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Re: [libvirt] [PATCH v3 20/20] nwfilter: convert virt drivers to use public API for nwfilter bindings




On 06/14/2018 08:33 AM, Daniel P. Berrangé wrote:
> Remove the callbacks that the nwfilter driver registers with the domain
> object config layer. Instead make the current helper methods call into
> the public API for creating/deleting nwfilter bindings.
> 
> Signed-off-by: Daniel P. Berrangé <berrange redhat com>
> ---
>  src/conf/domain_nwfilter.c             | 124 +++++++++++++++++++++----
>  src/conf/domain_nwfilter.h             |  13 ---
>  src/libvirt_private.syms               |   1 -
>  src/nwfilter/nwfilter_driver.c         |  84 +++--------------
>  src/nwfilter/nwfilter_gentech_driver.c |  42 ---------
>  src/nwfilter/nwfilter_gentech_driver.h |   4 -
>  6 files changed, 120 insertions(+), 148 deletions(-)
> 

I ran the more "aggressive" Avocado tests based on an old bz
(https://bugzilla.redhat.com/show_bug.cgi?id=1034807) and got the
following in my debug libvirtd output:

2018-06-15 15:46:18.683+0000: 18817: error :
virNWFilterBindingLookupByPortDev:589 : portdev in
virNWFilterBindingLookupByPortDev must not be NULL
2018-06-15 15:46:18.684+0000: 18817: error :
virNWFilterBindingLookupByPortDev:589 : portdev in
virNWFilterBindingLookupByPortDev must not be NULL

The first thing the test does is remove the defined interface:

   <interface type='bridge'>
      <mac address='52:54:00:9a:9b:9c'/>
      <source bridge='virbr0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
function='0x0'/>
    </interface>

and then replaces/adds with a new interface:

<interface type="bridge">
  <mac address="52:54:00:9a:9b:9c" />
  <source bridge="virbr0" />
  <model type="virtio" />
  <address bus="0x00" domain="0x0000" function="0x0" slot="0x03"
type="pci" />
  <filterref filter="allow-arp" />
</interface>

for the test domain via device attach.

Then 2 threads are started - 1 that continually starts/destroys the
domain and 1 that continually removes/adds allow-arp. The actual logic
in the test is busted because starting up a domain without a defined
filter will fail and the thread doing the start/stop has no retry
(try/except) logic. When I added the try/except logic and toned down the
retry logic a bit I could get the test to pass with a few adjustments to
the libvirt code here.  Ironically, when the test goes too fast it
caused my CPU's to get hot and generate a false positive failure because
there were dmesg events related to core temperature above threshold.

Anyway, I've noted a couple of places I think adjustments could/should
be made - hopefully they make sense as I started looking "backwards" to
see where things go introduced.


> diff --git a/src/conf/domain_nwfilter.c b/src/conf/domain_nwfilter.c
> index 7570e0ae83..ed45394918 100644
> --- a/src/conf/domain_nwfilter.c
> +++ b/src/conf/domain_nwfilter.c

[...]

>  
> +
>  int
>  virDomainConfNWFilterInstantiate(const char *vmname,
>                                   const unsigned char *vmuuid,
>                                   virDomainNetDefPtr net)

Revisiting my comment from patch 13 - it is possible to enter here with
net->filter being NULL. Is it worth returning 0 in that case under the
assumption that there is no filter so that the callers then don't have
to make that check? If portdev/ifname is NULL, not much is going to be
found as well.

>  {
> -    if (nwfilterDriver != NULL)
> -        return nwfilterDriver->instantiateFilter(vmname, vmuuid, net);
> +    virConnectPtr conn = virGetConnectNWFilter();
> +    virNWFilterBindingDefPtr def = NULL;
> +    virNWFilterBindingPtr binding = NULL;
> +    char *xml;
> +    int ret = -1;
> +
> +    VIR_DEBUG("vmname=%s portdev=%s filter=%s",
> +              vmname, NULLSTR(net->ifname), NULLSTR(net->filter));

Both being NULL probably is not a good thing - what filter for what portdev?

> +
> +    if (!conn)
> +        goto cleanup;
> +

Based on patch 16/19 comments and the thought above:

 if (!net->ifname ||
     (binding = virNWFilterBindingLookupByPortDev(conn, net->ifname))) {
     ret = 0;
     goto cleanup;
 }

where the !net->ifname may avoids the patch 13 comment issue and the ret
= 0 when finding the binding handles the filter already loaded issue.
The filter would be loaded for a running guest (after at least the
second libvirtd restart) by virNWFilterBindingObjListLoadAllConfigs.

> +    if (!(def = virNWFilterBindingDefForNet(vmname, vmuuid, net)))
> +        goto cleanup;
> +
> +    if (!(xml = virNWFilterBindingDefFormat(def)))
> +        goto cleanup;
> +
> +    if (!(binding = virNWFilterBindingCreateXML(conn, xml, 0)))
> +        goto cleanup;
> +
> +    ret = 0;
> +
> + cleanup:
> +    VIR_FREE(xml);
> +    virNWFilterBindingDefFree(def);
> +    virObjectUnref(binding);
> +    virObjectUnref(conn);
> +    return ret;
> +}
> +
> +
> +static void
> +virDomainConfNWFilterTeardownImpl(virConnectPtr conn,
> +                                  virDomainNetDefPtr net)
> +{
> +    virNWFilterBindingPtr binding;
>  
> -    virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
> -                   _("No network filter driver available"));
> -    return -1;
> +    binding = virNWFilterBindingLookupByPortDev(conn, net->ifname);
> +    if (!binding)

virNWFilterBindingLookupByPortDev will generate an error when there's no
filter defined for @net (if you're running libvirtd in a debugger you
see it).

Shouldn't the call be guarded by a "if (!net->filter)"?

    if (!net->filter ||
        !binding = vir...())
        return;

if not, then we probably should reset the last error since we're just
returning (error as in [1]).

> +        return;
> +
> +    virNWFilterBindingDelete(binding);
> +
> +    virObjectUnref(binding);
>  }
>  
> +
>  void
>  virDomainConfNWFilterTeardown(virDomainNetDefPtr net)
>  {
> -    if (nwfilterDriver != NULL)
> -        nwfilterDriver->teardownFilter(net);
> +    virConnectPtr conn = virGetConnectNWFilter();
> +
> +    if (!conn)
> +        return;
> +
> +    virDomainConfNWFilterTeardownImpl(conn, net);
> +
> +    virObjectUnref(conn);
>  }
>  

may as well add the blank line here from ...

>  void
>  virDomainConfVMNWFilterTeardown(virDomainObjPtr vm)
>  {
>      size_t i;
> +    virConnectPtr conn = virGetConnectNWFilter();
> +
> +    if (!conn)
> +        return;
> +

... here... or at least remove this extra blank line.

> +
> +    for (i = 0; i < vm->def->nnets; i++)
> +        virDomainConfNWFilterTeardownImpl(conn, vm->def->nets[i]);
>  
> -    if (nwfilterDriver != NULL) {
> -        for (i = 0; i < vm->def->nnets; i++)
> -            virDomainConfNWFilterTeardown(vm->def->nets[i]);
> -    }
> +    virObjectUnref(conn);
>  }

[...]

>  
> diff --git a/src/nwfilter/nwfilter_driver.c b/src/nwfilter/nwfilter_driver.c
> index 2b6856a36c..26e6e76b3b 100644
> --- a/src/nwfilter/nwfilter_driver.c
> +++ b/src/nwfilter/nwfilter_driver.c
> @@ -654,67 +654,6 @@ nwfilterGetXMLDesc(virNWFilterPtr nwfilter,
>  }
>  
>  

[...]

>  static virNWFilterBindingPtr
>  nwfilterBindingLookupByPortDev(virConnectPtr conn,
>                                 const char *portdev)
> @@ -725,8 +664,11 @@ nwfilterBindingLookupByPortDev(virConnectPtr conn,
>  
>      obj = virNWFilterBindingObjListFindByPortDev(driver->bindings,
>                                                   portdev);
> -    if (!obj)
> +    if (!obj) {
> +        virReportError(VIR_ERR_NO_NWFILTER_BINDING,
> +                       _("no nwfilter binding for port dev '%s'"), portdev);454

[1]
Adding this error here for someone running debug will cause those
virDomainConfNWFilterTeardownImpl consumers w/o a filter to display this
message. Of course removing it means the callers all have to add some
sort of message.

John

>          goto cleanup;
> +    }
>  
>      def = virNWFilterBindingObjGetDef(obj);
>      if (virNWFilterBindingLookupByPortDevEnsureACL(conn, def) < 0)

[...]


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