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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David S. Miller wrote:

>Hey guys, please try to take a look at this one.
>
>There are multiple confirmations that merely having ipt_MASQUERADE
>loaded or built into the kernel causes PMTU ICMP messages to be
>ignored in the current kernel.
>
>I suspect this is more fallout from Rusty's recent conntrack/nat
>stuff.  Maybe it'll result in some more nfsim testcases being
>added, so perhaps not such a bad thing afterall :-)
>
You were right, NAT messes up the inner packet pretty badly :)

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.

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


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===== net/ipv4/netfilter/ip_nat_proto_tcp.c 1.10 vs edited =====
--- 1.10/net/ipv4/netfilter/ip_nat_proto_tcp.c	2005-01-17 23:00:55 +01:00
+++ edited/net/ipv4/netfilter/ip_nat_proto_tcp.c	2005-01-28 02:13:06 +01:00
@@ -105,7 +105,7 @@
 		return 0;
 
 	iph = (struct iphdr *)((*pskb)->data + iphdroff);
-	hdr = (struct tcphdr *)((*pskb)->data + iph->ihl*4);
+	hdr = (struct tcphdr *)((*pskb)->data + hdroff);
 
 	if (maniptype == IP_NAT_MANIP_SRC) {
 		/* Get rid of src ip and src pt */