Re: Fw: Re: 2.6.11-rc2 TCP ignores PMTU ICMP (Re: Linux 2.6.11-rc2)

[Patrick McHardy <kaber@trash.net>]

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Patrick McHardy wrote:

> IP (tos 0xd0, ttl  64, id 40755, offset 0, flags [none], length: 88) 
> 172.16.1.123 > 172.16.1.123: icmp 68: type-#142 for IP (tos 0x10, ttl 
> 180, id 13605, offset 0, flags [DF], length: 60, bad cksum e8b3 
> (->73d8)!) 172.16.1.123 > 172.16.195.55:  ip-proto-225 40
>
> This patch fixes it.

This patch on top fixes corrupt checksums of ICMP errors. The
function returns before recalculating the checksum in some cases.

>
> Signed-off-by: Patrick McHardy <kaber@trash.net>



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===== net/ipv4/netfilter/ip_nat_core.c 1.67 vs edited =====
--- 1.67/net/ipv4/netfilter/ip_nat_core.c	2005-01-18 21:27:23 +01:00
+++ edited/net/ipv4/netfilter/ip_nat_core.c	2005-01-28 02:48:04 +01:00
@@ -450,6 +450,13 @@
 		       !manip))
 		return 0;
 
+	/* Reloading "inside" here since manip_pkt inner. */
+	inside = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4;
+	inside->icmp.checksum = 0;
+	inside->icmp.checksum = csum_fold(skb_checksum(*pskb, hdrlen,
+						       (*pskb)->len - hdrlen,
+						       0));
+
 	/* Change outer to look the reply to an incoming packet
 	 * (proto 0 means don't invert per-proto part). */
 
@@ -468,13 +475,6 @@
 			return 0;
 	}
 
-	/* Reloading "inside" here since manip_pkt inner. */
-	inside = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4;
-
-	inside->icmp.checksum = 0;
-	inside->icmp.checksum = csum_fold(skb_checksum(*pskb, hdrlen,
-						       (*pskb)->len - hdrlen,
-						       0));
 	return 1;
 }