[Dnsmasq-discuss] Netboot drops DNSMasq DHCP offer

Simon Kelley simon at thekelleys.org.uk
Thu Apr 4 15:10:32 BST 2019


On 03/04/2019 19:47, Conrad Kostecki wrote:
> Hi,
> in order to make PXE possible with older notebooks, I've compiled for
> myself Netboot.
> This is a piece of software, which starts from floppy, where you can
> load your dos paket driver and start PXE.
> Basically, it makes possible to boot with PXE by using PCMCIA networks
> cards from floppy, when nothing else is possible to boot from.
> 
> Netboot itself is working so far fine, it initializes itself fine, loads
> my dos packet driver and starts DHCP.
> I can clearly see, that a DHCP broadcast comes into my DNSMasq, which
> replies with a DHCP offer.
> And here it stops. It seems, Netboot can't correctly handle that offer
> by DNSMasq, as it silently drops it and tries again.
> So I see multiple broadcast searches and DHCP offers.
> 
> BUT: If I use DHCP from an ordinary AVM Fritz!Box 7490 (Router), Netboot
> succeeds and can handle the reply from it.
> So the question is, what could go wrong? Can I debug this somehow? Any
> solutions to make this possible work with Netboot?
> 
> Note: Netboot is pretty old, latest release is from 2007. I suspect,
> that maybe DNSMasq does some RFC correct, which is "too new" for those
> old clients.
> Any help would be appreciated.
> 
> Conrad
> 

The packet captures are pretty much identical.

How are you producing the dnsmasq captures? on the host running dnsmasq,
or elsewhere on the network?

The DHCP is asking for, and getting, broadcast replies (ie to
255.255.255.255) It's just possible that : 1) no other DHCP clients
you've used ask for this 2) the firewall configuration on the host
running dnsmasq blocks packets with destination 255.255.255.255.


That's the only theory I can think if at the moment.

Simon.




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