[FS#1137] dnsmasq static hosts configuration should support client-id

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - Isaac Richter (irichter) 

Attached to Project - LEDE Project
Summary - dnsmasq static hosts configuration should support client-id
Task Type - Bug Report
Category - Packages
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Low
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - By design, dnsmasq does not assume that two requests from the same source MAC address are for the same client if their client-id is different. Put another way, the requester is effectively identified by a  pair. This is discussed in the dnsmasq FAQ [[http://www.thekelleys.org.uk/dnsmasq/docs/FAQ]] under the question "I'm network booting my machines, and trying to give them static DHCP-assigned addresses..."

As a result, a machine that has been assigned a static address, which first requests an IP address without sending a client-id, and later makes a request with a client-id, will not be given the assigned static IP in response to the subsequent request. (The static IP will bind to the initial  pair with the null client-ID.)

To resolve this, one of the following options could be implemented:

  - Mention the problem in the documentation, and advise the user to append ",id:*" to the MAC address if they run into this issue. (This will cause issues for luci users because this will be considered a malformed MAC address, and luci will refuse to save changes.)
  - The dnsmasq init script could always insert ",id:*" immediately after the mac address on the generated dhcp-host configuration line.
  - The dhcp.host entry could be extended with an "allow-any-client-id" or "ignore-client-id" boolean, which, if selected, would cause ",id:*" to be inserted as above.
  - The dhcp.host entry could be extended with an optional "client-id" field, which would allow an explicit DHCP client-id to be set for the host. That ID could be used instead of or in addition to the existing "mac" entry. Semantics would need to be defined to make sure that the handling is well-defined.

Whichever option is chosen, the documentation should be updated. If an entry is added to the dhcp.host schema, bugs should be filed on other DHCP server packages (e.g.: isc-dhcp-server-ipv4) so that they can also implement the new functionality.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1137