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

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  22
  23 <refentry>
  24
  25 <refentryinfo>
  26 <date>Jun 30, 2000</date>
  27 </refentryinfo>
  28
  29 <refmeta>
  30   <refentrytitle>lwres_resutil</refentrytitle>
  31   <manvolnum>3</manvolnum>
  32   <refmiscinfo>BIND9</refmiscinfo>
  33 </refmeta>
  34
  35   <docinfo>
  36     <copyright>
  37       <year>2004</year>
  38       <year>2005</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 *b</paramdef>
  63 <paramdef>char **c</paramdef>
  64 <paramdef>lwres_uint16_t *len</paramdef>
  65 </funcprototype>
  66 <funcprototype>
  67 <funcdef>
  68 lwres_result_t
  69 <function>lwres_addr_parse</function></funcdef>
  70 <paramdef>lwres_buffer_t *b</paramdef>
  71 <paramdef>lwres_addr_t *addr</paramdef>
  72 </funcprototype>
  73 <funcprototype>
  74 <funcdef>
  75 lwres_result_t
  76 <function>lwres_getaddrsbyname</function></funcdef>
  77 <paramdef>lwres_context_t *ctx</paramdef>
  78 <paramdef>const char *name</paramdef>
  79 <paramdef>lwres_uint32_t addrtypes</paramdef>
  80 <paramdef>lwres_gabnresponse_t **structp</paramdef>
  81 </funcprototype>
  82 <funcprototype>
  83 <funcdef>
  84 lwres_result_t
  85 <function>lwres_getnamebyaddr</function></funcdef>
  86 <paramdef>lwres_context_t *ctx</paramdef>
  87 <paramdef>lwres_uint32_t addrtype</paramdef>
  88 <paramdef>lwres_uint16_t addrlen</paramdef>
  89 <paramdef>const unsigned char *addr</paramdef>
  90 <paramdef>lwres_gnbaresponse_t **structp</paramdef>
  91 </funcprototype>
  92 </funcsynopsis>
  93 </refsynopsisdiv>
  94
  95 <refsect1>
  96 <title>DESCRIPTION</title>
  97
  98 <para>
  99 <function>lwres_string_parse()</function> retrieves a DNS-encoded
 100 string starting the current pointer of lightweight resolver buffer
 101 <parameter>b</parameter>: i.e.  <constant>b-&gt;current</constant>.
 102 When the function returns, the address of the first byte of the
 103 encoded string is returned via <parameter>*c</parameter> and the
 104 length of that string is given by <parameter>*len</parameter>.  The
 105 buffer's current pointer is advanced to point at the character
 106 following the string length, the encoded string, and the trailing
 107 <type>NULL</type> character.
 108 </para>
 109
 110 <para>
 111 <function>lwres_addr_parse()</function> extracts an address from the
 112 buffer <parameter>b</parameter>.  The buffer's current pointer
 113 <constant>b-&gt;current</constant> is presumed to point at an encoded
 114 address: the address preceded by a 32-bit protocol family identifier
 115 and a 16-bit length 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 of
 118 the address that was copied.  <constant>b-&gt;current</constant> is
 119 advanced to point at the next byte of available data in the buffer
 120 following the encoded address.
 121 </para>
 122
 123 <para>
 124 <function>lwres_getaddrsbyname()</function>
 125 and
 126 <function>lwres_getnamebyaddr()</function>
 127 use the
 128 <type>lwres_gnbaresponse_t</type>
 129 structure defined below:
 130 <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>
 144 The contents of this structure are not manipulated directly but
 145 they are controlled through the
 146 <citerefentry>
 147 <refentrytitle>lwres_gabn</refentrytitle><manvolnum>3
 148 </manvolnum>
 149 </citerefentry>
 150 functions.
 151 </para>
 152
 153 <para>
 154 The lightweight resolver uses
 155 <function>lwres_getaddrsbyname()</function> to perform foward lookups.
 156 Hostname <parameter>name</parameter> is looked up using the resolver
 157 context <parameter>ctx</parameter> for memory allocation.
 158 <parameter>addrtypes</parameter> is a bitmask indicating which type of
 159 addresses are to be looked up.  Current values for this bitmask are
 160 <type>LWRES_ADDRTYPE_V4</type> for IPv4 addresses and
 161 <type>LWRES_ADDRTYPE_V6</type> for IPv6 addresses.  Results of the
 162 lookup are returned in <parameter>*structp</parameter>.
 163 </para>
 164
 165 <para>
 166 <function>lwres_getnamebyaddr()</function> performs reverse lookups.
 167 Resolver context <parameter>ctx</parameter> is used for memory
 168 allocation.  The address type is indicated by
 169 <parameter>addrtype</parameter>: <type>LWRES_ADDRTYPE_V4</type> or
 170 <type>LWRES_ADDRTYPE_V6</type>.  The address to be looked up is given
 171 by <parameter>addr</parameter> and its length is
 172 <parameter>addrlen</parameter> bytes.  The result of the function call
 173 is made available through <parameter>*structp</parameter>.
 174 </para>
 175 </refsect1>
 176
 177 <refsect1>
 178 <title>RETURN VALUES</title>
 179 <para>
 180 Successful calls to
 181 <function>lwres_string_parse()</function>
 182 and
 183 <function>lwres_addr_parse()</function>
 184 return
 185 <errorcode>LWRES_R_SUCCESS.</errorcode>
 186 Both functions return
 187 <errorcode>LWRES_R_FAILURE</errorcode>
 188 if the buffer is corrupt or
 189 <errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
 190 if the buffer has less space than expected for the components of the
 191 encoded string or address.
 192 </para>
 193 <para>
 194 <function>lwres_getaddrsbyname()</function>
 195 returns
 196 <errorcode>LWRES_R_SUCCESS</errorcode>
 197 on success and it returns
 198 <errorcode>LWRES_R_NOTFOUND</errorcode>
 199 if the hostname
 200 <parameter>name</parameter>
 201 could not be found.
 202 </para>
 203 <para>
 204 <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>
 226 <citerefentry>
 227 <refentrytitle>lwres_buffer</refentrytitle><manvolnum>3</manvolnum>
 228 </citerefentry>,
 229
 230 <citerefentry>
 231 <refentrytitle>lwres_gabn</refentrytitle><manvolnum>3</manvolnum>
 232 </citerefentry>.
 233 </para>
 234
 235 </refsect1>
 236 </refentry>