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

[Jason Baron]

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)) {
                     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);
+                    }
                 }
                 break;
 
-- 
2.7.4