

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

On Mon, Jul 31, 2023 at 2:55 PM Daniel Xu <dxu@dxuuu.xyz> wrote:
>
> Before, we were getting this warning:
>
>   net/netfilter/nf_bpf_link.c:32:1: warning: 'get_proto_defrag_hook' defined but not used [-Wunused-function]
>
> Guard the definition with CONFIG_NF_DEFRAG_IPV[4|6].
>
> Fixes: 91721c2d02d3 ("netfilter: bpf: Support BPF_F_NETFILTER_IP_DEFRAG in netfilter link")

since that commit is in bpf-next only
please use [PATCH bpf-next] in the future to make sure BPF CI can test it.

I've applied it after manual testing, but very much prefer
the automation to do it for me.