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From: Changli Gao on 29 May 2010 06:50
fix the wrong checksum when addr isn't in old_addr/mask

When addr isn't in old_addr/mask we don't do SNAT or DNAT, and we should not
update the checksum too.

Signed-off-by: Changli Gao <xiaosuo(a)gmail.com>
----
net/sched/act_nat.c | 32 +++++++++++++++++---------------
1 file changed, 17 insertions(+), 15 deletions(-)
diff --git a/net/sched/act_nat.c b/net/sched/act_nat.c
index d885ba3..f9b12a9 100644
--- a/net/sched/act_nat.c
+++ b/net/sched/act_nat.c
@@ -142,24 +142,25 @@ static int tcf_nat(struct sk_buff *skb, struct tc_action *a,
else
addr = iph->daddr;

- if (!((old_addr ^ addr) & mask)) {
- if (skb_cloned(skb) &&
- !skb_clone_writable(skb, sizeof(*iph)) &&
- pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
- goto drop;
+ if ((old_addr ^ addr) & mask)
+ goto out;

- new_addr &= mask;
- new_addr |= addr & ~mask;
+ if (skb_cloned(skb) &&
+ !skb_clone_writable(skb, sizeof(*iph)) &&
+ pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
+ goto drop;

- /* Rewrite IP header */
- iph = ip_hdr(skb);
- if (egress)
- iph->saddr = new_addr;
- else
- iph->daddr = new_addr;
+ new_addr &= mask;
+ new_addr |= addr & ~mask;

- csum_replace4(&iph->check, addr, new_addr);
- }
+ /* Rewrite IP header */
+ iph = ip_hdr(skb);
+ if (egress)
+ iph->saddr = new_addr;
+ else
+ iph->daddr = new_addr;
+
+ csum_replace4(&iph->check, addr, new_addr);

ihl = iph->ihl * 4;

@@ -247,6 +248,7 @@ static int tcf_nat(struct sk_buff *skb, struct tc_action *a,
break;
}

+out:
return action;

drop:
--
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Next: linux-kernel@vger.kernel.org