[klibc] ipconfig and boot filename option

H. Peter Anvin hpa at zytor.com
Sun May 25 22:25:43 PDT 2008

Άλκης Γεωργόπουλος wrote:
> So, as far as I can tell, we're back to square one.
> We need another option for ipconfig that ignores the router answer and
> accepts only the answer from the ltsp server.
>> "ipappend 2" gives the MAC address of the booting interface, which you can
>> match up with the appropriate interface (and then only bring up the relevant
>> interface.)
> I'm not worried about which interface to bring up, the clients usually
> have only one interface. Maybe my English failed me in the first post,
> we just want the ltsp clients to ignore the router dhcp offer.
> Excuse my ignorance, I'm trying to find a way to solve a problem that
> we have and I still don't see how.

Get a large cannon, aim it at your head, and pull the trigger.

Seriously speaking, this is really messy.  You need to consider not just 
how this will affect ipconfig, but how it will affect whatever DHCP 
client you are using that is actually respecting the DHCP lease times, 
renewing your lease, etc.

Given that, you probably want to do something like this:

- Use linux.c32 from pxelinux to get the full DHCP packet information 
passed to initramfs;
- Use "ipappend 1" to get an ip= string that you can pass directly to 
ipconfig; this will get you past the ipconfig phase;
- Use the DHCP packet information from linux.c32 to pre-seed the lease 
information in dhclient, udhcpcd or whatever fullfeatured DHCP client 
you're using.  You should be able to get it to start at the DHCPREQUEST 
state, as opposed to the DHCPDISCOVER state which is where it starts 
when it lacks a lease.

The handover of this information and converting it to a format involves 
software that would have to be written.  This doesn't have anything to 
do with ipconfig directly.


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