VDSM pluggable networking – VDSM networking modules – Host networking Hooks

VDSM networking modules

Define setupNetworks path.

Define getCaps path.

Introduce configurators.

explain library usage.

Host networking Hooks

• before_network_setup
  • Input: JSON of setupNetworks API command (nets and bonds definitions)
  • Output: JSON dump of network and bonding definitions for setupNetworks to apply
• after_network_setup
  • Input: JSON of what was set for setupNetworks to apply

Example that integrates with journald

#!/usr/bin/env python
from systemd import journal
from vdsm import netinfo
import json, os, sys

with open(os.environ['_hook_json']) as data_file:
    setup_nets_config = json.load(data_file)

networks = netinfo.networks()  # Current nets
for network, data in setup_nets_config['request']['networks'].items():
    if 'remove' in data:
        journal.send('VDSM to remove network %s' % network)
    else:
        journal.send('VDSM to configure network %s' % network,
                     NEWNET=network in networks, DEF=str(data))
                                        

VM networking Hooks

• before_nic_hotplug
• after_nic_hotplug
• after_nic_hotplug_fail

Example that overrides vnic net

#!/usr/bin/env python
import hooking, os, sys, xml.dom

libvirt_net = os.environ.get('extnet')
if libvirt_net is not None:
    doc_xml = hooking.read_domxml()
    vnic_xml, = doc_xml.getElementsByTagName('interface')

    # Replace net from vnic xml
    source, = vnic_xml.getElementsByTagName('source')
    source.removeAttribute('bridge')
    source.setAttribute('network', libvirt_net)
    vnic_xml.setAttribute('type', 'network')

    hooking.write_domxml(doc)  # Write back the xml for vdsm/libvirt
                                        

This could be used in:

• before_device_create
• before_nic_hotplug

some shipped hooks

• Cisco UCS vNIC
• extnet
• macspoofing filter removal
• openstack nets for vNIC
• Attach sriov to VMs
• QoS (obsoleted by new API)

Configurators

• Apply network configuration to the system
• Operates on network device objects
• Advantages:
  • Using different networking systems
  • Supporting multiple distributions
  • Controlling each step of the network configuration
• Pain points:
  • Each configurator can have different persistence semantics
  • Dealing with transactions

Mandatory API

• begin

Optional API

• configureLibvirtNetwork
• removeLibvirtNetwork

Configurator flow

configure Vlan example

def configureVlan(self, vlan, **opts):
    vlan.device.configure(**opts)
    ipwrapper.linkAdd(name=vlan.name, linkType='vlan',
                      link=vlan.device.name args=['id', str(vlan.tag)])
    if vlan.ip:
        ipwrapper.addrFlush(vlan.name)
        ipwrapper.addrAdd(vlan.name, vlan.ipConfig.ipaddr,
                          ipConfig.netmask)
        if vlan.ipConfig.gateway and vlan.ipConfig.defaultRoute:
            ipwrapper.routeAdd(['default', 'via', vlan.ipConfig.gateway])
    if vlan.mtu:
        ipwrapper.linkSet(vlan.name, ['mtu', str(mtu)])
    ipwrapper.linkSet(vlan.name, ['up'])
    if vlan.ipConfig.bootproto == 'dhcp':
        DhcpClient(vlan.name).start(vlan.ipConfig.async)
                                        

Shipped configurators

• ifcfg (Fedora, el6)
• iproute2

Unified persistence: Addressing Configurator pain points

• Abstracts away the network configuration persistence
• Deals with transactionality
• File system based
• One JSON file per each network and/or bond
• Introduces:
  • Running Configuration
  • Persistent Configuration

Running Configuration

• On tmpfs: /var/run/vdsm/netconf/{nets,bonds}
• Exact vdsm network and bond state
• Written on successful network operation
• Can be persisted atomically by setSafeNetworkConfig

Persistent Configuration

• On: /var/lib/vdsm/persistence/netconf/{nets,bonds}
• Configuration to roll back to when rebooting or restoring connectivity
• netconf is a link to the latest snapshot copied from Running Configuration
• Allows recovery from wrong configurations

Creation flow

Reboot flow

Restore flow