Comment 9 for bug 610391

Ok, so here is the breakdown of what i was able to find.

DHCP server using dnsmasq (2.65.5.el6) on CentoOS 6.4 a kvm guest with virtio
+ Also running cobbler with some preseed building scripts based on 12.04 LTS

node-1 a bare (guest) to PXE boot from DHCP server, on its own linux bridge (node_1_net) in routed mode, guest nic is virtio
node-2 a bare (guest) to PXE boot from DHCP server, on its own linux bridge (node_2_net) in routed mode, guest nic is e1000
node-3 a bare (guest) to PXE from DHCP server on the same linux bridge as DHCP server with virtio nic

In the kvm host I have stopped dnsmasq (which starts automatically) on default, node_1_net, node_2_net
In the kvm host I have started dhcp-helper -i node_1_net -i node_2_net -s <DHCP server IP> (dhcp-helper 1.1)

when booting node-1 it will PXE just fine, but when running the installer, the node aborts attempting to request and address from DHCP, running dhclient by hand yields the magical "bad udp checksum" message.

when booting node-2 it will boot and install just fine, the only change being the nic driver
when booting node-3 it will boot and install just fine but in this case, the DHCP requests aren't relayed over dhcp-helper.

So it appears that some drivers won't perform the udp checksum when some dhcp servers / relays are involved in the conversation.

I will try to test the same using a 13.10 loader and report back