深入理解 Docker 网络原理
作者 | 渡、
来源 | CSDN博客
veth pair将两个网络veth0和veth1连通。
2. 理解Docker0
这里我们分析可得，有三个网络：
lo 127.0.0.1 # 本机回环地址eth0 172.31.179.120 # 阿里云的私有IP（如果你是虚拟机就是虚拟机的ip）docker0 172.17.0.1 # docker网桥
lo和eth0在我们的虚拟机启动的时候就会创建，但是docker0在我们安装了docker的时候就会创建。docker0用来和虚拟机之间通信。
[][]REPOSITORY TAG IMAGE ID CREATED SIZEtomcat latest fb5657adc892 2 months ago 680MB[]914a7d82b017f63f81c6eba49af5471441f1946c9d45509b69ab2c50c2713b6f[]
这里启动了tomcat01，我们再来查看网络
发现：我们前面查看的时候还是三组网卡，当启动了一个tomcat容器之后，多了一组网卡201: vethad33778@if200，而且还是成对的。同样我们再来启动一个tomcat02会又多出一对网卡。
说明：tomcat02对应的ip为172.17.0.3，也可以ping通。
也可以通过inspect查看。
[root@jiangnan tomcat1]# docker network lsNETWORK ID NAME DRIVER SCOPE4d3e75606593 bridge bridge local # 这个就是docker08e92ee24e5f6 host host locale85ffb1f2cc3 none null local[root@jiangnan tomcat1]# docker inspect 4d3e75606593"IPAM": {"Driver": "default","Options": null,"Config": [{"Subnet": "172.17.0.0/16","Gateway": "172.17.0.1" # 网关}]},"Containers": { # 容器"15910ee083965d60c46bf9b3b292570fef9b8925905aa4df90c6d48142bb2eee": {"Name": "tomcat01","EndpointID": "9c7a5ab65f1fc91b1d92ad61dec9b2f518f67f69f662522483dca789616f42aa","MacAddress": "02:42:ac:11:00:02","IPv4Address": "172.17.0.2/16","IPv6Address": ""},"6c9a6a5d8eca9ad52926008c7b30516d23293ff8ad1f38947957d571431d5297": {"Name": "tomcat02","EndpointID": "f83c1e643236cd65f50fba03929ca14d5df8d135b1f6cb8adf203cf96084f7aa","MacAddress": "02:42:ac:11:00:03","IPv4Address": "172.17.0.3/16","IPv6Address": ""}},
在这里，我们可以看到Docker0相当于一个路由器的作用，任何一个容器启动默认都是docker0网络。 docker默认会给容器分配一个可用ip，并把它同docke0相连。使用到的就是veth pair技术。
3. 容器互联–Link
[root@jiangnan tomcat1]# docker exec -it tomcat01 cat /etc/hosts127.0.0.1 localhost::1 localhost ip6-localhost ip6-loopbackfe00::0 ip6-localnetff00::0 ip6-mcastprefixff02::1 ip6-allnodesff02::2 ip6-allrouters172.17.0.2 3ecb3204e2dcroot@3ecb3204e2dc:/usr/local/tomcat#
[root@jiangnan tomcat1]# docker exec -it tomcat02 cat /etc/hosts127.0.0.1 localhost::1 localhost ip6-localhost ip6-loopbackfe00::0 ip6-localnetff00::0 ip6-mcastprefixff02::1 ip6-allnodesff02::2 ip6-allrouters172.17.0.3 6c9a6a5d8eca[root@jiangnan tomcat1]#
发现：他们的hosts中只有各自的ip地址。
[root@jiangnan tomcat1]# docker run -d -p 8083:8080 --name tomcat03 --link tomcat02 tomcatdb75c42f7f7f609218deb290d3e923e3c7da6bcf8c0b38cde27962fb2b9e9a54[root@jiangnan tomcat1]# docker exec -it tomcat03 cat /etc/hosts127.0.0.1 localhost::1 localhost ip6-localhost ip6-loopbackfe00::0 ip6-localnetff00::0 ip6-mcastprefixff02::1 ip6-allnodesff02::2 ip6-allrouters172.17.0.3 tomcat02 e4060ea4ee28 # 发现tomcat2直接被写在这里172.17.0.4 db75c42f7f7froot@db75c42f7f7f:/usr/local/tomcat#
发现：使用了–link，不但有了自己的ip，而且还有了tomcat02的服务名。但是tomcat02中并没有tomcat03的，因为–link是单向的。
-
它是默认的 -
域名访问不通 -
–link 域名通了，但是删了又不行
[root@jiangnan tomcat1]# docker network lsNETWORK ID NAME DRIVER SCOPE4d3e75606593 bridge bridge local8e92ee24e5f6 host host locale85ffb1f2cc3 none null local[root@jiangnan tomcat1]#
这其中默认使用的是bridge，也就是我们的docker0网卡。
[]这个--net是默认的，所以被省略了。
# 自定义创建的默认default "bridge"[root@jiangnan tomcat1]# docker network create --driver bridge --subnet 192.168.0.0/16 --gateway 192.168.0.1 mynet3136d64109c6f285bc69d3ee4be901524292d0e5ddd9e414d49197dfa6c19ba1[root@jiangnan tomcat1]# docker network lsNETWORK ID NAME DRIVER SCOPE4d3e75606593 bridge bridge local8e92ee24e5f6 host host local3136d64109c6 mynet bridge local # 多了一个mynete85ffb1f2cc3 none null local[root@jiangnan tomcat1]# docker network inspect mynet[{"Name": "mynet","Id": "3136d64109c6f285bc69d3ee4be901524292d0e5ddd9e414d49197dfa6c19ba1","Created": "2022-02-27T14:15:44.676693958+08:00","Scope": "local","Driver": "bridge","EnableIPv6": false,"IPAM": {"Driver": "default","Options": {},"Config": [{"Subnet": "192.168.0.0/16", # 子网地址"Gateway": "192.168.0.1" # 网关}]},"Internal": false,"Attachable": false,"Ingress": false,"ConfigFrom": {"Network": ""},"ConfigOnly": false,"Containers": {},"Options": {},"Labels": {}}][root@jiangnan tomcat1]#
[root@jiangnan tomcat1]# docker run -d -p 8081:8080 --name tomcat-net-01 --net mynet tomcat675439c851dc29355c03f82bb163f9e5a326e230447d86d40d53ff08766cfd06[root@jiangnan tomcat1]# docker run -d -p 8082:8080 --name tomcat-net-02 --net mynet tomcat31f12c9332e8b4b6e66619dc988533f2863b80e71dbf490c8313694637814ca1[root@jiangnan tomcat1]# docker psCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES31f12c9332e8 tomcat "catalina.sh run" 3 seconds ago Up 2 seconds 0.0.0.0:8082->8080/tcp, :::8082->8080/tcp tomcat-net-02675439c851dc tomcat "catalina.sh run" 12 seconds ago Up 12 seconds 0.0.0.0:8081->8080/tcp, :::8081->8080/tcp tomcat-net-01[root@jiangnan tomcat1]#
查看网络
[][{: ,: ,: ,: ,: ,: false,: {: ,: {},: [{: ,:}]},"Internal": false,"Attachable": false,"Ingress": false,"ConfigFrom": {"Network": ""},"ConfigOnly": false,"Containers": {"31f12c9332e8b4b6e66619dc988533f2863b80e71dbf490c8313694637814ca1": {"Name": "tomcat-net-02","EndpointID": "1c0e9dbffff295f2326bfd1e2847c0f1d9136ff00519101bb11d922e7da4f818","MacAddress": "02:42:c0:a8:00:03","IPv4Address": "192.168.0.3/16","IPv6Address": ""},"675439c851dc29355c03f82bb163f9e5a326e230447d86d40d53ff08766cfd06": {"Name": "tomcat-net-01","EndpointID": "2653da0a25d166f0d7222235e85d8231d9424e19949b6e6b7cfa1a3eddcc462b","MacAddress": "02:42:c0:a8:00:02","IPv4Address": "192.168.0.2/16","IPv6Address": ""}},"Options": {},"Labels": {}}][]
[]PING 192.168.0.3 (192.168.0.3) 56(84) bytes of data.64 bytes from 192.168.0.3: icmp_seq=1 ttl=64 time=0.093 ms[]PING tomcat-net-02 (192.168.0.3) 56(84) bytes of data.64 bytes from tomcat-net-02.mynet (192.168.0.3): icmp_seq=1 ttl=64 time=0.063 ms64 bytes from tomcat-net-02.mynet (192.168.0.3): icmp_seq=2 ttl=64 time=0.066 ms
发现：不用 --link也可以直接通过服务名ping通了。
5. 网络连通
[][][{: ,: ,: ,: ,: ,: false,: {: ,: {},: [{: ,:}]},"Internal": false,"Attachable": false,"Ingress": false,"ConfigFrom": {"Network": ""},"ConfigOnly": false,"Containers": {"2e709013935463c29caf28771bb49925fee4e02842459b339d7dd1ad5dedf9b7": {"Name": "tomcat-net-01","EndpointID": "9f3a46bad37ade7935e283715caa5699e9a7e22175b592f4a4792a37c351d969","MacAddress": "02:42:c0:a8:00:02","IPv4Address": "192.168.0.2/16","IPv6Address": ""},"5c0c544f2507d9f5f456feceddbd853ebccc07cea8c39c8479693731e480bf55": {"Name": "tomcat01","EndpointID": "d05abb2d31af4067c5a45f299ce7b4401b1fa81638a44b6c09f3de7f8f4221fe","MacAddress": "02:42:c0:a8:00:04","IPv4Address": "192.168.0.4/16","IPv6Address": ""},"d6066db5fdd0b508514107a896ed20b639eaa47dbd97a025ad0c52250766c8a4": {"Name": "tomcat-net-02","EndpointID": "3a5f6f2a07d900303382b290825c9f52640689c859608c741c7c7d81031e107e","MacAddress": "02:42:c0:a8:00:03","IPv4Address": "192.168.0.3/16","IPv6Address": ""}},"Options": {},"Labels": {}}][]
通过这种方式直接将tomcat01加到了mynet网络中。
6. 总结
-
veth pair是成对出现的一种虚拟网络设备接口，一端连着网络协议栈，一端彼此相连。 -
docker中默认使用docker0网络。 -
docker0相当于一个路由器的作用，任何一个容器启动默认都是docker0网络。 -
docker0是容器和虚拟机之间通信的桥梁。 -
推荐使用自定义网络，更好实现使用服务名的连通方式，避免ip改变的尴尬。 -
网络之间不能直接连通，网络连通是将一个容器和一个网络之间的连通，实现跨网络操作。