[libvirt] [PATCH] qemu: handle multicast overflow on macvtap for NIC_RX_FILTER_CHANGED

[Michal Privoznik]

On 11/26/18 5:10 PM, Michal Privoznik wrote:
> On 11/21/18 4:04 PM, Jason Baron wrote:
>> Guest network devices can set 'overflow' when there are a number of multicast
>> ips configured. For virtio_net, the limit is only 64. In this case, the list
>> of mac addresses is empty and the 'overflow' condition is set. Thus, the guest
>> will currently receive no multicast traffic in this state.
>>
>> When 'overflow' is set in the guest, let's turn this into ALLMULTI on the host.
>>
>> Signed-off-by: Jason Baron <jbaron at akamai.com>
>> ---
>>  src/qemu/qemu_driver.c | 26 +++++++++++++++++++-------
>>  1 file changed, 19 insertions(+), 7 deletions(-)
>>
>> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
>> index 7fb9102..ea36db8 100644
>> --- a/src/qemu/qemu_driver.c
>> +++ b/src/qemu/qemu_driver.c
>> @@ -4443,11 +4443,11 @@ static void
>>  syncNicRxFilterMultiMode(char *ifname, virNetDevRxFilterPtr guestFilter,
>>                           virNetDevRxFilterPtr hostFilter)
>>  {
>> -    if (hostFilter->multicast.mode != guestFilter->multicast.mode) {
>> +    if (hostFilter->multicast.mode != guestFilter->multicast.mode ||
>> +        guestFilter->multicast.overflow) {
>>          switch (guestFilter->multicast.mode) {
>>              case VIR_NETDEV_RX_FILTER_MODE_ALL:
>>                  if (virNetDevSetRcvAllMulti(ifname, true)) {
>> -
>>                      VIR_WARN("Couldn't set allmulticast flag to 'on' for "
>>                               "device %s while responding to "
>>                               "NIC_RX_FILTER_CHANGED", ifname);
>> @@ -4455,17 +4455,29 @@ syncNicRxFilterMultiMode(char *ifname, virNetDevRxFilterPtr guestFilter,
>>                  break;
>>  
>>              case VIR_NETDEV_RX_FILTER_MODE_NORMAL:
>> -                if (virNetDevSetRcvMulti(ifname, true)) {
>> +                if (guestFilter->multicast.overflow &&
>> +                    (hostFilter->multicast.mode == VIR_NETDEV_RX_FILTER_MODE_ALL)) {
>> +                    break;
>> +                }
>>  
>> +                if (virNetDevSetRcvMulti(ifname, true)) {

Ah, please do proper error check: if (func() < 0) { ... }.

>>                      VIR_WARN("Couldn't set multicast flag to 'on' for "
>>                               "device %s while responding to "
>>                               "NIC_RX_FILTER_CHANGED", ifname);
>>                  }
>>  
>> -                if (virNetDevSetRcvAllMulti(ifname, false)) {
>> -                    VIR_WARN("Couldn't set allmulticast flag to 'off' for "
>> -                             "device %s while responding to "
>> -                             "NIC_RX_FILTER_CHANGED", ifname);
>> +                if (guestFilter->multicast.overflow == true) {
>> +                    if (virNetDevSetRcvAllMulti(ifname, true)) {
>> +                        VIR_WARN("Couldn't set allmulticast flag to 'on' for "
>> +                                 "device %s while responding to "
>> +                                 "NIC_RX_FILTER_CHANGED", ifname);
>> +                    }
>> +                } else {
>> +                    if (virNetDevSetRcvAllMulti(ifname, false)) {
>> +                         VIR_WARN("Couldn't set allmulticast flag to 'off' for "
>> +                                  "device %s while responding to "
>> +                                  "NIC_RX_FILTER_CHANGED", ifname);

I wonder if we can do something like:

if (virNetDevSetRcvAllMulti(ifname,
                            guestFilter->multicast.overflow) < 0) {
    VIR_WARN("Couldn't set allmulticast flag to '%s' for "
             "device %s while responding to "
             "NIC_RX_FILTER_CHANGED",
             virTristateSwitchTypeToString(virTristateSwitchFromBool(guestFilter->multicast.overflow)),
             ifname);
}


Otherwise looking good.

Michal