Re: [Xen-users] Setting vifX.Y's MTU automatically in Xen 3

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Fri, Apr 15, 2011 at 07:28:00AM -0400, Digimer wrote:
> On 04/15/2011 06:12 AM, Pasi Kärkkäinen wrote:
> > On Wed, Apr 13, 2011 at 07:33:49AM -0400, Digimer wrote:
> >> Hi all,
> >>
> >>   I've got Xen 3.0 (stock as available on CentOS 5.6). I'm trying to use
> >> jumbo frames, but when Xen creates vifX.Y interfaces, it uses 1500. This
> >> brings the xenbrX bridges down to 1500, and effectively messes up
> >> anything thinking that it can use the larger packet size.
> >>
> >>   So how can I make sure that all vifX.Y interfaces created by Xen are
> >> set to a given MTU? I've grepped the files under /etc/xen, but haven't
> >> seen a specific place to set it.
> >>
> >> Thanks!
> >>
> > 
> > I think first I'd try to modify vif-bridge script and make sure
> > MTU of the vif is adjusted before attaching to the bridge.
> > 
> > Verify you get that working, and then let's figure out what's the best way..
> > 
> > -- Pasi
> 
> This fails. I tried adding to 'vif-bridge':
> 
> ====
> case "$command" in
>     online)
>         setup_bridge_port "$vif"
>         ifconfig $vif mtu 9000


Try doing it before setup_bridge_port ?
Do you need to specify a patch for ifconfig?


>         add_to_bridge "$bridge" "$vif"
>         ;;
> ====
> 
> Alternatively, I tried adding to 'xen-network-common.sh':
> 
> ====
> add_to_bridge () {
>     local bridge=$1
>     local dev=$2
> 
>     # Don't add $dev to $bridge if it's already on a bridge.
>     if [ -e "/sys/class/net/${bridge}/brif/${dev}" ]; then
>         ip link set ${dev} up || true
>         return
>     fi
>     ifconfig ${dev} mtu 9000
>     brctl addif ${bridge} ${dev}
>     ip link set ${dev} up
> }
> ====
> 
> Both cases caused the start of the domU to fail, complaining that the
> scripts failed.
> 

Well something goes wrong then.. 

> http://pastebin.com/xstkgYzx
> 

-- Pasi


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