[gPXE] gpxe 1.0.0 chainloading and disabling use-cached to make new second dhcp request

[Pasi Kärkkäinen]

On Fri, Sep 17, 2010 at 09:35:33PM +0300, Pasi Kärkkäinen wrote:
> Hello,
> 
> I'm booting a physical machine with PXE (broadcom NIC) 
> and I've configured the dhcp server (isc dhcpd in centos5) 
> to hand out "filename /gpxelinux.0".
> 
> That goes all fine. I can see gPXE 1.0.0 getting loaded,
> and then gPXE does the second dhcp request.
> 
> And here things go wrong.. on the console of the machine
> I can see gPXE saying "Getting cached packet", and by snooping
> the second DHCP request I can see it doesn't contain gPXE 
> identification strings..
> 


Oh, and forgot to mention that gPXE also says:
"DHCP (net0 mac) using cached":

So it's definitely using the cached mode as a default.. 


> So now I cannot identify this second dhcp request and give gPXE
> specific configuration from the dhcp server to the second dhcp request..
> 
> Any ideas how to resolve this? 
> 
> I noticed there's a "use-cached" setting/options in gPXE 1.0:
> http://support.etherboot.org/index.php?do=details&task_id=57&project=1&status[0]=
> 
> But how can I disable use-cached for chainloaded gpxelinux.0?
> 
> There's an example:
> "- Set use-cached on the DHCP server"
> How do I set that in dhcpd.conf?
> 
> I'm using syslinux-4.02 el5 rf rpm, which contains gpxe 1.0.0.
> 

I tried this in dhcpd.conf .. but it doesn't seem to work:

option space gpxe;
option gpxe-encap-opts code 175 = encapsulate gpxe;
option gpxe.bus-id code 177 = string;
option gpxe.use-cached code 178 = unsigned integer 8;

class "pxeclients" {
   match if substring(option vendor-class-identifier, 0, 9) = "PXEClient";
   next-server 10.0.0.1;

   if not exists gpxe.bus-id {
      filename "/gpxelinux.0";
      option gpxe.use-cached 0;
   }
   else {
      filename "http://10.0.0.1/gpxe/";
   }
}

Any ideas? 

-- Pasi