Re: [Xen-devel] reboot driver domain, vifX.Y = NO-CARRIER?

[Jason Cooper <xen@xxxxxxxxxxxxxx>]

correction:

On Mon, Apr 30, 2018 at 06:17:54PM +0000, Jason Cooper wrote:
> On Mon, Apr 30, 2018 at 05:38:55PM +0100, George Dunlap wrote:
> > On Mon, Apr 30, 2018 at 5:16 PM, Jason Cooper <xen@xxxxxxxxxxxxxx> wrote:
> > > Hi Ian,
> > >
> > > On Mon, Apr 30, 2018 at 04:22:30PM +0100, Ian Jackson wrote:
> > >> Wei Liu writes ("Re: [Xen-devel] reboot driver domain, vifX.Y = 
> > >> NO-CARRIER?"):
> > >> > To implement reuse_domid in a sane way, either the toolstack needs to
> > >> > manage all domids and always sets domid when creating domain or the
> > >> > hypervisor needs to cooperate -- to have interface to reserve /
> > >> > pre-allocate domids.
> > >>
> > >> I think this is entirely the wrong approach.
> > >
> > > Whew.  Glad I didn't start hacking yet...
> > >
> > >> I think the right answer is that this is simply a bug in the
> > >> frontends.  frontends should cope if the backend path pointer in the
> > >> frontend directory is updated, and should start reading the new
> > >> backend instead.
> > >
> > > Ok, so I'm new to the guts of Xen.  The bug, at a high level, is that
> > > "When a driver domain is rebooted (domid changed), previously connected
> > > client domUs can't gain network connectivity to/through the driver
> > > domain via 'xl network-attach client_domu mac=... bridge=...
> > > backend=drv_dom'"
> > 
> > Hang on -- just to clarify, something like the following doesn't work
> > (or wouldn't, you suspect, work)?
> > 
> > * Start driver domain
> > * Start domU A with no network
> 
> My setup is different here.  I include the vif = [... backend=...]
> declaration in my domain config.
> 
> > * xl network-attach A backend=drv_dom
> 
> So I don't do this step manually.
> 
> > * [do some stuff]
> > * xl network-detach A [network devid]
> > * Restart driver domain
> > * xl network-attach A backend=drv_dom
> 
> Otherwise, this is all correct.  Then I get the NO-CARRIER in domU A.

Sorry, I get NO-CARRIER in the just rebooted driver domain.  And the
interface is still UP in domU A.

thx,

Jason.

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