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794b79e6bbc3f5db1ea6ae154d739b9f1ef1a375Tinderbox User - Copyright (C) 2004, 2005, 2007, 2014 Internet Systems Consortium, Inc. ("ISC")
75c0816e8295e180f4bc7f10db3d0d880383bc1cMark Andrews - Copyright (C) 2000, 2001 Internet Software Consortium.
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60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
794b79e6bbc3f5db1ea6ae154d739b9f1ef1a375Tinderbox User<a name="id2476274"></a><div class="titlepage"></div>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p>lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr — lightweight resolver utility functions</p>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<pre class="funcsynopsisinfo">#include <lwres/lwres.h></pre>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austeinlwres_result_t
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<b class="fsfunc">lwres_string_parse</b>(</code></td>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<var class="pdparam">len</var><code>)</code>;</td>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austeinlwres_result_t
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<b class="fsfunc">lwres_addr_parse</b>(</code></td>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<var class="pdparam">addr</var><code>)</code>;</td>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austeinlwres_result_t
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<b class="fsfunc">lwres_getaddrsbyname</b>(</code></td>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<var class="pdparam">structp</var><code>)</code>;</td>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0">
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austeinlwres_result_t
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<b class="fsfunc">lwres_getnamebyaddr</b>(</code></td>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<var class="pdparam">structp</var><code>)</code>;</td>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><code class="function">lwres_string_parse()</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein retrieves a DNS-encoded string starting the current pointer of
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein lightweight resolver buffer <em class="parameter"><code>b</code></em>: i.e.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="constant">b->current</code>. When the function returns,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein the address of the first byte of the encoded string is returned
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein via <em class="parameter"><code>*c</code></em> and the length of that string is
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein given by <em class="parameter"><code>*len</code></em>. The buffer's current
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein pointer is advanced to point at the character following the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein string length, the encoded string, and the trailing
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><code class="function">lwres_addr_parse()</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein extracts an address from the buffer <em class="parameter"><code>b</code></em>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The buffer's current pointer <code class="constant">b->current</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein is presumed to point at an encoded address: the address preceded
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein by a 32-bit protocol family identifier and a 16-bit length
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein field. The encoded address is copied to
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="constant">addr->address</code> and
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="constant">addr->length</code> indicates the size in bytes
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein of the address that was copied.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="constant">b->current</code> is advanced to point at the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein next byte of available data in the buffer following the encoded
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><code class="function">lwres_getaddrsbyname()</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein and <code class="function">lwres_getnamebyaddr()</code> use the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="type">lwres_gnbaresponse_t</span> structure defined below:
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austeintypedef struct {
8eea877894ea5bcf5cdd9ca124a8601ad421d753Andreas Gustafsson lwres_uint32_t flags;
8eea877894ea5bcf5cdd9ca124a8601ad421d753Andreas Gustafsson lwres_uint16_t naliases;
8eea877894ea5bcf5cdd9ca124a8601ad421d753Andreas Gustafsson lwres_uint16_t naddrs;
8eea877894ea5bcf5cdd9ca124a8601ad421d753Andreas Gustafsson char *realname;
8eea877894ea5bcf5cdd9ca124a8601ad421d753Andreas Gustafsson char **aliases;
8eea877894ea5bcf5cdd9ca124a8601ad421d753Andreas Gustafsson lwres_uint16_t realnamelen;
8eea877894ea5bcf5cdd9ca124a8601ad421d753Andreas Gustafsson lwres_uint16_t *aliaslen;
8eea877894ea5bcf5cdd9ca124a8601ad421d753Andreas Gustafsson lwres_addrlist_t addrs;
8eea877894ea5bcf5cdd9ca124a8601ad421d753Andreas Gustafsson size_t baselen;
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein} lwres_gabnresponse_t;
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The contents of this structure are not manipulated directly but
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein they are controlled through the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3)</span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein The lightweight resolver uses
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="function">lwres_getaddrsbyname()</code> to perform
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein foward lookups.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Hostname <em class="parameter"><code>name</code></em> is looked up using the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein context <em class="parameter"><code>ctx</code></em> for memory allocation.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>addrtypes</code></em> is a bitmask indicating
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein which type of
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein addresses are to be looked up. Current values for this bitmask are
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="type">LWRES_ADDRTYPE_V4</span> for IPv4 addresses and
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="type">LWRES_ADDRTYPE_V6</span> for IPv6 addresses. Results of the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein lookup are returned in <em class="parameter"><code>*structp</code></em>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><code class="function">lwres_getnamebyaddr()</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein performs reverse lookups. Resolver context
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>ctx</code></em> is used for memory allocation. The
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein address type is indicated by <em class="parameter"><code>addrtype</code></em>:
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="type">LWRES_ADDRTYPE_V6</span>. The address to be looked up is
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein given by <em class="parameter"><code>addr</code></em> and its length is
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>addrlen</code></em> bytes. The result of the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein function call is made available through
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>*structp</code></em>.
794b79e6bbc3f5db1ea6ae154d739b9f1ef1a375Tinderbox User<a name="id2543608"></a><h2>RETURN VALUES</h2>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Successful calls to
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="function">lwres_string_parse()</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="function">lwres_addr_parse()</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein Both functions return
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein if the buffer is corrupt or
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein if the buffer has less space than expected for the components of the
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein encoded string or address.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><code class="function">lwres_getaddrsbyname()</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein returns <span class="errorcode">LWRES_R_SUCCESS</span> on success and it
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein returns <span class="errorcode">LWRES_R_NOTFOUND</span> if the hostname
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <em class="parameter"><code>name</code></em> could not be found.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><span class="errorcode">LWRES_R_SUCCESS</span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein is returned by a successful call to
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="function">lwres_getnamebyaddr()</code>.
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="function">lwres_getaddrsbyname()</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <code class="function">lwres_getnamebyaddr()</code>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein when memory allocation requests fail and
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein if the buffers used for sending queries and receiving replies are too
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein<p><span class="citerefentry"><span class="refentrytitle">lwres_buffer</span>(3)</span>,
60e5e10f8d2e2b0c41e8abad38cacd867caa6ab2Rob Austein <span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3)</span>.