CODEWITHSUNDEEP
libvirt
Shashwat shagun
Shashwat shagun

Reputation: 131

KVM/Libvirt: How do i get total traffic used by KVM/libvirt Virtual machine

i'm want to get the total bandwidth used by a kvm/libvirt VM in C (language). is there function in libvirt?

so, for example if a VM crosses 1TB then i would suspend its network.

Upvotes: 2

Views: 2424

Answers (2)

DanielB
DanielB

Reputation: 2836

In the libvirt XML you need to look at the element to identify the backend device name. eg

<interface type='network'>
  <mac address='52:54:00:b4:fc:f2'/>
  <source network='default' bridge='virbr0'/>
  <target dev='vnet2'/>
  <model type='virtio'/>
  <alias name='net0'/>
  <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
</interface>

here the backend is 'vnet2'. Once you have that you can invoke the C API virDomainInterfaceStats (or via a language binding of your choice) to get the rx/tx stats. As an example using virsh tool:

# virsh domifstat demo vnet2
vnet2 rx_bytes 5040490379
vnet2 rx_packets 3292604
vnet2 rx_errs 0
vnet2 rx_drop 0
vnet2 tx_bytes 167286952
vnet2 tx_packets 1859239
vnet2 tx_errs 0
vnet2 tx_drop 0

Upvotes: 2

bocian85
bocian85

Reputation: 130

When you start a KVM guest the host system creates a vnet interface for each individual network interface within the guest, for example vnet3 vnet4. After that you can monitor the send / received amount of those interfaces by polling the files on the host machine :

cat /sys/class/net/vnet3/statistics/rx_bytes
173110677
cat /sys/class/net/vnet3/statistics/tx_bytes
1640468389

Alternatively you can set up iptables rules with fwmark like in this tutorial :
http://www.tldp.org/HOWTO/Adv-Routing-HOWTO/lartc.netfilter.html
and measure the stats with iptables, but I guess that would be too much of a hassle in C.

Upvotes: 0

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