文章目录
1. Linux内核实现名称空间的创建
1.1 ip netns命令
可以借助ip netns命令来完成对 Network Namespace 的各种操作。ip netns命令来自于iproute安装包,一般系统会默认安装,如果没有的话,请自行安装。
**注意:**普通用户使用ip netns命令修改网络配置时需要 sudo 权限。
可以通过ip netns命令完成对Network Namespace 的相关操作,可以通过ip netns help查看命令帮助信息:
[root@docker ~]# ip netns help
Usage: ip netns list //查看所有名称空间
ip netns add NAME //创建名称空间
ip netns set NAME NETNSID //管理
ip [-all] netns delete [NAME]
ip netns identify [PID]
ip netns pids NAME
ip [-all] netns exec [NAME] cmd ...
ip netns monitor
ip netns list-id
默认情况下,Linux系统中是没有任何 Network Namespace的,所以ip netns list命令不会返回任何信息。
1.2 创建Network Namespace
命令:ip netns add <name>
示例:
通过命令创建一个名为ns0的命名空间:
1.查看名称空间
[root@docker ~]# ip netns list
2.创建名称ns0名称空间
[root@docker ~]# ip netns add ns0
3.查看创建的名称空间
[root@docker ~]# ip netns list
ns0
4.重复创建会出现报错如下:
[root@docker ~]# ip netns add ns0
Cannot create namespace file "/var/run/netns/ns0": File exists
新创建的 Network Namespace 会出现在/var/run/netns/
目录下。
[root@docker ~]# ls /var/run/netns/
ns0
每个 Network Namespace 会有自己独立的网卡、路由表、ARP 表、iptables 等和网络相关的资源。
1.3 操作Network Namespace
ip命令提供了ip netns exec
子命令可以在对应的 Network Namespace 中执行命令。
查看新创建 Network Namespace 的网卡ns0的信息
[root@docker ~]# ip netns exec ns0 ip address
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
新创建的 Network Namespace 中默认只有一个lo回环网卡,切该网卡为关闭状态,此时,尝试去 ping 该lo回环网卡,会提示Network is unreachable
[root@docker ~]# ip netns exec ns0 ping 127.0.0.1
connect: Network is unreachable
启用ns0的lo回环网卡:
1.开启网卡
[root@docker ~]# ip netns exec ns0 ip link set lo up
2.查看网卡是否开启
[root@docker ~]# ip netns exec ns0 ip add
1: 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
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
3.尝试是否可以ping通
[root@docker ~]# ip netns exec ns0 ping 127.0.0.1
PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.063 ms
64 bytes from 127.0.0.1: icmp_seq=2 ttl=64 time=0.057 ms
1.4 转移设备
可以在不同的 Network Namespace 之间转移设备(如veth)。由于一个设备只能属于一个 Network Namespace ,所以转移后在这个 Network Namespace 内就看不到这个设备了。
其中,veth设备属于可转移设备,而很多其它设备(如lo、vxlan、ppp、bridge等)是不可以转移的。
1.4.1 veth pair
veth pair 全称是 Virtual Ethernet Pair,是一个成对的端口,所有从这对端口一 端进入的数据包都将从另一端出来,反之也是一样。
引入veth pair是为了在不同的 Network Namespace 直接进行通信,利用它可以直接将两个 Network Namespace 连接起来。
1.4.2 创建veth pair
1.创建veth
[root@docker ~]# ip link add type veth
2.查看veth,创建的veth出现了一对veth pair
[root@docker ~]# ip a
...省略N行
58: veth0@veth1: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN group default qlen 1000
link/ether ee:80:fb:76:6c:2c brd ff:ff:ff:ff:ff:ff
59: veth1@veth0: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noop state DOWN group default qlen 1000
link/ether d6:93:76:11:cd:27 brd ff:ff:ff:ff:ff:ff
可以看到,此时系统中新增了一对veth pair,将veth0和veth1两个虚拟网卡连接了起来,此时这对 veth pair 处于”未启用“状态。
1.4.3 删除veth pair
1.删除veth
[root@docker ~]# ip link delete veth0
2.查看网卡信息,删除veth0时会,同时删除veth1
[root@docker ~]# ip a
1: 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
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:16:3e:0d:73:7c brd ff:ff:ff:ff:ff:ff
inet 172.26.169.24/20 brd 172.26.175.255 scope global dynamic eth0
valid_lft 314806322sec preferred_lft 314806322sec
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:53:74:03:90 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
1.5 实现Network Namespace间通信
利用veth pair实现两个不同的 Network Namespace 之间的通信。
刚才我们已经创建了一个名为ns0的 Network Namespace,下面再创建一个信息Network Namespace,命名为ns1
[root@docker ~]# ip netns add ns1
[root@docker ~]# ip netns list
ns1
ns0
1.5.1 将虚拟网卡veth加入名称空间(从主机上移走至命名空间)
命令:ip link set <veth*> netns <Namespace>
示例:
1.将veth0加入到ns0,将veth1加入到ns1
[root@docker ~]# ip link set veth0 netns ns0
[root@docker ~]# ip link set veth1 netns ns1
2.查看主机网卡信息,veth网卡已经不在本机
[root@docker ~]# ip a
1: 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
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:16:3e:0d:73:7c brd ff:ff:ff:ff:ff:ff
inet 172.26.169.24/20 brd 172.26.175.255 scope global dynamic eth0
valid_lft 314804457sec preferred_lft 314804457sec
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:53:74:03:90 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
3.查看命名空间网卡信息
[root@docker ~]# ip netns exec ns0 ifconfig -a
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 6 bytes 504 (504.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 6 bytes 504 (504.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
veth0: flags=4098<BROADCAST,MULTICAST> mtu 1500
inet 10.0.0.1 netmask 255.255.255.0 broadcast 0.0.0.0
ether f2:2a:64:26:cf:68 txqueuelen 1000 (Ethernet)
RX packets 12 bytes 936 (936.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 12 bytes 936 (936.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
[root@docker ~]# ip netns exec ns1 ifconfig -a
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
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
veth1: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
inet 10.0.0.2 netmask 255.255.255.0 broadcast 0.0.0.0
inet6 fe80::3097:39ff:fefb:aba1 prefixlen 64 scopeid 0x20<link>
ether 32:97:39:fb:ab:a1 txqueuelen 1000 (Ethernet)
RX packets 12 bytes 936 (936.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 12 bytes 936 (936.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
1.5.2 启用veth pair,并配置上ip地址
1.开启ns0上的网卡,并配置ip地址为10.0.0.1/24
[root@docker ~]# ip netns exec ns0 ip link set lo up
[root@docker ~]# ip netns exec ns0 ip link set veth0 up
[root@docker ~]# ip netns exec ns0 ip addr add 10.0.0.1/24 dev veth0
2.开启ns1上的网卡,并配置ip地址为10.0.0.2/24
[root@docker ~]# ip netns exec ns1 ip link set lo up
[root@docker ~]# ip netns exec ns1 ip link set veth1 up
[root@docker ~]# ip netns exec ns1 ip addr add 10.0.0.2/24 dev veth1
3.查看ns0、ns1网卡状态
[root@docker ~]# ip netns exec ns0 ip a
1: 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
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
60: veth0@if61: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
link/ether f2:2a:64:26:cf:68 brd ff:ff:ff:ff:ff:ff link-netnsid 1
inet 10.0.0.1/24 scope global veth0
valid_lft forever preferred_lft forever
inet6 fe80::f02a:64ff:fe26:cf68/64 scope link
valid_lft forever preferred_lft forever
[root@docker ~]# ip netns exec ns1 ip a
1: 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
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
61: veth1@if60: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
link/ether 32:97:39:fb:ab:a1 brd ff:ff:ff:ff:ff:ff link-netnsid 0
inet 10.0.0.2/24 scope global veth1
valid_lft forever preferred_lft forever
inet6 fe80::3097:39ff:fefb:aba1/64 scope link
valid_lft forever preferred_lft forever
1.5.3 测试是否连通
测试ns0可以ping通10.0.0.2
[root@docker ~]# ip netns exec ns0 ping 10.0.0.2
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=0.064 ms
64 bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=0.058 ms
1.6 veth设备重命名
1.关闭网卡
[root@docker ~]# ip netns exec ns0 ip link set veth0 down
2.重命名veth0为eth0
[root@docker ~]# ip netns exec ns0 ip link set dev veth0 name eth0
3.查看ns0的网卡信息
[root@docker ~]# ip netns exec ns0 ifconfig -a
eth0: flags=4098<BROADCAST,MULTICAST> mtu 1500
inet 10.0.0.1 netmask 255.255.255.0 broadcast 0.0.0.0
ether f2:2a:64:26:cf:68 txqueuelen 1000 (Ethernet)
RX packets 12 bytes 936 (936.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 12 bytes 936 (936.0 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
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 6 bytes 504 (504.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 6 bytes 504 (504.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0