Re: [Xen-devel] Masquerading problems - XenU 3.0 on x86_64

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 9 Apr 2006, at 01:01, Jim Pick wrote:

> I'm trying to migrate my Xen sessions installed on 32-bit Xen 2.0 
> server to a 64-bit Xen 3.0 server.
> On the Xen 2.0 server (32-bit), I built a DomU kernel with 
> masquerading, and I use that to do NAT for some private networks 
> running on the same box.
> When I tried to do it with Xen 3.0 (64-bit), I couldn't get it to 
> work.  I had to build a custom DomU kernel (from xen-3.0-testing.hg, 
> 2.6.16, 2 days ago) in order to include the netfilter/iptables code.  
> ICMP works.  TCP doesn't.  Non-masquerading traffic is OK.  I had the 
> same problems with the 2.6.12 kernel from Xen 3.0.1.
> I captured some of the traffic, and ethereal is showing that the 
> masqueraded traffic being output has bad TCP checksums.
> I'm going to have to do some debugging to try to figure out what's 
> going wrong.
> Has anybody else encountered this?  Also, if it's already been fixed 
> somewhere, I'd love to know.  Any Netfilter debugging tips would also 
> be appreciated.
Turn off tx checksum offload in your domU's using ethtool. We had fixed 
some forms of NAT with our checksum offload, but maybe not for your 
type of setup.
 -- Keir



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