57 lines
2.8 KiB
Plaintext
57 lines
2.8 KiB
Plaintext
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/*
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* Copyright (c) 1996,1999 by Internet Software Consortium.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
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* ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
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* CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
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* DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
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* PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
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* ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
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* SOFTWARE.
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*/
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This is the Information Retrieval Service (IRS).
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Designed by Paul Vixie (ISC) and Ted T'so (MIT), 1995.
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Written by Paul Vixie, Ted T'so and Sam Stoller, 1996.
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Id: README,v 1.5 1999/01/08 19:23:52 vixie Exp
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Introduction:
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The /etc/irs.conf file defines access methods (like DNS or NIS or
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LOCAL) for each map (like PASSWD or GROUP or HOSTS). One of the access
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methods is "generic" in that it uses the rules from /etc/irs.conf to decide
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which of potentially several different access methods to use for any given
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map. Stubs have been written for all of the system getXbyY() functions so
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that old programs can get this new "multiple access method" capability without
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any source code changes.
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Thread Safety:
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It is possible for a thread safe program to be altered to call the
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underlying interface (rather than the standard getXbyY() stubs) and get some
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reentrance capabilities. Note that the underlying libraries (which we call)
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are not all thread-safe, for example, the YP and DNS resolvers. A lot more
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work will need to be done before we have full thread safety. But we believe
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that the native API for this system does not impose any reentrancy problems.
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We don't use global or static variables anywhere except in the getXbyY() stubs.
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Apologies:
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We did cheap object orientation without using C++. This stuff is
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standard C, and it suffers from some of the defects shared by all object
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systems implemented in C. Even so, this is the smallest design we could
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think of that would be extensible to more access methods, more map types,
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and more map operations (like BYNAME or BYGID or whatever) in the future.
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There's a fair amount of duplicated code between the different
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access methods for a given map. For example, the code that parses the
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passwd entries is almost identical between the DNS and NIS map objects. To
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clean this up, the almost-identical functions need to be split into similar
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and dissimilar parts, and some parts of the "struct pvt"'s need to be made
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shared via substructures.
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