dhcpd.conf: three small nuisances

[Peter Rabbitson]

Hello,

I have a couple of questions about dhcpd. I got the things to work, but 
I don't really like my workarounds, hence the questions:

I am trying to make my dhcpd the central configuration place for both 
dhcp and internal dns records. This rules out host declarations, as they 
have no mechanism to cleaning out a zone once the fixed-address changes. 
Also most computers are identified by their option host-name (yes, I 
know what the man page says). A solution I came up looks like this:

...
    class "cc-ups1" {
        match if option host-name = "cc-ups1";
    }
    pool {
        range 192.168.58.30 192.168.58.30;
        default-lease-time 86400;
        min-lease-time 60;
        max-lease-time 172800;

        ddns-hostname = "ups1.lan.domain.com";

        allow members of "cc-ups1";
    }


    class "cc-ups2" {
        match if option host-name = "cc-ups2";
    }
    pool {
        range 192.168.58.31 192.168.58.31;
        default-lease-time 86400;
        min-lease-time 60;
        max-lease-time 172800;

        ddns-hostname = "ups2.lan.domain.com";

        allow members of "cc-ups2";
    }


    class "00:0a:e6:e9:91:72" {
        match if binary-to-ascii (
		16,
		8, 
		":", 
		substring (hardware, 1, 6)
	) 
	= "0:a:e6:e9:91:72";
    }
    pool {
        range 192.168.58.66 192.168.58.66;
        default-lease-time 86400;
        min-lease-time 60;
        max-lease-time 172800;

        ddns-hostname = "station3.lan.domain.com";

        allow members of "00:0a:e6:e9:91:72";
    }


    pool {
        range 192.168.58.128 192.168.58.191;
        default-lease-time 900;
        min-lease-time 60;
        max-lease-time 1800;

        ddns-hostname = concat (
		pick-first-value 
			(option host-name, "unknown"),
		"-",
		binary-to-ascii (10, 8, "-", leased-address), 
		".unknown.lan.domain.com"	
	);

        deny members of "cc-ups1";
        deny members of "cc-ups2";
	deny members of "00:0a:e6:e9:91:72";
	...
    }
...

This does exactly what I want but has a couple of shortcommings 
(besides being bulky, but I wrote myself a config generator).

* In order to match the hardware value I need to strip leading zeroes 
from the string I am matching against. Is there any way to deal with 
this?

* As many declaration might have a different ddns-hostname domain, I am 
supplying FQDNs directly to ddns-hostname. However I must specify
ddns-domainname ""; which forces concatenation of the empty sting with a 
dot inbetween thus resulting in a real FQDN. Is there a way to disable 
consulting ddns-domainname altogether? Another way would be to 
dynamically update ddns-domainname before every declaration much like 
BINDs $ORIGIN, but since I have FQDNs at hand I would like to avoid it.

* For my dynamic pool I want to see the computername that the client 
sent, hence the pick-first-value (option host-name, "unknown"). However 
if the windows computer name contains an underscore character not 
allowed in DNS the update will fail. It is a minor nuisance but is 
there any way around it?

Thank you in advance for your great help.

Peter