Friday, July 11, 2014

A DHCP client (fail?)

I was hoping to implement a DHCP client in the GA144 as mentioned in a previous blog. I'm more familiar with Perl than C these days so I downloaded the Net::DHCP::Packet module from CPAN and proceeded to use some of the examples to test out the DHCP server on my router. It's a lot easier to single-step through Perl code (for me at least) than using GDB on a compiled C program.

The sample dhcp daemon and test scripts work well. But when I tried talking to my router I was able to get a DHCPOFFER but was unable to get a DHCPACK reply. And even that would only work when I used the MAC address of my Mac(!). I couldn't use any other MAC address. I just don't know enough about DHCP to know if the router is acting correctly or not. The router's log says it receives the DHCP request and that it sends an OFFER and an ACK but the ACK packet doesn't seem to arrive. Possibly issues with firewalls etc.

There's a lot of code in Net::DHCP::Packet and it occurred to me that a DHCP client is not really necessary for this project. Nice to have but maybe not this iteration. I can load the IP address I've assigned to it using the code in the previous blog so there will be no conflict with my network devices.

So I'll proceed to step 2: a 'Hello world' server which simply sends the same reply to whatever inquiry it receives.


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