Re: [Xen-users] Trouble with manual bridging on Xen3/CentOS 5

[Teck Choon Giam <giamteckchoon@xxxxxxxxx>]

On Sun, May 1, 2011 at 12:50 AM, Digimer <linux@xxxxxxxxxxx> wrote:
> On 04/29/2011 06:26 PM, Teck Choon Giam wrote:
>> On Sat, Apr 30, 2011 at 6:08 AM, Digimer <linux@xxxxxxxxxxx> wrote:
>>> Hi all,
>>>
>>>  While trying to sort out/test some patches, I was told that it's best
>>> to create bridges manually in
>>> /etc/sysconfig/network-scripts/ifcfg-xenbr*. I did this, commented out
>>> (network-script network-bridge) and restarted the network and Xen.
>>
>> Yes, using system network configuration will be better.  Which
>> distribution is this?  CentOS/RHEL 5?
>> You commented out (network-script network-bridge)?  If you are using
>> system network configuration to configure your bridge, have you try
>> the following instead of commented out?
>>
>> (network-script /bin/true)
>
> That was the ticket. I was able to provision a new VM with two
> interfaces, however, the vifs were at MTU 1500 so I still have work to
> do. :)

Glad to hear that ;)

Whereby for MTU... maybe you want to try manually set those?  For example:

To get the link of various ip link... ...
ip link show

Then if you want to set the mtu for vif1.0 for instance... do something like:

ip link set dev vif1.0 mtu 1412

Of course in your case, vif1.0 or whatever appended with .0 for vif#.0
will be your xenbr0/eth0... so you might want to do something like:

ip link set dev eth0 mtu 1412 << This can be configure in ifcfg-eth0
ip link set dev xenbr0 mtu 1412 << This also can be set in ifcfg-xenbr0
ip link set dev vif1.0 mtu 1412
ip link set dev vif2.0 mtu 1412

OR using ifconfig to set the related interface mtu.

so on... ... I don't think this is difficult to find the vif related
script in /etc/xen/scripts/ to add in the appropriate link for your
desired mtu value... ... IMO.  I think this is vif-common.sh as the
below codes:

if [ "$type_if" = vif ]; then
    # Check presence of compulsory args.
    XENBUS_PATH="${XENBUS_PATH:?}"
    dev="${dev:?}"

    vifname=$(xenstore_read_default "$XENBUS_PATH/vifname" "")
    if [ "$vifname" ]
    then
        if [ "$command" == "online" ] && ! ip link show "$vifname" >&/dev/null
        then
            do_or_die ip link set "$dev" name "$vifname" << THIS IS
WHERE YOU CAN ADD BUT I HAVE NOT EXPLODE THIS NOR TEST THIS WITH
APPENDED mtu "$mtu"
        fi
        dev="$vifname"
    fi
elif [ "$type_if" = tap ]; then
    # Check presence of compulsory args.
    : ${INTERFACE:?}

    # Get xenbus_path from device name.
    # The name is built like that: "tap${domid}.${devid}".
    dev_=${dev#tap}
    domid=${dev_%.*}
    devid=${dev_#*.}

    XENBUS_PATH="/local/domain/0/backend/vif/$domid/$devid"
fi


Something like:

do_or_die ip link set "$dev" name "$vifname" mtu "$vifmtu"

Or if doesn't work just split to another line:

do_or_die ip link set "$dev" name "$vifname"
do_or_die ip link set dev "$vifname" mtu "$vifmtu"

Or use ifconfig... ...

Of course you will need to set $vifmtu somewhere before the above or
use a function/line to get its bridge/parent interface name
(xenbr0/eth0) mtu value ... ... this is purely talking rubbish from me
without testing... just thoughts/ideas :p

Example:

Get parent/bridge interface mtu value for xenbr0:

local vifmtu=`ip link show xenbr0|head -n 1|sed 's@.*\Wmtu\W@@'|sed 's@\W.*@@'`

Or even better way is we know vif#.N where N will be the bridge number:

local myxenbrN=`echo $vifname | cut -f2 -d '.'`
local myxenbrname="xenbr${myxenbrN}"
local vifmtu=`ip link show ${myxenbrname}|head -n 1|sed
's@.*\Wmtu\W@@'|sed 's@\W.*@@'`
do_or_die ip link set "$dev" name "$vifname" mtu "$vifmtu"

Again, the above are ideas/thoughts without testing at all and I might
be totally wrong :p

Hope this helps!

Thanks.

Kindest regards,
Giam Teck Choon

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users