Dnsmasq from version 2.52 has a couple of rather application-specific
features designed to allow for implementation of the DHCP part of CPE
WAN management protocol.

http://www.broadband-forum.org/technical/download/TR-069_Amendment-2.pdf
http://en.wikipedia.org/wiki/TR-069

The relevant sections are F.2.1 "Gateway Requirements" and F.2.5 "DHCP
Vendor Options".

First, dnsmasq checks for DHCP requests which contain an option-125
vendor-class option which in turn holds a vendor section for IANA
enterprise number 3561 which contains sub-options codes 1 and 2. If
this is present  then the network-tag "cpewan-id" is set. 
This allows dnsmasq to be configured to reply with the correct 
GatewayManufacturerOUI, GatewaySerialNumber and GatewayProductClass like this:

dhcp-option=cpewan-id,vi-encap:3561,4,"<GatewayManufacturerOUI>"
dhcp-option=cpewan-id,vi-encap:3561,5,"<SerialNumber>"
dhcp-option=cpewan-id,vi-encap:3561,6,"<ProductClass>"

Second, the received sub-options 1, 2, and 3 are passed to the DHCP
lease-change script as the environment variables DNSMASQ_CPEWAN_OUI,
DNSMASQ_CPEWAN_SERIAL, and DNSMASQ_CPEWAN_CLASS respectively. This allows
the script to be used to maintain a ManageableDevice table as
specified in F.2.1. Note that this data is not retained in dnsmasq's
internal DHCP lease database, so it is not available on every call to 
the script (this is the same as some other data such as vendor and
user classes). It will however be available for at least the "add"
call, and should be stored then against the IP address as primary 
key for future use.


This feature was added to dnsmasq under sponsorship from Ericsson.