网络名称空间

了解下网络名称空间，更加利于理解docker中的overlay网络。还有k8s中的endpoint，服务发现等。随笔记录
在每个容器里面都会这样的一个设备叫做endpoint，它的作用就是把容器（sandbox）接入到network中去，endpoint最典型的案例就是veth pair。
就是把两个网络头子，端对端的连接起来。两个网络头子置于不同的网络名称空间就可以使其互相通信
实验操作一下就理解了：
Ip netns add //添加新的网络名称空间

[root@emporerlinux ~]# ip netns  add net1
[root@emporerlinux ~]# ip netns list
net1

进入net1 名称空间查看ip: ip netns exec net1 ifconfig -a 默认未开启使用 -a 参数。
Ip link add 创建虚拟网卡对加入名称空间。
Ip link add name veth1.1 type veth peer name veth1.2
Ip link show 两张网卡成对出现。

[root@emporerlinux ~]# ip link add name veth1.1 type veth peer name veth1.2
[root@emporerlinux ~]# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT group default qlen 1000
    link/ether 00:0c:29:f6:84:ad brd ff:ff:ff:ff:ff:ff
3: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default 
    link/ether 02:42:36:cf:f5:db brd ff:ff:ff:ff:ff:ff
5: veth6bdff3b@if4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP mode DEFAULT group default 
    link/ether fe:52:73:ea:ba:22 brd ff:ff:ff:ff:ff:ff link-netnsid 0
7: vethf5c9f74@if6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP mode DEFAULT group default 
    link/ether 7e:09:db:ca:10:71 brd ff:ff:ff:ff:ff:ff link-netnsid 1
8: veth1.2@veth1.1: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 7a:5d:43:b7:a2:6c brd ff:ff:ff:ff:ff:ff
9: veth1.1@veth1.2: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether ee:d4:a6:cc:9a:e9 brd ff:ff:ff:ff:ff:ff

1.1 和1.2 相当于一根网线连接两头。可以把一端加入一个名称空间实现互通。

Ip link set dev veth1.2 netns net1 //把veth1.2 这张网卡加入net1名称空间。
Ip netns exec net1 ifconfig -a //进入net1 名称空间。查看有1.2这张网卡。

[root@emporerlinux ~]# ip link set dev veth1.2 netns net1
[root@emporerlinux ~]# ip netns exec net1 ip a
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
8: veth1.2@if9: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 7a:5d:43:b7:a2:6c brd ff:ff:ff:ff:ff:ff link-netnsid 0

Ip netns exec net1 ip link set dev veth1.2 name eth0 //更改net1中veth1.2 网卡名称为eth0
Ifconfig veth1.1 192.168.1./24 up //给本机veth1.1网卡配置ip 激活。

[root@emporerlinux ~]# ifconfig  veth1.1 192.168.1.1/24 up
[root@emporerlinux ~]# ip a |grep veth
5: veth6bdff3b@if4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP group default 
7: vethf5c9f74@if6: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP group default 
9: veth1.1@if8: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state LOWERLAYERDOWN group default qlen 1000
    inet 192.168.1.1/24 brd 192.168.1.255 scope global veth1.1

Ip netns exec net1ifconfig etho0 10.1.0.2/24 up //配置名称空间net1内另一端ip地址即可通信

[root@emporerlinux ~]# ip  netns exec net1 ifconfig eth0 192.168.1.2/24 up
[root@emporerlinux ~]# ip  netns exec net1 ip a
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
8: eth0@if9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 7a:5d:43:b7:a2:6c brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 192.168.1.2/24 brd 192.168.1.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::785d:43ff:feb7:a26c/64 scope link 
       valid_lft forever preferred_lft forever
       
       
       
 net1 ping 测试
 [root@emporerlinux ~]# ip  netns exec net1  ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=0.103 ms
64 bytes from 192.168.1.1: icmp_seq=2 ttl=64 time=0.096 ms
^C
--- 192.168.1.1 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 999ms
rtt min/avg/max/mdev = 0.096/0.099/0.103/0.010 ms

也可以把 veth1.1 移到另外一个名称空间内当做一张网卡也相当于一张网卡把两个名称空间连接起来。。
Ip link set dev veth1.1 netns net2 //把veth1.1这张网卡移动给net2名称空间使用。宿主机就没有veth1.1这张网卡了
Ip netns exec net2 ifconfig -a //可查看veth1.1这张网卡。
Ip netns exec net2 ifconfig veth1.1 10.1.0.3/24 up //给net2名称空间的veth1.1网卡添加ip并启动。
Ip netns exec net2 ifconfig //查看veth1.1 有ip且ping 通10.1.0.2 实现两个名称空间互通

查看ip：
[root@emporerlinux ~]# ip netns exec net2 ip link show
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
9: veth1.1@if8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether ee:d4:a6:cc:9a:e9 brd ff:ff:ff:ff:ff:ff link-netnsid 0
[root@emporerlinux ~]# ip netns exec net1 ip link show
1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
8: eth0@if9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 7a:5d:43:b7:a2:6c brd ff:ff:ff:ff:ff:ff link-netnsid 1
    配置net1 ip地址
    [root@emporerlinux ~]# ip netns exec net1  ifconfig eth0 192.168.6.1/24 up
    配置net2 ip地址
    [root@emporerlinux ~]# ip netns exec net2 ifconfig veth1.1 192.168.6.2/24 up
    ping测试
    [root@emporerlinux ~]# ip netns exec net2 ping 192.168.6.1
PING 192.168.6.1 (192.168.6.1) 56(84) bytes of data.
64 bytes from 192.168.6.1: icmp_seq=1 ttl=64 time=0.111 ms
64 bytes from 192.168.6.1: icmp_seq=2 ttl=64 time=0.086 ms
64 bytes from 192.168.6.1: icmp_seq=3 ttl=64 time=0.092 ms
^C
--- 192.168.6.1 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1999ms
rtt min/avg/max/mdev = 0.086/0.096/0.111/0.013 ms
[root@emporerlinux ~]# ip netns exec net1 ping 192.168.6.2
PING 192.168.6.2 (192.168.6.2) 56(84) bytes of data.
64 bytes from 192.168.6.2: icmp_seq=1 ttl=64 time=0.099 ms
64 bytes from 192.168.6.2: icmp_seq=2 ttl=64 time=0.101 ms

64 bytes from 192.168.6.2: icmp_seq=3 ttl=64 time=0.113 ms
^C
--- 192.168.6.2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2000ms
rtt min/avg/max/mdev = 0.099/0.104/0.113/0.010 ms