Docker实践 -- 使用Open vSwitch实现跨主机通信

作为目前最火热的容器技术，docker在网络实现和管理方面还存在不足。最开始的docker是依赖于Linux Bridge实现的网络设置，只能在容器里创建一个网卡。后来随着docker/libnetwork项目的进展，docker的网络管理功能逐渐多了起来。尽管如此，跨主机通信对于docker来说还是一个需要面对的问题，这一点对于kubernetes类的容器管理系统异常重要。目前市面上主流的解决方法有flannel, weave, Pipework, Open vSwitch等。
Open vSwitch实现比较简单，成熟且功能强大，所以很适合作为解决docker底层网络互联互通的工具。言归正传，如下是基本架构图：


具体的实现步骤如下：1. 安装docker, bridge-utils和openvswitch

[root@dockerserver1 ~]# yum install docker bridge-utils -y
[root@dockerserver1 ~]# yum install wget openssl-devel -y
[root@dockerserver1 ~]# yum groupinstall "Development Tools"
[root@dockerserver1 ~]# adduser ovswitch
[root@dockerserver1 ~]# su - ovswitch
[ovswitch@dockerserver1 ~]$ wget http://openvswitch.org/releases/openvswitch-2.3.0.tar.gz [ovswitch@dockerserver1 ~]$ tar -zxvpf openvswitch-2.3.0.tar.gz
[ovswitch@dockerserver1 ~]$ mkdir -p ~/rpmbuild/SOURCES
[ovswitch@dockerserver1 ~]$ sed 's/openvswitch-kmod, //g' openvswitch-2.3.0/rhel/openvswitch.spec > openvswitch-2.3.0/rhel/openvswitch_no_kmod.spec
[ovswitch@dockerserver1 ~]$ cp openvswitch-2.3.0.tar.gz rpmbuild/SOURCES/

[ovswitch@dockerserver1 ~]$ rpmbuild -bb --without check ~/openvswitch-2.3.0/rhel/openvswitch_no_kmod.spec

[ovswitch@dockerserver1 ~]$ exit

[root@dockerserver1 ~]# yum localinstall /home/ovswitch/rpmbuild/RPMS/x86_64/openvswitch-2.3.0-1.x86_64.rpm -y
[root@dockerserver1 ~]# mkdir /etc/openvswitch
[root@dockerserver1 ~]# setenforce 0

2. 在dockerserver1上编辑/usr/lib/systemd/system/docker.service文件，添加docker启动选项"--bip=10.0.0.1/24"，如下：

[root@dockerserver1 ~]# cat /usr/lib/systemd/system/docker.service
[Unit]
Description=Docker Application Container Engine
Documentation=http://docs.docker.com
After=network.target rhel-push-plugin.socket registries.service
Wants=docker-storage-setup.service
Requires=docker-cleanup.timer

[Service]
Type=notify
NotifyAccess=all
EnvironmentFile=-/run/containers/registries.conf
EnvironmentFile=-/etc/sysconfig/docker
EnvironmentFile=-/etc/sysconfig/docker-storage
EnvironmentFile=-/etc/sysconfig/docker-network
Environment=GOTRACEBACK=crash
Environment=DOCKER_HTTP_HOST_COMPAT=1
Environment=PATH=/usr/libexec/docker:/usr/bin:/usr/sbin
ExecStart=/usr/bin/dockerd-current \
--add-runtime docker-runc=/usr/libexec/docker/docker-runc-current \
--default-runtime=docker-runc \
--exec-opt native.cgroupdriver=systemd \
--userland-proxy-path=/usr/libexec/docker/docker-proxy-current \
--bip=10.0.0.1/24 \
$OPTIONS \
$DOCKER_STORAGE_OPTIONS \
$DOCKER_NETWORK_OPTIONS \
$ADD_REGISTRY \
$BLOCK_REGISTRY \
$INSECURE_REGISTRY\
$REGISTRIES
ExecReload=/bin/kill -s HUP $MAINPID
LimitNOFILE=1048576
LimitNPROC=1048576
LimitCORE=infinity
TimeoutStartSec=0
Restart=on-abnormal
MountFlags=slave
KillMode=process

[Install]
WantedBy=multi-user.target
[root@dockerserver1 ~]#

3. 在dockerserver2上编辑/usr/lib/systemd/system/docker.service文件，添加docker启动选项"--bip=10.0.1.1/24"，如下：

[root@dockerserver2 ~]# cat /usr/lib/systemd/system/docker.service
[Unit]
Description=Docker Application Container Engine
Documentation=http://docs.docker.com
After=network.target rhel-push-plugin.socket registries.service
Wants=docker-storage-setup.service
Requires=docker-cleanup.timer

[Service]
Type=notify
NotifyAccess=all
EnvironmentFile=-/run/containers/registries.conf
EnvironmentFile=-/etc/sysconfig/docker
EnvironmentFile=-/etc/sysconfig/docker-storage
EnvironmentFile=-/etc/sysconfig/docker-network
Environment=GOTRACEBACK=crash
Environment=DOCKER_HTTP_HOST_COMPAT=1
Environment=PATH=/usr/libexec/docker:/usr/bin:/usr/sbin
ExecStart=/usr/bin/dockerd-current \
--add-runtime docker-runc=/usr/libexec/docker/docker-runc-current \
--default-runtime=docker-runc \
--exec-opt native.cgroupdriver=systemd \
--userland-proxy-path=/usr/libexec/docker/docker-proxy-current \
--bip=10.0.1.1/24 \
$OPTIONS \
$DOCKER_STORAGE_OPTIONS \
$DOCKER_NETWORK_OPTIONS \
$ADD_REGISTRY \
$BLOCK_REGISTRY \
$INSECURE_REGISTRY\
$REGISTRIES
ExecReload=/bin/kill -s HUP $MAINPID
LimitNOFILE=1048576
LimitNPROC=1048576
LimitCORE=infinity
TimeoutStartSec=0
Restart=on-abnormal
MountFlags=slave
KillMode=process

[Install]
WantedBy=multi-user.target
[root@dockerserver2 ~]#

4. 在两个主机上启动docker服务

# systemctl start docker
# systemctl enable docker

5. docker服务启动后，可以看到一个新的bridge docker0被创建出来，并且被赋予了我们之前配置的IP地址:

[root@dockerserver1 ~]# brctl show
bridge name     bridge id               STP enabled     interfaces
docker0         8000.02427076111e       no
[root@dockerserver1 ~]# ifconfig docker0
docker0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
inet 10.0.0.1  netmask 255.255.255.0  broadcast 0.0.0.0
ether 02:42:70:76:11:1e  txqueuelen 0  (Ethernet)
RX packets 0  bytes 0 (0.0 B)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 0  bytes 0 (0.0 B)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@dockerserver1 ~]#

[root@dockerserver2 ~]# brctl show
bridge name     bridge id               STP enabled     interfaces
docker0         8000.0242ba00c394       no
[root@dockerserver2 ~]# ifconfig docker0
docker0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
inet 10.0.1.1  netmask 255.255.255.0  broadcast 0.0.0.0
ether 02:42:ba:00:c3:94  txqueuelen 0  (Ethernet)
RX packets 0  bytes 0 (0.0 B)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 0  bytes 0 (0.0 B)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@dockerserver2 ~]#

6. 在两个主机上启动openvswitch

# systemctl start openvswitch
# chkconfig openvswitch on

7. 在两个主机上创建隧道网桥br-tun，并通过VXLAN协议创建隧道

[root@dockerserver1 ~]# ovs-vsctl add-br br-tun
[root@dockerserver1 ~]# ovs-vsctl add-port br-tun vxlan0 -- set Interface vxlan0 type=vxlan options:remote_ip=10.10.172.204
[root@dockerserver1 ~]# brctl show
bridge name     bridge id               STP enabled     interfaces
docker0         8000.02427076111e       no              br-tun

[root@dockerserver2 ~]# ovs-vsctl add-br br-tun
[root@dockerserver2 ~]# ovs-vsctl add-port br-tun vxlan0 -- set Interface vxlan0 type=vxlan options:remote_ip=10.10.172.203
[root@dockerserver2 ~]# brctl show
bridge name     bridge id               STP enabled     interfaces
docker0         8000.0242ba00c394       no              br-tun

8. 将br-tun作为接口加入docker0网桥

[root@dockerserver1 ~]# brctl addif docker0 br-tun
[root@dockerserver2 ~]# brctl addif docker0 br-tun

9. 由于两个主机的容器处于不同的网段，需要添加路由才能让两边的容器互相通信

[root@dockerserver1 ~]# ip route add 10.0.1.0/24 via 10.10.172.204 dev eth0
[root@dockerserver2 ~]# ip route add 10.0.0.0/24 via 10.10.172.203 dev eth0

10. 在两个主机上各自启动一个docker容器，验证互相能否通信。

[root@dockerserver1 ~]# docker run --rm -it centos /bin/bash
[root@8f3cac41a7d5 /]# yum install net-tools -y
[root@8f3cac41a7d5 /]# ifconfig eth0
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
inet 10.0.0.2  netmask 255.255.255.0  broadcast 0.0.0.0
inet6 fe80::42:aff:fe00:2  prefixlen 64  scopeid 0x20<link>
ether 02:42:0a:00:00:02  txqueuelen 0  (Ethernet)
RX packets 4266  bytes 13337782 (12.7 MiB)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 4144  bytes 288723 (281.9 KiB)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@8f3cac41a7d5 /]#

[root@dockerserver2 ~]# docker run --rm -it centos /bin/bash
[root@3edc0ed8f805 /]# yum install net-tools -y
[root@3edc0ed8f805 /]# ifconfig eth0
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
inet 10.0.1.2  netmask 255.255.255.0  broadcast 0.0.0.0
inet6 fe80::42:aff:fe00:102  prefixlen 64  scopeid 0x20<link>
ether 02:42:0a:00:01:02  txqueuelen 0  (Ethernet)
RX packets 4536  bytes 13344451 (12.7 MiB)
RX errors 0  dropped 0  overruns 0  frame 0
TX packets 4381  bytes 301685 (294.6 KiB)
TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@3edc0ed8f805 /]# ping 10.0.0.2
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_seq=1 ttl=62 time=1.68 ms
^C
--- 10.0.0.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.683/1.683/1.683/0.000 ms
[root@3edc0ed8f805 /]#

11.查看两个docker宿主机的网卡信息

[root@dockerserver1 ~]# ip addr list
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
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: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
link/ether 00:50:56:86:3e:d8 brd ff:ff:ff:ff:ff:ff
inet 10.10.172.203/24 brd 10.10.172.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::250:56ff:fe86:3ed8/64 scope link
valid_lft forever preferred_lft forever
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN
link/ether 02:42:70:76:11:1e brd ff:ff:ff:ff:ff:ff
inet 10.0.0.1/24 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::42:70ff:fe76:111e/64 scope link
valid_lft forever preferred_lft forever
4: ovs-system: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN
link/ether 06:19:20:ae:f6:61 brd ff:ff:ff:ff:ff:ff
5: br-tun: <BROADCAST,MULTICAST> mtu 1500 qdisc noop master docker0 state DOWN
link/ether 42:2c:39:7f:a2:4a brd ff:ff:ff:ff:ff:ff
[root@dockerserver1 ~]#

[root@dockerserver2 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN
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: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
link/ether 00:50:56:86:22:d8 brd ff:ff:ff:ff:ff:ff
inet 10.10.172.204/24 brd 10.10.172.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::250:56ff:fe86:22d8/64 scope link
valid_lft forever preferred_lft forever
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN
link/ether 02:42:ba:00:c3:94 brd ff:ff:ff:ff:ff:ff
inet 10.0.1.1/24 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::42:baff:fe00:c394/64 scope link
valid_lft forever preferred_lft forever
4: ovs-system: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN
link/ether be:d4:64:ee:cb:29 brd ff:ff:ff:ff:ff:ff
5: br-tun: <BROADCAST,MULTICAST> mtu 1500 qdisc noop master docker0 state DOWN
link/ether 6e:3d:3e:1a:6a:4e brd ff:ff:ff:ff:ff:ff
[root@dockerserver2 ~]#