Subject: Re: [PATCH net] netfilter: nf_nat: fix action not being set for all ct states

From: Simon Horman <[email-masked]>
Date: Sat, 23 Dec 2023 21:13:06 +0000

+ Xin Long <[email-masked]>
  Aaron Conole <[email-masked]>
  [email-masked]

On Fri, Dec 22, 2023 at 11:43:11AM +1300, Brad Cowie wrote:
> This fixes openvswitch's handling of nat packets in the related state.
> 
> In nf_ct_nat_execute(), which is called from nf_ct_nat(), ICMP/ICMPv6
> packets in the IP_CT_RELATED or IP_CT_RELATED_REPLY state, which have
> not been dropped, will follow the goto, however the placement of the
> goto label means that updating the action bit field will be bypassed.
> 
> This causes ovs_nat_update_key() to not be called from ovs_ct_nat()
> which means the openvswitch match key for the ICMP/ICMPv6 packet is not
> updated and the pre-nat value will be retained for the key, which will
> result in the wrong openflow rule being matched for that packet.
> 
> Move the goto label above where the action bit field is being set so
> that it is updated in all cases where the packet is accepted.
> 
> Fixes: ebddb1404900 ("net: move the nat function to nf_nat_ovs for ovs and tc")
> Signed-off-by: Brad Cowie <[email-masked]>

Thanks Brad,

I agree with your analysis and that the problem appears to
have been introduced by the cited commit.

I am curious to know what use case triggers this /
why it when unnoticed for a year.

But in any case, this fix looks good to me.

Reviewed-by: Simon Horman <[email-masked]>

> ---
>  net/netfilter/nf_nat_ovs.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/net/netfilter/nf_nat_ovs.c b/net/netfilter/nf_nat_ovs.c
> index 551abd2da614..0f9a559f6207 100644
> --- a/net/netfilter/nf_nat_ovs.c
> +++ b/net/netfilter/nf_nat_ovs.c
> @@ -75,9 +75,10 @@ static int nf_ct_nat_execute(struct sk_buff *skb, struct nf_conn *ct,
>  	}
>  
>  	err = nf_nat_packet(ct, ctinfo, hooknum, skb);
> +out:
>  	if (err == NF_ACCEPT)
>  		*action |= BIT(maniptype);
> -out:
> +
>  	return err;
>  }
>  
> -- 
> 2.34.1
> 
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