sdn (software defines network)
看了些相关的资料，这里记录一下自己对 sdn 的理解，能力有限，如有错误欢迎指正。
sdn 软件定义网络，目的是想要利用软件来模拟网络设备，如交换机，路由器之类的。
为什么需要这么做? 一个主要原因是云计算的高速发展，给传统的数据中心带来了更加灵活和复杂的组网需求。
传统网络设备完成数据中心服务器的组网，在此之上，通过 sdn 来完成虚机和容器之间的连通
ovs (openvSwitch)
官方的说法：Open vSwitch 是一款高质量的多层虚拟交换机，以开源 Apache 2 许可证授权，非常适合在虚拟机环境中充当 2 层交换机。支持多种基于 Linux 的虚拟化技术，包括 Xen / XenServer、KVM 和 VirtualBox。
支持 Open Flow 协议，所以可以很方便的通过编程实现大规模网络的自动化，被大量运用于 SDN 网络中。
架构和原理之类的文章很多，这里就不在一一阐述，本文以实践为主。
安装
# 安装 docker
yum install -y docker-1.13.1
# 预安装
yum -y install wget openssl-devel gcc make python-devel openssl-devel kernel-devel graphviz kernel-debug-devel autoconf automake rpm-build redhat-rpm-config libtool python-twisted-core python-zope-interface PyQt4 desktop-file-utils libcap-ng-devel groff checkpolicy selinux-policy-devel
# 安装 open vswitch:
yum install -y openvswitch-2.8.2-1.el7.x86_64 # 此版本包含 ovs-docker
systemctl start openvswitch.service
systemctl is-active openvswitch
systemctl enable openvswitchovs 单机连通性
创建容器, 设置 net=none 可以防止 docker0 默认网桥影响连通性测试
docker run -itd --name con6 --net=none ubuntu:14.04 /bin/bash
docker run -itd --name con7 --net=none ubuntu:14.04 /bin/bash
docker run -itd --name con8 --net=none ubuntu:14.04 /bin/bash创建网桥
ovs-vsctl add-br ovs0使用 ovs-docker 给容器添加网卡，并挂到 ovs0 网桥上
ovs-docker add-port ovs0 eth0 con6 --ipaddress=192.168.1.2/24
ovs-docker add-port ovs0 eth0 con7 --ipaddress=192.168.1.3/24
ovs-docker add-port ovs0 eth0 con8 --ipaddress=192.168.1.4/24查看网桥
[root@controller /]# ovs-vsctl show
21e4d4c5-cadd-4dac-b025-c20b8108ad09
Bridge "ovs0"
Port "b167e3dcf8db4_l"
Interface "b167e3dcf8db4_l"
Port "f1c0a9d0994d4_l"
Interface "f1c0a9d0994d4_l"
Port "121c6b2f221c4_l"
Interface "121c6b2f221c4_l"
Port "ovs0"
Interface "ovs0"
type: internal
ovs_version: "2.8.2"测试连通性
[root@controller /]# docker exec -it con8 sh
# ping 192.168.1.2
PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=0.886 ms
^C
--- 192.168.1.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.886/0.886/0.886/0.000 ms
#
# ping 192.168.1.3
PING 192.168.1.3 (192.168.1.3) 56(84) bytes of data.
64 bytes from 192.168.1.3: icmp_seq=1 ttl=64 time=0.712 ms
^C
--- 192.168.1.3 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.712/0.712/0.712/0.000 ms
# 设置 VLAN tag
查看网桥
[root@controller /]# ovs-vsctl show
21e4d4c5-cadd-4dac-b025-c20b8108ad09
Bridge "ovs0"
Port "b167e3dcf8db4_l"
Interface "b167e3dcf8db4_l"
Port "f1c0a9d0994d4_l"
Interface "f1c0a9d0994d4_l"
Port "121c6b2f221c4_l"
Interface "121c6b2f221c4_l"
Port "ovs0"
Interface "ovs0"
type: internal
ovs_version: "2.8.2"查看 interface
[root@controller /]# ovs-vsctl list interface f1c0a9d0994d4_l
_uuid : cf400e7c-d2d6-4e0a-ad02-663dd63d1751
admin_state : up
duplex : full
error : []
external_ids : {container_id="con6", container_iface="eth0"}
ifindex : 239
ingress_policing_burst: 0
ingress_policing_rate: 0
lacp_current : []
link_resets : 1
link_speed : 10000000000
link_state : up
mac_in_use : "96:91:0a:c9:02:d6"
mtu : 1500
mtu_request : []
name : "f1c0a9d0994d4_l"
ofport : 3
other_config : {}
statistics : {collisions=0, rx_bytes=1328, rx_crc_err=0, rx_dropped=0, rx_errors=0, rx_frame_err=0, rx_over_err=0, rx_packets=18, tx_bytes=3032, tx_dropped=0, tx_errors=0, tx_packets=40}
status : {driver_name=veth, driver_version="1.0", firmware_version=""}
type : ""设置 vlan tag
ovs-vsctl set port f1c0a9d0994d4_l tag=100 //con6
ovs-vsctl set port b167e3dcf8db4_l tag=100 //con8
ovs-vsctl set port 121c6b2f221c4_l tag=200 //con7测试连通性
[root@controller /]# docker exec -it con8 sh
#
# ping 192.168.1.2 -c 3
PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=0.413 ms
64 bytes from 192.168.1.2: icmp_seq=2 ttl=64 time=0.061 ms
64 bytes from 192.168.1.2: icmp_seq=3 ttl=64 time=0.057 ms
--- 192.168.1.2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2044ms
rtt min/avg/max/mdev = 0.057/0.177/0.413/0.166 ms
#
# ping 192.168.1.3 -c 3
PING 192.168.1.3 (192.168.1.3) 56(84) bytes of data.
From 192.168.1.4 icmp_seq=1 Destination Host Unreachable
From 192.168.1.4 icmp_seq=2 Destination Host Unreachable
--- 192.168.1.3 ping statistics ---
3 packets transmitted, 0 received, +3 errors, 100% packet loss, time 2068ms
pipe 3
# 跨主机连通性
环境
host1 172.29.101.123
网桥: ovs0
容器:
con6 192.168.1.2
con7 192.168.1.3
con8 192.168.1.4 创建方式依上
host2 172.29.101.82
网桥: ovs1
容器: con11准备环境
创建网桥
ovs-vsctl add-br ovs1
创建容器
docker run -itd --name con11 --net=none ubuntu:14.04 /bin/bash
挂到 ovs0 网桥
ovs-docker add-port ovs1 eth0 con11 --ipaddress=192.168.1.6/24查看网桥 ovs1
[root@compute82 /]# ovs-vsctl show
380ce027-8edf-4844-8e89-a6b9c1adaff3
Bridge "ovs1"
Port "0384251973e64_l"
Interface "0384251973e64_l"
Port "ovs1"
Interface "ovs1"
type: internal
ovs_version: "2.8.2"设置 vxlan
在 host1 上
[root@controller /]# ovs-vsctl add-port ovs0 vxlan1 -- set interface vxlan1 type=vxlan options:remote_ip=172.29.101.82 options:key=flow
[root@controller /]#
[root@controller /]# ovs-vsctl show
21e4d4c5-cadd-4dac-b025-c20b8108ad09
Bridge "ovs0"
Port "b167e3dcf8db4_l"
tag: 100
Interface "b167e3dcf8db4_l"
Port "f1c0a9d0994d4_l"
tag: 100
Interface "f1c0a9d0994d4_l"
Port "121c6b2f221c4_l"
tag: 200
Interface "121c6b2f221c4_l"
Port "ovs0"
Interface "ovs0"
type: internal
Port "vxlan1"
Interface "vxlan1"
type: vxlan
options: {key=flow, remote_ip="172.29.101.82"}
ovs_version: "2.8.2"在 host2 上
[root@compute82 /]# ovs-vsctl add-port ovs1 vxlan1 -- set interface vxlan1 type=vxlan options:remote_ip=172.29.101.123 options:key=flow
[root@compute82 /]#
[root@compute82 /]# ovs-vsctl show
380ce027-8edf-4844-8e89-a6b9c1adaff3
Bridge "ovs1"
Port "0384251973e64_l"
Interface "0384251973e64_l"
Port "vxlan1"
Interface "vxlan1"
type: vxlan
options: {key=flow, remote_ip="172.29.101.123"}
Port "ovs1"
Interface "ovs1"
type: internal
ovs_version: "2.8.2"设置 vlan tag
ovs-vsctl set port 0384251973e64_l tag=100连通性测试
[root@compute82 /]# docker exec -ti con11 bash
root@c82da61bf925:/# ping 192.168.1.2
PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=0.161 ms
64 bytes from 192.168.1.2: icmp_seq=2 ttl=64 time=0.206 ms
^C
--- 192.168.1.2 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1000ms
root@c82da61bf925:/#
root@c82da61bf925:/# ping 192.168.1.3
PING 192.168.1.3 (192.168.1.3) 56(84) bytes of data.
^C
--- 192.168.1.3 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2027ms
root@c82da61bf925:/#
root@c82da61bf925:/# exit结论
vxlan 只能连通两台机器的 ovs 上同一个网段的容器，无法连通 ovs 上不同网段的容器。如果需要连通不同网段的容器，接下来我们尝试通过 ovs 的流表来解决这个问题。
OpenFlow
flow table
支持 openflow 的交换机中可能包含多个 flow table。每个 flow table 包含多条规则，每条规则包含匹配条件和执行动作。flow table 中的每条规则有优先级，优先级高的优先匹配，匹配到规则以后，执行 action，如果匹配失败，按优先级高低，继续匹配下一条。如果都不匹配，每张表会有默认的动作，一般为 drop 或者转给下一张流表。
实践
环境
host1 172.29.101.123
网桥: ovs0
容器:
con6 192.168.1.2 tag=100
con7 192.168.1.3 tag=100host2 172.29.101.82
网桥: ovs1
容器:
con9: 192.168.2.2 tag=100
con10：192.168.2.3 tag=100
con11: 192.168.1.5 tag=100查看默认流表
在 host1 上查看默认流表
[root@controller msxu]# ovs-ofctl dump-flows ovs0
cookie=0x0, duration=27858.050s, table=0, n_packets=5253660876, n_bytes=371729202788, priority=0 actions=NORMAL在容器 con6 中 ping con7，网络连通
[root@controller /]# docker exec -ti con6 bash
root@9ccc5c5664f9:/#
root@9ccc5c5664f9:/# ping 192.168.1.3
PING 192.168.1.3 (192.168.1.3) 56(84) bytes of data.
64 bytes from 192.168.1.3: icmp_seq=1 ttl=64 time=0.613 ms
64 bytes from 192.168.1.3: icmp_seq=2 ttl=64 time=0.066 ms
--- 192.168.1.3 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1058ms
rtt min/avg/max/mdev = 0.066/0.339/0.613/0.274 ms
root@9ccc5c5664f9:/# 删除默认流表
[root@controller /]# ovs-ofctl del-flows ovs0
[root@controller /]#
[root@controller /]# ovs-ofctl dump-flows ovs0
[root@controller /]# 测试网络连通性，发现网络已经不通
[root@controller /]# docker exec -ti con6 bash
root@9ccc5c5664f9:/#
root@9ccc5c5664f9:/# ping 192.168.1.3
PING 192.168.1.3 (192.168.1.3) 56(84) bytes of data.
^C
--- 192.168.1.3 ping statistics ---
2 packets transmitted, 0 received, 100% packet loss, time 1025ms
root@9ccc5c5664f9:/# 添加流表
如果要 con6 和 con7 能够通信，需要建立规则，让 ovs 转发对应的数据
查看 con6 和 con7 在 ovs 上的网络端口
[root@controller /]# ovs-vsctl show
21e4d4c5-cadd-4dac-b025-c20b8108ad09
Bridge "ovs0"
Port "f1c0a9d0994d4_l"
tag: 100
Interface "f1c0a9d0994d4_l"
Port "121c6b2f221c4_l"
tag: 100
Interface "121c6b2f221c4_l"
Port "ovs0"
Interface "ovs0"
type: internal
Port "vxlan1"
Interface "vxlan1"
type: vxlan
options: {key=flow, remote_ip="172.29.101.82"}
ovs_version: "2.8.2"
[root@controller /]# ovs-vsctl list interface f1c0a9d0994d4_l |grep ofport
ofport : 3
ofport_request : []
[root@controller /]#
[root@controller /]# ovs-vsctl list interface 121c6b2f221c4_l |grep ofport
ofport : 4
ofport_request : []添加规则：
[root@controller /]#ovs-ofctl add-flow ovs0 "priority=1,in_port=3,actions=output:4"
[root@controller /]#ovs-ofctl add-flow ovs0 "priority=2,in_port=4,actions=output:3"
[root@controller /]# ovs-ofctl dump-flows ovs0
cookie=0x0, duration=60.440s, table=0, n_packets=0, n_bytes=0, priority=1,in_port="f1c0a9d0994d4_l" actions=output:"121c6b2f221c4_l"
cookie=0x0, duration=50.791s, table=0, n_packets=0, n_bytes=0, priority=1,in_port="121c6b2f221c4_l" actions=output:"f1c0a9d0994d4_l"
[root@controller /]#测试连通性：con6 和 con7 已通
[root@controller msxu]# docker exec -ti con6 bash
root@9ccc5c5664f9:/# ping 192.168.1.3
PING 192.168.1.3 (192.168.1.3) 56(84) bytes of data.
64 bytes from 192.168.1.3: icmp_seq=1 ttl=64 time=0.924 ms
64 bytes from 192.168.1.3: icmp_seq=2 ttl=64 time=0.058 ms
^C
--- 192.168.1.3 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1057ms
rtt min/avg/max/mdev = 0.058/0.491/0.924/0.433 ms
root@9ccc5c5664f9:/# 设置一条优先级高的规则：
[root@controller /]# ovs-ofctl add-flow ovs0 "priority=2,in_port=4,actions=drop"
[root@controller /]#
[root@controller /]# docker exec -ti con6 bash
root@9ccc5c5664f9:/#
root@9ccc5c5664f9:/# ping 192.168.1.3
PING 192.168.1.3 (192.168.1.3) 56(84) bytes of data.
^C
--- 192.168.1.3 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2087ms
root@9ccc5c5664f9:/#
root@9ccc5c5664f9:/# 流表中的规则是有优先级的，priority 数值越大，优先级越高。流表中，优先级高的优先匹配，并执行匹配规则的 actions。如果不匹配，继续匹配优先级低的下一条。
跨网段连通
在上一个 vxlan 的实践中，通过设置 vxlan 可以打通两个机器上的 ovs，但我们提到两个机器 ovs 上的容器得在同一个网段上才能通信。
在 ip 为 192.168.2.2 的 con9 上 ping 另一台机上的 con6 192.168.1.2
[root@compute82 /]# docker exec -ti con9 bash
root@b55602aad0ac:/#
root@b55602aad0ac:/# ping 192.168.1.2
connect: Network is unreachable
root@b55602aad0ac:/# 添加流表规则：
在 host1 上：
[root@controller /]# ovs-ofctl add-flow ovs0 "priority=4,in_port=6,actions=output:3"
[root@controller /]#
[root@controller /]# ovs-ofctl add-flow ovs0 "priority=4,in_port=3,actions=output:6"
[root@controller /]# ovs-ofctl dump-flows ovs0
cookie=0x0, duration=3228.737s, table=0, n_packets=7, n_bytes=490, priority=1,in_port="f1c0a9d0994d4_l" actions=output:"121c6b2f221c4_l"
cookie=0x0, duration=3215.544s, table=0, n_packets=0, n_bytes=0, priority=1,in_port="121c6b2f221c4_l" actions=output:"f1c0a9d0994d4_l"
cookie=0x0, duration=3168.297s, table=0, n_packets=9, n_bytes=546, priority=2,in_port="121c6b2f221c4_l" actions=drop
cookie=0x0, duration=12.024s, table=0, n_packets=0, n_bytes=0, priority=4,in_port=vxlan1 actions=output:"f1c0a9d0994d4_l"
cookie=0x0, duration=3.168s, table=0, n_packets=0, n_bytes=0, priority=4,in_port="f1c0a9d0994d4_l" actions=output:vxlan1
在 host2 上
[root@compute82 /]# ovs-ofctl add-flow ovs1 "priority=1,in_port=1,actions=output:6"
[root@compute82 /]#
[root@compute82 /]# ovs-ofctl add-flow ovs1 "priority=1,in_port=6,actions=output:1"
[root@compute82 /]# ovs-ofctl dump-flows ovs1
cookie=0x0, duration=1076.522s, table=0, n_packets=27, n_bytes=1134, priority=1,in_port="0384251973e64_l" actions=output:vxlan1
cookie=0x0, duration=936.403s, table=0, n_packets=0, n_bytes=0, priority=1,in_port=vxlan1 actions=output:"0384251973e64_l"
cookie=0x0, duration=70205.443s, table=0, n_packets=7325, n_bytes=740137, priority=0 actions=NORMAL
测试连通性
在 host2 con9 上 ping 192.168.1.2
[root@compute82 /]# docker exec -ti con9 bash
root@b55602aad0ac:/#
root@b55602aad0ac:/# ping 192.168.1.2
connect: Network is unreachable
root@b55602aad0ac:/# 发现网络并不通，查看发现路由规则有问题，添加默认路由规则，注意这里需要已 privileged 权限进入容器
[root@compute82 /]# docker exec --privileged -ti con9 bash
root@b55602aad0ac:/#
root@b55602aad0ac:/# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
root@b55602aad0ac:/# route add default dev eth0
root@b55602aad0ac:/#
root@b55602aad0ac:/# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 0 eth0
192.168.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
root@b55602aad0ac:/# 在 host1 和 host2 的容器中都添加好路由规则后，测试连通性
[root@compute82 /]# docker exec --privileged -ti con9 bash
root@b55602aad0ac:/#
root@b55602aad0ac:/# ping 192.168.1.2
PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=1.16 ms
64 bytes from 192.168.1.2: icmp_seq=2 ttl=64 time=0.314 ms
^C
--- 192.168.1.2 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1002ms
rtt min/avg/max/mdev = 0.314/0.739/1.165/0.426 ms已成功通过 ovs，vxlan 打通两台机器上不同网段容器