[libvirt] [PATCH v2] qemu: handle multicast overflow on macvtap 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 <***@akamai.com>
---
v1->v2:
1. check for < 0 in virNetDevSetRcvAllMulti() (Michal Privoznik)
2. restrict overflow check to VIR_NETDEV_RX_FILTER_MODE_NORMAL mode as to
avoid unnecessarily calling rx filter updates for other modes
3. update virNetDevSetRcvAllMulti() call to use guestFilter->multicast.overflow
directly (Michal Privoznik)

src/qemu/qemu_driver.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 7fb9102..f4bbfea 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -4443,11 +4443,12 @@ 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 &&
+ guestFilter->multicast.mode == VIR_NETDEV_RX_FILTER_MODE_NORMAL)) {
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 +4456,24 @@ 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 (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);
}
break;

[Michael S. Tsirkin]

Post by 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.
---
1. check for < 0 in virNetDevSetRcvAllMulti() (Michal Privoznik)
2. restrict overflow check to VIR_NETDEV_RX_FILTER_MODE_NORMAL mode as to
avoid unnecessarily calling rx filter updates for other modes
3. update virNetDevSetRcvAllMulti() call to use guestFilter->multicast.overflow
directly (Michal Privoznik)
src/qemu/qemu_driver.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 7fb9102..f4bbfea 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -4443,11 +4443,12 @@ 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 &&
+ guestFilter->multicast.mode == VIR_NETDEV_RX_FILTER_MODE_NORMAL)) {
switch (guestFilter->multicast.mode) {
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 +4456,24 @@ syncNicRxFilterMultiMode(char *ifname, virNetDevRxFilterPtr guestFilter,
break;
- 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 (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);
}
break;
--
2.7.4

[Michal Privoznik]

Post by 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.
---
1. check for < 0 in virNetDevSetRcvAllMulti() (Michal Privoznik)
2. restrict overflow check to VIR_NETDEV_RX_FILTER_MODE_NORMAL mode as to
avoid unnecessarily calling rx filter updates for other modes
3. update virNetDevSetRcvAllMulti() call to use guestFilter->multicast.overflow
directly (Michal Privoznik)
src/qemu/qemu_driver.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)

ACK

We're currently in a freeze. While this is a bug fix I'm not sure it's
that critical. The freeze should be over any minute now, so do you mind
if I merge it after that?

Michal

[Michal Privoznik]

Post by 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.
---
1. check for < 0 in virNetDevSetRcvAllMulti() (Michal Privoznik)
2. restrict overflow check to VIR_NETDEV_RX_FILTER_MODE_NORMAL mode as to
avoid unnecessarily calling rx filter updates for other modes
3. update virNetDevSetRcvAllMulti() call to use guestFilter->multicast.overflow
directly (Michal Privoznik)
src/qemu/qemu_driver.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)

ACK

Huh, the release happened as I was reviewing this. This is now merged.

Congratulations on your first libvirt contribution!

Michal

[Michael S. Tsirkin]

Post by Michal Privoznik

Post by 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.
---
1. check for < 0 in virNetDevSetRcvAllMulti() (Michal Privoznik)
2. restrict overflow check to VIR_NETDEV_RX_FILTER_MODE_NORMAL mode as to
avoid unnecessarily calling rx filter updates for other modes
3. update virNetDevSetRcvAllMulti() call to use guestFilter->multicast.overflow
directly (Michal Privoznik)
src/qemu/qemu_driver.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)

ACK
We're currently in a freeze. While this is a bug fix I'm not sure it's
that critical. The freeze should be over any minute now, so do you mind
if I merge it after that?
Michal

FYI It's a blocker for some people as multicast stops working completely.