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

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  21 <!-- $Id: lwres_resutil.docbook,v 1.12 2007/06/18 23:47:51 tbox Exp $ -->
  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       <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
  40     </copyright>
  41     <copyright>
  42       <year>2000</year>
  43       <year>2001</year>
  44       <holder>Internet Software Consortium.</holder>
  45     </copyright>
  46   </docinfo>
  47
  48   <refnamediv>
  49     <refname>lwres_string_parse</refname>
  50     <refname>lwres_addr_parse</refname>
  51     <refname>lwres_getaddrsbyname</refname>
  52     <refname>lwres_getnamebyaddr</refname>
  53     <refpurpose>lightweight resolver utility functions</refpurpose>
  54   </refnamediv>
  55   <refsynopsisdiv>
  56     <funcsynopsis>
  57 <funcsynopsisinfo>#include &lt;lwres/lwres.h&gt;</funcsynopsisinfo>
  58 <funcprototype>
  59         <funcdef>
  60 lwres_result_t
  61 <function>lwres_string_parse</function></funcdef>
  62         <paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
  63         <paramdef>char **<parameter>c</parameter></paramdef>
  64         <paramdef>lwres_uint16_t *<parameter>len</parameter></paramdef>
  65         </funcprototype>
  66 <funcprototype>
  67         <funcdef>
  68 lwres_result_t
  69 <function>lwres_addr_parse</function></funcdef>
  70         <paramdef>lwres_buffer_t *<parameter>b</parameter></paramdef>
  71         <paramdef>lwres_addr_t *<parameter>addr</parameter></paramdef>
  72         </funcprototype>
  73 <funcprototype>
  74         <funcdef>
  75 lwres_result_t
  76 <function>lwres_getaddrsbyname</function></funcdef>
  77         <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
  78         <paramdef>const char *<parameter>name</parameter></paramdef>
  79         <paramdef>lwres_uint32_t <parameter>addrtypes</parameter></paramdef>
  80         <paramdef>lwres_gabnresponse_t **<parameter>structp</parameter></paramdef>
  81         </funcprototype>
  82 <funcprototype>
  83         <funcdef>
  84 lwres_result_t
  85 <function>lwres_getnamebyaddr</function></funcdef>
  86         <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
  87         <paramdef>lwres_uint32_t <parameter>addrtype</parameter></paramdef>
  88         <paramdef>lwres_uint16_t <parameter>addrlen</parameter></paramdef>
  89         <paramdef>const unsigned char *<parameter>addr</parameter></paramdef>
  90         <paramdef>lwres_gnbaresponse_t **<parameter>structp</parameter></paramdef>
  91       </funcprototype>
  92 </funcsynopsis>
  93   </refsynopsisdiv>
  94
  95   <refsect1>
  96     <title>DESCRIPTION</title>
  97
  98     <para><function>lwres_string_parse()</function>
  99       retrieves a DNS-encoded string starting the current pointer of
 100       lightweight resolver buffer <parameter>b</parameter>: i.e.
 101       <constant>b-&gt;current</constant>.  When the function returns,
 102       the address of the first byte of the encoded string is returned
 103       via <parameter>*c</parameter> and the length of that string is
 104       given by <parameter>*len</parameter>.  The buffer's current
 105       pointer is advanced to point at the character following the
 106       string length, the encoded string, and the trailing
 107       <type>NULL</type> character.
 108     </para>
 109
 110     <para><function>lwres_addr_parse()</function>
 111       extracts an address from the buffer <parameter>b</parameter>.
 112       The buffer's current pointer <constant>b-&gt;current</constant>
 113       is presumed to point at an encoded address: the address preceded
 114       by a 32-bit protocol family identifier and a 16-bit length
 115       field.  The encoded address is copied to
 116       <constant>addr-&gt;address</constant> and
 117       <constant>addr-&gt;length</constant> indicates the size in bytes
 118       of the address that was copied.
 119       <constant>b-&gt;current</constant> is advanced to point at the
 120       next byte of available data in the buffer following the encoded
 121       address.
 122     </para>
 123
 124     <para><function>lwres_getaddrsbyname()</function>
 125       and <function>lwres_getnamebyaddr()</function> use the
 126       <type>lwres_gnbaresponse_t</type> structure defined below:
 127     </para>
 128
 129 <para><programlisting>
 130 typedef struct {
 131         lwres_uint32_t          flags;
 132         lwres_uint16_t          naliases;
 133         lwres_uint16_t          naddrs;
 134         char                   *realname;
 135         char                  **aliases;
 136         lwres_uint16_t          realnamelen;
 137         lwres_uint16_t         *aliaslen;
 138         lwres_addrlist_t        addrs;
 139         void                   *base;
 140         size_t                  baselen;
 141 } lwres_gabnresponse_t;
 142 </programlisting></para>
 143
 144     <para>
 145       The contents of this structure are not manipulated directly but
 146       they are controlled through the
 147       <citerefentry>
 148         <refentrytitle>lwres_gabn</refentrytitle><manvolnum>3</manvolnum>
 149       </citerefentry>
 150       functions.
 151     </para>
 152
 153     <para>
 154       The lightweight resolver uses
 155       <function>lwres_getaddrsbyname()</function> to perform
 156       foward lookups.
 157       Hostname <parameter>name</parameter> is looked up using the
 158       resolver
 159       context <parameter>ctx</parameter> for memory allocation.
 160       <parameter>addrtypes</parameter> is a bitmask indicating
 161       which type of
 162       addresses are to be looked up.  Current values for this bitmask are
 163       <type>LWRES_ADDRTYPE_V4</type> for IPv4 addresses and
 164       <type>LWRES_ADDRTYPE_V6</type> for IPv6 addresses.  Results of the
 165       lookup are returned in <parameter>*structp</parameter>.
 166     </para>
 167
 168     <para><function>lwres_getnamebyaddr()</function>
 169       performs reverse lookups.  Resolver context
 170       <parameter>ctx</parameter> is used for memory allocation.  The
 171       address type is indicated by <parameter>addrtype</parameter>:
 172       <type>LWRES_ADDRTYPE_V4</type> or
 173       <type>LWRES_ADDRTYPE_V6</type>.  The address to be looked up is
 174       given by <parameter>addr</parameter> and its length is
 175       <parameter>addrlen</parameter> bytes.  The result of the
 176       function call is made available through
 177       <parameter>*structp</parameter>.
 178     </para>
 179   </refsect1>
 180
 181   <refsect1>
 182     <title>RETURN VALUES</title>
 183     <para>
 184       Successful calls to
 185       <function>lwres_string_parse()</function>
 186       and
 187       <function>lwres_addr_parse()</function>
 188       return
 189       <errorcode>LWRES_R_SUCCESS.</errorcode>
 190       Both functions return
 191       <errorcode>LWRES_R_FAILURE</errorcode>
 192       if the buffer is corrupt or
 193       <errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
 194       if the buffer has less space than expected for the components of the
 195       encoded string or address.
 196     </para>
 197
 198     <para><function>lwres_getaddrsbyname()</function>
 199       returns <errorcode>LWRES_R_SUCCESS</errorcode> on success and it
 200       returns <errorcode>LWRES_R_NOTFOUND</errorcode> if the hostname
 201       <parameter>name</parameter> could not be found.
 202     </para>
 203     <para><errorcode>LWRES_R_SUCCESS</errorcode>
 204       is returned by a successful call to
 205       <function>lwres_getnamebyaddr()</function>.
 206     </para>
 207
 208     <para>
 209       Both
 210       <function>lwres_getaddrsbyname()</function>
 211       and
 212       <function>lwres_getnamebyaddr()</function>
 213       return
 214       <errorcode>LWRES_R_NOMEMORY</errorcode>
 215       when memory allocation requests fail and
 216       <errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
 217       if the buffers used for sending queries and receiving replies are too
 218       small.
 219     </para>
 220
 221   </refsect1>
 222   <refsect1>
 223     <title>SEE ALSO</title>
 224     <para><citerefentry>
 225         <refentrytitle>lwres_buffer</refentrytitle><manvolnum>3</manvolnum>
 226       </citerefentry>,
 227
 228       <citerefentry>
 229         <refentrytitle>lwres_gabn</refentrytitle><manvolnum>3</manvolnum>
 230       </citerefentry>.
 231     </para>
 232
 233   </refsect1>
 234 </refentry><!--
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