[Dnsmasq-discuss] Small dnsmasq 2.22 issue

[Simon Kelley]

Ron Frederick wrote:
> I recently started the "dnsmasq" program as part of the OpenWRT distribution
> on my Linksys WRT54GS wireless router. It replaced an ISC 'dhcpd' I was
> running on a desktop Linux machine. However, I ran into one problem when I
> switched over. I noticed that the DHCP OFFER responses were no longer
> including the DHCP 'host-name' option. This option was included in DHCP ACK
> responses to the same host later on, but it was missing from the initial
> OFFER response. I have a Rio Digital Audio Receiver here which depends on
> seeing the hostname in the OFFER response to boot properly. So, I took a
> look at the source code to see if I could find the problem.
> 
> It turned out to be quite straightforward to fix it. All I had to do was
> to change the call to do_req_options() in the OFFER case to pass 'hostname'
> as an argument instead of NULL, just as is done later when sending the ACK.
> I'm not sure if there was a specific reason why the hostname was omitted
> from the OFFER response, but the ISC dhcpd does include it and as I
> mentioned above my Rio seemed to require it.
> 


Ron,

I honestly can't find for sure any reason why the hostname isn't sent in 
a DHCP offer. It never has been, in any version way back to 2.0, the 
first to include an DHCP server. I guess this effect has never come up 
before. (DHCP is a madenningly under-specified protocol: the de-facto 
spec seems to be "What the ISC server does", hence  these interesting 
corner cases.)

I have a very vague memory about not sending a different hostname to one 
supplied in a DHCPDISCOVER, in case the offer is rejected due to the 
name mismatch, but I can't remember if that was based on a real problem, 
or a guess on my part that it might be. In any case, it only applies 
when the client sends one hostname, and dnsmasq overides it with a 
different one.

I think the best thing would probably be to elaborate your patch to 
continue the current behaviour when dnsmasq overrides a hostname sent in 
DHCPDISCOVER, but otherwise to always include the configured hostname.

I'll do a test release with that behaviour over the weekend.

Thanks for your input.

Cheers,

Simon.