On Wed, Sep 07, 2005 at 05:20:57AM -0700, Andrew Morton <[EMAIL PROTECTED]>
wrote:
>
>
> Begin forwarded message:
Hi, I gather you wanted to reply, but all I got was my own mail, it seems.
Either I overlooked something, you changed your mind, or something has been
lost.
> Date: Tue, 6 Sep 2005 19:29:30 +0200
> From: Marc Lehmann <[EMAIL PROTECTED]>
> To: linux-kernel@vger.kernel.org
> Subject: masquerading failure for at least icmp and tcp+sack on amd64
>
>
> Hi!
>
> I recently upgraded a 32 bit machine to a new amd64 board+cpu. I took the
> same kernel (2.6.13-rc7) and just recompiled it for 64 bit, plus upgraded
> userspace to 64 bit.
>
> Firewall config stayed the same.
>
> Problem: neither ping nor tcp was being masqueraded properly. I created
> the following test-set-up:
>
> iptables -t mangle -F
> iptables -t filter -F
> iptables -t nat -F
> iptables -t nat -A POSTROUTING -p all -s 10.0.0.0/8 -d \! 10.0.0.0/8 -j
> MASQUERADE
>
> i..e the above masquerade rule should be the only firewall rule, and all
> fules shoul[d have policy ACCEPT.
>
> The effect was that tcp packets and icmp packets coming from 10.0.0.1 on
> interface eth0 were properly masqueraded on the outgoing "inet" interface
> (ppp0 renamed):
>
> eth0:
> 19:17:24.364351 IP 10.0.0.1.44320 > 129.13.162.95.80: S
> 3745828676:3745828676(0) win 5840 <mss 1460,nop,nop,sackOK>
>
> inet:
> 19:17:24.364505 IP 84.56.237.68.44320 > 129.13.162.95.80: S
> 3745828676:3745828676(0) win 5840 <mss 1452,nop,nop,sackOK>
> 19:17:24.378029 IP 129.13.162.95.80 > 84.56.237.68.44320: S
> 3777391404:3777391404(0) ack 3745828677 win 5840 <mss 1460,nop,nop,sackOK>
> 19:17:24.378103 IP 84.56.237.68.44320 > 129.13.162.95.80: R
> 3745828677:3745828677(0) win 0
>
> However, the reverse packets were rejected. ip_conntrack showed this:
>
> tcp 6 52 SYN_SENT src=10.0.0.1 dst=129.13.162.95 sport=44320 dport=80
> [UNREPLIED] src=129.13.162.95 dst=84.56.237.68 sport=80 dport=44320 mark=0
> use=1
>
> ICMP echo replies were also masqueraded, but the reply was ignored.
>
> Weird observation 1:
>
> ip route del default
> ip add default via 10.0.0.17
>
> Resulted in working masquerading, this time over device "vpn0", which is
> a tuntap-interface. Working means that outgoing packets were correctly
> re-written with source 10.0.0.5 (local address of vpn0) and replie were
> correctly "un"-translated.
>
> Weird obervation 2:
>
> Some sites could be connected to with TCP. It turned out that those
> sites did not support TCP SACK. Indeed, turning off SACK either on the
> remote side of a connection or on the origonator side resulted in workign
> masquerading:
>
> eth0:
> 19:23:29.928470 IP 10.0.0.1.45611 > 129.13.162.95.80: S
> 4113365634:4113365634(0) win 5840 <mss 1460>
> 19:23:29.942246 IP 129.13.162.95.80 > 10.0.0.1.45611: S
> 4161877683:4161877683(0) ack 4113365635 win 5840 <mss 1460>
> 19:23:29.942313 IP 10.0.0.1.45611 > 129.13.162.95.80: . ack 1 win 5840
>
> inet:
> 19:23:29.928249 IP 84.56.237.68.45611 > 129.13.162.95.80: S
> 4113365634:4113365634(0) win 5840 <mss 1452>
> 19:23:29.942199 IP 129.13.162.95.80 > 84.56.237.68.45611: S
> 4161877683:4161877683(0) ack 4113365635 win 5840 <mss 1460>
> 19:23:29.942332 IP 84.56.237.68.45611 > 129.13.162.95.80: . ack 1 win 5840
>
> However, ICMP still is not masqueraded.
>
> Kernels that worked:
>
> 2.6.13-rc7, 2.6.12.5, 2.6.11 and lower, compiled for x86 with gcc-3.4
>
> Kernels that don't work:
>
> 2.6.13-rc7 (compiled with gcc-3.4 and 4.0.2 debian), 2.6.13 (gcc-4.02)
>
> Kernel configuration was exactly the same for the 2.6.13-rc7 kernels,
> modulo the cpu and architectrue selections.
>
> I have a somewhat nontrivial source routing set-up on that machine that I
> could document more if that could be a possible reason for that problem. I
> am confident that this is not a configuration error, as the configuraiton
> worked basically unchanged since the 2.4 days, and I am confident it's not
> a iptables setup problem either, as I can reproduce it with empty rules
> except for the masquerading rule.
>
> I did not mention UDP because I didn't test it, but it's likely that UDP
> masquerading also fails.
>
> Any idea at what I could look at or try out to find out more about this
> problem?
>
--
The choice of a
-----==- _GNU_
----==-- _ generation Marc Lehmann
---==---(_)__ __ ____ __ [EMAIL PROTECTED]
--==---/ / _ \/ // /\ \/ / http://schmorp.de/
-=====/_/_//_/\_,_/ /_/\_\ XX11-RIPE
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
