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phunix/external/bsd/bind/dist/lib/lwres/man/lwres_resutil.html
David van Moolenbroek 00b67f09dd Import NetBSD named(8) 
Also known as ISC bind.  This import adds utilities such as host(1),
dig(1), and nslookup(1), as well as many other tools and libraries.

Change-Id: I035ca46e64f1965d57019e773f4ff0ef035e4aa3
2017-03-21 22:00:06 +00:00

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<!-- Id -->
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>lwres_resutil</title>
<meta name="generator" content="DocBook XSL Stylesheets V1.71.1">
</head>
<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="id2543476"></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
forward 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="id2543614"></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="id2543686"></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>
</div></body>
</html>
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