docker网络实现

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通过上图，可以清楚的表示容器的网络结构，其中容器中的网卡eth0和绑定在Docker0网桥上的vethxxx设备是一对veth设备对。其中vethxxx由于绑定到docker0网桥，所以没有IP地址，容器中的eth0分配了和docker0同一网段的地址，这样就实现了容器的互联。

3、查看运行两个容器的宿主：

 # ip a

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 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
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 52:54:00:15:c2:12 brd ff:ff:ff:ff:ff:ff
    inet 192.168.20.17/24 brd 192.168.20.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::5054:ff:fe15:c212/64 scope link 
       valid_lft forever preferred_lft forever
3: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP 
    link/ether 02:42:fa:6f:13:18 brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 scope global docker0
       valid_lft forever preferred_lft forever
    inet6 fe80::42:faff:fe6f:1318/64 scope link 
       valid_lft forever preferred_lft forever
7: veth37e9040@if6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP 
    link/ether f2:4e:50:a5:fb:b8 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet6 fe80::f04e:50ff:fea5:fbb8/64 scope link 
       valid_lft forever preferred_lft forever
19: veth36fb1f6@if18: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP 
    link/ether 7a:96:bc:c7:03:d8 brd ff:ff:ff:ff:ff:ff link-netnsid 1
    inet6 fe80::7896:bcff:fec7:3d8/64 scope link 
       valid_lft forever preferred_lft forever

4、通过查看桥接网卡信息,可以验证这两个veth绑定在docker0上：

# brctl  show
bridge name bridge id       STP enabled interfaces
docker0     8000.0242fa6f1318   no      veth36fb1f6
                                        veth37e9040

5、查看容器的network namespace

# docker inspect 506a694d09fb|grep Pid
            "Pid": 2737,
            "PidMode": "",
            "PidsLimit": 0,

# mkdir /var/run/netns

# ln -s /proc/2737/ns/net /var/run/netns/506a694d09fb

# ip netns list
506a694d09fb (id: 0)
6d9742fb3c2d (id: 1)

分别查看两个容器的IP:

# ip netns exec 506a694d09fb ip a 
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 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
6: eth0@if7: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP 
    link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 172.17.0.2/16 scope global eth0
       valid_lft forever preferred_lft foreve

# ip netns exec 6d9742fb3c2d ip a 
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 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
18: eth0@if19: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP 
    link/ether 02:42:ac:11:00:03 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 172.17.0.3/16 scope global eth0
       valid_lft forever preferred_lft forever

可以发现这两个容器属于不同网络命名空间，但是在同一网段，通过veth设备对，绑定docker0互联。
通过ethtool -S veth-name 可以查看到对应的peer端，这里就不再演示，其实通过veth的名称（vethxxx@ifNO）也可以发现所指的接口信息。

6、如果执行ip netns exec命令报错，说明docker把网络netns又隐藏了一层，可以先进入docker守护进程的mount命名空间，在进入对应的网络命名空间，执行下面的nsenter命令。

[root@jumpserver ~]# nsenter -t 6807 -m nsenter --net=/var/run/docker/netns/a4fdba0d4cd4 ip add
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    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
46: eth0@if47: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP 
    link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 172.17.0.2/16 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::42:acff:fe11:2/64 scope link 
       valid_lft forever preferred_lft forever

6807为docker主进程pid，可以通过pstree -p命令获取。

参考文章:
http://blog.51cto.com/tryingstuff/2165805

docker网络实现

标签：unknown   tns   ever   multicast   exec   使用   scope   守护进程   fast   

原文地址：http://blog.51cto.com/1011779/2349907