linux-kernel - [PATCH v2] act_nat: fix the wrong checksum when addr isn't in old

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Message-Id: <1275179219-10424-1-git-send-email-xiaosuo@gmail.com>
Date:	Sun, 30 May 2010 08:26:59 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Jamal Hadi Salim <hadi@...erus.ca>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Changli Gao <xiaosuo@...il.com>
Subject: [PATCH v2] act_nat: fix the wrong checksum when addr isn't in old_addr/mask

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@...il.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:
--
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