学习OpenStack之（6）：Neutron 深入学习之 OVS + GRE 之 Compute node 篇

0.环境

硬件环境见上一篇博客：学习OpenStack之（5）：在Mac上部署Juno版本OpenStack 四节点环境

OpenStack网络配置：一个tenant， 2个虚机

• Type driver： GRE， Mechanism driver： OVS
• 一个public network： ext-net 和相应的subnet ext-subnet
• 一个VM network：demo-net 和相应的subnet：demo-subnet
• 一个router连接ext-subnet和demo-subnet

1、Compute 节点上networking组件

下面会用到OVS的两个重要命令：

• ovs-vsctl： 查询和更新ovs-vswitchd的配置
• ovs-ofctl： 查询和控制OpenFlow交换机和控制器

首先查询Compute节点上ovs-vswitchd的配置的配置：

root@compute1:/var/lib/nova# ovs-vsctl show
205a13a2-1ad6-4ae0-8c84-abed97444aa9
    Bridge br-int //OVS integration 桥 br-int
        fail_mode: secure
        Port "qvo37b25c08-e8" //端口，用来连接一个虚机网卡的TAP设备所连接的linux bridge
            tag: 1
            Interface "qvo37b25c08-e8"
        Port patch-tun //端口，用来连接桥br-tun
            Interface patch-tun
                type: patch
                options: {peer=patch-int} //和桥 br-tun上的patch-int是对等端口
        Port br-int
            Interface br-int
                type: internal
        Port "qvo155845ae-5e" //端口，用来连接另一个虚机网卡的TAP设备所连接的linux bridge
            tag: 1
            Interface "qvo155845ae-5e"
    Bridge br-tun //OVS Tunnel 桥br-tun
        Port br-tun
            Interface br-tun
                type: internal
        Port patch-int //端口patch-int，用来连接桥br-int
            Interface patch-int
                type: patch
                options: {peer=patch-tun}
        Port "gre-0a000115" //端口，连接GRE Tunnel
            Interface "gre-0a000115"
                type: gre
                options: {df_default="true", in_key=flow, local_ip="10.0.1.31", out_key=flow, remote_ip="10.0.1.21"}
    ovs_version: "2.0.2" //GRE Tunnel是点到点之间建立的，这头的IP为10.0.1.31，那头的IP地址为 10.0.1.21

继续看桥 br-tun：

root@compute1:/var/lib/nova# ovs-ofctl show br-tun
OFPT_FEATURES_REPLY (xid=0x2): dpid:0000f6b428614747
n_tables:254, n_buffers:256
capabilities: FLOW_STATS TABLE_STATS PORT_STATS QUEUE_STATS ARP_MATCH_IP
actions: OUTPUT SET_VLAN_VID SET_VLAN_PCP STRIP_VLAN SET_DL_SRC SET_DL_DST SET_NW_SRC SET_NW_DST SET_NW_TOS SET_TP_SRC SET_TP_DST ENQUEUE
 1(patch-int): addr:3e:7b:d5:fa:26:8d //端口 patch-int的ID 是 1
     config:     0
     state:      0
     speed: 0 Mbps now, 0 Mbps max
 2(gre-0a000115): addr:2a:26:b2:99:f3:5a //端口 gre-0a000115的ID 是 2
     config:     0
     state:      0
     speed: 0 Mbps now, 0 Mbps max
 LOCAL(br-tun): addr:f6:b4:28:61:47:47
     config:     0
     state:      0
     speed: 0 Mbps now, 0 Mbps max
OFPT_GET_CONFIG_REPLY (xid=0x4): frags=normal miss_send_len=0

每个虚机有个虚机网卡 eth0，eth0和host上的一个TAP设备连接，该TAP设备直接挂载在一个Linux Bridge上，该Linux Bridge和OVS integration bridge br-int相连。其实理想情况下，TAP设备能和OVS Integration Bridge 直接相连就好了，但是，因为OpenStack实现Security Group的需要，这里要多加一层Linux bridge。OpenStack使用Linux TAP设备上的iptables来实现Security Group规则，而OVS不支持直接和br-int桥相连的TAP设备上的iptables。通过查看虚机的libvirt XML定义文件 /var/lib/nova/instances/<instance-id>/libvirt.xml可以看出来虚机所连接的TAP设备：

<interface type="bridge">
      <mac address="fa:16:3e:fe:c7:87"/> //
      <source bridge="qbr37b25c08-e8"/> //虚机TAP设备所挂接的linux bridge
      <target dev="tap37b25c08-e8” /> //虚机所连接的interface 
</interface>

通过以上信息，我们可以画出compute 节点上的网络组建图：

2. Neutron使用TAP设备的iptables来实现Security groups

查看第一个虚机的TAP设备上的iptables：

root@compute1:/var/lib/nova# iptables -S | grep tap37b25c08-e8
-A neutron-openvswi-FORWARD -m physdev --physdev-out tap37b25c08-e8 --physdev-is-bridged -j neutron-openvswi-sg-chain
-A neutron-openvswi-FORWARD -m physdev --physdev-in tap37b25c08-e8 --physdev-is-bridged -j neutron-openvswi-sg-chain
-A neutron-openvswi-INPUT -m physdev --physdev-in tap37b25c08-e8 --physdev-is-bridged -j neutron-openvswi-o37b25c08-e
-A neutron-openvswi-sg-chain -m physdev --physdev-out tap37b25c08-e8 --physdev-is-bridged -j neutron-openvswi-i37b25c08-e
-A neutron-openvswi-sg-chain -m physdev --physdev-in tap37b25c08-e8 --physdev-is-bridged -j neutron-openvswi-o37b25c08-e

OpenStack Neutron在neutron-openvswi-sg-chain上实现security groups。在使用默认security group的情况下：

• neutron-openvswi-o37b25c08-e 控制从虚机出去的traffic

-A neutron-openvswi-o37b25c08-e -p udp -m udp --sport 68 --dport 67 -j RETURN
-A neutron-openvswi-o37b25c08-e -j neutron-openvswi-s37b25c08-e
-A neutron-openvswi-o37b25c08-e -p udp -m udp --sport 67 --dport 68 -j DROP
-A neutron-openvswi-o37b25c08-e -m state --state INVALID -j DROP
-A neutron-openvswi-o37b25c08-e -m state --state RELATED,ESTABLISHED -j RETURN
-A neutron-openvswi-o37b25c08-e -j RETURN
-A neutron-openvswi-o37b25c08-e -j neutron-openvswi-sg-fallback

• neutron-openvswi-i37b25c08-e 控制进入虚机的traffic

-A neutron-openvswi-i37b25c08-e -m state --state INVALID -j DROP
-A neutron-openvswi-i37b25c08-e -m state --state RELATED,ESTABLISHED -j RETURN
-A neutron-openvswi-i37b25c08-e -s 10.0.0.116/32 -p udp -m udp --sport 67 --dport 68 -j RETURN
-A neutron-openvswi-i37b25c08-e -p tcp -m tcp --dport 22 -j RETURN
-A neutron-openvswi-i37b25c08-e -p icmp -j RETURN
-A neutron-openvswi-i37b25c08-e -m set --match-set IPv48c0dc337-0a6d-4ad7-9 src -j RETURN
-A neutron-openvswi-i37b25c08-e -j neutron-openvswi-sg-fallback

使用下面的命令来添加一条secrutiy group 规则来允许使用TCP 22端口：

neutron security-group-rule-create --protocol tcp --port-range-min 22 --port-range-max 22 --direction ingress default

那么该TAP设备的iptables会出现下面的变化：

root@compute1:/var/lib/nova# iptables -S | grep 22
-A FORWARD -d 192.168.122.0/24 -o virbr0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -s 192.168.122.0/24 -i virbr0 -j ACCEPT
-A neutron-openvswi-i155845ae-5 -p tcp -m tcp --dport 22 -j RETURN
-A neutron-openvswi-i155845ae-5 -p tcp -m tcp --dport 22 -j RETURN
-A neutron-openvswi-i37b25c08-e -p tcp -m tcp --dport 22 -j RETURN
-A neutron-openvswi-i37b25c08-e -p tcp -m tcp --dport 22 -j RETURN

3. OVS integration 桥 br-int添加和删除traffic的VLAN ID

每一个使用 neutron net-create 命令创建的network都有一个新的 VLAN ID.本例中因为只有一个network，所以VLAN ID是1，见ovsctl-vsctl show命令中的port tag值。

4. OVS Tunnel 桥 br-tun 处理 VLAN ID 和 Tunnel ID的转化

从以下OpenFlow rule tables可见两种ID的处理过程：

root@compute1:/var/lib/nova# ovs-ofctl dump-flows br-tun
NXST_FLOW reply (xid=0x4):
 cookie=0x0, duration=11509.036s, table=0, n_packets=1059, n_bytes=116533, idle_age=740, priority=1,in_port=1 actions=resubmit(,2) //从端口1及patch-int进来的traffic会被重新执行table 2的rule
 cookie=0x0, duration=2089.491s, table=0, n_packets=1082, n_bytes=115494, idle_age=741, priority=1,in_port=2 actions=resubmit(,3) //从端口2 即 gre 端口进来的traffic重新执行table 3
 cookie=0x0, duration=11508.939s, table=0, n_packets=5, n_bytes=390, idle_age=11500, priority=0 actions=drop
 cookie=0x0, duration=11508.84s, table=2, n_packets=955, n_bytes=106446, idle_age=741, priority=0,dl_dst=00:00:00:00:00:00/01:00:00:00:00:00 actions=resubmit(,20) //重新执行table 20的rule
 cookie=0x0, duration=11508.745s, table=2, n_packets=104, n_bytes=10087, idle_age=740, priority=0,dl_dst=01:00:00:00:00:00/01:00:00:00:00:00 actions=resubmit(,22)
 cookie=0x0, duration=2260.307s, table=3, n_packets=1082, n_bytes=115494, idle_age=741, priority=1,tun_id=0x1 actions=mod_vlan_vid:1,resubmit(,10) //从neutron node来的traffic，打上VLAN ID 1，重新执行table 10的 rule
 cookie=0x0, duration=11508.646s, table=3, n_packets=15, n_bytes=1274, idle_age=2098, priority=0 actions=drop
 cookie=0x0, duration=11508.495s, table=4, n_packets=0, n_bytes=0, idle_age=11508, priority=0 actions=drop
 cookie=0x0, duration=11508.293s, table=10, n_packets=1082, n_bytes=115494, idle_age=741, priority=1 actions=learn(table=20,hard_timeout=300,priority=1,NXM_OF_VLAN_TCI[0..11],NXM_OF_ETH_DST[]=NXM_OF_ETH_SRC[],load:0->NXM_OF_VLAN_TCI[],load:NXM_NX_TUN_ID[]->NXM_NX_TUN_ID[],output:NXM_OF_IN_PORT[]),output:1 //学习规则 table 20，从port 1 即 patch-int发出
 cookie=0x0, duration=11508.093s, table=20, n_packets=0, n_bytes=0, idle_age=11508, priority=0 actions=resubmit(,22) //重新执行table 22的rule
 cookie=0x0, duration=2260.372s, table=22, n_packets=77, n_bytes=7817, idle_age=740, hard_age=2089, dl_vlan=1 actions=strip_vlan,set_tunnel:0x1,output:2,output:2 //去掉VLAN ID，打上TUNNEL ID 1 即 neutron 节点的TUNNEL ID，从端口2 即 gre 端口发出
 cookie=0x0, duration=11507.901s, table=22, n_packets=27, n_bytes=2270, idle_age=1664, priority=0 actions=drop

下一节将neutron节点。