Docker容器网络的数据链路是什么

汽车电子技术 2023-02-15 617

汽车电子技术

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描述

单主机容器网络可能存在多个docker，分属于不同的bridge，它们之间有通信的需求。其基础的数据链路为：

Docker

下面进行数据链路的分析。

一、环境信息：

  1. 系统环境
操作系统为ubuntu14.04；
Docker version 17.05.0-ce
  1. 查看容器网络：docker network list
NETWORK ID          NAME                DRIVER              SCOPE
844c74ceea9d        bridge              bridge              local
93b0f2d679ed        docker_gwbridge     bridge              local
baa5b46a5057        host                host                local
852747e4d566        none                null                local

默认提供bridge模式的容器网络。

二、Docker基础链路

  1. 启动docker服务后，一个名为docker0的Linux bridge被创建，默认子网是172.17.0.0/16，docker0的地址是172.17.0.1。

（1）查询网络设备：ifconfig

docker0   Link encap:Ethernet  HWaddr 02:42:93:6f:2e:4f  
inet addr:172.17.0.1  Bcast:0.0.0.0  Mask:255.255.0.0
inet6 addr: fe80::42:93ff:fe6f:2e4f/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:21 errors:0 dropped:0 overruns:0 frame:0
TX packets:48 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0 
          RX bytes:1204 (1.2 KB)  TX bytes:6659 (6.6 KB)
eth0      Link encap:Ethernet  HWaddr fa:16:3e:2e:6d:3f  
inet addr:30.0.1.48  Bcast:30.0.1.255  Mask:255.255.255.0
inet6 addr: fe80::f816:3eff:fe2e:6d3f/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1450  Metric:1
RX packets:28352 errors:0 dropped:0 overruns:0 frame:0
TX packets:23242 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000 
RX bytes:56315936 (56.3 MB)  TX bytes:1637368 (1.6 MB)


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:8 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0 
RX bytes:480 (480.0 B)  TX bytes:480 (480.0 B)

（2）查看容器网络bridge的配置信息

docker network inspect bridge

[
    {
"Name": "bridge",
"Id": "844c74ceea9d98cd31a7bb7c0298894cecf8ba1b175dc74824c3688490336a3c",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
                {
"Subnet": "172.17.0.0/16",
"Gateway": "172.17.0.1"
                }
            ]
        }       
    }
]
  1. Docker会对从docker0流向外部的数据包进行NAT操作。这样就可以使得多个容器共享宿主机IP地址，与其他主机的实体进行通信。

（1）查看路由：ip route

default via 30.0.1.1 dev eth0 
30.0.1.0/24 dev eth0  proto kernel  scope link  src 30.0.1.48
172.17.0.0/16 dev docker0  proto kernel  scope link  src 172.17.0.1

说明：iproute2的ip route命令与net-tools的route命令类似。

（2）查看iptables规则链：iptables -L -t nat

Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination         
DOCKER     all  --  anywhere             anywhere             ADDRTYPE match dst-type LOCAL


Chain INPUT (policy ACCEPT)
target     prot opt source               destination         


Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         
DOCKER     all  --  anywhere            !127.0.0.0/8          ADDRTYPE match dst-type LOCAL


Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination         
MASQUERADE  all  --  172.17.0.0/16        anywhere            
MASQUERADE  all  --  bogon/16             anywhere            


Chain DOCKER (2 references)
target     prot opt source               destination         
RETURN     all  --  anywhere             anywhere            
RETURN     all  --  anywhere             anywhere

Docker的基础链路信息为：

Docker

三、Docker的数据链路

1.单bridge

不指定网络选项的情况下，创建新容器将默认在docker0，IP地址为172.17.0.0/16的一个未使用地址，通常按顺序分配，如172.17.0.2、172.17.0.3。

（1）启busydox容器：docker run -it -d --name=box3 busybox

说明：busybox集成常用的linux命令和工具的软件，适应于资源有限的嵌入式系统，可以看作精简版的shell。

（2）查看docker进程：docker ps

CONTAINER ID        IMAGE               COMMAND              CREATED             STATUS              PORTS                NAMES
b2a846aef8c3        busybox             "sh"                 2 hours ago         Up 2 hours

（3）进入docker容器：docker exec -it b2a8 sh

/ # busybox ls
bin   dev   etc   home  proc  root  sys   tmp   usr   var
/ # ifconfig
eth0      Link encap:Ethernet  HWaddr 02:42:AC:11:00:02  
inet addr:172.17.0.2  Bcast:0.0.0.0  Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:46 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:7996 (7.8 KiB)  TX bytes:0 (0.0 B)


lo        Link encap:Local Loopback  
inet addr:127.0.0.1  Mask:255.0.0.0
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)

（4）访问外网：ping www.baidu.com。默认情况下，连接到docker0上的容器可以进行通信。

（5）删除SNAT规则，以序号标记查询iptables规则，执行：iptables -L -n --line-numbers

Chain PREROUTING (policy ACCEPT)
num  target     prot opt source               destination         
1    DOCKER     all  --  0.0.0.0/0            0.0.0.0/0            ADDRTYPE match dst-type LOCAL


Chain INPUT (policy ACCEPT)
num  target     prot opt source               destination         


Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination         
1    DOCKER     all  --  0.0.0.0/0           !127.0.0.0/8          ADDRTYPE match dst-type LOCAL


Chain POSTROUTING (policy ACCEPT)
num  target     prot opt source               destination         
6    MASQUERADE  all  --  172.17.0.0/16        0.0.0.0/0           
7    MASQUERADE  all  --  172.18.0.0/16        0.0.0.0/0           


Chain DOCKER (2 references)
num  target     prot opt source               destination         
1    RETURN     all  --  0.0.0.0/0            0.0.0.0/0           
2    RETURN     all  --  0.0.0.0/0            0.0.0.0/0

这里可以看到POST ROUTING链，源地址为172.17.0.0，目的地址是任意地址。数据包通过这个链时，便执行了NAT操作。

删除序号为6的规则（172.17.0.0/16）：iptables -t nat -D POSTROUTING 6

Chain PREROUTING (policy ACCEPT)
num  target     prot opt source               destination         
1    DOCKER     all  --  0.0.0.0/0            0.0.0.0/0            ADDRTYPE match dst-type LOCAL


Chain INPUT (policy ACCEPT)
num  target     prot opt source               destination         


Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination         
1    DOCKER     all  --  0.0.0.0/0           !127.0.0.0/8          ADDRTYPE match dst-type LOCAL


Chain POSTROUTING (policy ACCEPT)
num  target     prot opt source               destination         
6    MASQUERADE  all  --  172.18.0.0/16        0.0.0.0/0           


Chain DOCKER (2 references)
num  target     prot opt source               destination         
1    RETURN     all  --  0.0.0.0/0            0.0.0.0/0           
2    RETURN     all  --  0.0.0.0/0            0.0.0.0/0

说明：MASQUERADE与SNAT类似，可以从服务器的网卡上自动获取当前ip地址来做NAT。

此时，ping www.baidu.com，则无法访问。

这样，单个主机的Docker容器网络为：

Docker

再新启docker进程，docker run -it -d --name=busybox1 busybox

Docker容器网络为：

Docker

2.双bridge

默认情况下，连接到docker0上的容器可以进行通信，但不同bridge上的容器是无法通信的。

（1）创建名为nwtest的bridge，子网为10.0.0.0/24

docker network create --driver=bridge --subnet=10.0.0.0/24 nwtest

（2）查看网络设备：ifconfig

br-8d3ef22d71a6 Link encap:Ethernet  HWaddr 02:42:11:0d:c7:67  
inet addr:10.0.0.1  Bcast:0.0.0.0  Mask:255.255.255.0
UP BROADCAST MULTICAST  MTU:1500  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)




docker0   Link encap:Ethernet  HWaddr 02:42:c9:84:d8:fc  
inet addr:172.17.0.1  Bcast:0.0.0.0  Mask:255.255.0.0
inet6 addr: fe80::42:c9ff:fe84:d8fc/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:27 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0 
RX bytes:0 (0.0 B)  TX bytes:4667 (4.6 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:8 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0 
RX bytes:480 (480.0 B)  TX bytes:480 (480.0 B)




vethdb9a3fb Link encap:Ethernet  HWaddr 7e:9c:93:1d:1d:81  
inet6 addr: fe80::7c9c:93ff:fe1d:1d81/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:46 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0 
RX bytes:0 (0.0 B)  TX bytes:7996 (7.9 KB)




vethec487c4 Link encap:Ethernet  HWaddr 6e:90:8e:40:5c:1d  
inet6 addr: fe80::6c90:8eff:fe40:5c1d/64 Scope:Link
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:20 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0 
RX bytes:0 (0.0 B)  TX bytes:3399 (3.3 KB)

（3）查看docker网络：docker network list

NETWORK ID          NAME                DRIVER              SCOPE
57d56a34c3c8        bridge              bridge              local
93b0f2d679ed        docker_gwbridge     bridge              local
baa5b46a5057        host                host                local
852747e4d566        none                null                local
8d3ef22d71a6        nwtest              bridge              local

（4）新建Docker容器，执行命令

dockerrun -it -d --network=nwtest --name=busybox6 busybox

（5）将容器busybox1关联到网络nwtest

dockernetwork connect nwtest busybox1

（5）容器busybox1执行命令，测试是否能连通

docker exec -it 99f9 sh
/ # ifconfig
eth0      Link encap:Ethernet  HWaddr 02:42:AC:11:00:02  
inet addr:172.17.0.2  Bcast:0.0.0.0  Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:46 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:7996 (7.8 KiB)  TX bytes:0 (0.0 B)


eth1      Link encap:Ethernet  HWaddr 02:42:0A:00:00:03  
inet addr:10.0.0.3  Bcast:0.0.0.0  Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
RX packets:19 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:3398 (3.3 KiB)  TX bytes:0 (0.0 B)


lo        Link encap:Local Loopback  
inet addr:127.0.0.1  Mask:255.0.0.0
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)
/ # ping 10.0.0.2
PING 10.0.0.2 (10.0.0.2): 56 data bytes
64 bytes from 10.0.0.2: seq=0 ttl=64 time=0.952 ms
64 bytes from 10.0.0.2: seq=1 ttl=64 time=0.124 ms
64 bytes from 10.0.0.2: seq=2 ttl=64 time=0.188 ms
64 bytes from 10.0.0.2: seq=3 ttl=64 time=0.168 ms
64 bytes from 10.0.0.2: seq=4 ttl=64 time=0.186 ms
64 bytes from 10.0.0.2: seq=5 ttl=64 time=0.160 ms

综上，Docker容器网络的数据链路为：

Docker

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