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Re: gethostbyname (was Re: (DNS) draft wording for W.G. review. )

From: <hallam@w3.org>
Date: Wed, 27 Mar 96 16:43:10 -0500
Message-Id: <9603272143.AA14831@zorch.w3.org>
To: "Donald E. Eastlake 3rd" <dee@cybercash.com>, Anawat Chankhunthod <chankhun@catarina.usc.edu>, 'Paul Vixie' <paul@vix.com>, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com, iip@tis.com
Cc: hallam@w3.org, paulle@microsoft.com

Now I'm back into remembering when and why I wrote the code I remember that I 
gave up on it precisely because of the security stuff.

I'm pretty indifferent to the interface except that:-

1) It should allow access to whatever data is avaliable

2) It should be possible to use it in a non blocking fashion.

(2) is a problem since it would mean that the interface could not be abstracted 
off the network layer to the extent I would like. On the other hand it might be 
possible to work out something that would be based on sockets as opposed to UDP.
E.g.

DNS_initialize (&context, DNS_default)	
		//returns a dns query context with the system default
		//DNS lookup daemons instantiated. Note that context is an
		//opaque structure, the calling program is not allowed to 
		//meddle with it.
DNS_add_resolver (context, &address}
		//address = {18.24.1.191, weight} i.e. we give it an extra
		//resolver to look at, this structure could have a weight
		//associated with it allowing information. 
		//This is particularly usefull when doing higher level
		//hacking, e.g. looking to find an authoratative server.
DNS_query (context, &name, &address, &query_id, flag)
		//flag can be
		//  DNS_SYNC	- wait for DNS query to return
		//  DNS_ASYNC	- asynchronous, if query cannot be resolved
		//		immediately will return a socket which can be
		//		waited on as part of query_id.
DNS_test (context, query_id, flag)
		//Checks to see if a query has completed. Flag allows caller to 
		//chose to wait. Note that this function would generally
		//be called after a select on the query_id socket. The idea
		//being to allow multiple DNS queries to be grouped on the
		//same socket.
		//Alternatively context could have a pointer to a linked list
		//of resolved query_id structures. An application could then
		//avoid having to check each outstanding DNS query in turn.
		//Internaly the code is likely to want to use a hash table or
		//balanced tree to match queries with responses.
DNS_close (context, query_id)
		//Dispose of query, return
DNS_terminate (context)
		//Free any structures held open (e.g. application level cache)

Note that this is a considerably more complex interface than people are used to. 
I think that this is unavoidable if we are to have something that will work in 
multiprocessor environments (I believe that we will be using boxes with large 
arrays of MIMD processors in the realatively near future. By large I mean 64+, 
not the 4 to 16 that shared memory models give you).

Note that the idea of the context is not a very Berkley or UNIX style of API but 
it does mean that progams can avoid using global variables. This is essential if 
code is to run in multithreaded, multiprocessor environments.

The sort of place where this code would be of most use would be in code to do 
bulk DNS queries to build up databases - e.g. to asist in analysis of log files 
or as a prefilter inside a mailing list distributor.


I think that the right place for this battle is a cabal in the back of an IETF 
meeting rather than POSIX or such like. 

		Phill
Received on Wednesday, 27 March 1996 13:48:54 EST

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