On Tue, May 08, 2007 at 12:41:02PM -0500, Mike McGrath wrote: > Daniel P. Berrange wrote: > >On Tue, May 08, 2007 at 11:39:14AM -0500, Mike McGrath wrote: > > > >>We're using xen heavily in Fedora's Infrastructure and presently a > >>number of the xen domU hosts are experiencing terrible checksum issues. > >>I've tried the ethtool -K eth0 tx off fix and it didn't work. > > > >What sort of network config have you got with these ? Briding straight > >to physical device, or NAT'd ? > Bridge That's good - should avoid the NAT related bugs there then. > >There are a couple issues at play: > > > > - There is a general bug in 2.6.20 that breaks checksum offload > > when used with NAT. > > - In 2.6.19 or later Dom0 will transmits to guests using checksum > > offload, so DHCP client in the guest will mistakenly thing it > > has a corrupt checksum. > > > >To address the first bug requires disabling checksum offload in the eth0 in > >the guest. ethtool -K eth0 tx off in the guest should do it. > > > >To address the 2nd is really difficult since the FC6 install images > >themsves > >have a broken DHCP client for example, so we need to workaround it in the > >kernel. This can be done by disabling checksums on the device in Dom0 - any > >of vifN.0, xenbr0, phet0 should have ethtook -K <dev> tx off done. > > > >NB, ignore eth0 in Dom0, that's a fake device so turning off tx on that > >does > >not fix things. > > > >So in summary, to get it working in general case requires: > > > > ethtool -K eth0 tx off in guest > > > >And > > > > ethtool -K <dev> tx off on whatever bridge device the guest is > > attached to > > > I've actually run that on every interface on every dom[0,U] on the box > :). I've also tried it on two other hosts. One a RHEL5 dom0 and the > other had different hardware but was also a FC6 dom0. I can arrange > access to the box if you're interested. Ok that makes absolutely no sense to me now :-) Everytime I hit it I was able to solve it eventually by setting 'tx off' on some combo of devices. The RHEL-5 Dom0 kernel also already has the neccessary fixes in which is even odder that it doesn't work for you. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=| -- Fedora-xen mailing list Fedora-xen@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-xen
