Unicast DHCP OFFER?

Knaack Phillip-PKNAACK1 Phillip.Knaack at motorola.com
Sun Sep 17 08:02:02 EST 2006


Greetings!

This isn't really a powerpc question, more of a general 
Linux question, although I'm working on an embedded powerpc
target board.  It's a stupid question about DHCP.

My target is running udhcpc over a wireless (not wi-fi)
interface to a remote radio which is running a dhcp relay
agent. I see the DHCP discover sent out, and I see (at the
driver level) the DHCP offer coming back.  However, the 
offer is being sent unicast directly to my (new) IP address,
which I don't know yet.  As a result, the ip stack is dropping
the packet because of "no route".  So I ask myself, how can I
receive a UDP packet addressed directly to me if I don't yet
know my own address?  It defies logic.
And the odd part is, it works with another version of this card
on Windows, though I wouldn't be surprised if they just hacked
it up to "just work" anyway.

Because of the nature of this wireless connection, it really needs
to be unicast.  I'm thinking of recognizing a UDP/DHCP packet in
the radio driver and hacking the iphdr source addr to be a broadcast,
so the raw socket in udhcpc will receive it, but this shouldn't be
necessary.

So-- how is a unicast dhcp offer supposed to work?

-Phil K



More information about the Linuxppc-embedded mailing list