Re: Re: [Etherboot-users] [PATCH] ISC dhcpd siaddr (next-server) zero default change in 3.0.2

Marty,

I've had a dialog with David Hankins of ISC, and he pointed out that the
intended behaviour of a dhcp client should be, if a netbooting client
gets an offer that has a siaddr field of zeros, then it should ignore
that offer and hope for a better offer from another dhcp server.

In my testing of PXE clients, that's not how they behave.  They do
exactly what what you proposed.  That is, if they get zeros in siaddr,
then they assume that the dhcp server is the boot server.

So, I don't think it would be inappropriate for you to add your proposed
change to etherboot, but that isn't going to help the millions of users
out there now using Etherboot.  Updating the bootrom is usually not an
option.

For LTSP users, i'm just suggesting that they add a 'next-server' entry
to their dhcpd.conf file, and then the problem goes away.

I tried to convince ISC to change it back, but they claim it goes
against the RFC.  My feeling is that the RFC is so vague in this area
that it's really open to interpretation.

So, at least the fix is simple.  It's just those poor sysadmins who do
the 'apt-get upgrade', and end up with a broken dhcpd and hundreds of
users unable to boot their thin clients.

ciao,

Jim McQuillan
[email protected]



On Wed, 14 Sep 2005, Marty Connor wrote:

> > On Sep 14, 2005, at 8:36 AM, Harald Welte wrote:
> > 2) dhcp-3.0.2 suddenly changed the default from the dhcp server address
> >    to 0.0.0.0.  ...
>
> Looks like we're not the only ones that have been bitten by this new behavior:
>
>     http://weblog.barnet.com.au/edwin/000110.html
>
> There may be a reason for the change, and I'm kind of wondering if we might be
> able to say something like:
>
>     if ( we_have_the_dhcp_server_address AND no_next_server_specified ) {
>          next_server = dhcp_server_address;
>          print ("invalid next_server_address, using address of dhcp server.");
>     }
>
> I could see the argument that it might be better to have people fix their
> dhcpd 3.0.3 configs, but...
>
> Looks like the updating of the web page sub-project just got more urgent.
> Actually, a SourceForge news item on the project page might be just the thing,
> along with a link from the home page.
>
>
>
>
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