do not respond to DHCPINFORM requests

[Sergey Skobkarev]

Hi Glenn,

Thank you for your advise. It seems like a viable workaround for my Windows
7 machines issue.

However, I also used DHCPINFORM's for assigning hostnames to my lab
computers after their re-imaging, and unfortunately your solution will not
help in that case, so I'm still going to revise the server's code and try
to fix it if it won't take to much time and effort.

Cheers,

--
Sergey Skobkarev
CIS System Administrator
University of the Fraser Valley



On Thu, May 9, 2013 at 4:21 AM, Glenn Satchell
<glenn.satchell at uniq.com.au>wrote:

> Hi Sergey and Randall
>
> Several years ago I added this to my dhcpd.conf to try to work around one
> cause of dhcpinform: the browser querying for wpad options. Not sure if
> the \000 is still needed, but it does no harm. In the comments PRL is the
> "parameter request list".
>
> # Windows systems accept the WPAD option for setting up their proxy server
> # (Autodetect proxy settings):
> # (According to Ted Lemon, "text" will get the Microsoft
> # NUL termination bug heuristic applied, and "string" won't!
> option wpad code 252 = text;
> option wpad "http://proxy/proxy.pac\000";
>
> # Special config for Windows ("MSFT 5.0") systems.
> # Note this does not catch Windows CE.
> class "MSFT" {
>   match if substring(option vendor-class-identifier, 0, 4) = "MSFT";
>   # They put 252 on the DHCPINFORM's, but not on the DHCPREQUEST's
>   # PRL.  So we over-ride the PRL to include 252 = 0xFC, which will
>   # send the option at DHCPDISCOVER/DHCPREQUEST time, and wil also
>   # suppress the DHCPINFORMS!  They seem to cache it.
>   option dhcp-parameter-request-list = concat(option
> dhcp-parameter-request-list, fc);
> }
>
> regards,
> -glenn
>
> On Thu, May 9, 2013 9:44 am, Sergey Skobkarev wrote:
> > Hi Randall,
> >
> > I'm having the same problem with 'custom' groups inside subnets. Windows
> 7
> > machines successfully get IP, domain, DNS server and other parameters on
> > IP renew, but then they (IE?) send DHCPINFORM request, receive wrong DNS
> > server and domain information and "fix" their lease details. As a result,
> > I cannot assign proper 'custom' options.
> >
> > If I remove 'authorative' from the configuration file, dhcpd stops
> > responding to DHCPINFORM requests, so it works as a temporary solution.
> > However, I however have some other usage for DHCPINFORM's and would like
> > to fix the server and get proper INFORM answers.
> >
> > I was going to hack the code, but then saw your message and decided to
> ask
> > if you succeeded in that already and if you did, would you send me a
> patch
> > or at least point out where should I start?
> >
> > My DHCP server's version is 4.1.1 (Release: 34.P1.el6.centos), but I'll
> > probably use the latest code for hacking/recompiling.
> >
> > Thank you,
> >
> >
> > --
> > Sergey Skobkarev
> >
> >
> > _______________________________________________
> > dhcp-users mailing list
> > dhcp-users at lists.isc.org
> > https://lists.isc.org/mailman/listinfo/dhcp-users
>
>
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