[Dnsmasq-discuss] [PATCH] Add dhcp-ignore-clid configuration option

Simon Kelley simon at thekelleys.org.uk
Mon Oct 7 18:14:44 BST 2019

On 03/10/2019 06:52, Geert Stappers wrote:
> On Mon, Sep 16, 2019 at 11:09:30PM +0100, Simon Kelley wrote:
>> On 16/09/2019 08:03, Florent Fourcot wrote:
>>> On 20/06/2019 10:26, Florent Fourcot wrote:
>>>> The idea of this option was already discussed years ago on the mailing
>>>> list:
>>>> https://dnsmasq-discuss.thekelleys.org.narkive.com/ZoFQNaGo/always-ignore-client-identifier#post4
>>>> In our production environnement, we discovered that some devices are
>>>> using 'client identifier' not unique at all, resulting on IP addresses
>>>> conflicts between several devices (we saw up to four devices using same
>>>> IP address).
>>>> The root cause is probably a buggy operating system/configuration of
>>>> decices, but this patch add a configuration workaround on server side
>>>> when fixing clients is impossible.
>>>> Signed-off-by: Charles Daymand <charles.daymand at wifirst.fr>
>>>> Signed-off-by: Florent Fourcot <florent.fourcot at wifirst.fr>
>>>> ---
>>> Hello Simon,
>>> Could you have a look on this patch? Please let me know if something is
>>> missing, I'm ready to work on a v2.
>> Apologies for ignoring you. The principle is a good one, but it's worth
>> making this conditional, so that only clients which cause a particular
>> tag to be set see the new behaviour.
>> See, for example, --dhcp-broadcast for how it works.
>> I'm happy to add that to the work you've already done. Will take me a
>> few days, probably.
> Who is waiting on who?  Or whatever takes the proposed patch forward.

Well, I've got back to it, and reloaded enough context to make some

Re-reading the original message, it seems that there is already a
solution to this in dnsmasq that might work quite well in this case.

In the man page section for dhcp-host we have

For DHCPv4, the  special option id:* means "ignore any client-id and use
MAC addresses only."

So for machines which are broken, list their mac addresses like so


That should solve the problem of the broken machines, without affecting
machines which work.

Of course, it involves enumerating the broken machines, rather than a
blanket setting covering everything, but that's probably a good thing.
It's what I wanted to provide with the tag extension I suggested, and
rather renders that redundant.

What do you thin Florent? Is this enough, or would you like the new
blanket option as well?


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