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From: mohta@necom830.cc.titech.ac.jp (Masataka Ohta)
Newsgroups: comp.unix.internals
Subject: Re: Shared libraries
Message-ID: <166@titccy.cc.titech.ac.jp>
Date: 9 May 91 05:38:13 GMT
References: <161@titccy.cc.titech.ac.jp> <1991May7.145228.423@batcomputer.tn.cornell.edu> <163@titccy.cc.titech.ac.jp> <1991May8.173813.27064@batcomputer.tn.cornell.edu>
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Organization: Tokyo Institute of Technology
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In article <1991May8.173813.27064@batcomputer.tn.cornell.edu>
	shore@theory.tn.cornell.edu (Melinda Shore) writes:

>>But hosts with muptiple IP addresses become common with the introduction
>>of DNS.

>Again, it has *absolutely* *nothing* to do with name service.

It dose have.

And shared libraries dose *NOT* help the transition from /etc/hosts to DNS.

Let's see more detailed facts.

With the introduction of DNS, struct hostent, a structure returned by
gethostbyname(), was changed. A new field, h_addr_list, was added and
an old field, h_addr, was replaced by a #define.

Let's see new /usr/include/netdb.h.

:	char	**h_addr_list;	/* list of addresses from name server */
:#define	h_addr	h_addr_list[0]	/* address, for backward compatiblity */

As indicated by the comment, the change was done because a name server
returns multiple IP addresses.

Moreover, as clearly seen, the change dose require recompilation, even
if we want to use old code which dose not support a host with mutiple
IP addresses.

>>"fix the routing code"? Routing code has nothing to do with the problem.
>
>No, but the routing code in this particular driver used ip addresses
>as hash keys.  Duh.

Well, perhaps, you are talking about a case of a single network interface
with multiple IP addresses, while we are talking about a single host with
multiple network interfaces and thus with multiple IP addresses.

						Masataka Ohta