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307 lines
7.9 KiB
Text
307 lines
7.9 KiB
Text
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN">
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<!--
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- Copyright (C) 2001, 2003 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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<!-- $Id: lwres_getipnode.docbook,v 1.4.2.2 2003/03/06 04:38:26 marka 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_getipnode</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_getipnodebyname</refname>
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<refname>lwres_getipnodebyaddr</refname>
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<refname>lwres_freehostent</refname>
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<refpurpose>lightweight resolver nodename / address translation API</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <lwres/netdb.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>
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struct hostent *
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<function>lwres_getipnodebyname</function></funcdef>
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<paramdef>const char *name</paramdef>
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<paramdef>int af</paramdef>
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<paramdef>int flags</paramdef>
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<paramdef>int *error_num</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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struct hostent *
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<function>lwres_getipnodebyaddr</function></funcdef>
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<paramdef>const void *src</paramdef>
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<paramdef>size_t len</paramdef>
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<paramdef>int af</paramdef>
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<paramdef>int *error_num</paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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void
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<function>lwres_freehostent</function></funcdef>
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<paramdef>struct hostent *he</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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These functions perform thread safe, protocol independent
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nodename-to-address and address-to-nodename
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translation as defined in RFC2553.
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</para>
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<para>
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They use a
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<type>struct hostent</type>
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which is defined in
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<filename>namedb.h</filename>:
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<programlisting>
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struct hostent {
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char *h_name; /* official name of host */
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char **h_aliases; /* alias list */
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int h_addrtype; /* host address type */
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int h_length; /* length of address */
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char **h_addr_list; /* list of addresses from name server */
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};
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#define h_addr h_addr_list[0] /* address, for backward compatibility */
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</programlisting>
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</para>
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<para>
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The members of this structure are:
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<variablelist>
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<varlistentry><term><constant>h_name</constant></term>
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<listitem>
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<para>
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The official (canonical) name of the host.
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</para>
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</listitem></varlistentry>
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<varlistentry><term><constant>h_aliases</constant></term>
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<listitem>
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<para>
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A NULL-terminated array of alternate names (nicknames) for the host.
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</para>
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</listitem></varlistentry>
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<varlistentry><term><constant>h_addrtype</constant></term>
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<listitem>
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<para>
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The type of address being returned - usually
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<type>PF_INET</type>
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or
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<type>PF_INET6</type>.
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</para>
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</listitem></varlistentry>
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<varlistentry><term><constant>h_length</constant></term>
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<listitem>
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<para>
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The length of the address in bytes.
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</para>
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</listitem></varlistentry>
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<varlistentry><term><constant>h_addr_list</constant></term>
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<listitem>
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<para>
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A
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<type>NULL</type>
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terminated array of network addresses for the host.
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Host addresses are returned in network byte order.
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</para>
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</listitem></varlistentry>
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</variablelist>
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</para>
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<para>
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<function>lwres_getipnodebyname()</function>
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looks up addresses of protocol family
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<parameter>af</parameter>
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for the hostname
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<parameter>name</parameter>.
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The
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<parameter>flags</parameter>
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parameter contains ORed flag bits to
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specify the types of addresses that are searched
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for, and the types of addresses that are returned.
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The flag bits are:
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<variablelist>
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<varlistentry><term><constant>AI_V4MAPPED</constant></term>
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<listitem>
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<para>
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This is used with an
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<parameter>af</parameter>
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of AF_INET6, and causes IPv4 addresses to be returned as IPv4-mapped
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IPv6 addresses.
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</para>
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</listitem></varlistentry>
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<varlistentry><term><constant>AI_ALL</constant></term>
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<listitem>
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<para>
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This is used with an
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<parameter>af</parameter>
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of AF_INET6, and causes all known addresses (IPv6 and IPv4) to be returned.
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If AI_V4MAPPED is also set, the IPv4 addresses are return as mapped
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IPv6 addresses.
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</para>
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</listitem></varlistentry>
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<varlistentry><term><constant>AI_ADDRCONFIG</constant></term>
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<listitem>
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<para>
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Only return an IPv6 or IPv4 address if here is an active network
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interface of that type. This is not currently implemented
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in the BIND 9 lightweight resolver, and the flag is ignored.
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</para>
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</listitem></varlistentry>
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<varlistentry><term><constant>AI_DEFAULT</constant></term>
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<listitem>
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<para>
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This default sets the
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<constant>AI_V4MAPPED</constant>
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and
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<constant>AI_ADDRCONFIG</constant>
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flag bits.
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</para>
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</listitem></varlistentry>
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</variablelist>
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</para>
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<para>
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<function>lwres_getipnodebyaddr()</function>
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performs a reverse lookup
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of address
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<parameter>src</parameter>
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which is
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<parameter>len</parameter>
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bytes long.
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<parameter>af</parameter>
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denotes the protocol family, typically
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<type>PF_INET</type>
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or
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<type>PF_INET6</type>.
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</para>
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<para>
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<function>lwres_freehostent()</function>
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releases all the memory associated with
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the
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<type>struct hostent</type>
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pointer
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<parameter>he</parameter>.
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Any memory allocated for the
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<constant>h_name</constant>,
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<constant>h_addr_list</constant>
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and
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<constant>h_aliases</constant>
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is freed, as is the memory for the
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<type>hostent</type>
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structure itself.
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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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If an error occurs,
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<function>lwres_getipnodebyname()</function>
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and
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<function>lwres_getipnodebyaddr()</function>
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set
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<parameter>*error_num</parameter>
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to an appropriate error code and the function returns a
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<type>NULL</type>
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pointer.
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The error codes and their meanings are defined in
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<filename><lwres/netdb.h></filename>:
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<variablelist>
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<varlistentry><term><constant>HOST_NOT_FOUND</constant></term>
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<listitem>
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<para>
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No such host is known.
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</para>
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</listitem></varlistentry>
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<varlistentry><term><constant>NO_ADDRESS</constant></term>
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<listitem>
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<para>
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The server recognised the request and the name but no address is
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available. Another type of request to the name server for the
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domain might return an answer.
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</para>
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</listitem></varlistentry>
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<varlistentry><term><constant>TRY_AGAIN</constant></term>
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<listitem>
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<para>
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A temporary and possibly transient error occurred, such as a
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failure of a server to respond. The request may succeed if
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retried.
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</para>
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</listitem></varlistentry>
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<varlistentry><term><constant>NO_RECOVERY</constant></term>
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<listitem>
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<para>
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An unexpected failure occurred, and retrying the request
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is pointless.
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</para>
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</listitem></varlistentry>
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</variablelist>
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</para>
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<para>
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<citerefentry>
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<refentrytitle>lwres_hstrerror</refentrytitle><manvolnum>3
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</manvolnum>
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</citerefentry>
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translates these error codes to suitable error messages.
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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>RFC2553</refentrytitle>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>lwres</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>lwres_gethostent</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>lwres_getaddrinfo</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>lwres_getnameinfo</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>lwres_hstrerror</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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