Re: [Xen-users] crc checksum problems

[Renà Pfeiffer <lynx@xxxxxxxxx>]

On Jan 17, 2006 at 0830 -0600, Daniel Goertzen appeared and said:
> Instead of adding a dummy interface to the bridge try adding another vif0.x.
> 
> The xen drivers try to optimize networking by skipping out on 
> checksumming at various stages, because the assumption is that 
> inter-domain network transport is immune to error.  My theory is that if 
> you don't properly use the vifx.y/vethx interfaces, you bypass some of 
> these checksum optimizations and end up performing integrity checks when 
> you shouldn't. [...]

Aha, that sounds plausible. I think I will try it with rearranged
interfaces on my test server. I worked around this problem by using TCP
proxies for the ports in question. Since it was for HTTP & HTTPS a
reverse proxy is better for filtering anyway.

> Again, that's only my theory based on my experience.  If someone really 
> knows whats going on, I look forward to hearing about it.

Me too. I'd like to have a switch to change this behaviour, because I am
exploring Xen for use as educational tool for my students. We always run
out of physical space when setting up demo networks with multiple
routers and clients. Teaching TCP checksum errors isn't the goal of the
course. ;)

Best,
Lynx.

-- 
"From the delicate strands,
 between minds we weave our mesh:
 a blanket to warm the soul."
 --- Lady Deirdre Skye (SMAC) ---


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