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[Bug 823376] New: SUSE Xen Server does not appear to forward packets properly when the GRO is enabled.
  • From: bugzilla_noreply@xxxxxxxxxx
  • Date: Wed, 5 Jun 2013 16:09:07 +0000
  • Message-id: <>

Summary: SUSE Xen Server does not appear to forward packets
properly when the GRO is enabled.
Classification: openSUSE
Product: openSUSE 11.4
Version: Factory
Platform: x86-64
OS/Version: openSUSE 11.2
Status: NEW
Severity: Normal
Priority: P5 - None
Component: Xen
AssignedTo: jdouglas@xxxxxxxx
ReportedBy: rcnagara@xxxxxxxxxxx
QAContact: qa-bugs@xxxxxxx
Found By: ---
Blocker: ---

User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36
(KHTML, like Gecko) Chrome/27.0.1453.94 Safari/537.36

SUSE Xen Server is not forwarding packets properly when the GRO is enabled.


Create a bridge on physical interface which does GRO, from xen server. Add a
virtual network interface on to this bridge to a VM running linux.

# uname -r

# rpm -qa | grep xen

# brctl show
bridge name bridge id STP enabled interfaces
br0 8000.6cae8b223762 no eth0
br1 8000.6eae8b223761 no usb0
br2 8000.8c7cff352002 no eth4 << Physical
interface with GRO enabled.
vif10.1 << VM's

Run ping from VM to an external host. It will result in 95% packet loss.

Looking at the tcpdump, eth4 sends out ICMP requests & receives the ICMP
reponse. But the 'br2' interface does not 95% of those packets. With GRO
enabled the driver is properly handing over packets to the kernel via
napi_gro_frags(). But 'br2' is not receiving it.

If the IP address is configured on eth4 directly and is removed from bridge
'br2', there won't be any packet drops with GRO enabled.

The problem disappears if the GRO disabled on the physical interface. In that
case, the driver uses netif_receive_skb() to handover packets to the kernel.
The VM receives all packets and there will be no packet loss.

Is there a known issue with SUSE Xen server bridging when the GRO is enabled
OR does it need any configuration to enable proper bridging ?

Reproducible: Always

Steps to Reproduce:
Provided in 'Details' section above.
Actual Results:
95% of the packets are dropped.

Expected Results:
There should not be any packet drops.

This may not be issue, if there is only related to configuration. In such a
case, please consider this as a query and suggest.

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