Setup dhcpd/dhcpdv6 server

搭建DHCP server在许多网络应用中是非常必要的，尤其是测试IPv6相关的功能时，本文就来介绍下针对IPv4和IPv6该如何搭建DHCP server.

Install dhcpd server

首先通过apt安装isc-dhcp-server

sudo apt install isc-dhcp-server

Setup dhcpd

Config interfaces

通过ifconfig获取以太网口的接口名称, 下面省略了loopback接口lo，后面也是一样默认省略。

$ ifconfig
enp4s0f0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
        ether 20:6a:8a:6c:0f:da  txqueuelen 1000 (Ethernet)
        RX packets 154583  bytes 186953698 (186.9 MB)
        RX errors 0  dropped 2  overruns 0  frame 0
        TX packets 77038  bytes 6244250 (6.2 MB)
        Tx erros 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 19

编辑配置文件/etc/default/isc-dhcp-server，修改最后两行，设置为刚刚获取到的interface

$ tail -n 2 /etc/default/isc-dhcp-server
INTERFACESv4="enp4s0f0"
INTERFACESv6="enp4s0f0"

Config dhcpd server

首先针对IPv4配置dhcpd server，配置文件为/etc/dhcp/dhcpd.conf, 配置内容包括网段，子网掩码，默认路由，默认DNS

$ tail -n 5 /etc/dhcp/dhcpd.conf
subnet 10.0.0.0 netmask 255.255.255.0 {
    range 10.0.0.10 10.0.0.99;
    option routers 10.0.0.138;
    option domain-name-servers 10.0.0.138;
}

Add static ipv4

此时只要再给网口设置一个静态IP就可以了

sudo ifconfig enp4s0f0 10.0.0.138 netmask 255.255.255.0

Start isc-dhcp-server

sudo service isc-dhcp-server start
sudo service isc-dhcp-server status

通过第二条指令可以查看当前dhcpd的状态，显示running表示已经正常工作

$ sudo service isc-dhcp-server status
● isc-dhcp-server.service - ISC DHCP IPv4 server
   Loaded: loaded (/lib/systemd/system/isc-dhcp-server.service; enabled; vendor preset: enabled)
   Active: active (running) since Sat 2020-01-18 04:22:28 CST; 7s ago
     Docs: man:dhcpd(8)
 Main PID: 13291 (dhcpd)
    Tasks: 1 (limit: 4915)
   CGroup: /system.slice/isc-dhcp-server.service
           └─13291 dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf /etc/dhcp/dhcpd.conf

1月 18 04:22:28 litreily-Aspire-4750 dhcpd[13291]: PID file: /run/dhcp-server/dhcpd.pid
1月 18 04:22:28 litreily-Aspire-4750 sh[13291]: Wrote 1 leases to leases file.
1月 18 04:22:28 litreily-Aspire-4750 dhcpd[13291]: Wrote 1 leases to leases file.
1月 18 04:22:28 litreily-Aspire-4750 dhcpd[13291]: Listening on LPF/enp4s0f0/20:6a:8a:6c:0f:da/10.0.0.0/24
1月 18 04:22:28 litreily-Aspire-4750 dhcpd[13291]: Sending on   LPF/enp4s0f0/20:6a:8a:6c:0f:da/10.0.0.0/24
1月 18 04:22:28 litreily-Aspire-4750 sh[13291]: Listening on LPF/enp4s0f0/20:6a:8a:6c:0f:da/10.0.0.0/24
1月 18 04:22:28 litreily-Aspire-4750 sh[13291]: Sending on   LPF/enp4s0f0/20:6a:8a:6c:0f:da/10.0.0.0/24
1月 18 04:22:28 litreily-Aspire-4750 sh[13291]: Sending on   Socket/fallback/fallback-net
1月 18 04:22:28 litreily-Aspire-4750 dhcpd[13291]: Sending on   Socket/fallback/fallback-net
1月 18 04:22:28 litreily-Aspire-4750 dhcpd[13291]: Server starting service.

Setup dhcpdv6

配置IPv6的dhcpd与IPv4类似，上面已经配置过/etc/default/interfaces，此处省略

config dhcpdv6 server

配置文件/etc/dhcp/dhcpd6.conf

$ tail -n 5 /etc/dhcp/dhcpd6.conf
subnet6 2001:470:19:1316::/64 {
    range6 2001:470:19:1316::100 2001:470:19:1316::0fff;
    option dhcp6.name-servers fe80::226a:8aff:fe6c:0fda;
    prefix6 2001:470:19:1316:2:: 2001:470:19:1316:0fff:: /80;
}

上面配置了IPv6的网段，分配范围，默认dns，以及IPv6前缀

Add static IPv6

对于IPv6，需要添加两个ip，一个以fe80::开头的本地ip，另外一个静态global ip

sudo ifconfig enp4s0f0 inet6 add 2001:470:19:1316::1/64
sudo ifconfig enp4s0f0 inet6 add fe80::226a:8aff:fe6c:fda/64

Start isc-dhcp-server6

dhcpdv6对应的server名称多了个6，启动方式自然也是一样的

sudo service isc-dhcp-server6 start
sudo service isc-dhcp-server6 status

Notice

在手动配置时，注意在启动服务之前，一定要记得配置好静态IP，否则无法启动server，并在查看状态时显示以下信息

$ sudo service isc-dhcp-server status
● isc-dhcp-server.service - ISC DHCP IPv4 server
   Loaded: loaded (/lib/systemd/system/isc-dhcp-server.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Sat 2020-01-18 04:23:23 CST; 10s ago
     Docs: man:dhcpd(8)
  Process: 13864 ExecStart=/bin/sh -ec      CONFIG_FILE=/etc/dhcp/dhcpd.conf;      if [ -f /etc/ltsp/dhcpd.conf ]; then CONFIG_FILE=/etc/ltsp/dhcpd.conf; fi;      [ -e /var/lib/dhcp/dhcpd.leases ] || touch /var/lib/dhcp/dhcpd.leases;      chown root:dhcpd /var/lib/dhcp /var/lib/dhcp/dhcpd.leases;      chmod 775 /var/lib/dhcp ; chmod 664 /var/lib/dhcp/dhcpd.leases;      exec dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf $CONFIG_FILE $INTERFACES (code=exited, status=1/FAILURE)
 Main PID: 13864 (code=exited, status=1/FAILURE)

1月 18 04:23:23 litreily-Aspire-4750 dhcpd[13864]:
1月 18 04:23:23 litreily-Aspire-4750 dhcpd[13864]: If you think you have received this message due to a bug rather
1月 18 04:23:23 litreily-Aspire-4750 dhcpd[13864]: than a configuration issue please read the section on submitting
1月 18 04:23:23 litreily-Aspire-4750 systemd[1]: isc-dhcp-server.service: Main process exited, code=exited, status=1/FAILURE
1月 18 04:23:23 litreily-Aspire-4750 dhcpd[13864]: bugs on either our web page at www.isc.org or in the README file
1月 18 04:23:23 litreily-Aspire-4750 dhcpd[13864]: before submitting a bug.  These pages explain the proper
1月 18 04:23:23 litreily-Aspire-4750 systemd[1]: isc-dhcp-server.service: Failed with result 'exit-code'.
1月 18 04:23:23 litreily-Aspire-4750 dhcpd[13864]: process and the information we find helpful for debugging..
1月 18 04:23:23 litreily-Aspire-4750 dhcpd[13864]:
1月 18 04:23:23 litreily-Aspire-4750 dhcpd[13864]: exiting.

Shell script

为了方便配置server，我写了一个简单的执行脚本，network servers control, 简称nsc

$ cat nsc
#!/bin/zsh
# network servers control

IFCONFIG=1
INTERFACE=enp4s0f0

IPv4=10.0.0.138
IPv6=2001:470:19:1316::1/64
IPv6_local=fe80::226a:8aff:fe6c:fda/64

stop_dhcp() {
    # stop services
    sudo service isc-dhcp-server stop
    sudo service isc-dhcp-server6 stop

    # del all default ip
    if [ $IFCONFIG -eq 1 ]; then
        sudo ifconfig $INTERFACE 0.0.0.0
        sudo ifconfig $INTERFACE del $IPv6
        sudo ifconfig $INTERFACE del $IPv6_local
    else
        sudo ip addr delete $IPv4/24 dev enp4s0f0
        sudo ip addr delete $IPv6 dev enp4s0f0
        sudo ip addr delete $IPv6_local dev enp4s0f0
    fi
}

start_dhcp() {
    # setup default ip
    if [ $IFCONFIG -eq 1 ]; then
        sudo ifconfig $INTERFACE $IPv4 netmask 255.255.255.0
        sudo ifconfig $INTERFACE inet6 add $IPv6
        sudo ifconfig $INTERFACE inet6 add $IPv6_local
    else
        sudo ip addr add $IPv4/24 dev enp4s0f0
        sudo ip addr add $IPv6 dev enp4s0f0
        sudo ip addr add $IPv6_local dev enp4s0f0
    fi

    # start services
    sudo service isc-dhcp-server start
    [ $? -eq 0 ] && echo "start dhcpd success!"
    sudo service isc-dhcp-server6 start
    [ $? -eq 0 ] && echo "start dhcpdv6 success!"
}

case "$1" in
    "stop")
        stop_dhcp
        ;;
    "start")
        start_dhcp
        ;;
esac

脚本中通过$IFCONFIG变量来选择使用ifconfig指令还是ip指令进行配置。使用时只需执行nsc start打开server, 执行nsc stop关闭server.