lwres/man/lwres_resutil.html

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<title>lwres_resutil</title>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
<a name="id2476275"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2>Name</h2>
<p>lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr &#8212; lightweight resolver utility functions</p>
</div>
<div class="refsynopsisdiv">
<h2>Synopsis</h2>
<div class="funcsynopsis">
<pre class="funcsynopsisinfo">#include &lt;lwres/lwres.h&gt;</pre>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_string_parse</b>(</code></td>
<td>lwres_buffer_t *�</td>
<td>
<var class="pdparam">b</var>, </td>
</tr>
<tr>
<td>�</td>
<td>char **�</td>
<td>
<var class="pdparam">c</var>, </td>
</tr>
<tr>
<td>�</td>
<td>lwres_uint16_t *�</td>
<td>
<var class="pdparam">len</var><code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_addr_parse</b>(</code></td>
<td>lwres_buffer_t *�</td>
<td>
<var class="pdparam">b</var>, </td>
</tr>
<tr>
<td>�</td>
<td>lwres_addr_t *�</td>
<td>
<var class="pdparam">addr</var><code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_getaddrsbyname</b>(</code></td>
<td>lwres_context_t *�</td>
<td>
<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td>�</td>
<td>const char *�</td>
<td>
<var class="pdparam">name</var>, </td>
</tr>
<tr>
<td>�</td>
<td>lwres_uint32_t �</td>
<td>
<var class="pdparam">addrtypes</var>, </td>
</tr>
<tr>
<td>�</td>
<td>lwres_gabnresponse_t **�</td>
<td>
<var class="pdparam">structp</var><code>)</code>;</td>
</tr>
</table>
<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
<tr>
<td><code class="funcdef">
lwres_result_t
<b class="fsfunc">lwres_getnamebyaddr</b>(</code></td>
<td>lwres_context_t *�</td>
<td>
<var class="pdparam">ctx</var>, </td>
</tr>
<tr>
<td>�</td>
<td>lwres_uint32_t �</td>
<td>
<var class="pdparam">addrtype</var>, </td>
</tr>
<tr>
<td>�</td>
<td>lwres_uint16_t �</td>
<td>
<var class="pdparam">addrlen</var>, </td>
</tr>
<tr>
<td>�</td>
<td>const unsigned char *�</td>
<td>
<var class="pdparam">addr</var>, </td>
</tr>
<tr>
<td>�</td>
<td>lwres_gnbaresponse_t **�</td>
<td>
<var class="pdparam">structp</var><code>)</code>;</td>
</tr>
</table>
</div>
</div>
<div class="refsect1" lang="en">
<a name="id2543463"></a><h2>DESCRIPTION</h2>
<p><code class="function">lwres_string_parse()</code>
      retrieves a DNS-encoded string starting the current pointer of
      lightweight resolver buffer <em class="parameter"><code>b</code></em>: i.e.
      <code class="constant">b-&gt;current</code>.  When the function returns,
      the address of the first byte of the encoded string is returned
      via <em class="parameter"><code>*c</code></em> and the length of that string is
      given by <em class="parameter"><code>*len</code></em>.  The buffer's current
      pointer is advanced to point at the character following the
      string length, the encoded string, and the trailing
      <span class="type">NULL</span> character.
    </p>
<p><code class="function">lwres_addr_parse()</code>
      extracts an address from the buffer <em class="parameter"><code>b</code></em>.
      The buffer's current pointer <code class="constant">b-&gt;current</code>
      is presumed to point at an encoded address: the address preceded
      by a 32-bit protocol family identifier and a 16-bit length
      field.  The encoded address is copied to
      <code class="constant">addr-&gt;address</code> and
      <code class="constant">addr-&gt;length</code> indicates the size in bytes
      of the address that was copied.
      <code class="constant">b-&gt;current</code> is advanced to point at the
      next byte of available data in the buffer following the encoded
      address.
    </p>
<p><code class="function">lwres_getaddrsbyname()</code>
      and <code class="function">lwres_getnamebyaddr()</code> use the
      <span class="type">lwres_gnbaresponse_t</span> structure defined below:
    </p>
<pre class="programlisting">
typedef struct {
        lwres_uint32_t          flags;
        lwres_uint16_t          naliases;
        lwres_uint16_t          naddrs;
        char                   *realname;
        char                  **aliases;
        lwres_uint16_t          realnamelen;
        lwres_uint16_t         *aliaslen;
        lwres_addrlist_t        addrs;
        void                   *base;
        size_t                  baselen;
} lwres_gabnresponse_t;
</pre>
<p>
      The contents of this structure are not manipulated directly but
      they are controlled through the
      <span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3)</span>
      functions.
    </p>
<p>
      The lightweight resolver uses
      <code class="function">lwres_getaddrsbyname()</code> to perform
      foward lookups.
      Hostname <em class="parameter"><code>name</code></em> is looked up using the
      resolver
      context <em class="parameter"><code>ctx</code></em> for memory allocation.
      <em class="parameter"><code>addrtypes</code></em> is a bitmask indicating
      which type of
      addresses are to be looked up.  Current values for this bitmask are
      <span class="type">LWRES_ADDRTYPE_V4</span> for IPv4 addresses and
      <span class="type">LWRES_ADDRTYPE_V6</span> for IPv6 addresses.  Results of the
      lookup are returned in <em class="parameter"><code>*structp</code></em>.
    </p>
<p><code class="function">lwres_getnamebyaddr()</code>
      performs reverse lookups.  Resolver context
      <em class="parameter"><code>ctx</code></em> is used for memory allocation.  The
      address type is indicated by <em class="parameter"><code>addrtype</code></em>:
      <span class="type">LWRES_ADDRTYPE_V4</span> or
      <span class="type">LWRES_ADDRTYPE_V6</span>.  The address to be looked up is
      given by <em class="parameter"><code>addr</code></em> and its length is
      <em class="parameter"><code>addrlen</code></em> bytes.  The result of the
      function call is made available through
      <em class="parameter"><code>*structp</code></em>.
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2543602"></a><h2>RETURN VALUES</h2>
<p>
      Successful calls to
      <code class="function">lwres_string_parse()</code>
      and
      <code class="function">lwres_addr_parse()</code>
      return
      <span class="errorcode">LWRES_R_SUCCESS.</span>
      Both functions return
      <span class="errorcode">LWRES_R_FAILURE</span>
      if the buffer is corrupt or
      <span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
      if the buffer has less space than expected for the components of the
      encoded string or address.
    </p>
<p><code class="function">lwres_getaddrsbyname()</code>
      returns <span class="errorcode">LWRES_R_SUCCESS</span> on success and it
      returns <span class="errorcode">LWRES_R_NOTFOUND</span> if the hostname
      <em class="parameter"><code>name</code></em> could not be found.
    </p>
<p><span class="errorcode">LWRES_R_SUCCESS</span>
      is returned by a successful call to
      <code class="function">lwres_getnamebyaddr()</code>.
    </p>
<p>
      Both
      <code class="function">lwres_getaddrsbyname()</code>
      and
      <code class="function">lwres_getnamebyaddr()</code>
      return
      <span class="errorcode">LWRES_R_NOMEMORY</span>
      when memory allocation requests fail and
      <span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
      if the buffers used for sending queries and receiving replies are too
      small.
    </p>
</div>
<div class="refsect1" lang="en">
<a name="id2543673"></a><h2>SEE ALSO</h2>
<p><span class="citerefentry"><span class="refentrytitle">lwres_buffer</span>(3)</span>,

      <span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3)</span>.
    </p>
</div>
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