RE: [PATCH v2 4/4] tools/hotplug: modify set_mtu() to inform the frontend via xenstore

[Paul Durrant <xadimgnik@gmail.com>]

> -----Original Message-----
> From: Ian Jackson <ian.jackson@citrix.com>
> Sent: 04 August 2020 12:14
> To: Paul Durrant <paul@xen.org>
> Cc: xen-devel@lists.xenproject.org; Paul Durrant <pdurrant@amazon.com>; Wei Liu <wl@xen.org>
> Subject: Re: [PATCH v2 4/4] tools/hotplug: modify set_mtu() to inform the frontend via xenstore
> 
> Paul Durrant writes ("[PATCH v2 4/4] tools/hotplug: modify set_mtu() to inform the frontend via
> xenstore"):
> > From: Paul Durrant <pdurrant@amazon.com>
> >
> > set_mtu() currently sets the backend vif MTU but does not inform the frontend
> > what it is. This patch adds code to write the MTU into a xenstore node. See
> > netif.h for a specification of the node.
> >
> > NOTE: There is also a small modification replacing '$mtu' with '${mtu}'
> >       for style consistency.
> >
> > Signed-off-by: Paul Durrant <pdurrant@amazon.com>
> 
> Reviewed-by: Ian Jackson <ian.jackson@eu.citrix.com>
> 

Thanks.

> > diff --git a/tools/hotplug/Linux/xen-network-common.sh b/tools/hotplug/Linux/xen-network-common.sh
> > index 37e71cfa9c..24fc42d9cf 100644
> > --- a/tools/hotplug/Linux/xen-network-common.sh
> > +++ b/tools/hotplug/Linux/xen-network-common.sh
> > @@ -164,9 +164,21 @@ remove_from_bridge () {
> >  set_mtu () {
> >      local bridge=$1
> >      local dev=$2
> > +    local type_if=$3
> > +
> >      mtu="`ip link show dev ${bridge}| awk '/mtu/ { print $5 }'`"
> >      if [ -n "$mtu" ] && [ "$mtu" -gt 0 ]
> >      then
> > -            ip link set dev ${dev} mtu $mtu || :
> > +            ip link set dev ${dev} mtu ${mtu} || :
> > +    fi
> > +
> > +    if [ ${type_if} = vif ]
> > +    then
> > +       dev_=${dev#vif}
> > +       domid=${dev_%.*}
> > +       devid=${dev_#*.}
> > +
> > +       XENBUS_PATH="/local/domain/$domid/device/vif/$devid"
> > +       xenstore_write "$XENBUS_PATH/mtu" ${mtu}
> 
> It's surprising to me that this code doesn't have the xenbus path
> already in some variable.  But I guess from the fact that you've added
> this code, that it doesn't.
> 

It is set, but set to the backend path. For safety I guess it's probably best if I use a local in this instance. Can I keep your R-b
with such a change?

  Paul

> Ian.