dhcpd 3.1.1, linux vlans since 2.6.27 and listening on the untagged device
David W. Hankins
David_Hankins at isc.org
Mon Nov 10 22:50:46 UTC 2008
On Sat, Nov 08, 2008 at 02:03:22PM +0100, Oliver Wagner wrote:
> Some investigation suggests, however, that this is a problem in dhcpd3
> which just didn't always show up in 8.04. There is a change regarding the
> handling of VLAN packets and packet filters in kernel 2.6.27 which makes
> sure that vlan tagged packets are always presented to filters on the
> underlying device (eth0 in this case) with the vlan tag removed from the
> packet data. Previously (depending on the ethernet driver, from what I
> could understand) the raw data was also presented, but with the vlan tag
> still present.
Why in the world would they do that?
> If the analysis is correct, this needs to be fixed upstream in dhcpd's
> linux interfacing code.
If that analysis is correct, I can't imagine a DHCP software scopable
solution. How can we differentiate between eth0 and vlanx input
except by using very specifically crafted packet filters on those
Ash bugud-gul durbatuluk agh burzum-ishi krimpatul.
Why settle for the lesser evil? https://secure.isc.org/store/t-shirt/
David W. Hankins "If you don't do it right the first time,
Software Engineer you'll just have to do it again."
Internet Systems Consortium, Inc. -- Jack T. Hankins
More information about the dhcp-users