Adding host entry dynamically using dhcpctl functions ( dhcp hungs )

Johnson koil Raj johnson.raj at
Tue Jul 5 13:21:18 UTC 2011

Hi All,

     One of our requirement is not to change IPs of a machines once 
assigned. (first time assigning IPs will be dynamic).

     In order to reserver same IP for ever we decided to add the host 
entry using dhcpctl functions after dhcp assign IP for first time. So at 
the 'on commit' we decided to use 'execute' to run a script which will 
make an host entry by passing required parameters. But DHCP got hung 
when it was executing the script, the same script works properly when I 
execute from shell prompt.

on commit {
     log(debug, "On commit method");
     set ClientIP = binary-to-ascii(10, 8, ".", leased-address);
     set ClientMac =  binary-to-ascii (16, 8, ":", substring(hardware, 
1, 6));
*    set ClientHostname = concat ("node-",
                     suffix (concat ("0", binary-to-ascii (16, 8, 
"",substring(hardware, 4, 1))),2),"-",
                     suffix (concat ("0", binary-to-ascii (16, 8, 
"",substring(hardware, 5, 1))),2),"-",
                     suffix (concat ("0", binary-to-ascii (16, 8, 
"",substring(hardware, 6, 1))),2));

     log(debug, concat("Add Static entry HOSTNAME: ", ClientHostname, " 
IP: ", ClientIP, " Mac: ", ClientMac));


     unset ClientIP;
     unset ClientMac;
     unset ClientHostName;

 From the log I came to know that it got struck at dhcpctl_connect call
status = dhcpctl_connect (&connection, "", 9991, 0);  --> here 
call not returning dhcp hungs.
Why the server is not able to connect when the same script used at 
execute method ?

[root at LdapVM dhcpd]# netstat -anp | grep 9991
tcp        0      0       *                   LISTEN      15923/dhcpd
tcp        8      0                  ESTABLISHED -
tcp        0      0                  ESTABLISHED 15935/add_static_ip

Any other way to reserve an IP to a Machine ( static IP configuration at 
DHCP server side) *not at the machine.*

Any help would be grateful.


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