整合Open vSwitch与DNSmasq为虚拟机提供DHCP功能

继上文《Ubuntu14.04安装配置Open vSwitch》安装好Open vSwitch后，这里我们将要创建两个KVM虚拟机，并通过DNSmasq来为这两个虚拟机自动分配私网IP地址。

虚拟机与宿主机网络结构图大致如下所示：

测试环境说明：

1）测试私网段：172.17.0.0/24

2）测试 vlan tag：100

下面简要介绍下整个配置流程：

1、安装dnsmasq：

◄►  sudo apt-get install dnsmasq
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
  dnsmasq
 upgraded,  newly installed,  to remove and  not upgraded.
Need to get 14.9 kB of archives.
After this operation,  kB of additional disk space will be used.
Get: http://cn.archive.ubuntu.com/ubuntu/ trusty-updates/universe dnsmasq all 2.68-1ubuntu0.1 [14.9 kB]
Fetched 14.9 kB in 0s ( kB/s)
Selecting previously unselected package dnsmasq.
(Reading database ...  files and directories currently installed.)
Preparing to unpack .../dnsmasq_2.-1ubuntu0.1_all.deb ...
Unpacking dnsmasq (2.68-1ubuntu0.) ...
Processing triggers for ureadahead (0.100.-) ...
ureadahead will be reprofiled on next reboot
Setting up dnsmasq (2.68-1ubuntu0.) ...
 * Starting DNS forwarder and DHCP server dnsmasq                                                                                               [ OK ]
Processing triggers for ureadahead (0.100.-) ...
◄►  sudo ps -ea | grep dns
  ?        :: dnsmasq

2、通过 ovs 创建一个 internal port，这里取名为 qdhcp，并设置 vlan id 为100，供下文的 dnsmasq 进程使用：

◄►  sudo ovs-vsctl add-port br0 qdhcp tag=
◄►  sudo ovs-vsctl set Interface qdhcp type=internal

3、查看已经创建的 qdhcp port：

◄►  sudo ovs-vsctl show
1e6548a9-956e-4b86-b743-f8da0aa2b922
    Bridge "br0"
        Port "br0"
            Interface "br0"
                type: internal
        Port qdhcp
            tag:
            Interface qdhcp
                type: internal
        Port "eth0"
            Interface "eth0"
    ovs_version: "2.0.2"
◄►  ifconfig 
 
qdhcp     Link encap:Ethernet  HWaddr :6c:a8:c2::
          inet6 addr: fe80::706c:a8ff:fec2:/ Scope:Link
          UP BROADCAST RUNNING  MTU:  Metric:
          RX packets: errors: dropped: overruns: frame:
          TX packets: errors: dropped: overruns: carrier:
          collisions: txqueuelen:
          RX bytes: (0.0 B)  TX bytes: (578.0 B)

4、给 qdhcp 虚拟网卡配置 IP 地址，这里IP地址必须为测试私网内的，这里我们就分配 172.17.0.1 给qdhcp：

◄►  sudo ifconfig qdhcp 172.17.0.1 netmask 255.255.255.0 up
◄►  ifconfig
 
qdhcp     Link encap:Ethernet  HWaddr :6c:a8:c2::
          inet addr:172.17.0.1  Bcast:172.17.0.255  Mask:255.255.255.0
          inet6 addr: fe80::706c:a8ff:fec2:/ Scope:Link
          UP BROADCAST RUNNING  MTU:  Metric:
          RX packets: errors: dropped: overruns: frame:
          TX packets: errors: dropped: overruns: carrier:
          collisions: txqueuelen:
          RX bytes: (0.0 B)  TX bytes: (648.0 B)

5、启动一个 dnsmasq 进程，监听 qdhcp 虚拟网卡：

◄►  sudo /usr/sbin/dnsmasq --strict-order --bind-interfaces --interface=qdhcp --except-interface=lo --pid-file=/var/run/dnsmasq/qdhcp.pid --leasefile-ro --dhcp-range=172.17.0.2,172.17.0.254,255.255.255.0,12h --conf-file=

6、查看已经启动的 dnsmasq 进程：

◄►  ps aux | grep dnsmasq
nobody      0.0  0.0     ?        S    :   : /usr/sbin/dnsmasq --strict-order --bind-interfaces --interface=qdhcp --except-interface=lo --pid-file=/var/run/dnsmasq/qdhcp.pid --leasefile-ro --dhcp-range=172.17.0.2,172.17.0.254,255.255.255.0,12h --conf-file=

7、下面就是整理两个虚拟机VM1、VM2的配置文件，这里仅展示 interface 这块配置项：

VM1：
    <interface type='bridge'>
      <source bridge='br0'/>
      <vlan>
        <tag id='100'/>
      </vlan>
      <virtualport type='openvswitch'/>
      <target dev='tap0'/>
      <model type='virtio'/>
    </interface>
 
VM2：
    <interface type='bridge'>
      <source bridge='br0'/>
      <vlan>
        <tag id='100'/>
      </vlan>
      <virtualport type='openvswitch'/>
      <target dev='tap0'/>
      <model type='virtio'/>
    </interface>

这里将两个虚拟机的虚拟网卡的 vlan id 都设为 100，即必须保证和 qdhcp port在同一个vlan中。

8、启动VM1、VM2，并查看 ovs 虚拟网卡 tap0、tap1 的情况：

◄►  sudo ovs-vsctl show
1e6548a9-956e-4b86-b743-f8da0aa2b922
    Bridge "br0"
        Port "tap1"
            tag:
            Interface "tap1"
        Port "br0"
            Interface "br0"
                type: internal
        Port qdhcp
            tag:
            Interface qdhcp
                type: internal
        Port "eth0"
            Interface "eth0"
        Port "tap0"
            tag:
            Interface "tap0"
    ovs_version: "2.0.2"

由此，我们已经将VM1、VM2和qdhcp port分在了同一个VLAN里了。

10、通过VNC登陆到VM1、VM2中，查看其是否获取到指定私网段IP地址：

VM1：

VM2：

11、从VM1 ping VM2：

至此，整合Open vSwitch与DNSmasq的功能就完成了，两个虚拟机之间就可以愉快地玩耍了。