dhcpd conf 语法错误 - 从 RHEL6 升级到 RHEL7 - dhcp 4.2

如何解决dhcpd conf 语法错误 - 从 RHEL6 升级到 RHEL7 - dhcp 4.2

谁能帮我弄清楚这里的语法问题。此块在 RHEL6 dhcpd.conf (dhcp-4.1.1-63.P1.el6_10.x86_64) 文件中工作，但在我升级到 RHEL7 (dhcp-4.2.5-82.el7.x86_64) 时抛出错误>

 30 on commit {
 31         if (not static and ((config-option server.ddns-updates = null) or (config-option server.ddns-updates != 0))) {
 32                 if exists oe-key {
 33                         set ddns-rev-name = concat (binary-to-ascii (10,8,".",reverse (1,leased-address)),pick (config-option server.ddns-rev-domainname,"in-addr.arpa."));
 34                         set full-oe-key = option oe-key;
 35                         switch (ns-update (delete (IN,25,ddns-rev-name,null),add (IN,full-oe-key,lease-time / 2)))
 36                         {
 37                           default:
 38                           unset ddns-rev-name;
 39                           break;
 40                           case NOERROR:
 41                           on release or expiry {
 42                             switch (ns-update (delete (IN,null))) {
 43                               case NOERROR:
 44                               unset ddns-rev-name;
 45                               break;
 46                             }
 47                           }
 48                         }
 49                 }
 50         }
 51 }

错误

/etc/dhcp/dhcpd.conf line 35: expecting expression.
                        switch (ns-update (delete 

看来参数RELNOTES有一些变化

775 - Replaced ifconfig parameters "add" and "delete" with "alias" and "-alias" 
776 for IPv6 mode in the client scripts,netbsd and openbsd. This was 
777 preventing IPv6 addresses from being added or removed from interfaces. 778 Thanks to Tim Dean for reporting this issue. 779 [ISC-bugs #31573] 

现在有没有人更深入地了解如何构建这些 confs 以包括添加、删除和切换案例？