[libvirt] [PATCH] network: disallow <bandwidth>/<mac> for bridged/macvtap networks

[Laine Stump]

On 01/27/2014 06:08 PM, Michal Privoznik wrote:
> On 24.01.2014 13:18, Laine Stump wrote:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1057321 pointed out that
>> we weren't honoring the <bandwidth> element in libvirt networks using
>> <forward mode='bridge'/>. In fact, these networks are just a method of
>> giving a libvirt network name to an existing Linux host bridge on the
>> system, and even if it were technically possible for us to set
>> network-wide bandwidth limits for all the taps on a bridge, it's
>> probably not a polite thing to do since libvirt is just using a bridge
>> that was created by someone else for other purposes. So the proper
>> thing is to just log an error when someone tries to put a <bandwidth>
>> element in that type of network.
>>
>> While looking through the network XML documentation and comparing it
>> to the networkValidate function, I noticed that we also ignore the
>> presence of a mac address in the config, even though we do nothing
>> with it in this case either.
>>
>> This patch updates networkValidate() (which is called any time a
>> persistent network is defined, or a transient network created) to log
>> an error and fail if it finds either a <bandwidth> or <mac> element
>> and the network forward mode is anything except 'route'. 'nat', or
>> nothing. (Yes, neither of those elements is acceptable for any macvtap
>> mode, nor for a hostdev network).
>>
>> NB: This does *not* cause failure to start any existing network that
>> contains one of those elements, so someone might have erroneously
>> defined such a network in the past, and that network will continue to
>> function unmodified. I considered it too disruptive to suddenly break
>> working configs on the next reboot after a libvirt upgrade.
>> ---
>>   src/network/bridge_driver.c | 19 ++++++++++++++++++-
>>   1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/network/bridge_driver.c b/src/network/bridge_driver.c
>> index 0b43a67..3b9b58d 100644
>> --- a/src/network/bridge_driver.c
>> +++ b/src/network/bridge_driver.c
>> @@ -2407,8 +2407,17 @@ networkValidate(virNetworkDriverStatePtr driver,
>>           virNetworkSetBridgeMacAddr(def);
>>       } else {
>>           /* They are also the only types that currently support setting
>> -         * an IP address for the host-side device (bridge)
>> +         * a MAC or IP address for the host-side device (bridge), DNS
>> +         * configuration, or network-wide bandwidth limits.
>>            */
>> +        if (def->mac_specified) {
>> +            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> +                           _("Unsupported <mac> element in network %s "
>> +                             "with forward mode='%s'"),
>> +                           def->name,
>> +                          
>> virNetworkForwardTypeToString(def->forward.type));
>> +            return -1;
>> +        }
>>           if (virNetworkDefGetIpByIndex(def, AF_UNSPEC, 0)) {
>>               virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>>                              _("Unsupported <ip> element in network %s "
>> @@ -2433,6 +2442,14 @@ networkValidate(virNetworkDriverStatePtr driver,
>>                             
>> virNetworkForwardTypeToString(def->forward.type));
>>               return -1;
>>           }
>> +        if (def->bandwidth) {
>> +            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>> +                           _("Unsupported network-wide <bandwidth>
>> element "
>> +                             "in network %s with forward mode='%s'"),
>> +                           def->name,
>> +                          
>> virNetworkForwardTypeToString(def->forward.type));
>> +            return -1;
>> +        }
>>       }
>>
>>       /* We only support dhcp on one IPv4 address and
>>
>
> I think think this is exactly the opposite of what I've just pushed :)

Indeed :-) I really should get myself Cc'ed on more bugzilla
copmonents/products so that I notice these things sooner.

> I mean:
>
> commit 2996e6be19a13199ded7c2aa21039cca97318e01
> Author:     Michal Privoznik <mprivozn at redhat.com>
> AuthorDate: Wed Jan 22 18:58:33 2014 +0100
> Commit:     Michal Privoznik <mprivozn at redhat.com>
> CommitDate: Mon Jan 27 12:11:27 2014 +0100
>
>     networkAllocateActualDevice: Set QoS for bridgeless networks too
>
>     https://bugzilla.redhat.com/show_bug.cgi?id=1055484
>
>
>
> In the commit I'm trying to inherit network QoS to the interface that
> is just being created. Yes, it involves some magic but it works. I
> guess we need to agree if we want this approach or mine as they seem
> to be contradictionary.

Since you've reverted yours, should I push this?

After that, we may want to talk about 1) supporting use of the "dev"
attribute in <forward> to name a *single* forwarding interface, and
applying a network's <bandwidth> to that interface (while still failing
in other cases), and 2) maybe supporting Open vSwitch in a more thorough
manner so that projects like ovirt can use it to create intermediate
bridges and manage their bandwidth via libvirt <network> xml.