Dhcpd on commit

Show how to configure dhcpd to execute a hook on commit (lease added or updated) containing:

• Lease IP (10.0.x.y)
• Client hwaddr (aa:bb:cc:dd:ee:ff)
• Client requested hostname (foo)
• Client DDNS FQDN (foo.example.net.)

It also handles when different subnets have different ddns-domainname and will generate client hostnames with dynamically generated ones if needed.

Code: dhcpd.conf (view, download)

1. # Update DNS (including static leases)
2. ddns-update-style interim;
3. update-static-leases on;
4. ddns-domainname "example.net.";
5. ddns-rev-domainname "in-addr.arpa.";
6.  
7. # Add a hook which executes when a lease is added or updated
8. on commit {
9.   # Get the client name from the first of the following:
10.   #   1. Client DHCP Option FQDN
11.   #   2. Client DHCP Option hostname
12.   #   3. Name of static lease (host-decl-name)
13.   #   4. A generated name "dyn-${ip}" where ip is the lease IP with dashes, e.g. "dyn-10-0-1-123"
14.   set clientddns = lcase(pick-first-value (option fqdn.hostname, option host-name, host-decl-name, concat ("dyn-", binary-to-ascii(10,8,"-", leased-address)), ""));
15.  
16.   # Get the client dynamic dns domain (different for each subnet)
17.   set clientdomain = config-option server.ddns-domainname;
18.  
19.   # Get client hostname only (no generated or static). Used by the hook to show which hostname the client requested.
20.   set clienthost = pick-first-value (option fqdn.hostname, option host-name, "");
21.  
22.   # Get lease IP and hwaddr
23.   set clientip = binary-to-ascii(10, 8, ".", leased-address);
24.   set clientmac = binary-to-ascii(16, 8, ":", substring(hardware, 1, 6));
25.  
26.   # Update the dynamic hostname (which wont be set unless the client requested one, so update with the generated if needed)
27.   ddns-hostname = clientddns;
28.  
29.   # Execute the hook
30.   execute("/path/to/my/hook", "commit", clientip, concat(clientddns, ".", clientdomain), clienthost, clientmac);
31. }
32.  
33. # Subnet 1
34. subnet 10.0.1.0 netmask 255.255.255.0 {
35.   ddns-domainname "subnet1.example.net.";
36. }
37.  
38. # Subnet 2
39. subnet 10.0.2.0 netmask 255.255.255.0 {
40.   ddns-domainname "subnet2.example.net.";
41. }