Re: [PATCH bpf-next v8 1/7] net: move netfilter nf_reject_fill_skb_dst to core ipv4

["Emil Tsalapatis" <emil@etsalapatis.com>]

On Mon Jun 22, 2026 at 8:05 AM EDT, Mahe Tardy wrote:
> Move and rename nf_reject_fill_skb_dst from
> ipv4/netfilter/nf_reject_ipv4 to ip_route_reply_fill_dst in ipv4/route.c
> so that it can be reused in the following patches by BPF kfuncs.
>
> Netfilter uses nf_ip_route that is almost a transparent wrapper around
> ip_route_output_key so this patch inlines it.
>
> Reviewed-by: Jordan Rife <jordan@jrife.io>
> Signed-off-by: Mahe Tardy <mahe.tardy@gmail.com>

Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>

> ---
>  include/net/route.h                 |  1 +
>  net/ipv4/netfilter/nf_reject_ipv4.c | 19 ++-----------------
>  net/ipv4/route.c                    | 15 +++++++++++++++
>  3 files changed, 18 insertions(+), 17 deletions(-)
>
> diff --git a/include/net/route.h b/include/net/route.h
> index f90106f383c5..300d292cd9a1 100644
> --- a/include/net/route.h
> +++ b/include/net/route.h
> @@ -173,6 +173,7 @@ struct rtable *ip_route_output_flow(struct net *, struct flowi4 *flp,
>  				    const struct sock *sk);
>  struct dst_entry *ipv4_blackhole_route(struct net *net,
>  				       struct dst_entry *dst_orig);
> +int ip_route_reply_fill_dst(struct sk_buff *skb);
>
>  static inline struct rtable *ip_route_output_key(struct net *net, struct flowi4 *flp)
>  {
> diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c
> index fecf6621f679..c1c0724e4d4d 100644
> --- a/net/ipv4/netfilter/nf_reject_ipv4.c
> +++ b/net/ipv4/netfilter/nf_reject_ipv4.c
> @@ -252,21 +252,6 @@ static void nf_reject_ip_tcphdr_put(struct sk_buff *nskb, const struct sk_buff *
>  	nskb->csum_offset = offsetof(struct tcphdr, check);
>  }
>
> -static int nf_reject_fill_skb_dst(struct sk_buff *skb_in)
> -{
> -	struct dst_entry *dst = NULL;
> -	struct flowi fl;
> -
> -	memset(&fl, 0, sizeof(struct flowi));
> -	fl.u.ip4.daddr = ip_hdr(skb_in)->saddr;
> -	nf_ip_route(dev_net(skb_in->dev), &dst, &fl, false);
> -	if (!dst)
> -		return -1;
> -
> -	skb_dst_set(skb_in, dst);
> -	return 0;
> -}
> -
>  /* Send RST reply */
>  void nf_send_reset(struct net *net, struct sock *sk, struct sk_buff *oldskb,
>  		   int hook)
> @@ -279,7 +264,7 @@ void nf_send_reset(struct net *net, struct sock *sk, struct sk_buff *oldskb,
>  	if (!oth)
>  		return;
>
> -	if (!skb_dst(oldskb) && nf_reject_fill_skb_dst(oldskb) < 0)
> +	if (!skb_dst(oldskb) && ip_route_reply_fill_dst(oldskb) < 0)
>  		return;
>
>  	if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
> @@ -352,7 +337,7 @@ void nf_send_unreach(struct sk_buff *skb_in, int code, int hook)
>  	if (iph->frag_off & htons(IP_OFFSET))
>  		return;
>
> -	if (!skb_dst(skb_in) && nf_reject_fill_skb_dst(skb_in) < 0)
> +	if (!skb_dst(skb_in) && ip_route_reply_fill_dst(skb_in) < 0)
>  		return;
>
>  	if (skb_csum_unnecessary(skb_in) ||
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index 3f3de5164d6e..f24609933fbe 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -2942,6 +2942,21 @@ struct rtable *ip_route_output_flow(struct net *net, struct flowi4 *flp4,
>  }
>  EXPORT_SYMBOL_GPL(ip_route_output_flow);
>
> +int ip_route_reply_fill_dst(struct sk_buff *skb)
> +{
> +	struct rtable *rt;
> +	struct flowi4 fl4 = {
> +		.daddr = ip_hdr(skb)->saddr
> +	};
> +
> +	rt = ip_route_output_key(dev_net(skb->dev), &fl4);
> +	if (IS_ERR(rt))
> +		return PTR_ERR(rt);
> +	skb_dst_set(skb, &rt->dst);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(ip_route_reply_fill_dst);
> +
>  /* called with rcu_read_lock held */
>  static int rt_fill_info(struct net *net, __be32 dst, __be32 src,
>  			struct rtable *rt, u32 table_id, dscp_t dscp,
> --
> 2.34.1