Re: [PATCH 2/2 net v2] ipv4: nexthop: allocate skb dynamically in rtm_get_nexthop()

[Ido Schimmel <idosch@nvidia.com>]

On Wed, Apr 01, 2026 at 10:17:41AM +0200, Fernando Fernandez Mancera wrote:
> -static size_t nh_nlmsg_size_grp(struct nexthop *nh)
> +static size_t nh_nlmsg_size_grp(struct nexthop *nh, u32 op_flags)
>  {
>  	struct nh_group *nhg = rtnl_dereference(nh->nh_grp);
>  	size_t sz = sizeof(struct nexthop_grp) * nhg->num_nh;
> @@ -1013,6 +1013,21 @@ static size_t nh_nlmsg_size_grp(struct nexthop *nh)
>  	if (nhg->resilient)
>  		tot += nh_nlmsg_size_grp_res(nhg);
>  
> +	if (op_flags & NHA_OP_FLAG_DUMP_STATS) {
> +		tot += nla_total_size(0) +	  /* NHA_GROUP_STATS */
> +		       nla_total_size(4);	  /* NHA_HW_STATS_ENABLE */
> +		tot += nhg->num_nh *
> +		       (nla_total_size(0) +	  /* NHA_GROUP_STATS_ENTRY */
> +			nla_total_size(4) +	  /* NHA_GROUP_STATS_ENTRY_ID */
> +			nla_total_size_64bit(8)); /* NHA_GROUP_STATS_ENTRY_PACKETS */
> +
> +		if (op_flags & NHA_OP_FLAG_DUMP_HW_STATS) {
> +			tot += nhg->num_nh *
> +			       nla_total_size_64bit(8); /* NHA_GROUP_STATS_ENTRY_PACKETS_HW */
> +			tot += nla_total_size(4);	/* NHA_HW_STATS_USED */
> +		}
> +	}
> +

This looks correct

>  	return tot;
>  }
>  
> @@ -1047,14 +1062,14 @@ static size_t nh_nlmsg_size_single(struct nexthop *nh)
>  	return sz;
>  }
>  
> -static size_t nh_nlmsg_size(struct nexthop *nh)
> +static size_t nh_nlmsg_size(struct nexthop *nh, u32 op_flags)
>  {
>  	size_t sz = NLMSG_ALIGN(sizeof(struct nhmsg));
>  
>  	sz += nla_total_size(4); /* NHA_ID */
>  
>  	if (nh->is_group)
> -		sz += nh_nlmsg_size_grp(nh) +
> +		sz += nh_nlmsg_size_grp(nh, op_flags) +
>  		      nla_total_size(4) +	/* NHA_OP_FLAGS */
>  		      0;

But the AI review [1] also mentions missing accounting for NHA_FDB which
seems like a legit issue (even if we can't currently trigger it).

In the single nexthop case we have:

sz = nla_total_size(4);  /* NHA_OIF */

Which covers NHA_FDB since it's mutually exclusive with NHA_OIF.

[1] https://sashiko.dev/#/patchset/20260401081741.4273-1-fmancera%40suse.de