[libvirt] [PATCH 5/9] qemuDomainSetInterfaceParameters: Use new functions to update bandwidth

[Michal Privoznik]

As sketched in previous commits, imagine the following scenario:

  virsh # domiftune gentoo vnet0
  inbound.average: 100
  inbound.peak   : 0
  inbound.burst  : 0
  outbound.average: 100
  outbound.peak  : 0
  outbound.burst : 0

  virsh # domiftune gentoo vnet0 --inbound 0

  virsh # shutdown gentoo
  Domain gentoo is being shutdown

  virsh # list --all
  error: Failed to list domains
  error: Cannot recv data: Connection reset by peer

  Program received signal SIGSEGV, Segmentation fault.
  0x00007fffe80ea221 in networkUnplugBandwidth (net=0x7fff9400c1a0, iface=0x7fff940ea3e0) at network/bridge_driver.c:4881
  4881            net->floor_sum -= ifaceBand->in->floor;

This is rather unfortunate. We should not SIGSEGV here. The
problem is, that while in the second step the inbound QoS was
cleared out, the network part of it was not updated (moreover, we
don't report that vnet0 had inbound.floor set). Internal
structure therefore still had some fragments left (e.g.
class_id). So when qemuProcessStop() started to clean up the
environment it got to networkUnplugBandwidth(). Here, class_id is
set therefore function assumes that there is an inbound QoS. This
actually is a fair assumption to make, there's no need for a
special QoS box in network's QoS when there's no QoS to set.
Anyway, the problem is not the networkUnplugBandwidth() rather
than qemuDomainSetInterfaceParameters() which completely forgot
about QoS being disperse (some parts are set directly on
interface itself, some on bridge the interface is plugged into).

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 src/qemu/qemu_driver.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index b9278f8..171b58f 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -100,6 +100,7 @@
 #include "vircgroup.h"
 #include "virnuma.h"
 #include "dirname.h"
+#include "network/bridge_driver.h"
 
 #define VIR_FROM_THIS VIR_FROM_QEMU
 
@@ -11221,7 +11222,11 @@ qemuDomainSetInterfaceParameters(virDomainPtr dom,
                    sizeof(*newBandwidth->out));
         }
 
-        if (virNetDevBandwidthSet(net->ifname, newBandwidth, false) < 0) {
+        if (!networkBandwidthChangeAllowed(net, newBandwidth))
+            goto endjob;
+
+        if (virNetDevBandwidthSet(net->ifname, newBandwidth, false) < 0 ||
+            networkBandwidthUpdate(net, newBandwidth) < 0) {
             ignore_value(virNetDevBandwidthSet(net->ifname,
                                                net->bandwidth,
                                                false));
-- 
2.4.6