lib/liblwres/man/lwres_resutil.docbook

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  20
  21 <refentry>
  22
  23 <refentryinfo>
  24 <date>Jun 30, 2000</date>
  25 </refentryinfo>
  26
  27 <refmeta>
  28   <refentrytitle>lwres_resutil</refentrytitle>
  29   <manvolnum>3</manvolnum>
  30   <refmiscinfo>BIND9</refmiscinfo>
  31 </refmeta>
  32
  33 <refnamediv>
  34 <refname>lwres_string_parse</refname>
  35 <refname>lwres_addr_parse</refname>
  36 <refname>lwres_getaddrsbyname</refname>
  37 <refname>lwres_getnamebyaddr</refname>
  38 <refpurpose>lightweight resolver utility functions</refpurpose>
  39 </refnamediv>
  40 <refsynopsisdiv>
  41 <funcsynopsis>
  42 <funcsynopsisinfo>#include &lt;lwres/lwres.h&gt;</funcsynopsisinfo>
  43 <funcprototype>
  44 <funcdef>
  45 lwres_result_t
  46 <function>lwres_string_parse</function></funcdef>
  47 <paramdef>lwres_buffer_t *b</paramdef>
  48 <paramdef>char **c</paramdef>
  49 <paramdef>lwres_uint16_t *len</paramdef>
  50 </funcprototype>
  51 <funcprototype>
  52 <funcdef>
  53 lwres_result_t
  54 <function>lwres_addr_parse</function></funcdef>
  55 <paramdef>lwres_buffer_t *b</paramdef>
  56 <paramdef>lwres_addr_t *addr</paramdef>
  57 </funcprototype>
  58 <funcprototype>
  59 <funcdef>
  60 lwres_result_t
  61 <function>lwres_getaddrsbyname</function></funcdef>
  62 <paramdef>lwres_context_t *ctx</paramdef>
  63 <paramdef>const char *name</paramdef>
  64 <paramdef>lwres_uint32_t addrtypes</paramdef>
  65 <paramdef>lwres_gabnresponse_t **structp</paramdef>
  66 </funcprototype>
  67 <funcprototype>
  68 <funcdef>
  69 lwres_result_t
  70 <function>lwres_getnamebyaddr</function></funcdef>
  71 <paramdef>lwres_context_t *ctx</paramdef>
  72 <paramdef>lwres_uint32_t addrtype</paramdef>
  73 <paramdef>lwres_uint16_t addrlen</paramdef>
  74 <paramdef>const unsigned char *addr</paramdef>
  75 <paramdef>lwres_gnbaresponse_t **structp</paramdef>
  76 </funcprototype>
  77 </funcsynopsis>
  78 </refsynopsisdiv>
  79
  80 <refsect1>
  81 <title>DESCRIPTION</title>
  82
  83 <para>
  84 <function>lwres_string_parse()</function> retrieves a DNS-encoded
  85 string starting the current pointer of lightweight resolver buffer
  86 <parameter>b</parameter>: i.e.  <constant>b-&gt;current</constant>.
  87 When the function returns, the address of the first byte of the
  88 encoded string is returned via <parameter>*c</parameter> and the
  89 length of that string is given by <parameter>*len</parameter>.  The
  90 buffer's current pointer is advanced to point at the character
  91 following the string length, the encoded string, and the trailing
  92 <type>NULL</type> character.
  93 </para>
  94
  95 <para>
  96 <function>lwres_addr_parse()</function> extracts an address from the
  97 buffer <parameter>b</parameter>.  The buffer's current pointer
  98 <constant>b-&gt;current</constant> is presumed to point at an encoded
  99 address: the address preceded by a 32-bit protocol family identifier
 100 and a 16-bit length field.  The encoded address is copied to
 101 <constant>addr-&gt;address</constant> and
 102 <constant>addr-&gt;length</constant> indicates the size in bytes of
 103 the address that was copied.  <constant>b-&gt;current</constant> is
 104 advanced to point at the next byte of available data in the buffer
 105 following the encoded address.
 106 </para>
 107
 108 <para>
 109 <function>lwres_getaddrsbyname()</function>
 110 and
 111 <function>lwres_getnamebyaddr()</function>
 112 use the
 113 <type>lwres_gnbaresponse_t</type>
 114 structure defined below:
 115 <programlisting>
 116 typedef struct {
 117         lwres_uint32_t          flags;
 118         lwres_uint16_t          naliases;
 119         lwres_uint16_t          naddrs;
 120         char                   *realname;
 121         char                  **aliases;
 122         lwres_uint16_t          realnamelen;
 123         lwres_uint16_t         *aliaslen;
 124         lwres_addrlist_t        addrs;
 125         void                   *base;
 126         size_t                  baselen;
 127 } lwres_gabnresponse_t;
 128 </programlisting>
 129 The contents of this structure are not manipulated directly but
 130 they are controlled through the
 131 <citerefentry>
 132 <refentrytitle>lwres_gabn</refentrytitle><manvolnum>3
 133 </manvolnum>
 134 </citerefentry>
 135 functions.
 136 </para>
 137
 138 <para>
 139 The lightweight resolver uses
 140 <function>lwres_getaddrsbyname()</function> to perform foward lookups.
 141 Hostname <parameter>name</parameter> is looked up using the resolver
 142 context <parameter>ctx</parameter> for memory allocation.
 143 <parameter>addrtypes</parameter> is a bitmask indicating which type of
 144 addresses are to be looked up.  Current values for this bitmask are
 145 <type>LWRES_ADDRTYPE_V4</type> for IPv4 addresses and
 146 <type>LWRES_ADDRTYPE_V6</type> for IPv6 addresses.  Results of the
 147 lookup are returned in <parameter>*structp</parameter>.
 148 </para>
 149
 150 <para>
 151 <function>lwres_getnamebyaddr()</function> performs reverse lookups.
 152 Resolver context <parameter>ctx</parameter> is used for memory
 153 allocation.  The address type is indicated by
 154 <parameter>addrtype</parameter>: <type>LWRES_ADDRTYPE_V4</type> or
 155 <type>LWRES_ADDRTYPE_V6</type>.  The address to be looked up is given
 156 by <parameter>addr</parameter> and its length is
 157 <parameter>addrlen</parameter> bytes.  The result of the function call
 158 is made available through <parameter>*structp</parameter>.
 159 </para>
 160 </refsect1>
 161
 162 <refsect1>
 163 <title>RETURN VALUES</title>
 164 <para>
 165 Successful calls to
 166 <function>lwres_string_parse()</function>
 167 and
 168 <function>lwres_addr_parse()</function>
 169 return
 170 <errorcode>LWRES_R_SUCCESS.</errorcode>
 171 Both functions return
 172 <errorcode>LWRES_R_FAILURE</errorcode>
 173 if the buffer is corrupt or
 174 <errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
 175 if the buffer has less space than expected for the components of the
 176 encoded string or address.
 177 </para>
 178 <para>
 179 <function>lwres_getaddrsbyname()</function>
 180 returns
 181 <errorcode>LWRES_R_SUCCESS</errorcode>
 182 on success and it returns
 183 <errorcode>LWRES_R_NOTFOUND</errorcode>
 184 if the hostname
 185 <parameter>name</parameter>
 186 could not be found.
 187 </para>
 188 <para>
 189 <errorcode>LWRES_R_SUCCESS</errorcode>
 190 is returned by a successful call to
 191 <function>lwres_getnamebyaddr()</function>.
 192 </para>
 193
 194 <para>
 195 Both
 196 <function>lwres_getaddrsbyname()</function>
 197 and
 198 <function>lwres_getnamebyaddr()</function>
 199 return
 200 <errorcode>LWRES_R_NOMEMORY</errorcode>
 201 when memory allocation requests fail and
 202 <errorcode>LWRES_R_UNEXPECTEDEND</errorcode>
 203 if the buffers used for sending queries and receiving replies are too
 204 small.
 205 </para>
 206
 207 </refsect1>
 208 <refsect1>
 209 <title>SEE ALSO</title>
 210 <para>
 211 <citerefentry>
 212 <refentrytitle>lwres_buffer</refentrytitle><manvolnum>3</manvolnum>
 213 </citerefentry>,
 214
 215 <citerefentry>
 216 <refentrytitle>lwres_gabn</refentrytitle><manvolnum>3</manvolnum>
 217 </citerefentry>.
 218 </para>
 219
 220 </refsect1>
 221 </refentry>