目前在Juno版本的trunk中已经合入了DVR相关的代码，我的理解是在Juno版本中DVR是一个experimental feature。最好需要稳定一个版本以后再上生产环境。之前写过一篇博文是DVR相关的，当时代码还没有实现，与实际的实现有一些出入。当前的DVR的实现是基于VXLAN的。关于VXLAN的优势，有时间会写一些体会，今天暂且不谈。
建议先看一下以下文档，对DVR有一些了解:
https://docs.google.com/presentation/d/1ktCLAdglpKdsC–fQ2F_c2d3X1u-lyRGGUzRu9ITuWo/edit#slide=id.g2b6a14e30_036
https://docs.google.com/presentation/d/1ktCLAdglpKdsC–fQ2F_c2d3X1u-lyRGGUzRu9ITuWo/edit#slide=id.g2b6a14e30_030
首先看一下，没有使用DVR的问题在哪里：
从图中可以明显看到东西向和南北向的流量会集中到网络节点，这会使网络节点成为瓶颈。
那如果启用的DVR，情况会变成如下：
对于东西向的流量， 流量会直接在计算节点之间传递。 对于南北向的流量，如果有floating ip，流量就直接走计算节点。如果没有floating ip，则会走网络节点。
我的实验环境如下：
然后起了两个私有网络和一个DVR 路由器，拓扑如下:
注: 可以看到每个网络与DVR连接时有两个接口，以private1为例，有10.0.1.1和10.0.1.6。
可以看到10.0.1.6是centralized_snat的网关，这个地址是在网络节点上的。 10.0.1.1是router_interface_distributed地址，它是在每一个计算节点上的。虚机获取到的默认网关就是这个IP。
虚机情况如下：
注: 虚机privateX-computeY-VM表示，此虚机起在privateX网络，computeY节点上。在compute1节点的两台虚机拥有floating ip。
下面分析三种情况下traffic的是怎么走的： 1. 东西向流量：以private1-compute1-VM和private2-compute2-VM之间的通信为例。 2. 南北向流量： a) 带floating ip， 以private1-compute1-VM对外通信为例。 b) 不带floating ip， 以private1-compute2-VM对外通信为例。 第一种情况 — 东西向流量 首先我们看一下虚机private1-compute1-VM的IP和路由:
再看一下虚机private2-compute2-VM的IP和路由:
我们在private1-compute1-VM中ping 10.0.2.5(private2-compute2-VM的IP)。
当我们ping了之后，在首先会查询private1-compute1-VM的路由表，会将包发送到网关10.0.1.1。那么会首先会发送10.0.1.1的arp请求。 arp请求会发送到br-int上。 我们可以看到10.0.1.5的port id是4e843b99开头的： 
最终会转发到br-int的qvo4e843b99-fb:
https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ovs-vsctl show
67f121bd-cca7-41c2-95ab-23ed85d1305b
Bridge br-tun
Port patch-int
Interface patch-int
type: patch
options: {peer=patch-tun}
Port “vxlan-0ae09f91”
Interface “vxlan-0ae09f91”
type: vxlan
options: {df_default=”true”, in_key=flow, local_ip=”10.224.159.141″, out_key=flow, remote_ip=”10.224.159.145″}
Port “vxlan-0ae09f88”
Interface “vxlan-0ae09f88”
type: vxlan
options: {df_default=”true”, in_key=flow, local_ip=”10.224.159.141″, out_key=flow, remote_ip=”10.224.159.136″}
Port br-tun
Interface br-tun
type: internal
Bridge br-int
fail_mode: secure
Port “qvo111517d8-c5”
tag: 2
Interface “qvo111517d8-c5”
Port patch-tun
Interface patch-tun
type: patch
options: {peer=patch-int}
Port “qr-001d0ed9-01”
tag: 2
Interface “qr-001d0ed9-01”
type: internal
Port br-int
Interface br-int
type: internal
Port “qr-ddbdc784-d7”
tag: 1
Interface “qr-ddbdc784-d7”
type: internal
Port “qvo4e843b99-fb”
tag: 1
Interface “qvo4e843b99-fb”
Bridge br-ex
Port br-ex
Interface br-ex
type: internal
Port “fg-081d537b-06”
Interface “fg-081d537b-06”
type: internal
ovs_version: “2.0.2”
而端口qvo4e843b99-fb是属于vlan 1的，arp广播包会转发到”qr-ddbdc784-d7″和”patch-tun”。
首先看”qr-ddbdc784-d7″，这是interface_distributed的接口：
这个接口是在compute node的的DVR中的： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns
fip-fbd46644-c70f-4227-a414-862a00cbd1d2
qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa
qdhcp-401f678d-4518-446c-9a33-cd2fb054c104
qdhcp-db755841-0764-4a8f-b962-8df008ce6330
https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ifconfig
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
qr-001d0ed9-01 Link encap:Ethernet HWaddr fa:16:3e:69:b4:05
inet addr:10.0.2.1 Bcast:10.0.2.255 Mask:255.255.255.0
inet6 addr: fe80::f816:3eff:fe69:b405/64 Scope:Link
UP BROADCAST RUNNING MTU:1500 Metric:1
RX packets:35 errors:0 dropped:0 overruns:0 frame:0
TX packets:14 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:3510 (3.5 KB) TX bytes:1092 (1.0 KB)
qr-ddbdc784-d7 Link encap:Ethernet HWaddr fa:16:3e:66:13:af
inet addr:10.0.1.1 Bcast:10.0.1.255 Mask:255.255.255.0
inet6 addr: fe80::f816:3eff:fe66:13af/64 Scope:Link
UP BROADCAST RUNNING MTU:1500 Metric:1
RX packets:401 errors:0 dropped:0 overruns:0 frame:0
TX packets:378 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:38224 (38.2 KB) TX bytes:36224 (36.2 KB)
rfp-0fbb351e-a Link encap:Ethernet HWaddr ea:5c:56:9a:36:9c
inet addr:169.254.31.28 Bcast:0.0.0.0 Mask:255.255.255.254
inet6 addr: fe80::e85c:56ff:fe9a:369c/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:12 errors:0 dropped:0 overruns:0 frame:0
TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1116 (1.1 KB) TX bytes:1116 (1.1 KB)
接口qr-ddbdc784-d7拥有10.0.1.1。所以他会响应ARP请求。
回过头来看”patch-tun”, ARP请求转发到这个接口后，会转发到br-tun。看一下br-tun上的flow, 目前我们只需要看红色部分，他会将目标地址为10.0.1.1的ARP请求丢弃： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ovs-ofctl dump-flows br-tun
NXST_FLOW reply (xid=0x4):
。。。 cookie=0x0,
duration=64720.432s, table=1, n_packets=4, n_bytes=168, idle_age=64607,
priority=3,arp,dl_vlan=1,arp_tpa=10.0.1.1 actions=drop
cookie=0x0,
duration=62666.766s, table=1, n_packets=2, n_bytes=84, idle_age=62576,
priority=3,arp,dl_vlan=2,arp_tpa=10.0.2.1 actions=drop 。。。
回到我们虚机，当获取到了10.0.1.1的MAC地址后，会发出如下的包： Dest IP: 10.0.2.5 Souce IP: 10.0.1.5 Dest MAC: MAC of 10.0.1.1 Source MAC: MAC of 10.0.1.5
之后包被转发到compute1
的qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa 的namespace： 这里利用了内核的高级路由到了，首先看一下ip rule： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ip rule
0: from all lookup local
32766: from all lookup main
32767: from all lookup default
32768: from 10.0.1.5 lookup 16
32769: from 10.0.2.3 lookup 16
167772417: from 10.0.1.1/24 lookup 167772417
167772417: from 10.0.1.1/24 lookup 167772417
167772673: from 10.0.2.1/24 lookup 167772673
可以看到会先查找main表：
https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ip route list table main
10.0.1.0/24 dev qr-ddbdc784-d7 proto kernel scope link src 10.0.1.1
10.0.2.0/24 dev qr-001d0ed9-01 proto kernel scope link src 10.0.2.1
169.254.31.28/31 dev rfp-0fbb351e-a proto kernel scope link src 169.254.31.28
在main表中满足以下路由: 10.0.2.0/24 dev qr-001d0ed9-01 proto kernel scope link src 10.0.2.1
因此会从qr-001d0ed9-01转发出去。
之后需要去查询10.0.2.5的MAC地址， MAC是由neutron使用静态ARP的方式设定的： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ip nei
10.0.1.5 dev qr-ddbdc784-d7 lladdr fa:16:3e:da:75:6d PERMANENT
10.0.2.3 dev qr-001d0ed9-01 lladdr fa:16:3e:a4:fc:98 PERMANENT
10.0.1.6 dev qr-ddbdc784-d7 lladdr fa:16:3e:9f:55:67 PERMANENT
10.0.2.2 dev qr-001d0ed9-01 lladdr fa:16:3e:13:55:66 PERMANENT
10.0.2.5 dev qr-001d0ed9-01 lladdr fa:16:3e:51:99:b8 PERMANENT
10.0.1.4 dev qr-ddbdc784-d7 lladdr fa:16:3e:da:e3:6e PERMANENT
10.0.1.7 dev qr-ddbdc784-d7 lladdr fa:16:3e:14:b8:ec PERMANENT
169.254.31.29 dev rfp-0fbb351e-a lladdr 42:0d:9f:49:63:c6 STALE
由于Neutron知道所有虚机的信息，因此他可以事先设定好静态ARP。 至此，我们的ICMP包会变成以下形式从qr-001d0ed9-01转发出去： Dest IP: 10.0.2.5 Souce IP: 10.0.1.5 Dest MAC: MAC of 10.0.2.5 Source MAC: MAC of 10.0.2.1
当包转发到”br-tun”后，进开始查询openflow表。 首先我们看一下br-tun的接口状况：
https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ovs-ofctl show br-tun
OFPT_FEATURES_REPLY (xid=0x2): dpid:0000e2b7aa5da34a
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:76:ae:9f:b3:bf:c6
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
3(vxlan-0ae09f88): addr:92:61:e9:43:dd:99
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
4(vxlan-0ae09f91): addr:2e:cc:c0:4a:4e:d4
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
LOCAL(br-tun): addr:e2:b7:aa:5d:a3:4a
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
OFPT_GET_CONFIG_REPLY (xid=0x4): frags=normal miss_send_len=0
首先我们看一下br-tun的flowtable，首先会进入table 0，由于包是从br-int发过来的，因此in_port是patch-int(1)，之后会查询表1： cookie=0x0, duration=66172.51s, table=0, n_packets=58,
n_bytes=5731, idle_age=20810, hard_age=65534, priority=1,in_port=3
actions=resubmit(,4) cookie=0x0,
duration=67599.526s, table=0, n_packets=273, n_bytes=24999,
idle_age=1741, hard_age=65534, priority=1,in_port=1 actions=resubmit(,1) cookie=0x0, duration=64437.052s, table=0, n_packets=28,
n_bytes=2980, idle_age=20799, priority=1,in_port=4 actions=resubmit(,4) cookie=0x0, duration=67601.704s, table=0, n_packets=5, n_bytes=390,
idle_age=65534, hard_age=65534, priority=0 actions=drop
表1，这张表中会丢弃目标地址是interface_distributed接口的ARP和目的MAC是interface_distributed的包。以防止虚机发送给本地IR的包不会被转发到网络中。 我们的ICMP包会命中一下flow，它会把源MAC地址改为全局唯一和计算节点绑定的MAC:
cookie=0x0,
duration=66135.811s, table=1, n_packets=140, n_bytes=13720,
idle_age=65534, hard_age=65534,
priority=1,dl_vlan=1,dl_src=fa:16:3e:66:13:af
actions=mod_dl_src:fa:16:3f:fe:49:e9,resubmit(,2) cookie=0x0, duration=64082.141s, table=1, n_packets=2, n_bytes=200,
idle_age=64081, priority=1,dl_vlan=2,dl_src=fa:16:3e:69:b4:05
actions=mod_dl_src:fa:16:3f:fe:49:e9,resubmit(,2) cookie=0x0, duration=66135.962s, table=1, n_packets=1, n_bytes=98,
idle_age=65301, hard_age=65534,
priority=2,dl_vlan=1,dl_dst=fa:16:3e:66:13:af actions=drop cookie=0x0, duration=64082.297s, table=1, n_packets=0, n_bytes=0,
idle_age=64082, priority=2,dl_vlan=2,dl_dst=fa:16:3e:69:b4:05
actions=drop cookie=0x0, duration=66136.115s, table=1, n_packets=4, n_bytes=168,
idle_age=65534, hard_age=65534,
priority=3,arp,dl_vlan=1,arp_tpa=10.0.1.1 actions=drop cookie=0x0, duration=64082.449s, table=1, n_packets=2, n_bytes=84,
idle_age=63991, priority=3,arp,dl_vlan=2,arp_tpa=10.0.2.1 actions=drop cookie=0x0, duration=67599.22s, table=1, n_packets=123,
n_bytes=10687, idle_age=1741, hard_age=65534, priority=0
actions=resubmit(,2)
这个全局唯一和计算节点绑定的MAC地址，是由neutron全局分配的，数据库中可以看到这个MAC是每个host一个：
它的base MAC是可以在neutron.conf中配置的：
继续查询流表2，表2是VXLAN表，如果是广播包就会查询表22，如果是单播包就查询表20： cookie=0x0, duration=67601.554s, table=2, n_packets=176,
n_bytes=16981, idle_age=20810, hard_age=65534,
priority=0,dl_dst=00:00:00:00:00:00/01:00:00:00:00:00
actions=resubmit(,20) cookie=0x0, duration=67601.406s, table=2, n_packets=92,
n_bytes=7876, idle_age=1741, hard_age=65534,
priority=0,dl_dst=01:00:00:00:00:00/01:00:00:00:00:00
actions=resubmit(,22)
ICMP包是单播包，因此会查询表20，由于开启了L2 pop功能，在表20中会事先学习到应该转发到哪个VTEP。 cookie=0x0, duration=64076.431s, table=20, n_packets=0, n_bytes=0,
idle_age=64076, priority=2,dl_vlan=2,dl_dst=fa:16:3e:13:55:66
actions=strip_vlan,set_tunnel:0x3eb,output:3 cookie=0x0, duration=66130.899s, table=20, n_packets=152,
n_bytes=14728, idle_age=65534, hard_age=65534,
priority=2,dl_vlan=1,dl_dst=fa:16:3e:9f:55:67
actions=strip_vlan,set_tunnel:0x3e9,output:3 cookie=0x0, duration=66560.59s, table=20, n_packets=7, n_bytes=552,
idle_age=65534, hard_age=65534,
priority=2,dl_vlan=1,dl_dst=fa:16:3e:da:e3:6e
actions=strip_vlan,set_tunnel:0x3e9,output:2 cookie=0x0, duration=64436.717s, table=20, n_packets=0, n_bytes=0,
idle_age=64436, priority=2,dl_vlan=1,dl_dst=fa:16:3e:14:b8:ec
actions=strip_vlan,set_tunnel:0x3e9,output:4 cookie=0x0,
duration=64015.308s, table=20, n_packets=0, n_bytes=0, idle_age=64015,
priority=2,dl_vlan=2,dl_dst=fa:16:3e:51:99:b8
actions=strip_vlan,set_tunnel:0x3eb,output:4 cookie=0x0, duration=64032.699s, table=20, n_packets=9,
n_bytes=917, idle_age=20810,
priority=2,dl_vlan=2,dl_dst=fa:16:3e:bb:cf:66
actions=strip_vlan,set_tunnel:0x3eb,output:3 cookie=0x0, duration=67600.802s, table=20, n_packets=8,
n_bytes=784, idle_age=65534, hard_age=65534, priority=0
actions=resubmit(,22)
注： 由于L2 POP并不是本文的重点。因此不在此细说。如果有兴趣可以看以下blog: http://assafmuller.com/category/overlays/
此时包会变成如下形式： Dest IP: 10.0.2.5 Souce IP: 10.0.1.5 Dest MAC: MAC of 10.0.2.5 Source MAC:
fa:16:3f:fe:49:e9
之后包会从port 4发出：
https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ovs-vsctl show
67f121bd-cca7-41c2-95ab-23ed85d1305b
Bridge br-tun
Port patch-int
Interface patch-int
type: patch
options: {peer=patch-tun}
Port “vxlan-0ae09f91”
Interface “vxlan-0ae09f91”
type: vxlan
options: {df_default=”true”, in_key=flow, local_ip=”10.224.159.141″, out_key=flow, remote_ip=”10.224.159.145″}
Port “vxlan-0ae09f88”
Interface “vxlan-0ae09f88”
type: vxlan
options: {df_default=”true”, in_key=flow, local_ip=”10.224.159.141″, out_key=flow, remote_ip=”10.224.159.136″}
Port br-tun
Interface br-tun
type: internal
OVS会将此包进行VXLAN封装，将L2帧分装到VXLAN中，包头如下：
OVS会将此包进行VXLAN封装，将L2帧分装到VXLAN中，包头如下：
本文并不想具体讨论VXLAN是如何封装的，简单的说就是讲二层帧封到了一个UDP包中。
之后compute2会收到这个包，在compute2的br-tun上查询流表: 首先看一下接口情况：
root@dvr-compute2:~# ovs-ofctl show br-tun
OFPT_FEATURES_REPLY (xid=0x2): dpid:000062e9fb8b8f42
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:02:dc:f1:96:db:bd
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
3(vxlan-0ae09f88): addr:b6:4b:d0:83:07:52
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
4(vxlan-0ae09f8d): addr:12:e5:36:2c:1a:36
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
LOCAL(br-tun): addr:62:e9:fb:8b:8f:42
config: 0
state: 0
speed: 0 Mbps now, 0 Mbps max
OFPT_GET_CONFIG_REPLY (xid=0x4): frags=normal miss_send_len=0
在table0中可以看到，如果包是从外部发来的就会去查询表4： cookie=0x0, duration=66293.658s, table=0, n_packets=31,
n_bytes=3936, idle_age=22651, hard_age=65534, priority=1,in_port=3
actions=resubmit(,4) cookie=0x0, duration=69453.368s, table=0, n_packets=103,
n_bytes=9360, idle_age=22651, hard_age=65534, priority=1,in_port=1
actions=resubmit(,1) cookie=0x0, duration=66292.808s, table=0, n_packets=20,
n_bytes=1742, idle_age=3598, hard_age=65534, priority=1,in_port=4
actions=resubmit(,4) cookie=0x0, duration=69455.675s, table=0, n_packets=5, n_bytes=390,
idle_age=65534, hard_age=65534, priority=0 actions=drop
在表4中，会将tun_id对应的改为本地vlan id，之后查询表9: cookie=0x0, duration=65937.871s, table=4, n_packets=32,
n_bytes=3653, idle_age=22651, hard_age=65534, priority=1,tun_id=0x3eb
actions=mod_vlan_vid:3,resubmit(,9) cookie=0x0, duration=66294.732s, table=4, n_packets=19,
n_bytes=2025, idle_age=3598, hard_age=65534, priority=1,tun_id=0x3e9
actions=mod_vlan_vid:2,resubmit(,9) cookie=0x0, duration=69455.115s, table=4, n_packets=0, n_bytes=0, idle_age=65534, hard_age=65534, priority=0 actions=drop
在表9中，如果发现包的源地址是全局唯一并与计算节点绑定的MAC地址，就将其转发到br-int:
cookie=0x0,
duration=69453.507s, table=9, n_packets=0, n_bytes=0, idle_age=65534,
hard_age=65534, priority=1,dl_src=fa:16:3f:fe:49:e9 actions=output:1 cookie=0x0,
duration=69453.782s, table=9, n_packets=0, n_bytes=0, idle_age=65534,
hard_age=65534, priority=1,dl_src=fa:16:3f:72:3f:a7 actions=output:1 cookie=0x0, duration=69453.23s, table=9, n_packets=56,
n_bytes=6028, idle_age=3598, hard_age=65534, priority=0
actions=resubmit(,10)
由于我们的源MAC为fa:16:3f:fe:49:e9，我们的ICMP包就被转发到了br-int，之后查询br-int的流表： 在表0中，如果是全局唯一并与计算节点绑定的MAC地址就查询表1，否则就正常转发： cookie=0x0, duration=70039.903s, table=0, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534,
priority=2,in_port=6,dl_src=fa:16:3f:72:3f:a7 actions=resubmit(,1) cookie=0x0,
duration=70039.627s, table=0, n_packets=0, n_bytes=0, idle_age=65534,
hard_age=65534, priority=2,in_port=6,dl_src=fa:16:3f:fe:49:e9
actions=resubmit(,1) cookie=0x0, duration=70040.053s, table=0, n_packets=166,
n_bytes=15954, idle_age=4184, hard_age=65534, priority=1 actions=NORMAL
在表1中，事先设定好了flow，如果目的MAC是发送给private2-compute2-VM，就将源MAC改为private2的网关MAC地址： cookie=0x0,
duration=66458.695s, table=1, n_packets=0, n_bytes=0, idle_age=65534,
hard_age=65534, priority=4,dl_vlan=3,dl_dst=fa:16:3e:51:99:b8
actions=strip_vlan,mod_dl_src:fa:16:3e:69:b4:05,output:12 cookie=0x0, duration=66877.515s, table=1, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534,
priority=4,dl_vlan=2,dl_dst=fa:16:3e:14:b8:ec
actions=strip_vlan,mod_dl_src:fa:16:3e:66:13:af,output:9 cookie=0x0, duration=66877.369s, table=1, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534,
priority=2,ip,dl_vlan=2,nw_dst=10.0.1.0/24
actions=strip_vlan,mod_dl_src:fa:16:3e:66:13:af,output:9 cookie=0x0, duration=66458.559s, table=1, n_packets=0, n_bytes=0,
idle_age=65534, hard_age=65534,
priority=2,ip,dl_vlan=3,nw_dst=10.0.2.0/24
actions=strip_vlan,mod_dl_src:fa:16:3e:69:b4:05,output:12
还可以看到下面两条rule是网段flow的rule，他们的output是一个list，会将此包转发到所有连接到此network上。 如果所有的虚机的rule都已经事先设定好的话，这两条rule应该并没有实际作用，等到代码稳定后，这两条rule应该会被删除。
经过br-int的流表后，包会变成如下形式： Dest IP: 10.0.2.5 Souce IP: 10.0.1.5 Dest MAC: MAC of 10.0.2.5 Source MAC:
fa:16:3e:69:b4:05(MAC of 10.0.2.1 网关地址)
至此，虚机private2-compute2-VM就会收到来自private1-compute1-VM的包了。从通信的过程可以看到，跨网段的东西向流量没有经过网络节点。
第二种情况 — 南北向流量(虚机有floating ip) 以虚机private1-compute1-VM对外通信为例，此虚机拥有floating ip:
比如我们在虚机中ping 8.8.8.8 。首先在虚机中查询路由，和第一种情况一样，虚机会发送给网关。发送的包如下： Dest IP: 8.8.8.8 Souce IP: 10.0.1.5 Dest MAC: MAC of 10.0.1.1 Source MAC: MAC of 10.0.1.5
查看ip rule: https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ip rule
0: from all lookup local
32766: from all lookup main
32767: from all lookup default
32768: from 10.0.1.5 lookup 16
32769: from 10.0.2.3 lookup 16
167772417: from 10.0.1.1/24 lookup 167772417
167772417: from 10.0.1.1/24 lookup 167772417
167772673: from 10.0.2.1/24 lookup 167772673
在main表中没有合适的路由： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ip route list table main
10.0.1.0/24 dev qr-ddbdc784-d7 proto kernel scope link src 10.0.1.1
10.0.2.0/24 dev qr-001d0ed9-01 proto kernel scope link src 10.0.2.1
169.254.31.28/31 dev rfp-0fbb351e-a proto kernel scope link src 169.254.31.28
由于包是从10.0.1.5发来的之后会查看table 16: https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ip route list table 16
default via 169.254.31.29 dev rfp-0fbb351e-a 包会命中这条路由。
路由之后会通过netfilter的POSTROUTING链中进行SNAT： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa iptables -nvL -t nat 。。。 Chain neutron-l3-agent-float-snat (1 references) pkts bytes target prot opt in out source destination 0 0 SNAT all — * * 10.0.2.3 0.0.0.0/0 to:172.24.4.7 0 0 SNAT all — * * 10.0.1.5 0.0.0.0/0 to:172.24.4.5 。。。
之后就可以看到包会通过rfp-0fbb351e-a发送给169.254.31.29。
端口rfp-0fbb351e-a和fpr-0fbb351e-a是一对veth pair。在fip namespace中你可以看到这个接口：
https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec fip-fbd46644-c70f-4227-a414-862a00cbd1d2 ifconfig
fg-081d537b-06 Link encap:Ethernet HWaddr fa:16:3e:a4:eb:6b
inet addr:172.24.4.6 Bcast:172.24.4.255 Mask:255.255.255.0
inet6 addr: fe80::f816:3eff:fea4:eb6b/64 Scope:Link
UP BROADCAST RUNNING MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:50 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:2512 (2.5 KB)
fpr-0fbb351e-a Link encap:Ethernet HWaddr 42:0d:9f:49:63:c6
inet addr:169.254.31.29 Bcast:0.0.0.0 Mask:255.255.255.254
inet6 addr: fe80::400d:9fff:fe49:63c6/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:12 errors:0 dropped:0 overruns:0 frame:0
TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1116 (1.1 KB) TX bytes:1116 (1.1 KB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:13 errors:0 dropped:0 overruns:0 frame:0
TX packets:13 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1250 (1.2 KB) TX bytes:1250 (1.2 KB)
到了fip的namespace之后，会查询路由， 这里有通往公网的默认路由： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec fip-fbd46644-c70f-4227-a414-862a00cbd1d2 ip route
default via 172.24.4.1 dev fg-081d537b-06
169.254.31.28/31 dev fpr-0fbb351e-a proto kernel scope link src 169.254.31.29
172.24.4.0/24 dev fg-081d537b-06 proto kernel scope link src 172.24.4.6
172.24.4.5 via 169.254.31.28 dev fpr-0fbb351e-a
172.24.4.7 via 169.254.31.28 dev fpr-0fbb351e-a
通过fg-081d537b-06 发送到br-ex。这是从虚机发送到公网的过程。
反过来，从外网发起连接到虚机时，在fip的namespace会做arp代理： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec fip-fbd46644-c70f-4227-a414-862a00cbd1d2 sysctl net.ipv4.conf.fg-081d537b-06.proxy_arp
net.ipv4.conf.fg-081d537b-06.proxy_arp = 1
可以看到接口的arp代理是打开的，对于floating ip 有以下两条路由： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec fip-fbd46644-c70f-4227-a414-862a00cbd1d2 ip route
。。。
172.24.4.5 via 169.254.31.28 dev fpr-0fbb351e-a
172.24.4.7 via 169.254.31.28 dev fpr-0fbb351e-a 。。。
ARP会去通过VETH Pair到IR的namespace中去查询，在IR中可以看到，接口rfp-0fbb351e-a配置了floating ip:
https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: rfp-0fbb351e-a: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether ea:5c:56:9a:36:9c brd ff:ff:ff:ff:ff:ff
inet 169.254.31.28/31 scope global rfp-0fbb351e-a
valid_lft forever preferred_lft forever
inet 172.24.4.5/32 brd 172.24.4.5 scope global rfp-0fbb351e-a
valid_lft forever preferred_lft forever
inet 172.24.4.7/32 brd 172.24.4.7 scope global rfp-0fbb351e-a
valid_lft forever preferred_lft forever
inet6 fe80::e85c:56ff:fe9a:369c/64 scope link
valid_lft forever preferred_lft forever
17: qr-ddbdc784-d7: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
link/ether fa:16:3e:66:13:af brd ff:ff:ff:ff:ff:ff
inet 10.0.1.1/24 brd 10.0.1.255 scope global qr-ddbdc784-d7
valid_lft forever preferred_lft forever
inet6 fe80::f816:3eff:fe66:13af/64 scope link
valid_lft forever preferred_lft forever
19: qr-001d0ed9-01: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
link/ether fa:16:3e:69:b4:05 brd ff:ff:ff:ff:ff:ff
inet 10.0.2.1/24 brd 10.0.2.255 scope global qr-001d0ed9-01
valid_lft forever preferred_lft forever
inet6 fe80::f816:3eff:fe69:b405/64 scope link
valid_lft forever preferred_lft forever
因此fip的namespace会对这两个floating ip进行ARP回应。
外部发起目标地址为floating ip的请求后，fip会将其转发到IR中，IR的RPOROUTING链中规则如下： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa iptables -nvL -t nat 。。。 Chain neutron-l3-agent-PREROUTING (1 references) pkts bytes target prot opt in out source destination 0 0 REDIRECT tcp — * * 0.0.0.0/0 169.254.169.254 tcp dpt:80 redir ports 9697 0 0 DNAT all — * * 0.0.0.0/0 172.24.4.7 to:10.0.2.3 0 0 DNAT all — * * 0.0.0.0/0 172.24.4.5 to:10.0.1.5 。。。
这条DNAT规则会将floating ip地址转换为内部地址，之后进行路由查询： https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ip route
10.0.1.0/24 dev qr-ddbdc784-d7 proto kernel scope link src 10.0.1.1
10.0.2.0/24 dev qr-001d0ed9-01 proto kernel scope link src 10.0.2.1
169.254.31.28/31 dev rfp-0fbb351e-a proto kernel scope link src 169.254.31.28
目的地址是10.0.1.0/24网段的，因此会从qr-ddbdc784-d7转发出去。之后就会转发到br-int再到虚机。
第三种情况 — 南北向流量(虚机没有floating ip)
在虚机没有floating ip的情况下，从虚机发出的包会首先到IR，IR中查询路由：
https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ip rule
0: from all lookup local
32766: from all lookup main
32767: from all lookup default
32768: from 10.0.1.5 lookup 16
32769: from 10.0.2.3 lookup 16
167772417: from 10.0.1.1/24 lookup 167772417
167772417: from 10.0.1.1/24 lookup 167772417
167772673: from 10.0.2.1/24 lookup 167772673
会先查询main表，之后查询167772417表。 https://www.shuzhiduo.com/A/amd0mOZLzg/root@dvr-compute1:~# ip netns exec qrouter-0fbb351e-a65b-4790-a409-8fb219ce16aa ip route list table 167772417
default via 10.0.1.6 dev qr-ddbdc784-d7
这个表会将其转发给10.0.1.6,而这个IP就是在network node上的router_centralized_snat接口。
在network node的snat namespace中，我们可以看到这个接口：
https://www.shuzhiduo.com/A/amd0mOZLzg/stack@dvr-controller:/root$ sudo ip netns exec snat-0fbb351e-a65b-4790-a409-8fb219ce16aa ifconfig
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
qg-4d15b7f6-cb Link encap:Ethernet HWaddr fa:16:3e:24:0b:6b
inet addr:172.24.4.4 Bcast:172.24.4.255 Mask:255.255.255.0
inet6 addr: fe80::f816:3eff:fe24:b6b/64 Scope:Link
UP BROADCAST RUNNING MTU:1500 Metric:1
RX packets:5 errors:0 dropped:0 overruns:0 frame:0
TX packets:144 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:210 (210.0 B) TX bytes:13320 (13.3 KB)
sg-427653e4-a3 Link encap:Ethernet HWaddr fa:16:3e:9f:55:67
inet addr:10.0.1.6 Bcast:10.0.1.255 Mask:255.255.255.0
inet6 addr: fe80::f816:3eff:fe9f:5567/64 Scope:Link
UP BROADCAST RUNNING MTU:1500 Metric:1
RX packets:167 errors:0 dropped:0 overruns:0 frame:0
TX packets:52 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:16260 (16.2 KB) TX bytes:4460 (4.4 KB)
sg-5df1ec71-d3 Link encap:Ethernet HWaddr fa:16:3e:13:55:66
inet addr:10.0.2.2 Bcast:10.0.2.255 Mask:255.255.255.0
inet6 addr: fe80::f816:3eff:fe13:5566/64 Scope:Link
UP BROADCAST RUNNING MTU:1500 Metric:1
RX packets:34 errors:0 dropped:0 overruns:0 frame:0
TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:3412 (3.4 KB) TX bytes:952 (952.0 B)
https://www.shuzhiduo.com/A/amd0mOZLzg/stack@dvr-controller:/root$ sudo ip netns exec snat-0fbb351e-a65b-4790-a409-8fb219ce16aa iptables -nvL -t nat 。。。 Chain neutron-l3-agent-snat (1 references) pkts bytes target prot opt in out source destination 0 0 SNAT all — * * 10.0.1.0/24 0.0.0.0/0 to:172.24.4.4 0 0 SNAT all — * * 10.0.2.0/24 0.0.0.0/0 to:172.24.4.4 。。。
这里就和以前的L3类似，会将没有floating ip的包SNAT成一个172.24.4.4(DVR的网关臂)。这个过程是和以前L3类似的，不再累述。
https://www.shuzhiduo.com/A/amd0mOZLzg/stack@dvr-controller:/root$ sudo ip netns exec snat-0fbb351e-a65b-4790-a409-8fb219ce16aa iptables -nvL -t nat 。。。 Chain neutron-l3-agent-snat (1 references) pkts bytes target prot opt in out source destination 0 0 SNAT all — * * 10.0.1.0/24 0.0.0.0/0 to:172.24.4.4 0 0 SNAT all — * * 10.0.2.0/24 0.0.0.0/0 to:172.24.4.4 。。。
这里就和以前的L3类似，会将没有floating ip的包SNAT成一个172.24.4.4(DVR的网关臂)。这个过程是和以前L3类似的，不再累述。 本文转载自http://www.sxt.cn/u/756/blog/3168
