Bug 212826 - xen_net: Memory squeeze in netback driver.
xen_net: Memory squeeze in netback driver.
Product: Fedora
Classification: Fedora
Component: kernel-xen (Show other bugs)
x86_64 Linux
medium Severity medium
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Assigned To: Herbert Xu
Virtualization Bugs
Depends On:
Blocks: 213430
  Show dependency treegraph
Reported: 2006-10-29 07:53 EST by Heiko Jakob
Modified: 2009-12-14 15:38 EST (History)
1 user (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2008-02-26 18:35:43 EST
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Verified Versions:
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Heiko Jakob 2006-10-29 07:53:47 EST
Description of problem:

Networking between all domains fails. The following message is flodding all
domains ( dmo0 + domU ) /var/log/messages : "xen_net: Memory squeeze in netback

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. make network traffic between domU and dom0. For example:
root@xendom0# ping xendomU1

Actual results:
/var/log/messages get's flooded on dom0 and on all domU ( even those not on the
same virtual-network (bridge) )

Expected results:
Should work :-)

Additional info:
Comment 1 Stephen Tweedie 2006-10-30 06:32:24 EST
When do these occur?  On boot?  On domain creation?  Under load?  What
networking configuration are you using?
Comment 2 Heiko Jakob 2006-10-30 16:51:08 EST
They occure when the first few bytes are going over any bridge.
It doesn't matter from which system the data is comming from or going to as long
at least one of them is on xenbr(0-2), which actually means any domain in my

The System has 2 phys. networkinterfaces. Each of them is connected to a bridge.
One bridge for the LAN, another for the internet connection. There is also a
pure virtual bridge for the DMZ.

dom0         domU*(multiple internal systems)
 |             |
xenbr0-eth0 (LAN)
xenbr1 (DMZ) - domU*(multiple DMZ systems) 
xenbr2-eth1 (internet)
Comment 3 Heiko Jakob 2006-11-01 05:21:41 EST
Problem solved.
domU running kernel-xenU-2.6.17-1.2174_FC5 breaks networking with dom0

When all domUs are running 2.6.17-1.2187_FC5xenU everything works fine. Booting
one with kernel-xenU-2.6.17-1.2174_FC5 breaks everything on all xenbr*. After
stopping the "bad" domU everything resumed working.

Comment 4 Stephen Tweedie 2006-11-01 08:10:56 EST
So when you have one 2174 kernel running, all other domains fail all the time? 
That one domain breaks all the others?  Or is only the 2174 domain itself broken?
Comment 5 Heiko Jakob 2006-11-01 09:00:37 EST
Yes. All interfaces connected to a xenbridge become unavailable. Even those
which are not on the same xenbridge. The only devices that are still working are
the physical devices on dom0. 

I've removed all domains from autostart and started each domU manually.

First i've started my firewall/router domU which seperates the LAN from the DMZ
and pinged it from dom0 and it worked. Then started the outer firewall/router
domU and it was pingable too. After starting a domU connected to (xenbr0) with
the 2174 kernel the pings to my outer router stopped. After shutting it down the
pings made theire way again. Since it was the only domU still on 2174 i've
upgraded it and tried again and everything worked. Since i have the old kernel
still installed it's very easy form me to reproduce. If you want any traces
please let me know.

Regards Heiko

Comment 6 Herbert Xu 2006-11-06 13:48:27 EST
What do you see if you run a tcpdump on the interface of the 2174 domU (both in
the domU and in dom0)?
Comment 7 Red Hat Bugzilla 2007-07-24 21:34:22 EDT
change QA contact
Comment 8 Chris Lalancette 2008-02-26 18:35:43 EST
This report targets FC6, which is now end-of-life.

Please re-test against Fedora 7 or later, and if the issue persists, open a new bug.


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