[libvirt-users] Need help of virDomainInterfaceStats

hi,all I am using virDomainInterfaceStats to monitor the network flow of VM. But there is some strange things. the description of vnet in xml is: <interface type='bridge'> <mac address='00:16:3e:5d:aa:a8'/> <source bridge='br0'/> <target dev='vnet0'/> <model type='virtio'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> but when I call virDomainInterfaceStats to get network flow from vnet0, I get some wrong data: rx: 139972719907412 tx:7311107385599290735 after 2 seconds, I call it again and I get: rx: 31 tx:7311107385599290735 another 2 seconds: rx:155 tx:7311107385599290735 and... rx:110 tx:7311107385599290735 (rx:receive, tx:transmit) what do these data mean? Why there is no difference in tx at all? And why the difference in rx is so weird? Many thanks! regards zhangzhang