[Dnsmasq-discuss] Ignore single hosts for DHCPv4 but not for DHCPv6/SLAAC, SLAAC name resolution

Ziggy SpaceRat Ziggy.SpaceRat at gmx.de
Sat Sep 10 00:41:17 BST 2016


I would like to know if there is any way to achieve this:

While  I generally assign IPv4 addresses to all hosts in my network, I
do  not  want  to  do  this  for  a  few ones (Those that I've already
switched to IP(v6)-only operation).

I know that I can disable DHCP entirely for a specific host using


but what I want is more like


-» Gets no IPv4 address and no IPv6 address (as none entered), but the
entry is still used for host name probing in conjunction with SLAAC.

However what this really does is:
Gets a random IPv4 (and/or IPv6) address from the pool(s).

Is there any way I can configure this for *single* hosts?
- DHCPv4 completely disabled
- DHCPv6 announcing DNS server only (Just O flag)
- Still able to resolve name based on SLAAC

For the SLAAC resolution, I know that DNSMasq tries this:
When  a  DHCP  host entry exists, DNSMasq builds the stateless address
this  MAC  would  result  in  without the bullshit extensions and then
pings that host.

I  also  see  why  *this*  method  can not work for hosts without DHCP
address  assigning: DNSMasq doesn't notice *when* they configure their
addresses, as the triggering event (DHCP) is missing.

But I have two different approaches which might work even better:
1. Periodically check the NDP neighbourhood for hosts
2.  Build  the stateless address when the host's name gets queried and
ping it (Same method as now, just a different/additional trigger)
Would  of course delay the response but it's better than no resolution
at all ...

BTW:  Hosts  that  are  configured for DHCPv4 on the host side but are
ignored  by  DNSMasq  are  causing  terribly  high CPU load while they
hammer DNSMasq for a DHCP lease ...

Kind regards
Ziggy SpaceRat

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