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Re: [Xen-users] Strange network issue; Guest/DomU outgoing traffic

To: "Fajar A. Nugraha" <fajar@xxxxxxxxx>
Subject: Re: [Xen-users] Strange network issue; Guest/DomU outgoing traffic
From: eric van blokland <ericvanblokland@xxxxxxxxx>
Date: Thu, 26 Mar 2009 12:42:12 +0100
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Upgrading first is probably the best step, however, I would love to
hear from a developer if he knows any changes that might have fixed
this issue. Then I know at what version I could expect the issue to be
gone. Besides that, I would like to know what information I should
collect for them in order to investigate the issue in case it still
occurs after the update.

I know too little about the linux kernel, let alone the drivers to
come up with any serious theory. But could it be the DomU missed or
did not receive a transmit complete interrupt, leaving the network
driver in a weird state. If so, would it be still possible to receive
packets? And what about the send buffer? Wouldn't it overrun
eventually or will packets in the buffer timeout and removed from the
queue? Then again, I haven't got any serious evidence that it's
related to driver as Fisher said libpcap might be unreliable.

Just some thoughts...

On Thu, Mar 26, 2009 at 12:17 PM, Fajar A. Nugraha <fajar@xxxxxxxxx> wrote:
> On Thu, Mar 26, 2009 at 5:41 PM, eric van blokland
> <ericvanblokland@xxxxxxxxx> wrote:
>> Our reply packet is just never seen "on the wire".
>
>> How about poking a developer if he could imagine some race condition,
>> network driver/interrupt related, that could block outgoing traffic?
>> Or would they just yell at me for using those old kernels?
>
> I suspect the later.
> In xen upstream, bugfix will go to Xen 3.3.x, not on 3.1.x series.
> Plus Redhat's Xen is pretty much redhat-specific, not directly
> coresspond to any Xen release. I would've suggest you file a bug with
> Redhat (RH bugzilla is available for public), but since you're using
> an old release I imagine the the first reponse would be "please try
> the latest version" :)
>
> FYI, I actually had a similar problem on opensolaris dom0, Windows HVM
> domU with GPLV in that reply packets never arrived at domU. Turns out
> to be dom0 problem, and upgrading dom0 to snv_109 fixed it. So again,
> my suggestion is update your system.
>
> Regards,
>
> Fajar
>

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