[libvirt] [PATCH 1/2] lxc: stop incorrectly validating interface type

Laine Stump laine at laine.org
Thu Dec 6 14:37:09 UTC 2018

On 12/6/18 4:50 AM, Daniel P. Berrangé wrote:
> On Wed, Dec 05, 2018 at 09:35:12PM -0500, Laine Stump wrote:
>> Commit 017dfa27d changed a few switch statements in the LXC code to
>> have all possible enum values, and in the process changed the switch
>> statement in virLXCControllerGetNICIndexes() such that it returned
>> error status for any interfaces that weren't implemented with a veth
>> pair when it should have just been ignoring those interfaces.
>> Since the interface type will have already been validated before
>> reaching this function, we shouldn't be doing any validation at all -
>> just add the ifindex of the parent veth if its a veth pair, and ignore
>> it otherwise.
>> Resolves: https://bugzilla.redhat.com/1656463
>> Signed-off-by: Laine Stump <laine at laine.org>
>> ---
>>  src/lxc/lxc_controller.c | 17 +++++++++++------
>>  1 file changed, 11 insertions(+), 6 deletions(-)
>> diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
>> index e853d02d65..1c20f451af 100644
>> --- a/src/lxc/lxc_controller.c
>> +++ b/src/lxc/lxc_controller.c
>> @@ -364,6 +364,16 @@ static int virLXCControllerGetNICIndexes(virLXCControllerPtr ctrl)
>>      size_t i;
>>      int ret = -1;
>> +    /* Gather the ifindexes of the "parent" veths for all interfaces
>> +     * implemented with a veth pair. These will be used when calling
>> +     * virCgroupNewMachine (and eventually the dbus method
>> +     * CreateMachineWithNetwork). ifindexes for the child veths, and
>> +     * for macvlan interfaces, *should not* be in this list, as they
>> +     * will be moved into the container. Only the interfaces that will
>> +     * remain outside the container, but are used for communication
>> +     * with the container, should be added to the list.
>> +     */
>> +
>>      VIR_DEBUG("Getting nic indexes");
>>      for (i = 0; i < ctrl->def->nnets; i++) {
>>          int nicindex = -1;
>> @@ -394,14 +404,9 @@ static int virLXCControllerGetNICIndexes(virLXCControllerPtr ctrl)
>>          case VIR_DOMAIN_NET_TYPE_DIRECT:
>> -            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> -                           _("Unsupported net type %s"),
>> -                           virDomainNetTypeToString(ctrl->def->nets[i]->type));
>> -            goto cleanup;
>>          case VIR_DOMAIN_NET_TYPE_LAST:
>>          default:
>> -            virReportEnumRangeError(virDomainNetType, ctrl->def->nets[i]->type);
>> -            goto cleanup;
>> +           break;
>>          }
> This is removing too much. Only ethernet, bridge, network & direct are going
> to work with LXC. All others should always result in an error message here,
> and absolutely the LAST/default case must always report enum error.

I had originally done what you suggest, then went back and changed it in
order to not conflict with my commit comment saying that validation
shouldn't even be done in this function, since the value had already
been validated and doing it again would just be adding bulk to the code
for no reason.

However, now I see that my belief that the interface configs had been
validated is a bit "off". The config might have been validated by
libvirt, but lxc_controller.c code runs in a different process, so
"outside forces" could have changed things during the transition. And my
assumption of prior validation had been reinforced by seeing that the
function called directly before virLXCControllerGetNICIndexes() was
literally called virLXCControllerValidateNICs(), but when I actually
look at that function I see that the only thing it validates is that the
number of interfaces on the commandline matches the number of interfaces
in the config, which doesn't do us much good.

So okay, I'll change the patch to just make TYPE_DIRECT a NOP and leave
in the validation. (somebody with more drive an ambition might instead
expand *ValidateNICs to do a more complete job.)

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