network namespace
我有一个程序，监听某个端口，在一台Linux机器上，运行多个这样的程序，端口监听一样，冲突怎么办？
可以更改监听端口，这样即使端口不一样，但是程序还是一样的。
如果你硬要监听一样的端口，那么端口肯定是冲突的，除非你另外创建一个网络命名空间，把程序运行在这个命名空间中
可以实战操作一把
root@ubuntu:/home/ubuntu# ip netns --helpCommand "--help" is unknown, try "ip netns help". root@ubuntu:/home/ubuntu# ip netns helpUsage: ip netns list ip netns add NAME ip netns set NAME NETNSID 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
创建网络命名空间 demo
root@ubuntu:/home/ubuntu# ip netns add demoroot@ubuntu:/home/ubuntu# ip netns lsdemo
添加虚拟网络设备
下面命令添加了两个端对端的网络veth1veth2
ip link add veth1 type veth peer name veth2
将虚拟网络一端添加到命名空间中, 这里把veth1添加到网络命名空间
ip link set veth1 netns demo
配置网络设备，这里把veth2留在本机并配置IP
ip addr add 172.17.0.1/24 dev veth2
启动设备
ip link set dev veth2 up
查看网络
root@ubuntu:/home/ubuntu# ifconfig -v veth2veth2: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 172.17.0.1 netmask 255.255.255.0 broadcast 0.0.0.0 ether 8e:7e:64:ff:30:8a txqueuelen 1000 (Ethernet) 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
给网络命名空间虚拟设备配置IP，并启用网络设备
root@ubuntu:/home/ubuntu# ip netns exec demo ip addr add 172.17.0.2/24 dev veth1root@ubuntu:/home/ubuntu# ip netns exec demo ip link set dev veth1 uproot@ubuntu:/home/ubuntu# ip netns exec demo ifconfigveth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 172.17.0.2 netmask 255.255.255.0 broadcast 0.0.0.0 inet6 fe80::38d1:35ff:fe2a:757b prefixlen 64 scopeid 0x20<link> ether 3a:d1:35:2a:75:7b txqueuelen 1000 (Ethernet) RX packets 8 bytes 656 (656.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 8 bytes 656 (656.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
在默认网络与demo命名空间网络，互相ping，都是可以ping通的
但是，最后在demo命名空间中，ping 172.17.0.2 却是没有响应
root@ubuntu:/home/ubuntu# ping 172.17.0.1PING 172.17.0.1 (172.17.0.1) 56(84) bytes of data. 64 bytes from 172.17.0.1: icmp_seq=1ttl=64time=0.107 ms 64 bytes from 172.17.0.1: icmp_seq=2ttl=64time=0.159 ms 64 bytes from 172.17.0.1: icmp_seq=3ttl=64time=0.158 ms ^C ---172.17.0.1 ping statistics ---3 packets transmitted, 3 received, 0% packet loss, time 2025ms rtt min/avg/max/mdev =0.107/0.141/0.159/0.026 ms root@ubuntu:/home/ubuntu# ping 172.17.0.2PING 172.17.0.2 (172.17.0.2) 56(84) bytes of data. 64 bytes from 172.17.0.2: icmp_seq=1ttl=64time=0.162 ms 64 bytes from 172.17.0.2: icmp_seq=2ttl=64time=0.096 ms 64 bytes from 172.17.0.2: icmp_seq=3ttl=64time=0.092 ms ^C ---172.17.0.2 ping statistics ---3 packets transmitted, 3 received, 0% packet loss, time 2148ms rtt min/avg/max/mdev =0.092/0.116/0.162/0.034 ms root@ubuntu:/home/ubuntu# ip netns exec demo ping 172.17.0.1PING 172.17.0.1 (172.17.0.1) 56(84) bytes of data. 64 bytes from 172.17.0.1: icmp_seq=1ttl=64time=0.217 ms 64 bytes from 172.17.0.1: icmp_seq=2ttl=64time=0.090 ms 64 bytes from 172.17.0.1: icmp_seq=3ttl=64time=0.096 ms ^C ---172.17.0.1 ping statistics ---3 packets transmitted, 3 received, 0% packet loss, time 2115ms rtt min/avg/max/mdev =0.090/0.134/0.217/0.059 ms root@ubuntu:/home/ubuntu# ip netns exec demo ping 172.17.0.2PING 172.17.0.2 (172.17.0.2) 56(84) bytes of data.
进入demo命名空间排查,发现回环设备也无法ping通,通过启用lo设备,问题就解决了
root@ubuntu:/home/ubuntu# ping 127.0.0.1connect: Network is unreachable root@ubuntu:/home/ubuntu# ping 0.0.0.0connect: Network is unreachable root@ubuntu:/home/ubuntu# ip link set dev lo uproot@ubuntu:/home/ubuntu# ping 0.0.0.0PING 0.0.0.0 (127.0.0.1) 56(84) bytes of data. 64 bytes from 127.0.0.1: icmp_seq=1ttl=64time=0.070 ms 64 bytes from 127.0.0.1: icmp_seq=2ttl=64time=0.086 ms ^C ---0.0.0.0 ping statistics ---2 packets transmitted, 2 received, 0% packet loss, time 1013ms rtt min/avg/max/mdev =0.070/0.078/0.086/0.008 ms root@ubuntu:/home/ubuntu# ping 172.17.0.2PING 172.17.0.2 (172.17.0.2) 56(84) bytes of data. 64 bytes from 172.17.0.2: icmp_seq=1ttl=64time=0.077 ms 64 bytes from 172.17.0.2: icmp_seq=2ttl=64time=0.087 ms ^C ---172.17.0.2 ping statistics ---2 packets transmitted, 2 received, 0% packet loss, time 1022ms rtt min/avg/max/mdev =0.077/0.082/0.087/0.005 ms
发现demo网络命名空间，无法ping通外网
root@ubuntu:/home/ubuntu# ip netns exec demo ping 114.114.114.114connect: Network is unreachable
查看路由,发现并没有匹配的路由
root@ubuntu:/home/ubuntu# ip netns exec demo routeKernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 172.17.0.0 0.0.0.0 255.255.255.0 U 000 veth1
添加一条路由试试,enp0s2为默认网络空间的网络设备名
ip netns exec demo route add default gw 172.17.0.1 echo1 > /proc/sys/net/ipv4/ip_forward iptables -t nat -A POSTROUTING -s172.17.0.0/24 -o enp0s2 -j MASQUERADE
验证
root@ubuntu:/home/ubuntu# ip netns exec demo ping 114.114.114.114PING 114.114.114.114 (114.114.114.114) 56(84) bytes of data. 64 bytes from 114.114.114.114: icmp_seq=1ttl=58time=13.4 ms 64 bytes from 114.114.114.114: icmp_seq=2ttl=58time=7.34 ms 64 bytes from 114.114.114.114: icmp_seq=3ttl=58time=10.7 ms
发现demo网络命名空间无法ping通百度
root@ubuntu:/home/ubuntu# ip netns exec demo ping www.baidu.comping: www.baidu.com: Temporary failure in name resolution
进入命名空间创建dns解析
root@ubuntu:/home/ubuntu# ip netns exec demo bashroot@ubuntu:/home/ubuntu# mkdir -p /etc/netns/demoroot@ubuntu:/home/ubuntu# vim /etc/netns/demo/resolv.confroot@ubuntu:/home/ubuntu# cat /etc/netns/demo/resolv.confnameserver 114.114.114.114
在默认命名空间，执行如下命令
root@ubuntu:/home/ubuntu# strace -f ip netns exec demo sleep 1 2>&1|egrep '/etc/|clone|mount|unshare'|egrep -vw '/etc/ld.so|access'unshare(CLONE_NEWNS) =0mount("", "/", 0x55ebf359d725, MS_REC|MS_SLAVE, NULL) =0umount2("/sys", MNT_DETACH) =0mount("demo", "/sys", "sysfs", 0, NULL) =0openat(AT_FDCWD, "/etc/netns/demo", O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) =5mount("/etc/netns/demo/resolv.conf", "/etc/resolv.conf", 0x55ebf359d725, MS_BIND, NULL) =0
发现已经可以ping通百度了
root@ubuntu:/home/ubuntu# ip netns exec demo bashroot@ubuntu:/home/ubuntu# ping www.baidu.comPING www.a.shifen.com (36.152.44.95) 56(84) bytes of data. 64 bytes from 36.152.44.95 (36.152.44.95): icmp_seq=1ttl=49time=12.8 ms 64 bytes from 36.152.44.95 (36.152.44.95): icmp_seq=2ttl=49time=11.0 ms 64 bytes from 36.152.44.95 (36.152.44.95): icmp_seq=3ttl=49time=13.2 ms
