ac299c4f5c
perform assertion checks. Such statements are inappropriate as they document the implementation rather than the public interface. The functions are not required to perform assertion checks, but the caller is required to pass arguments that conform to the API requirements.
222 lines
7.0 KiB
Plaintext
222 lines
7.0 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 1.5 2001/06/18 22:56:34 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> retrieves a DNS-encoded
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string starting the current pointer of lightweight resolver buffer
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<parameter>b</parameter>: i.e. <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 <parameter>*c</parameter> and the
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length of that string is given by <parameter>*len</parameter>. The
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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> character.
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</para>
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<para>
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<function>lwres_addr_parse()</function> extracts an address from the
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buffer <parameter>b</parameter>. The buffer's current pointer
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<constant>b->current</constant> is presumed to point at an encoded
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address: the address preceded by a 32-bit protocol family identifier
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and a 16-bit length field. The encoded address is copied to
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<constant>addr->address</constant> and
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<constant>addr->length</constant> indicates the size in bytes of
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the address that was copied. <constant>b->current</constant> is
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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> to perform foward lookups.
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Hostname <parameter>name</parameter> is looked up using the resolver
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context <parameter>ctx</parameter> for memory allocation.
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<parameter>addrtypes</parameter> is a bitmask indicating which type of
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addresses are to be looked up. Current values for this bitmask are
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<type>LWRES_ADDRTYPE_V4</type> for IPv4 addresses and
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<type>LWRES_ADDRTYPE_V6</type> for IPv6 addresses. Results of the
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lookup are returned in <parameter>*structp</parameter>.
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</para>
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<para>
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<function>lwres_getnamebyaddr()</function> performs reverse lookups.
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Resolver context <parameter>ctx</parameter> is used for memory
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allocation. The address type is indicated by
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<parameter>addrtype</parameter>: <type>LWRES_ADDRTYPE_V4</type> or
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<type>LWRES_ADDRTYPE_V6</type>. The address to be looked up is given
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by <parameter>addr</parameter> and its length is
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<parameter>addrlen</parameter> bytes. The result of the function call
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is made available through <parameter>*structp</parameter>.
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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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