[ipxe-devel] Filename Option Precedence

[Shao Miller]

Tim Riker reported a behavioural difference between an Intel stack and iPXE.

In his scenario, the client receives an offer from both a DHCP server as
well as a PXE server.  Only the PXE server sends option 60.  The DHCP also
sends option 67.

Both the Intel stack and iPXE go through the DHCP motions with the DHCP
server.  Then they both go through the motions on UDP 4011 with the PXE
server.

The difference being that the Intel stack uses the filename option from the
PXE server, but iPXE uses the filename option from the DHCP server.

Something like:

  DHCPDISCOVER
  DHCPOFFER from 192.168.10.1:67 proxy
  DHCPDISCOVER
  DHCPOFFER from 192.168.10.1:67 proxy
  DHCPOFFER from 192.168.11.1:67 for 192.168.11.23
  entering request state
  DHCREQUEST to 192.168.11.1:67 for 192.168.11.23
  DHCPOFFER from 192.168.10.1:67
  DHCPACK from 192.168.11.1:67 for 192.168.11.23
  entering ProxyDHCP state
  ProxyDHCP REQUEST to 192.168.10.1
  ProxyDHCP REQUEST to 192.168.10.1
  DHCPACK from 192.168.10.1:4011

But then a look at 'show filename' shows net0.dhcp/filename instead of
proxydhcp/filename

I remember that there's been lots of discussion about this kind of thing in
the past, including Simon Kelly for dnsmasq, but I don't quite recall if
this particular precedence for the filename option is intentional or not.
If we're not going to use the option from the ProxyDHCP server, why do we
bother asking it? :)

- Shao