DISCOVER bursts

[Staffan.Ungsgard at teliasonera.com]

Yes Lars - That's exaxtly the scenario - right on target!

With or without lease limit the server offers different addresses on DISCOVERS from the same client if
the DISCOVERS arrive to close to eachother. Multiple DISCOVERs from the same host is quite natural behaviour
in DHCP negotiation, but this is the only box we've seen that have them arriving so close in time - and that
gives us the problem.

The box is an AT&T netgate.

I know that the server is single-threaded, but couldn't it be constructions with timers etc that could make it
possible for the dhcp server to show this behaviour.

Best Regards

-- Staffan


-----Original Message-----
From: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] On Behalf Of Lars Jacobsen
Sent: den 6 januari 2007 20:24
To: dhcp-users at isc.org
Subject: SV: DISCOVER bursts


Well I read the question as regardless of the CPE "misbehaver" (asking for an IP address 4 times) the server should NEVER offer more than max two addresses to a client in this particular config. But it does, why ?

I expect Staffan has:
spawn with option agent.circuit-id;
lease limit 2;
somewhere in his config.

Maybe as suggested an race/timing issue inside the server, keeping track on offered not yet acknowledged leases, compared to some of the rules for this specific client.


/Lars



> -----Oprindelig meddelelse-----
> Fra: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] På 
> vegne af Milton W. Schober, Jr.
> Sendt: 5. januar 2007 15:56
> Til: dhcp-users at isc.org
> Emne: Re: DISCOVER bursts
> 
> What is the CPE?  We have seen something similar with Thomson IPTV set 
> top boxes, but the problem is in the STB, not the server.
> 
> Milton Schober
> ----- Original Message -----
> From: <Staffan.Ungsgard at teliasonera.com>
> To: <dhcp-users at isc.org>
> Sent: Friday, January 05, 2007 3:55 AM
> Subject: DISCOVER bursts
> 
> 
> > Hi
> > We have problem with a special customers CPE, where the CPE send 
> > four rapid DHCPDISCOVERS with just 20 milliseconds apart.
> > When the DHCP server gets the DISCOVERS it issues different 
> > addresses on each discover. I have snoop logs of the traffic, and 
> > the DISCOVERS are indeed exactly the same in each DHCPDISCOVER. It 
> > seems that the when the server handles the second DISCOVER, it 
> > doesn't "remeber" that is has already offered a fresh ip address 
> > from an identical DHCPDISCOVER 20 ms earlier.
> > To furthermore illustrate this, we have a lease limit of two, so 
> > technically it shouldn't offer more than two addresses to the same 
> > line identifier even if the "Client Identifier" differed, but it 
> > isses three different addresses and only barfs at the fourth 
> > DHCPDISCOVER saying "no billing".
> >
> > Is there a race problem in the dhcp server ?
> >
> > The hardware is a Sun V210 running Solaris 8. No supermachine, but
> they're
> > still selling them.
> >
> > Best Regards
> >
> > -- Staffan Ungsgard
> >
> >
> >
> >
> >
> >
> >
> > --
> > No virus found in this incoming message.
> > Checked by AVG Free Edition.
> > Version: 7.1.410 / Virus Database: 268.16.5/616 - Release Date: 
> > 1/4/2007
> >
> >
> 
> 
> 
> 
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.410 / Virus Database: 268.16.6/617 - Release Date: 
> 05-01-2007
> 11:11