[PATCH] qemu: command: Don't attempt to set backend MTU for networks which don't use host backend directly
From: Peter Krempa <pkrempa(a)redhat.com>
Attempting to set MTU for network types which don't actually use the
network device on the host results in a failure. The 'mtu' property is
also used e.g. for the 'host_mtu' property of e.g. 'virtio-net-pci'
which is applied even in vhost-user mode.
Use the existing switch which selects devices without a network device
backend on the host side and skip setting the MTU.
Tested by running 'passt' in vhost-user mode manually:
passt -f --vhost-user -s /tmp/vh.sock
and the following XML:
<interface type="vhostuser">
<mac address="52:54:00:3d:91:97"/>
<source type="unix" path="/tmp/vh.sock"
mode="client"/>
<model type="virtio"/>
<mtu size="9999"/>
<address type="pci" domain="0x0000" bus="0x00"
slot="0x02" function="0x0"/>
</interface>
The OS in the guest reports MTU 9999.
Closes: https://gitlab.com/libvirt/libvirt/-/issues/717
Closes: https://gitlab.com/libvirt/libvirt/-/issues/192
Signed-off-by: Peter Krempa <pkrempa(a)redhat.com>
---
src/qemu/qemu_command.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index fec48edfc1..edafe1588c 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -8713,6 +8713,7 @@ qemuBuildInterfaceCommandLine(virQEMUDriver *driver,
bool requireNicdev = false;
g_autoptr(virJSONValue) hostnetprops = NULL;
qemuDomainNetworkPrivate *netpriv = QEMU_DOMAIN_NETWORK_PRIVATE(net);
+ bool setBackendMTU = true;
GSList *n;
if (qemuDomainValidateActualNetDef(net, qemuCaps) < 0)
@@ -8802,6 +8803,7 @@ qemuBuildInterfaceCommandLine(virQEMUDriver *driver,
case VIR_DOMAIN_NET_TYPE_NULL:
case VIR_DOMAIN_NET_TYPE_VDS:
case VIR_DOMAIN_NET_TYPE_LAST:
+ setBackendMTU = false;
/* These types don't use a network device on the host, but
* instead use some other type of connection to the emulated
* device in the qemu process.
@@ -8842,7 +8844,7 @@ qemuBuildInterfaceCommandLine(virQEMUDriver *driver,
}
}
- if (net->mtu && net->managed_tap != VIR_TRISTATE_BOOL_NO &&
+ if (net->mtu && setBackendMTU && net->managed_tap !=
VIR_TRISTATE_BOOL_NO &&
virNetDevSetMTU(net->ifname, net->mtu) < 0)
goto cleanup;
--
2.49.0