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   Chris, 
   
  I have to apologize. Turning off segmentation offloading may work as well. 
  Just now it fixed VNC issue on bare metal - CentOS 5.2 with Atansic Gigabit 
  Ethernet driver (ASUS P5KR) . I gonna try it at DomUs at my earliest
  convenience. 
   
  Boris. 
   
  --- On Fri, 4/24/09, Christophe Saout <christophe@xxxxxxxx>
  wrote: 
  From: Christophe Saout
  <christophe@xxxxxxxx> 
  Subject: Re: [Xen-devel] xen.git branch reorg 
  To: "Jeremy Fitzhardinge" <jeremy@xxxxxxxx> 
  Cc: bderzhavets@xxxxxxxxx, "Xen-devel"
  <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Ian Campbell"
  <Ian.Campbell@xxxxxxxxxx> 
  Date: Friday, April 24, 2009, 6:39 PM 
  Hi Jeremy, 
   
> >  In meantime time i see,  that  2.6.30-rc3&rc2&rc1-tip are 
affected. 
> > Solution is the same as on Solaris xVM Linux DomUs about one 
> > year ago -  is  to disable checksum (nothing else) offloading at 
Linux  
> > DomUs ( CentOS 5.3, Ubuntu 9.04) 
> > 
> > /usr/local/sbin/ethtool -K etho tx off 
> 
> OK, that's a good lead. 
   
Yes, I've been seeing this too (and meant to investigate it before 
claiming there's abug) and I can confirm that turning off segmentation 
offloading "cures" the problem here too. 
   
Now the tcpdump on Dom0 looks interesting.  It repeatedly sees a packet 
with 2880 byte from DomU coming in, which is then dropped and ICMP 
"fragmentation needed" sent back, the DomU resends a 1440 byte packet 
(after some delay), which then goes through, but then the next one is a 
2880 byte one again, and so on. 
   
FYI: My Dom0 is running NAT, in case this is relevant. 
   
   
           Christophe 
   
   
   
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