More questions about WINS, interfaces, etc

[Luke Kenneth Casson Leighton]

On Fri, 19 Sep 1997, Philip A. Prindeville wrote:

> > Date: Thu, 18 Sep 1997 17:02:38 +0100 (BST)
> > From: Luke Kenneth Casson Leighton <lkcl at switchboard.net>
> > To: mac at nibsc.ac.uk
> > Subject: Re: More questions about WINS, interfaces, etc
> 
> > On Thu, 18 Sep 1997 mac at nibsc.ac.uk wrote:
> 
> > > Hi all,
> > > 
> > > >> I have yet another question about WINS and DNS...  Why can't the
> > > >> DNS be used as the database of reference for name-to-address
> > > >> mappings when using NB over TCP/IP?
> > > >
> > > >we're working on that, for samba-2.
> > > 
> > > 
> > > No, no, NO !!!
> 
> > ??  i don't understand.
> 
> > ok.  i'll re-read (or, more like read) your question.  why can't dns be 
> > used as the database of reference for name-to-address mappings.
> 
> > it can be.  put "dns proxy = yes" in the [global] section of smb.conf.  
> > this will do a gethostbyname() call on the NetBIOS name, and cache the 
> > response received for up to two hours.  this is because gethostbyname() 
> > is a blocking call, which therefore disrupts your name services and 
> > browsing services until gethostbyname() returns.
> 
> OK, first a simple question:  why not just set it to the TTL of
> the DNS response?
> 
> And next, what if the DNS server was local and came back with an answer
> very quickly?  What if there was non-blocking code to make queries?
> Or for that matter, what if you wanted NIS or NIS+ to be the database 
> of reference?
> 
> > > Why can't I have completely separate DNS and NB namespaces?
> 
> > i don't understand the intent behind your question.  DNS and NetBIOS 
> > namespaces are on 
> 
> > > Windows clients support this quite happily, so why can't Samba?
> 
> > no they don't: only NT workstation supports DNS resolution of ip 
> > addresses instead of using NetBIOS name resolution of ip addresses.
> 
> > because of this limitation (in all windows clients to only use DNS, not 
> > NIS or NIS+, and in all windows clients except NT, which uses DNS 
> > directly), we have added an option "dns proxy = yes" which results in a 
> > gethostbyname() call if a NetBIOS name is not in the WINS cache in nmbd.
> 
> Sanity check here.  A host gets its address either statically, or via
> DHCP.  Its name is static.  It defends the name on the network, and
> in doing so gets noticed by the local NB name server (or domain
> controller?).  Next, when someone wants to resolve that host's name,
> do they ask the NB name server, or do they just broadcast the request,
> hoping that the host is local, and will respond itself (like ARP)?
> 
> What if DNS delay weren't an issue?  What if, for that matter, you
> wanted to use NIS+ as your database of reference?
> 
> > > Each system has its own repository of information (named, or WINS server)
> > > and distinct mechanisms exist for lookup and retrival of info.
> 
> IMHO this is a liability.  As long as the possibility of clashes
> or inconsistencies exist between two name spaces that allow the
> same name to exist in both spaces, you are setting yourself up
> for confusion (best case) and gapping wide security holes (worst
> case).
> 
> > true.  it is worth mentioning that the resolution of these names is on 
> > completely separate port numbers.  it is also worth mentioning that 
> > rfc1001/2.txt (NetBIOS) is based on rfc883.txt (DNS).
> 
> > > By all means give Samba the capability to use the DNS as the prime source
> > > of information, but please, please allow it also to keep the NB namespace
> > > uterly separate.
> 
> > we do.  DNS-looked-up names are marked with a special flag: "DNS" or 
> > "DNSFAIL" in the WINS cache.  if the NetBIOS name is subsequently 
> > registered (a pc gets switched on), then the DNS entry is deleted.
> 
> > luke
> 
> -Philip
> 

Luke Kenneth Casson Leighton (lkcl at switchboard.net)
Web site under construction  (http://mailhost.cb1.com/~lkcl)
"Confront difficulties while they are still easy"