This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] Linux TCP Checksum offload limitations

To: James Harper <james.harper@xxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Linux TCP Checksum offload limitations
From: Pasi Kärkkäinen <pasik@xxxxxx>
Date: Sat, 5 Apr 2008 13:17:39 +0300
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Sat, 05 Apr 2008 03:18:04 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <AEC6C66638C05B468B556EA548C1A77D013DC2D9@trantor>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <AEC6C66638C05B468B556EA548C1A77D013DC2D9@trantor>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mutt/1.5.13 (2006-08-11)
On Fri, Apr 04, 2008 at 10:04:53PM +1100, James Harper wrote:
> Some version of Windows appear to give the network adapter driver a
> packet broken up into fairly small pieces, eg
> Page 0: 14 bytes of Ethernet Header
> Page 1: 20 bytes of IP Header
> Page 2: 20 bytes of TCP Header
> Page 3: 1460 bytes of TCP Data
> When this happens, Linux appears to not pass the packets beyond the
> vifX.Y interface - a tcpdump on (say) vif455.0 shows packets but a
> tcpdump on eth0 does not show all the packets - packets with a bad
> checksum don't make it that far.
> Our best guess is that the Linux checksum offload code can't cope with
> the way Windows is fragmenting the packets, but maybe Xen is somehow
> involved in this...
> Can someone please confirm that this is a limitation of Linux and/or
> Xen?

What version of Windows has this problem? 

Did you find out anything about it yet? 

-- Pasi

Xen-devel mailing list