OpenStack虚拟机virtaulinterfance 网络设备在libvirt的代码梳理

nova创建虚机网卡实际设备的代码调用流程为

_create_domain_and_network---->plug_vifs-->LibvirtGenericVIFDriver.plug-----> plug_ovs_hybrid--->_plug_bridge_with_port。

virtualinterface使用的dirver，由vif_driver参数决定，默认值为vif_driver=nova.virt.libvirt.vif.LibvirtGenericVIFDriver

D:\code-program\官网nova-ocata\nova\virt\libvirt\vif.py
    def plug_ovs_hybrid(self, instance, vif):
        """Plug using hybrid strategy

        Create a per-VIF linux bridge, then link that bridge to the OVS
        integration bridge via a veth device, setting up the other end
        of the veth device just like a normal OVS port.  Then boot the
        VIF on the linux bridge using standard libvirt mechanisms.
	创建一个per-VIF linux网桥，然后通过一个veth设备将该网桥链接到OVS集成网桥，
	将veth设备的另一端设置为正常的OVS端口。
	然后使用标准libvirt机制在linux桥上引导VIF
        """
        self._plug_bridge_with_port(instance, vif, port='ovs')	

    def _plug_bridge_with_port(self, instance, vif, port):
        iface_id = self.get_ovs_interfaceid(vif)
	# 获取br_name, 以qbr开头
        br_name = self.get_br_name(vif['id'])
	# 获取veth_pair_name, 以qvb,qvo开头
        v1_name, v2_name = self.get_veth_pair_names(vif['id'])
	#v1_name是qvb,v2_name是qvo
	# 添加一个 qbr 网桥
        if not linux_net.device_exists(br_name):
            utils.execute('brctl', 'addbr', br_name, run_as_root=True)
            utils.execute('brctl', 'setfd', br_name, 0, run_as_root=True)
            utils.execute('brctl', 'stp', br_name, 'off', run_as_root=True)
            utils.execute('tee',
                          ('/sys/class/net/%s/bridge/multicast_snooping' %
                           br_name),
                          process_input='0',
                          run_as_root=True,
                          check_exit_code=[0, 1])
            disv6 = '/proc/sys/net/ipv6/conf/%s/disable_ipv6' % br_name
            if os.path.exists(disv6):
                utils.execute('tee',
                              disv6,
                              process_input='1',
                              run_as_root=True,
                              check_exit_code=[0, 1])

	# 创建添加一个 qvo设备
        if not linux_net.device_exists(v2_name):
            mtu = vif['network'].get_meta('mtu')
	    #v1_name是qvb,v2_name是qvo
	    # 将两个veth创建为一个peer-port
            linux_net._create_veth_pair(v1_name, v2_name, mtu)-----s1创建peer-port设备
            utils.execute('ip', 'link', 'set', br_name, 'up', run_as_root=True)
	   # 将qvb接口添加到qbr上
            utils.execute('brctl', 'addif', br_name, v1_name, run_as_root=True)
            if port == 'ovs':
	    # 将接口qvo桥接到br-int上
	    # 分别传入的参数为:br-int, qvo, port['id'], port的mac地址, instance-uuid
                linux_net.create_ovs_vif_port(self.get_bridge_name(vif),------s2 将qvo桥接到br-int上
                                              v2_name, iface_id,
                                              vif['address'], instance.uuid,
                                              mtu)
            elif port == 'ivs':
                linux_net.create_ivs_vif_port(v2_name, iface_id,
                                              vif['address'], instance.uuid)
s1创建peer-port设备
def _create_veth_pair(dev1_name, dev2_name, mtu=None):
    """Create a pair of veth devices with the specified names,
    deleting any previous devices with those names.
    """
    for dev in [dev1_name, dev2_name]:
        delete_net_dev(dev)

    utils.execute('ip', 'link', 'add', dev1_name, 'type', 'veth', 'peer',
                  'name', dev2_name, run_as_root=True)
    for dev in [dev1_name, dev2_name]:
        utils.execute('ip', 'link', 'set', dev, 'up', run_as_root=True)
        utils.execute('ip', 'link', 'set', dev, 'promisc', 'on',
                      run_as_root=True)
        _set_device_mtu(dev, mtu)

s2 将qvo桥接到br-int上
def _create_ovs_vif_cmd(bridge, dev, iface_id, mac,
                        instance_id, interface_type=None):
    # 将接口qvo桥接到br-int上
    # 分别传入的参数为:br-int, qvo, port['id'], port的mac地址, instance-uuid
    cmd = ['--', '--if-exists', 'del-port', dev, '--',
            'add-port', bridge, dev,
            '--', 'set', 'Interface', dev,
            'external-ids:iface-id=%s' % iface_id,
            'external-ids:iface-status=active',
            'external-ids:attached-mac=%s' % mac,
            'external-ids:vm-uuid=%s' % instance_id]
    if interface_type:
        cmd += ['type=%s' % interface_type]
    return cmd

def create_ovs_vif_port(bridge, dev, iface_id, mac, instance_id,
                        mtu=None, interface_type=None):
    _ovs_vsctl(_create_ovs_vif_cmd(bridge, dev, iface_id,
                                   mac, instance_id,
                                   interface_type))
    # Note at present there is no support for setting the
    # mtu for vhost-user type ports.
    if interface_type != network_model.OVS_VHOSTUSER_INTERFACE_TYPE:
        _set_device_mtu(dev, mtu)
    else:
        LOG.debug("MTU not set on %(interface_name)s interface "
                  "of type %(interface_type)s.",
                  {'interface_name': dev,
                   'interface_type': interface_type})

由代码可以看出,至此,<qbr>--(qvb)--(qvo)--<br-int>就已经连接上了，至于虚机是如何与<qbr>连上的,这个就是在virt内部做的了,执行以下的命令, 其中的source字段是你提供的qbr, tap则是virt生成的.

[root@test ~]# virsh domiflist 33
Interface Type Source Model MAC
-------------------------------------------------------
tap437153df-04 bridge qbr437153df-04 virtio fa:16:3e:e6:99:cd　　

从代码中可以了解到，Nova创建虚拟机时，网络设备的创建，本质上，执行,brctl,ovs-vsctl及ip link的命令行