277 lines
7.6 KiB
Plaintext
277 lines
7.6 KiB
Plaintext
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN">
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<!--
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- Copyright (C) 2001 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
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- DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
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- IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
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- INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
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- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
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- FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
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- NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
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- WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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-->
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<!-- $Id: lwres_resutil.docbook,v 1.3 2001/04/24 18:11:26 gson Exp $ -->
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<refentry>
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<refentryinfo>
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<date>Jun 30, 2000</date>
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</refentryinfo>
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<refmeta>
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<refentrytitle>lwres_resutil</refentrytitle>
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<manvolnum>3</manvolnum>
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<refmiscinfo>BIND9</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>lwres_string_parse</refname>
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<refname>lwres_addr_parse</refname>
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<refname>lwres_getaddrsbyname</refname>
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<refname>lwres_getnamebyaddr</refname>
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<refpurpose>lightweight resolver utility functions</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <lwres/lwres.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>
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lwres_result_t
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<function>lwres_string_parse</function></funcdef>
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<paramdef>lwres_buffer_t *b</paramdef>
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<paramdef>char **c</paramdef>
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<paramdef>lwres_uint16_t *len</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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lwres_result_t
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<function>lwres_addr_parse</function></funcdef>
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<paramdef>lwres_buffer_t *b</paramdef>
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<paramdef>lwres_addr_t *addr</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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lwres_result_t
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<function>lwres_getaddrsbyname</function></funcdef>
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<paramdef>lwres_context_t *ctx</paramdef>
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<paramdef>const char *name</paramdef>
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<paramdef>lwres_uint32_t addrtypes</paramdef>
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<paramdef>lwres_gabnresponse_t **structp</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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lwres_result_t
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<function>lwres_getnamebyaddr</function></funcdef>
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<paramdef>lwres_context_t *ctx</paramdef>
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<paramdef>lwres_uint32_t addrtype</paramdef>
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<paramdef>lwres_uint16_t addrlen</paramdef>
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<paramdef>const unsigned char *addr</paramdef>
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<paramdef>lwres_gnbaresponse_t **structp</paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>DESCRIPTION</title>
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<para>
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<function>lwres_string_parse()</function>
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retrieves a DNS-encoded string starting the current pointer of
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lightweight resolver buffer
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<parameter>b</parameter>:
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i.e.
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<constant>b->current</constant>.
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When the function returns, the address of the first byte of the
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encoded string is returned via
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<parameter>*c</parameter>
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and the length of that string is given by
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<parameter>*len</parameter>.
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The buffer's current pointer is advanced to point at the character
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following the string length, the encoded string, and the trailing
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<type>NULL</type>
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character.
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<function>lwres_string_parse()</function>
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has an assertion check that
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<parameter>b</parameter>
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is not
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<type>NULL</type>.
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</para>
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<para>
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<function>lwres_addr_parse()</function>
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extracts an address from the buffer
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<parameter>b</parameter>.
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It checks that
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<parameter>addr</parameter>
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is not null.
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The buffer's current pointer
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<constant>b->current</constant>
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is presumed to point at an encoded address: the address preceded by a
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32-bit protocol family identifier and a 16-bit length field.
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The encoded address is copied to
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<constant>addr->address</constant>
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and
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<constant>addr->length</constant>
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indicates the size in bytes of the address that was copied.
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<constant>b->current</constant>
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is advanced to point at the next byte of available data in the buffer
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following the encoded address.
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</para>
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<para>
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<function>lwres_getaddrsbyname()</function>
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and
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<function>lwres_getnamebyaddr()</function>
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use the
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<type>lwres_gnbaresponse_t</type>
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structure defined below:
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<programlisting>
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typedef struct {
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lwres_uint32_t flags;
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lwres_uint16_t naliases;
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lwres_uint16_t naddrs;
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char *realname;
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char **aliases;
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lwres_uint16_t realnamelen;
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lwres_uint16_t *aliaslen;
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lwres_addrlist_t addrs;
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void *base;
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size_t baselen;
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} lwres_gabnresponse_t;
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</programlisting>
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The contents of this structure are not manipulated directly but
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they are controlled through the
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<citerefentry>
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<refentrytitle>lwres_gabn</refentrytitle><manvolnum>3
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</manvolnum>
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</citerefentry>
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functions.
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</para>
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<para>
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The lightweight resolver uses
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<function>lwres_getaddrsbyname()</function>
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to perform foward lookups.
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Hostname
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<parameter>name</parameter>
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is looked up using the resolver context
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<parameter>ctx</parameter>
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for memory allocation.
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<parameter>addrtypes</parameter>
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is a bitmask indicating which type of addresses are to be looked up.
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Current values for this bitmask are
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<type>LWRES_ADDRTYPE_V4</type>
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for IPv4 addresses and
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<type>LWRES_ADDRTYPE_V6</type>
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for IPv6 addresses.
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Results of the lookup are returned in
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<parameter>*structp</parameter>.
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<function>lwres_getaddrsbyname()</function>
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checks that its pointer arguments are not
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<type>NULL</type>
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and that
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<parameter>addrtypes</parameter>
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is non-zero.
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</para>
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<para>
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<function>lwres_getnamebyaddr()</function>
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performs reverse lookups.
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Resolver context
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<parameter>ctx</parameter>
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is used for memory allocation.
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The address type is indicated by
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<parameter>addrtype</parameter>:
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<type>LWRES_ADDRTYPE_V4</type>
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or
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<type>LWRES_ADDRTYPE_V6</type>.
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The address to be looked up is given by
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<parameter>addr</parameter>
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and its length is
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<parameter>addrlen</parameter>
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bytes.
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The result of the function call is made available through
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<parameter>*structp</parameter>.
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Like
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<function>lwres_getaddrsbyname()</function>,
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<function>lwres_getnamebyaddr()</function>
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uses assertion checking to ensure its pointer arguments are not
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<type>NULL</type>
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and
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<parameter>addrtype</parameter>
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is not zero.
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<function>lwres_getaddrsbyname()</function>
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also checks that
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<parameter>addrlen</parameter>
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is non-zero.
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</para>
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</refsect1>
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<refsect1>
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<title>RETURN VALUES</title>
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<para>
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Successful calls to
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<function>lwres_string_parse()</function>
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and
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<function>lwres_addr_parse()</function>
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return
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<errorcode>LWRES_R_SUCCESS.</errorcode>
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Both functions return
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<errorcode>LWRES_R_FAILURE</errorcode>
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if the buffer is corrupt or
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<errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
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if the buffer has less space than expected for the components of the
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encoded string or address.
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</para>
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<para>
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<function>lwres_getaddrsbyname()</function>
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returns
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<errorcode>LWRES_R_SUCCESS</errorcode>
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on success and it returns
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<errorcode>LWRES_R_NOTFOUND</errorcode>
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if the hostname
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<parameter>name</parameter>
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could not be found.
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</para>
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<para>
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<errorcode>LWRES_R_SUCCESS</errorcode>
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is returned by a successful call to
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<function>lwres_getnamebyaddr()</function>.
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</para>
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<para>
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Both
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<function>lwres_getaddrsbyname()</function>
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and
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<function>lwres_getnamebyaddr()</function>
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return
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<errorcode>LWRES_R_NOMEMORY</errorcode>
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when memory allocation requests fail and
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<errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
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if the buffers used for sending queries and receiving replies are too
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small.
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</para>
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</refsect1>
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<refsect1>
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<title>SEE ALSO</title>
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<para>
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<citerefentry>
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<refentrytitle>lwres_buffer</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>lwres_gabn</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>.
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</para>
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</refsect1>
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</refentry>
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