contrib/bind9/lib/lwres/man/lwres_resutil.docbook

   1 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   2                "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
   3                [<!ENTITY mdash "&#8212;">]>
   4 <!--
   5  - Copyright (C) 2004, 2005, 2007, 2012  Internet Systems Consortium, Inc. ("ISC")
   6  - Copyright (C) 2000, 2001  Internet Software Consortium.
   7  -
   8  - Permission to use, copy, modify, and/or distribute this software for any
   9  - purpose with or without fee is hereby granted, provided that the above
  10  - copyright notice and this permission notice appear in all copies.
  11  -
  12  - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
  13  - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  14  - AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
  15  - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
  16  - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
  17  - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  18  - PERFORMANCE OF THIS SOFTWARE.
  19 -->
  20
  21 <!-- $Id$ -->
  22 <refentry>
  23
  24   <refentryinfo>
  25     <date>Jun 30, 2000</date>
  26   </refentryinfo>
  27
  28   <refmeta>
  29     <refentrytitle>lwres_resutil</refentrytitle>
  30     <manvolnum>3</manvolnum>
  31     <refmiscinfo>BIND9</refmiscinfo>
  32   </refmeta>
  33
  34   <docinfo>
  35     <copyright>
  36       <year>2004</year>
  37       <year>2005</year>
  38       <year>2007</year>
  39       <year>2012</year>
  40       <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
  41     </copyright>
  42     <copyright>
  43       <year>2000</year>
  44       <year>2001</year>
  45       <holder>Internet Software Consortium.</holder>
  46     </copyright>
  47   </docinfo>
  48
  49   <refnamediv>
  50     <refname>lwres_string_parse</refname>
  51     <refname>lwres_addr_parse</refname>
  52     <refname>lwres_getaddrsbyname</refname>
  53     <refname>lwres_getnamebyaddr</refname>
  54     <refpurpose>lightweight resolver utility functions</refpurpose>
  55   </refnamediv>
  56   <refsynopsisdiv>
  57     <funcsynopsis>
  58 <funcsynopsisinfo>#include &lt;lwres/lwres.h&gt;</funcsynopsisinfo>
  59 <funcprototype>
  60         <funcdef>
  61 lwres_result_t
  62 <function>lwres_string_parse</function></funcdef>
  63         <paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
  64         <paramdef>char **<parameter>c</parameter></paramdef>
  65         <paramdef>lwres_uint16_t *<parameter>len</parameter></paramdef>
  66         </funcprototype>
  67 <funcprototype>
  68         <funcdef>
  69 lwres_result_t
  70 <function>lwres_addr_parse</function></funcdef>
  71         <paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
  72         <paramdef>lwres_addr_t *<parameter>addr</parameter></paramdef>
  73         </funcprototype>
  74 <funcprototype>
  75         <funcdef>
  76 lwres_result_t
  77 <function>lwres_getaddrsbyname</function></funcdef>
  78         <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
  79         <paramdef>const char *<parameter>name</parameter></paramdef>
  80         <paramdef>lwres_uint32_t <parameter>addrtypes</parameter></paramdef>
  81         <paramdef>lwres_gabnresponse_t **<parameter>structp</parameter></paramdef>
  82         </funcprototype>
  83 <funcprototype>
  84         <funcdef>
  85 lwres_result_t
  86 <function>lwres_getnamebyaddr</function></funcdef>
  87         <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
  88         <paramdef>lwres_uint32_t <parameter>addrtype</parameter></paramdef>
  89         <paramdef>lwres_uint16_t <parameter>addrlen</parameter></paramdef>
  90         <paramdef>const unsigned char *<parameter>addr</parameter></paramdef>
  91         <paramdef>lwres_gnbaresponse_t **<parameter>structp</parameter></paramdef>
  92       </funcprototype>
  93 </funcsynopsis>
  94   </refsynopsisdiv>
  95
  96   <refsect1>
  97     <title>DESCRIPTION</title>
  98
  99     <para><function>lwres_string_parse()</function>
 100       retrieves a DNS-encoded string starting the current pointer of
 101       lightweight resolver buffer <parameter>b</parameter>: i.e.
 102       <constant>b-&gt;current</constant>.  When the function returns,
 103       the address of the first byte of the encoded string is returned
 104       via <parameter>*c</parameter> and the length of that string is
 105       given by <parameter>*len</parameter>.  The buffer's current
 106       pointer is advanced to point at the character following the
 107       string length, the encoded string, and the trailing
 108       <type>NULL</type> character.
 109     </para>
 110
 111     <para><function>lwres_addr_parse()</function>
 112       extracts an address from the buffer <parameter>b</parameter>.
 113       The buffer's current pointer <constant>b-&gt;current</constant>
 114       is presumed to point at an encoded address: the address preceded
 115       by a 32-bit protocol family identifier and a 16-bit length
 116       field.  The encoded address is copied to
 117       <constant>addr-&gt;address</constant> and
 118       <constant>addr-&gt;length</constant> indicates the size in bytes
 119       of the address that was copied.
 120       <constant>b-&gt;current</constant> is advanced to point at the
 121       next byte of available data in the buffer following the encoded
 122       address.
 123     </para>
 124
 125     <para><function>lwres_getaddrsbyname()</function>
 126       and <function>lwres_getnamebyaddr()</function> use the
 127       <type>lwres_gnbaresponse_t</type> structure defined below:
 128     </para>
 129
 130 <para><programlisting>
 131 typedef struct {
 132         lwres_uint32_t          flags;
 133         lwres_uint16_t          naliases;
 134         lwres_uint16_t          naddrs;
 135         char                   *realname;
 136         char                  **aliases;
 137         lwres_uint16_t          realnamelen;
 138         lwres_uint16_t         *aliaslen;
 139         lwres_addrlist_t        addrs;
 140         void                   *base;
 141         size_t                  baselen;
 142 } lwres_gabnresponse_t;
 143 </programlisting></para>
 144
 145     <para>
 146       The contents of this structure are not manipulated directly but
 147       they are controlled through the
 148       <citerefentry>
 149         <refentrytitle>lwres_gabn</refentrytitle><manvolnum>3</manvolnum>
 150       </citerefentry>
 151       functions.
 152     </para>
 153
 154     <para>
 155       The lightweight resolver uses
 156       <function>lwres_getaddrsbyname()</function> to perform
 157       foward lookups.
 158       Hostname <parameter>name</parameter> is looked up using the
 159       resolver
 160       context <parameter>ctx</parameter> for memory allocation.
 161       <parameter>addrtypes</parameter> is a bitmask indicating
 162       which type of
 163       addresses are to be looked up.  Current values for this bitmask are
 164       <type>LWRES_ADDRTYPE_V4</type> for IPv4 addresses and
 165       <type>LWRES_ADDRTYPE_V6</type> for IPv6 addresses.  Results of the
 166       lookup are returned in <parameter>*structp</parameter>.
 167     </para>
 168
 169     <para><function>lwres_getnamebyaddr()</function>
 170       performs reverse lookups.  Resolver context
 171       <parameter>ctx</parameter> is used for memory allocation.  The
 172       address type is indicated by <parameter>addrtype</parameter>:
 173       <type>LWRES_ADDRTYPE_V4</type> or
 174       <type>LWRES_ADDRTYPE_V6</type>.  The address to be looked up is
 175       given by <parameter>addr</parameter> and its length is
 176       <parameter>addrlen</parameter> bytes.  The result of the
 177       function call is made available through
 178       <parameter>*structp</parameter>.
 179     </para>
 180   </refsect1>
 181
 182   <refsect1>
 183     <title>RETURN VALUES</title>
 184     <para>
 185       Successful calls to
 186       <function>lwres_string_parse()</function>
 187       and
 188       <function>lwres_addr_parse()</function>
 189       return
 190       <errorcode>LWRES_R_SUCCESS.</errorcode>
 191       Both functions return
 192       <errorcode>LWRES_R_FAILURE</errorcode>
 193       if the buffer is corrupt or
 194       <errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
 195       if the buffer has less space than expected for the components of the
 196       encoded string or address.
 197     </para>
 198
 199     <para><function>lwres_getaddrsbyname()</function>
 200       returns <errorcode>LWRES_R_SUCCESS</errorcode> on success and it
 201       returns <errorcode>LWRES_R_NOTFOUND</errorcode> if the hostname
 202       <parameter>name</parameter> could not be found.
 203     </para>
 204     <para><errorcode>LWRES_R_SUCCESS</errorcode>
 205       is returned by a successful call to
 206       <function>lwres_getnamebyaddr()</function>.
 207     </para>
 208
 209     <para>
 210       Both
 211       <function>lwres_getaddrsbyname()</function>
 212       and
 213       <function>lwres_getnamebyaddr()</function>
 214       return
 215       <errorcode>LWRES_R_NOMEMORY</errorcode>
 216       when memory allocation requests fail and
 217       <errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
 218       if the buffers used for sending queries and receiving replies are too
 219       small.
 220     </para>
 221
 222   </refsect1>
 223   <refsect1>
 224     <title>SEE ALSO</title>
 225     <para><citerefentry>
 226         <refentrytitle>lwres_buffer</refentrytitle><manvolnum>3</manvolnum>
 227       </citerefentry>,
 228
 229       <citerefentry>
 230         <refentrytitle>lwres_gabn</refentrytitle><manvolnum>3</manvolnum>
 231       </citerefentry>.
 232     </para>
 233
 234   </refsect1>
 235 </refentry><!--
 236  - Local variables:
 237  - mode: sgml
 238  - End:
 239 -->