Re: [Xen-users] [Fwd: DHCP and DomUs troubles]

[Arnaud JAYET <ajayet@xxxxxxx>]

Fajar A. Nugraha wrote :
> On Sat, Jan 30, 2010 at 6:40 PM, Arnaud JAYET <ajayet@xxxxxxx> wrote:
> > 2) i'm using Debian Lenny + Xen 3.2-1 for Dom0 and DomU
> start with that.
>
> The usual debugging method is to try deactivating checksum offload on
> all interfaces (domU's ethx, dom0's vifx.y, dom0's ethx), try without
> vlan, or change to newer kernel. But the thing is the default kernel
> and Xen package on debian stable is simply old and unmaintained (I
> assume you use the default package, last updated 24 Mar 2009?), and is
> known to have some bugs, so sometimes it's a lot easier to simply jump
> to using a newer Xen and kernel version.
>
> Personally I use RHEL5 + default 2.6.18 kernel-xen + (on some servers)
> updated Xen 3.4.x RPM from Gitco, works great. But changing distros
> might be too much effort :D So what I suggest is you do is try see if
> debian has newer xen kernel available (from unstable?) and use it for
> dom0 and domU. If they don't have it, try using latest 2.6.31 kernel +
> patch from http://code.google.com/p/gentoo-xen-kernel/downloads/list.
You're maybe right, Xen 3.2 is not the last  version but i don't want to 
change my Debian Stable for RHEL, sorry ;-)
Well, i have solved the problem by disabling tx checksum Dom0's vifx.y 
of the domU.
let's say my domU has ID no. 39, after doing
'ethtool -k vif39.0 tx off' in dom0  it works ; when i launch dhclient 
on the domU, i get immediatly an IP address (tx is also disabled in domU 
by adding the line  'post-up ethtool -k eth0 tx off'  in 
/etc/network/interfaces

I wonder now how i can automate disabling tx offload on vifx.y 
interfaces created when a domU is started  ; manually by xm create 
command or at dom0 boot time with hard links in /etc/xen/auto to the 
config file ???

# xm list
Name       ID   Mem VCPUs      State   Time(s)
Domain-0    0   256     4     r-----     91.9
gwnat.dev   1   128     1     -b----     11.4
client.dev  3   256     1     r-----      1.4

# brctl show
bridge name     bridge id               STP enabled     interfaces
xenbr114                8000.0030482d925d       no              eth1.114
xenbr115                8000.0030482d925d       no              eth1.115
                                                        vif1.0
                                                        vif3.0

# ethtool -k xenbr115
Offload parameters for xenbr115:
Cannot get device rx csum settings: Operation not supported
Cannot get device flags: Operation not supported
rx-checksumming: off
==> tx-checksumming: off <===
scatter-gather: off
tcp segmentation offload: off
udp fragmentation offload: off
generic segmentation offload: off
large receive offload: off


DomU vif interfaces have tx-checksumming on by default :

# ethtool -k vif1.0
Offload parameters for vif1.0:
Cannot get device rx csum settings: Operation not supported
Cannot get device flags: Operation not supported
rx-checksumming: off
===> tx-checksumming: on <====
scatter-gather: on
tcp segmentation offload: on
udp fragmentation offload: off
generic segmentation offload: off
large receive offload: off

# ethtool -k vif3.0
Offload parameters for vif3.0:
Cannot get device rx csum settings: Operation not supported
Cannot get device flags: Operation not supported
rx-checksumming: off
===> tx-checksumming: on <====
scatter-gather: on
tcp segmentation offload: on
udp fragmentation offload: off
generic segmentation offload: off
large receive offload: off


------------

My dom0  /etc/network/interfaces file
eth0 = dom0 management (not used for xen bridges)
eth1 = vlans for domUs (here 2 tests VLAN 114 and 115) dot1q tagged

# Dom0 management interface
allow-hotplug eth0
iface eth0 inet static
        address 192.168.101.37
        netmask 255.255.255.0
        network 192.168.101.0
        broadcast 192.168.101.255
        gateway 192.168.101.254


### VLAN TEST 114
auto eth1.114
iface eth1.114 inet manual
auto xenbr114
iface xenbr114 inet manual
        netmask 255.255.255.0
        network 192.168.114.255
        bridge-ports eth1.114


### VLAN TEST 115
auto eth1.115
iface eth1.115 inet manual
auto xenbr115
iface xenbr115 inet manual
        netmask 255.255.255.0
        network 192.168.115.255
        bridge-ports eth1.115



--
Arnaud

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