Re: [PATCH v2] act_nat: fix the wrong checksum when addr isn't in old_addr/mask

[jamal <hadi@cyberus.ca>]

Copying Herbert, taking linux-kernel off...

On Sun, 2010-05-30 at 08:26 +0800, Changli Gao wrote:
> fix the wrong checksum when addr isn't in old_addr/mask
> 
> For TCP and UDP packets, when addr isn't in old_addr/mask we don't do SNAT or
> DNAT, and we should not update layer 4 checksum.
> 
> Signed-off-by: Changli Gao <xiaosuo@gmail.com>
> ----
>  net/sched/act_nat.c |    4 ++++
>  1 file changed, 4 insertions(+)
> diff --git a/net/sched/act_nat.c b/net/sched/act_nat.c
> index d885ba3..5709494 100644
> --- a/net/sched/act_nat.c
> +++ b/net/sched/act_nat.c
> @@ -159,6 +159,9 @@ static int tcf_nat(struct sk_buff *skb, struct tc_action *a,
>  			iph->daddr = new_addr;
>  
>  		csum_replace4(&iph->check, addr, new_addr);
> +	} else if ((iph->frag_off & htons(IP_OFFSET)) ||
> +		   iph->protocol != IPPROTO_ICMP) {
> +		goto out;
>  	}
>  
>  	ihl = iph->ihl * 4;
> @@ -247,6 +250,7 @@ static int tcf_nat(struct sk_buff *skb, struct tc_action *a,
>  		break;
>  	}
>  
> +out:
>  	return action;
>  
>  drop: