[syslinux] pxelinux, dhcp and multiple interfaces on the device

[david d zuhn]

Short version:
  Is there a way to find out which interface PXE booted from?

Long version:
  I'm working on a cluster of machines, each using a networked
root filesystem, booting via PXE.  Some of these machines have
multiple interfaces, some of which are going to be on networks
that have functioning DHCP servers that will offer addresses.

  I'd like to have modular network drivers.

  So I've got the linux kernel loading via PXE (we dictate that the 
the machine be installed so that the PXE boot happens on the right
network).  I've got an initrd that has all of the appropriate modules
available, so I can load the drivers.

  My problem is that once I have the drivers loaded, I have several
interfaces, without any indication of which one I booted from.  I
need to do network configuration, and further boot procedures using
the same interface that I got my kernel from.

  One thought is to do a dhcp query from each of my interfaces,
and compare the results against the information provided if I do
'IPAPPEND 1' in the pxelinux config.   
 
  Is this something that keeping the PXE stack around would help
with?   If so, any pointers to code that runs in the linux kernel
to use this stack?

  thanks for any suggestions...
 
david d zuhn,  zoo at unlimitedscale.com