五十九、Docker Swarm-Overlay网络详解

对于理解swarm的网络来讲，个人认为最重要的两个点：

• 第一是外部如何访问部署运行在swarm集群内的服务，可以称之为 入方向 流量，在swarm里我们通过 ingress 来解决
• 第二是部署在swarm集群里的服务，如何对外进行访问，这部分又分为两块:
  • 1. 东西向流量 ，也就是不同swarm节点上的容器之间如何通信，swarm通过 overlay 网络来解决；
  • 2. 南北向流量 ，也就是swarm集群里的容器如何对外访问，比如互联网，这个是 Linux bridge + iptables NAT 来解决的

创建 overlay 网络

vagrant@swarm-manager:~$ docker network create -d overlay mynet

这个网络会同步到所有的swarm节点上

创建服务

创建一个服务连接到这个 overlay网络， name 是 test ， replicas 是 2

vagrant@swarm-manager:~$ docker service create --network mynet --name test --replicas 2 busybox ping 8.8.8.8
vagrant@swarm-manager:~$ docker service ps test
ID             NAME      IMAGE            NODE            DESIRED STATE   CURRENT STATE            ERROR     PORTS
yf5uqm1kzx6d   test.1    busybox:latest   swarm-worker1   Running         Running 18 seconds ago
3tmp4cdqfs8a   test.2    busybox:latest   swarm-worker2   Running         Running 18 seconds ago

可以看到这两个容器分别被创建在worker1和worker2两个节点上

网络查看

到worker1和worker2上分别查看容器的网络连接情况

vagrant@swarm-worker1:~$ docker container ls
CONTAINER ID   IMAGE            COMMAND          CREATED      STATUS      PORTS     NAMES
cac4be28ced7   busybox:latest   "ping 8.8.8.8"   2 days ago   Up 2 days             test.1.yf5uqm1kzx6dbt7n26e4akhsu
vagrant@swarm-worker1:~$ docker container exec -it cac sh
/ # ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
    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
24: eth0@if25: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1450 qdisc noqueue
    link/ether 02:42:0a:00:01:08 brd ff:ff:ff:ff:ff:ff
    inet 10.0.1.8/24 brd 10.0.1.255 scope global eth0
    valid_lft forever preferred_lft forever
26: eth1@if27: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue
    link/ether 02:42:ac:12:00:03 brd ff:ff:ff:ff:ff:ff
    inet 172.18.0.3/16 brd 172.18.255.255 scope global eth1
    valid_lft forever preferred_lft forever
/ #

这个容器有两个接口 eth0和eth1， 其中eth0是连到了mynet这个网络，eth1是连到docker_gwbridge这个网络

vagrant@swarm-worker1:~$ docker network ls
NETWORK ID     NAME              DRIVER    SCOPE
a631a4e0b63c   bridge            bridge    local
56945463a582   docker_gwbridge   bridge    local
9bdfcae84f94   host              host      local
14fy2l7a4mci   ingress           overlay   swarm
lpirdge00y3j   mynet             overlay   swarm
c1837f1284f8   none              null      local

在这个容器里是可以直接ping通worker2上容器的IP 10.0.1.9的

docker-swarm-overlay

网络抓包

1. 查看新建的overlay网络mynet中的容器的ip有10.0.2.4和10.0.2.5

docker network inspect mynet

image.png

2. 进入work1的容器中查看网络信息

[vagrant@swarm-worker1 ~]$ docker exec -it 6f sh
/ # ip route
default via 172.18.0.1 dev eth1
10.0.2.0/24 dev eth0 scope link  src 10.0.2.3
172.18.0.0/16 dev eth1 scope link  src 172.18.0.3
/ #
/ # ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
    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
169: eth0@if170: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1450 qdisc noqueue
    link/ether 02:42:0a:00:02:03 brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.3/24 brd 10.0.2.255 scope global eth0
       valid_lft forever preferred_lft forever
171: eth1@if172: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue
    link/ether 02:42:ac:12:00:03 brd ff:ff:ff:ff:ff:ff
    inet 172.18.0.3/16 brd 172.18.255.255 scope global eth1
       valid_lft forever preferred_lft forever

3. 进入work2的容器中查看网络信息

[vagrant@swarm-worker2 ~]$ docker exec -it 7a sh
/ #
/ # ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue qlen 1000
    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
162: eth0@if163: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1450 qdisc noqueue
    link/ether 02:42:0a:00:02:07 brd ff:ff:ff:ff:ff:ff
    inet 10.0.2.7/24 brd 10.0.2.255 scope global eth0
       valid_lft forever preferred_lft forever
164: eth1@if165: <BROADCAST,MULTICAST,UP,LOWER_UP,M-DOWN> mtu 1500 qdisc noqueue
    link/ether 02:42:ac:12:00:03 brd ff:ff:ff:ff:ff:ff
    inet 172.18.0.3/16 brd 172.18.255.255 scope global eth1
       valid_lft forever preferred_lft forever
/ #
/ # ip route
default via 172.18.0.1 dev eth1
10.0.2.0/24 dev eth0 scope link  src 10.0.2.7
172.18.0.0/16 dev eth1 scope link  src 172.18.0.3

4. 在work1容器中ping 我work2容器的eth0口的overlay网络10.0.2.7，然后在work2中进行抓包tcpdump -i eth0 port 4789，其中4789端口是vxlan的端口。会抓到8个数据包，包括四个请求和四个响应。