WARNING - OLD ARCHIVES

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/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] e1000: Problem with "disable CRC stripping workaround" patch

To: jesse.brandeburg@xxxxxxxxx
Subject: [Xen-devel] e1000: Problem with "disable CRC stripping workaround" patch
From: Mark McLoughlin <markmc@xxxxxxxxxx>
Date: Thu, 20 Jul 2006 17:11:08 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Thu, 20 Jul 2006 09:11:44 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
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>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Hi Jesse,
        I just came across this:

  http://www.mail-archive.com/netdev@xxxxxxxxxxxxxxx/msg14547.html

        I'm seeing a problem with this currently under Xen's bridging
configuration.

        Basically, with the patch, packets are being dropped at this point in
net/bridge/br_forward.c:

---
int br_dev_queue_push_xmit(struct sk_buff *skb)
{
        /* drop mtu oversized packets except gso */
        if (packet_length(skb) > skb->dev->mtu && !skb_is_gso(skb)) {
                kfree_skb(skb);
--

        What's happening that a 1500 byte packet comes in from e1000, onto the
bridge and is to be forwarded to a device whose mtu is 1500. Because the
CRC hasn't been stripped, skb->len is 1504 and the packet is dropped.

        One option is to fix this specific problem is to subtract the CRC
length from skb->len in e1000, another is to raise the MTU on the
receive side of Xen's loopback interface. I've attached a patch for the
latter, but I've no real opinion on which is more correct.

Cheers,
Mark.

Attachment: xen-netback-jumbo-mtu-on-vif.patch
Description: Text Data

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
<Prev in Thread] Current Thread [Next in Thread>