[Samba] dhcp lease time hardware in script at dhcpd/Bind/Samba wiki page

[Sebastian Arcus]

There seems to be a slight issue with the instructions at the following 
wiki page:

https://wiki.samba.org/index.php/Configure_DHCP_to_update_DNS_records_with_BIND9

The /usr/local/bin/dhcp-dyndns.sh script seems to use a hardwired value 
for the lease expiry time of 3600 - independent of whatever is 
configured in dhcpd.conf. With the examples provided, it should work, as 
the example dhcpd.conf uses 1800 for lease expiry time - so dhcpd will 
try to renew the lease before it actually expires. However, when I 
implemented the script, I didn't notice that the lease time is hardwired 
in the dhcp-dyndns.sh script - so I've set a higher value in dhcpd.conf. 
This seems to have caused all sorts of strange behaviour, as 
Bind/samba_dlz were expiring leases and dhcpd wasn't renewing them - 
thinking they are still valid.

Would it be possible to pass the max lease time value from dhcpd.conf to 
the dhcp-dyndns.sh script somehow? I would have made a suggestion 
myself, but for the life of me I can't find anywhere on the net a 
reference of standard variable which can be used in dhcpd.conf.

If the above is not possible, maybe a max-lease-time variable should be 
placed at the top of the dhcp-dyndns.sh script. so that at least it is 
obvious that this is set again in this script, and not carried over from 
dhcpd.conf?