Subject: Re: [PATCH] net/sched: act_ct: add nat mangle action only for NAT-conntrack

From: Marcelo Ricardo Leitner <[email-masked]>
Date: Fri, 29 May 2020 14:56:50 -0300

On Fri, May 29, 2020 at 12:07:45PM +0800, [email-masked] wrote:
> From: wenxu <[email-masked]>
> 
> Currently add nat mangle action with comparing invert and ori tuple.
> It is better to check IPS_NAT_MASK flags first to avoid non necessary
> memcmp for non-NAT conntrack.
> 
> Signed-off-by: wenxu <[email-masked]>
> ---
>  net/sched/act_ct.c | 19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)
> 
> diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
> index c50a86a..d621152 100644
> --- a/net/sched/act_ct.c
> +++ b/net/sched/act_ct.c
> @@ -198,18 +198,21 @@ static int tcf_ct_flow_table_add_action_nat(struct net *net,
>  					    struct flow_action *action)
>  {
>  	const struct nf_conntrack_tuple *tuple = &ct->tuplehash[dir].tuple;
> +	bool nat = ct->status & IPS_NAT_MASK;
>  	struct nf_conntrack_tuple target;

[A]

>  
>  	nf_ct_invert_tuple(&target, &ct->tuplehash[!dir].tuple);
>  
>  	switch (tuple->src.l3num) {
>  	case NFPROTO_IPV4:
> -		tcf_ct_flow_table_add_action_nat_ipv4(tuple, target,
> -						      action);
> +		if (nat)

Why do the same check multiple times, on all actions? As no other
action is performed if not doing a nat, seems at [A] above, it could
just:

if (!nat)
	return 0;

> +			tcf_ct_flow_table_add_action_nat_ipv4(tuple, target,
> +							      action);
>  		break;
>  	case NFPROTO_IPV6:
> -		tcf_ct_flow_table_add_action_nat_ipv6(tuple, target,
> -						      action);
> +		if (nat)
> +			tcf_ct_flow_table_add_action_nat_ipv6(tuple, target,
> +							      action);
>  		break;
>  	default:
>  		return -EOPNOTSUPP;
> @@ -217,10 +220,14 @@ static int tcf_ct_flow_table_add_action_nat(struct net *net,
>  
>  	switch (nf_ct_protonum(ct)) {
>  	case IPPROTO_TCP:
> -		tcf_ct_flow_table_add_action_nat_tcp(tuple, target, action);
> +		if (nat)
> +			tcf_ct_flow_table_add_action_nat_tcp(tuple, target,
> +							     action);
>  		break;
>  	case IPPROTO_UDP:
> -		tcf_ct_flow_table_add_action_nat_udp(tuple, target, action);
> +		if (nat)
> +			tcf_ct_flow_table_add_action_nat_udp(tuple, target,
> +							     action);
>  		break;
>  	default:
>  		return -EOPNOTSUPP;
> -- 
> 1.8.3.1
>