Re: [libvirt] [PATCH] macvtap: libvirtd forgot macvtap device name during a shutdown/restart cycle
On 11/02/2010 11:47 AM, Daniel P. Berrange wrote:
On Tue, Nov 02, 2010 at 11:35:44AM -0400, Stefan Berger wrote:
> During a shutdown/restart cycle libvirtd forgot the macvtap device name
> that it had created on behalf of a VM so that a stale macvtap device
> remained on the host when the VM terminated. Libvirtd has to actively
> tear down a macvtap device and it uses its name for identifying which
> device to tear down.
>
> The solution is to not blank out the<target dev='...'/> completely,
but
> only blank it out on VMs that are not active. So, if a VM is active, the
> device name makes it into the XML and is also being parsed. If a VM is
> not active, the device name is discarded.
>
> Signed-off-by: Stefan Berger<stefanb(a)us.ibm.com>
>
> ---
> src/conf/domain_conf.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> Index: libvirt-acl/src/conf/domain_conf.c
> ===================================================================
> --- libvirt-acl.orig/src/conf/domain_conf.c
> +++ libvirt-acl/src/conf/domain_conf.c
> @@ -2343,7 +2343,8 @@ virDomainNetDefParseXML(virCapsPtr caps,
> def->data.direct.linkdev = dev;
> dev = NULL;
>
> - VIR_FREE(ifname);
> + if ((flags& VIR_DOMAIN_XML_INACTIVE))
> + VIR_FREE(ifname);
The conditional isn't required here - it is already dealt
with earlier on in the file. Just remove the VIR_FREE
completely.
The conditional further above is this code fragment here:
} else if ((ifname == NULL) &&
xmlStrEqual(cur->name, BAD_CAST "target")) {
ifname = virXMLPropString(cur, "dev");
if ((ifname != NULL) &&
((flags & VIR_DOMAIN_XML_INACTIVE) &&
(STRPREFIX((const char*)ifname, "vnet")))) {
/* An auto-generated target name, blank it out */
VIR_FREE(ifname);
}
Unfortunately it is also testing for the prefix 'vnet'.
In case of a macvtap device I don't want to pick up the name of the
macvtap device from the XML unless it's attached to a running domain. So
that's why I remove it above.
If the domain went down without libvirt 'seeing' it then we miessed out
on tearing it down and in that case there may be a stale device, but I
don't support this case. So I also want to have that cleared.
Further, I also don't accept user-provided interface names for the
reason of tear-down in case of failures while trying to start a VM. In
the failure-case it is not clear anymore whether the name was
user-provided and was previously created and needs to be torn down or
simply is a user-provided name of an interface that wasn't created and
thus should not be torn down because it may actually be clashing with
the user-provided name of a running VM. I had that before and this ended
up running danger of tearing down interfaces of running VMs when a
failure-path was invoked.
So, in case a ifname is given in case of macvtap (type 'direct') it
means it was started before and needs to be torn down. After every
tear-down the ifname is also free()d.
> @@ -5801,6 +5802,8 @@ virDomainNetDefFormat(virBufferPtr buf,
> virBufferAddLit(buf, "/>\n");
> virVirtualPortProfileFormat(buf,
> &def->data.direct.virtPortProfile,
> " ");
> + if ((flags& VIR_DOMAIN_XML_INACTIVE))
> + VIR_FREE(def->ifname);
This seems dubious. Formatting XML should never require
changing 'def' at all.
Let me remove it and test it only with the modification above kept as-is.
Stefan
Daniel.