Re: [Xen-users] unstable network problem

[Mogens Valentin <monz@xxxxxxxxx>]

Ernst Bachmann wrote:
> On Monday 08 August 2005 15:34, Tim Durack wrote:
>
> > I must be doing something wrong:
> >
> > Have set up a basic Xen system, Dom0 + one Xen0 guest. Configured for
> > a routed network.
> >
> > Ping Dom0 -> guest works.
> > Ping guest -> Dom0 works.
> >
> > nmap Dom0 -> guest reports port 22 open.
> >
> > Ssh Dom0 -> guest hangs.
> > ssh guest -> Dom0 hangs. Same behaviour. Watching a packet capture
> > shows traffic passing but with retransmits and poor performance.
> >
> > If I build a gre tunnel between Dom0 and guest, everything works fine,
> > with the exception that I must generate some traffic from the guest
> > first.
> >
> > I have no iptables rules configured, so it's not that. Looks like
> > there is maybe some issue with tcp traffic between domains.
> >
> > Looks like a bug to me, but I'm posting to the user list first.
>
> There was a long thread about this problem maybe one or two weeks ago...
> I think the problem was that the virtual eth devices had packet queueing 
> disabled (txqueuelen:0 on ifconfig), and had a 4k size max. ring buffer for 
> transfering packets between domains.
> Whenever that buffer would run full, packets are dropped...
A too-small network buffer should never be able to hang a system; then 
again, it's unclear what Tim means by 'hang'.

--
Kind regards,
Mogens Valentin


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