Docker 网络介绍

docker网络主要是解决容器联网问题，也是我们使用容器中最重要的一个环节，如果容器没有网络则无法向网络中提供服务。

网络管理命令：docker network

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docker network --help

Usage: docker network COMMAND

Manage networks

Commands:
  connect     Connect a container to a network
  create      Create a network
  disconnect  Disconnect a container from a network
  inspect     Display detailed information on one or more networks
  ls          List networks
  prune       Remove all unused networks
  rm          Remove one or more networks

Run 'docker network COMMAND --help' for more information on a command.

docker网络类型

创建容器的时候可以通过—network命令来指定容器的网络，网络类型有以下四种

  • bridge
  • host
  • none
  • 容器网络或联盟网络

bridge

桥接网络是指容器通过桥接的方式将容器网卡桥接到宿主机的docker0网桥，然后在通过宿主机防火墙的NAT表实现与外网的联系。

宿主机docker0网桥

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ifconfig
#docker0网桥
docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.17.0.1  netmask 255.255.0.0  broadcast 172.17.255.255
        inet6 fe80::42:c7ff:fe37:8e8  prefixlen 64  scopeid 0x20<link>
        ether 02:42:c7:37:08:e8  txqueuelen 0  (Ethernet)
        RX packets 6618  bytes 277975 (271.4 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 8152  bytes 24675021 (23.5 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

#容器网卡，每创建一个桥接网络的容器就会生成一个对应的网卡
vethf75a942: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::9085:f5ff:fe34:77b5  prefixlen 64  scopeid 0x20<link>
        ether 92:85:f5:34:77:b5  txqueuelen 0  (Ethernet)
        RX packets 2850  bytes 158484 (154.7 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 3397  bytes 11613136 (11.0 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

#如果想看更清楚一下  可以使用  ip  add  show命令
ip add show

docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
    link/ether 02:42:c7:37:08:e8 brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
       valid_lft forever preferred_lft forever
    inet6 fe80::42:c7ff:fe37:8e8/64 scope link
       valid_lft forever preferred_lft forever

#容器网卡
14: vethf75a942@if13: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP group default
    link/ether 92:85:f5:34:77:b5 brd ff:ff:ff:ff:ff:ff link-netnsid 1
    inet6 fe80::9085:f5ff:fe34:77b5/64 scope link
       valid_lft forever preferred_lft forever

注意：
这里的vethf75a942@if13指的就是容器网卡，V代表虚拟网卡的意思，eth 以太网卡，f75a942网卡编号，if13指的是宿主机网桥(docekr0)的一个端口，对应容器的网卡编号加一。
所以容器内的网卡编号应该是 eth0@if14

通过在容器中执行命令 ip add show 也可以看到

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docker exec centos1 ip add show
lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default 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
eth0@if14: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
    link/ether 02:42:ac:11:00:03 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 172.17.0.3/16 brd 172.17.255.255 scope global eth0
       valid_lft forever preferred_lft forever

防火墙的NAT表内容

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iptables -t nat -L
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            !loopback/8           ADDRTYPE match dst-type LOCAL

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

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

docker0 与容器网卡桥接

通过brctl show命令可以看到容器网卡和docker0网卡的桥接信息

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brctl show
bridge name bridge id  STP enabled interfaces
docker0  8000.0242c73708e8 no  vethf75a942

创建一个网络为bridge类型的容器，不指定默认也是这个类型

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docker run -d --network bridge --name centos1 baishuming2020/centos_nginx

host

容器和真机共用网卡及对应的端口，缺点就是同一个端口只能宿主机或者某个容器使用，其他容器不能用。

创建一个网络类型host的容器

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docker run -d --network host --name centos2 baishuming2020/centos_nginx

none

容器仅有lo网卡，是一个不能联网的本地容器

创建一个网络类型为lo的容器

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docker run -d --network none --name centos3 baishuming2020/centos_nginx

实现网桥网络

目的：不同的服务容器组应用不同的网桥，避免同一网络内容器太多，保持容器网络独立性。

关于新网桥联网问题：创建网桥后，宿主机会自动帮你做NAT，所以不用担心联网问题

查看网络-ls

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docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
80982d2613cd        bridge              bridge              local
40c179ab420a        docker1             bridge              local
04aadb7475c0        docker100           bridge              local
ce79e9d7525a        host                host                local
8f0358469e57        none                null                local

NETWORK ID     网桥ID
NAME           名称
DRIVER         网络类型
SCOPE      作用范围

创建网桥-create

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docker network create -d bridge --subnet 192.168.1.0/24 --gateway 192.168.1.1 mydocker0
6a410e27b66ea587142d967f7dff6f36c04ced3c27116a79831412f3743aba56

docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
6ee1e928b710        bridge              bridge              local
ce79e9d7525a        host                host                local
6a410e27b66e        mydocker0           bridge              local
8f0358469e57        none                null                local

修改docker网桥名字
1、关闭新建网桥

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ip link set dev br-6a410e27b66e down

2、修改名字

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ip link set dev br-6a410e27b66e name  mydocker0

3、启动网桥

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ip link set dev mydocker0 up

4、重启docker服务

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systemctl restart docker

删除未使用的网桥-prune

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docker network prune
WARNING! This will remove all networks not used by at least one container.
Are you sure you want to continue? [y/N] y
Deleted Networks:
docker1

删除某个网桥-rm

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docker network rm docker100
docker100

注意：
不能被活动容器占用

容器连接到网桥

前提是该容器是桥接网络

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docker network connect docker1 centos1
docker exec centos1 ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 172.17.0.2  netmask 255.255.0.0  broadcast 172.17.255.255
        ether 02:42:ac:11:00:02  txqueuelen 0  (Ethernet)
        RX packets 8  bytes 656 (656.0 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
#发现centos1容器多了一块网卡，使用的正是docker1的网段
eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.2  netmask 255.255.255.0  broadcast 192.168.1.255
        ether 02:42:c0:a8:01:02  txqueuelen 0  (Ethernet)
        RX packets 16  bytes 1312 (1.2 KiB)
        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

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        loop  txqueuelen 1000  (Local Loopback)
        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

容器断开网桥

将centos1容器的网络从docker1网桥断开

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docker network disconnect docker1 centos1

常见故障

FAQ1：使用改名后的新网桥的容器可能无法解析域名

原因：没有配置新网桥的DNS

解决方法：为容器手动配置一个DNS地址即可

FAQ2：Networking will not work

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docker run -d --network docker100 --name centos4 baishuming2020/centos_nginx
WARNING: IPv4 forwarding is disabled. Networking will not work.
67f2c276123c993cd66b9d7a99ba22402331a13f9ea8817e57324a934896b805

解决方案
1、打开转发

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echo "net.ipv4.ip_forward=1" >>  /usr/lib/sysctl.d/00-system.conf

2、重启网络

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systemctl restart network