dhcpd losing hostnames

Chris Buechler cmb at pfsense.org
Tue Jul 12 03:58:35 UTC 2016

On Mon, Jul 11, 2016 at 9:52 PM, Michael Vincent <vyncebox at gmail.com> wrote:
> A few pfSense 2.3.1 (based on FreeBSB 10.3) users have noticed an
> issue with the dhcp server (ISC DHCP Server 4.3.3-P1) losing client
> hostnames regularly. Packet captures have proven that while hostnames
> are always provided by clients and generally recorded in dhcpd.leases,
> the hostnames often disappear from dhcpd.leases after some period of
> time. We haven't been able to conclusively prove that dhcpd itself is
> to blame, but investigations of packet captures and logs are pointing
> in that direction.
> Background is available in this thread:
> https://forum.pfsense.org/index.php?topic=110011.0 and a bug ticket
> has been opened here: https://redmine.pfsense.org/issues/6589

To elaborate on this a bit, the reason for the root problem is
dhcpd.leases file doesn't always have client-hostname specified,
though the client always sends it. We have a daemon that processes
dhcpd.leases and registers hostnames in dnsmasq and/or Unbound from
that (since they can't do proper DDNS), which is kind of a hack, but
the only way to accommodate those in that circumstance.

Prior to dhcpd 4.3, this was always fine, the client-hostname was
always recorded in the lease in dhcpd.leases going back a number of
versions across a decade or so. Now in 4.3.3 and 4.3.4, the presence
of client-hostname is hit and miss for some people. With no apparent
reason as to why some have the issue and others don't.

So it appears there's a regression in 4.3.x with recording
client-hostname to the leases file.

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