Bad DHCP Checksums over VLANs

[Eric van Gyzen]

Folks,

I'm running head (ALPHA4-ish) on a DHCP server and a client.  DHCP works 
fine on the physical interfaces, but when I run it on a VLAN, I get

	5 bad udp checksums in 5 packets

from dhclient.  Full details here:

	https://people.freebsd.org/~vangyzen/dhcp_vlan/

This happens for /all/ clients.

This is a new setup, so I don't know when it got broken, and I can't bisect.

The server NIC is common (I211), so maybe it's easy to reproduce.  I'll 
help as much as I can, of course.

Eric