Subject: Re: [PATCH nf] netfilter: nft_fwd_netdev: use recursion counter in neigh egress path

From: Florian Westphal <[email-masked]>
Date: Thu, 9 Apr 2026 11:50:34 +0200

Weiming Shi <[email-masked]> wrote:
> Fixes: f87b9464d152 ("netfilter: nft_fwd_netdev: Support egress hook")
> Reported-by: Xiang Mei <[email-masked]>
> Signed-off-by: Weiming Shi <[email-masked]>
> ---
>  include/net/netfilter/nf_dup_netdev.h |  4 ++++
>  net/netfilter/nf_dup_netdev.c         | 18 ++++++++++++++++++
>  net/netfilter/nft_fwd_netdev.c        |  7 +++++++
>  3 files changed, 29 insertions(+)
> 
> diff --git a/include/net/netfilter/nf_dup_netdev.h b/include/net/netfilter/nf_dup_netdev.h
> index b175d271aec9..17362f76d1d1 100644
> --- a/include/net/netfilter/nf_dup_netdev.h
> +++ b/include/net/netfilter/nf_dup_netdev.h
> @@ -7,6 +7,10 @@
>  void nf_dup_netdev_egress(const struct nft_pktinfo *pkt, int oif);
>  void nf_fwd_netdev_egress(const struct nft_pktinfo *pkt, int oif);
>  
> +bool nf_dup_netdev_has_recursed(void);
> +void nf_dup_netdev_recursion_inc(void);
> +void nf_dup_netdev_recursion_dec(void);
> +
>  struct nft_offload_ctx;
>  struct nft_flow_rule;
>  
> diff --git a/net/netfilter/nf_dup_netdev.c b/net/netfilter/nf_dup_netdev.c
> index fab8b9011098..e2fe8bb6fe0d 100644
> --- a/net/netfilter/nf_dup_netdev.c
> +++ b/net/netfilter/nf_dup_netdev.c
> @@ -29,6 +29,24 @@ static u8 *nf_get_nf_dup_skb_recursion(void)
>  
>  #endif
>  
> +bool nf_dup_netdev_has_recursed(void)
> +{
> +	return *nf_get_nf_dup_skb_recursion() > NF_RECURSION_LIMIT;
> +}
> +EXPORT_SYMBOL_GPL(nf_dup_netdev_has_recursed);

I think thats a bit too heavy-handed.
nf_get_nf_dup_skb_recursion() fetches from pcpu counter or current->.

Can you move nf_get_nf_dup_skb_recursion to a shared header file
and make it inline instead of having a function call?