DHCP discovery of WINS servers

Christopher R. Hertel crh at nts.umn.edu
Tue Sep 4 08:28:27 GMT 2001

Hi Shirish!  Missed you at the conference.
(Shirish did the initial work on Samba's DFS.)

Regarding the use of DHCP to grab WINS info...

Can't we form a DHCP request that asks for only the netbios-name-servers
field?  We would need to do the dhcp discover to find the dhcp server.

This is where Windows integration of NBT into the kernel is an advantage. 
They can (and probably do, but I haven't checked) include the request for 
the netbios-name-serevers in the initial DHCP exchange.

> I've been thinkg about this, and there are a few other issues:  
>  - we now have the start of wins fail-over support, so we now cope with
> multiple wins servers (in HEAD, where I would apply such a patch).
>  - we don't want to be doing a dhcp operation for *every* client
> operation.  While its fine to do it each time the server starts, doing
> it every time a client (like smbclient) starts could be a little
> overkill.

We would--possibly--keep the response once we got it.  Perhaps we could
store a file (text would do, tdb is overkill) in the same location as
wins.dat and browser.dat.  As with a real DHCP lease, we would want to
store a lease expiration time so we know when we need to recheck the DHCP

Question: If we do a DHCPdiscover and request the netbios-name-servers
option, will that mess up the system's IP address lease?  I don't think so
(shouldn't) but it's worth checking.  Also, is it possible to query the 
lease time for a system so we know when the host system will be doing a 
"real" DHCP update?

>  - what if our request is lost?  UDP is lossy, should we at least make
> some attempt to send a second request?

I think that default DHCP behavior is to retry three times.

> Other than that the patch looks good, but I'm a little snowed under at
> the moment.

Aren't we all.  ;)

Chris -)-----

Christopher R. Hertel -)-----                   University of Minnesota
crh at nts.umn.edu              Networking and Telecommunications Services

    Ideals are like stars; you will not succeed in touching them
    with your hands...you choose them as your guides, and following
    them you will reach your destiny.  --Carl Schultz

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