Re: [PATCH nf v3 1/1] ipvs: bound LBLCR and LBLC cache growth

[Julian Anastasov <ja@ssi.bg>]

	Hello,

On Fri, 21 Aug 2026, Zhiling@mx.ssi.bg wrote:

> From: Zhiling Zou <zhilinz@nebusec.ai>
> 
> ip_vs_lblcr_new() and ip_vs_lblc_new() create cache entries for
> every previously unseen destination address. The table max_size only
> tells the periodic collector to reclaim entries after the cache has
> already exceeded the limit. It does not reclaim entries that the
> attacker continues to use.
> 
> Reject new cache entries once either table reaches max_size * 3 / 2.
> The extra headroom lets the periodic collector catch up while the
> existing scheduler fallback continues to use the selected destination
> when cache creation fails. New traffic therefore stays serviceable
> without growing the tables further.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable@vger.kernel.org
> Reported-by: Vega <vega@nebusec.ai>
> Suggested-by: Julian Anastasov <ja@ssi.bg>
> Signed-off-by: Zhiling Zou <zhilinz@nebusec.ai>

	Looks good to me, thanks!

Acked-by: Julian Anastasov <ja@ssi.bg>

> ---
> changes in v3:
> - Allow 50% headroom above max_size before rejecting new cache entries,
>   as suggested by Julian Anastasov.
> - Apply the max_size * 3 / 2 cutoff to both LBLC and LBLCR.
> - v2 Link: https://lore.kernel.org/all/17cbb1d0649f4e19aa2e407ab4b528d42b8edac4.1786949472.git.zhilinz@nebusec.ai/
> 
> changes in v2:
> - Change the LBLCR limit check from >= max_size to > max_size.
> - Apply the same cache growth bound to LBLC.
> - Add Suggested-by: Julian Anastasov <ja@ssi.bg>.
> - v1 Link: https://lore.kernel.org/all/62790a9f94ac5318f107a1811cff5a1f2fc7e0bf.1786884824.git.zhilinz@nebusec.ai/
>  net/netfilter/ipvs/ip_vs_lblc.c  | 3 +++
>  net/netfilter/ipvs/ip_vs_lblcr.c | 3 +++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_lblc.c b/net/netfilter/ipvs/ip_vs_lblc.c
> index 693bcc82ccb77..8180a7ba9f538 100644
> --- a/net/netfilter/ipvs/ip_vs_lblc.c
> +++ b/net/netfilter/ipvs/ip_vs_lblc.c
> @@ -204,6 +204,9 @@ ip_vs_lblc_new(struct ip_vs_lblc_table *tbl, const union nf_inet_addr *daddr,
>  			return en;
>  		ip_vs_lblc_del(en);
>  	}
> +	if (atomic_read(&tbl->entries) >= tbl->max_size * 3 / 2)
> +		return NULL;
> +
>  	en = kmalloc_obj(*en, GFP_ATOMIC);
>  	if (!en)
>  		return NULL;
> diff --git a/net/netfilter/ipvs/ip_vs_lblcr.c b/net/netfilter/ipvs/ip_vs_lblcr.c
> index f53f05ceea36f..858393b1d2d17 100644
> --- a/net/netfilter/ipvs/ip_vs_lblcr.c
> +++ b/net/netfilter/ipvs/ip_vs_lblcr.c
> @@ -363,6 +363,9 @@ ip_vs_lblcr_new(struct ip_vs_lblcr_table *tbl, const union nf_inet_addr *daddr,
>  
>  	en = ip_vs_lblcr_get(af, tbl, daddr);
>  	if (!en) {
> +		if (atomic_read(&tbl->entries) >= tbl->max_size * 3 / 2)
> +			return NULL;
> +
>  		en = kmalloc_obj(*en, GFP_ATOMIC);
>  		if (!en)
>  			return NULL;
> -- 
> 2.43.0

Regards

--
Julian Anastasov <ja@ssi.bg>