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28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<p>lwres_string_parse, lwres_addr_parse, lwres_getaddrsbyname, lwres_getnamebyaddr — lightweight resolver utility functions</p>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<pre class="funcsynopsisinfo">#include <lwres/lwres.h></pre>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-freelwres_result_t
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<b class="fsfunc">lwres_string_parse</b>(</code></td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_buffer_t *<var class="pdparam">b</var>, </td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_uint16_t *<var class="pdparam">len</var><code>)</code>;</td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-freelwres_result_t
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<b class="fsfunc">lwres_addr_parse</b>(</code></td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_buffer_t *<var class="pdparam">b</var>, </td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_addr_t *<var class="pdparam">addr</var><code>)</code>;</td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-freelwres_result_t
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<b class="fsfunc">lwres_getaddrsbyname</b>(</code></td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_context_t *<var class="pdparam">ctx</var>, </td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>const char *<var class="pdparam">name</var>, </td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_uint32_t <var class="pdparam">addrtypes</var>, </td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_gabnresponse_t **<var class="pdparam">structp</var><code>)</code>;</td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-freelwres_result_t
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<b class="fsfunc">lwres_getnamebyaddr</b>(</code></td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_context_t *<var class="pdparam">ctx</var>, </td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_uint32_t <var class="pdparam">addrtype</var>, </td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_uint16_t <var class="pdparam">addrlen</var>, </td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>const unsigned char *<var class="pdparam">addr</var>, </td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<td>lwres_gnbaresponse_t **<var class="pdparam">structp</var><code>)</code>;</td>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<p><code class="function">lwres_string_parse()</code>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free retrieves a DNS-encoded string starting the current pointer of
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free lightweight resolver buffer <em class="parameter"><code>b</code></em>: i.e.
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <code class="constant">b->current</code>. When the function returns,
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free the address of the first byte of the encoded string is returned
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free via <em class="parameter"><code>*c</code></em> and the length of that string is
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free given by <em class="parameter"><code>*len</code></em>. The buffer's current
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free pointer is advanced to point at the character following the
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free string length, the encoded string, and the trailing
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<p><code class="function">lwres_addr_parse()</code>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free extracts an address from the buffer <em class="parameter"><code>b</code></em>.
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free The buffer's current pointer <code class="constant">b->current</code>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free is presumed to point at an encoded address: the address preceded
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free by a 32-bit protocol family identifier and a 16-bit length
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free field. The encoded address is copied to
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <code class="constant">addr->address</code> and
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <code class="constant">addr->length</code> indicates the size in bytes
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free of the address that was copied.
2b0e2e6c2dde5d6cb739785016e91189888ff483tavmjong-free <code class="constant">b->current</code> is advanced to point at the
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free next byte of available data in the buffer following the encoded
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<p><code class="function">lwres_getaddrsbyname()</code>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free and <code class="function">lwres_getnamebyaddr()</code> use the
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="type">lwres_gnbaresponse_t</span> structure defined below:
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-freetypedef struct {
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free lwres_uint32_t flags;
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free lwres_uint16_t naliases;
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free lwres_uint16_t naddrs;
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free char *realname;
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free char **aliases;
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free lwres_uint16_t realnamelen;
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free lwres_uint16_t *aliaslen;
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free lwres_addrlist_t addrs;
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free size_t baselen;
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free} lwres_gabnresponse_t;
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free The contents of this structure are not manipulated directly but
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free they are controlled through the
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3)</span>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free The lightweight resolver uses
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <code class="function">lwres_getaddrsbyname()</code> to perform
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free forward lookups.
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free Hostname <em class="parameter"><code>name</code></em> is looked up using the
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free context <em class="parameter"><code>ctx</code></em> for memory allocation.
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <em class="parameter"><code>addrtypes</code></em> is a bitmask indicating
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free which type of
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free addresses are to be looked up. Current values for this bitmask are
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="type">LWRES_ADDRTYPE_V4</span> for IPv4 addresses and
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="type">LWRES_ADDRTYPE_V6</span> for IPv6 addresses. Results of the
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free lookup are returned in <em class="parameter"><code>*structp</code></em>.
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<p><code class="function">lwres_getnamebyaddr()</code>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free performs reverse lookups. Resolver context
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <em class="parameter"><code>ctx</code></em> is used for memory allocation. The
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free address type is indicated by <em class="parameter"><code>addrtype</code></em>:
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="type">LWRES_ADDRTYPE_V4</span> or
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="type">LWRES_ADDRTYPE_V6</span>. The address to be looked up is
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free given by <em class="parameter"><code>addr</code></em> and its length is
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <em class="parameter"><code>addrlen</code></em> bytes. The result of the
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free function call is made available through
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <em class="parameter"><code>*structp</code></em>.
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free Successful calls to
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <code class="function">lwres_string_parse()</code>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <code class="function">lwres_addr_parse()</code>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="errorcode">LWRES_R_SUCCESS.</span>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free Both functions return
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="errorcode">LWRES_R_FAILURE</span>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free if the buffer is corrupt or
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free if the buffer has less space than expected for the components of the
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free encoded string or address.
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<p><code class="function">lwres_getaddrsbyname()</code>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free returns <span class="errorcode">LWRES_R_SUCCESS</span> on success and it
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free returns <span class="errorcode">LWRES_R_NOTFOUND</span> if the hostname
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <em class="parameter"><code>name</code></em> could not be found.
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<p><span class="errorcode">LWRES_R_SUCCESS</span>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free is returned by a successful call to
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <code class="function">lwres_getnamebyaddr()</code>.
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <code class="function">lwres_getaddrsbyname()</code>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <code class="function">lwres_getnamebyaddr()</code>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="errorcode">LWRES_R_NOMEMORY</span>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free when memory allocation requests fail and
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="errorcode">LWRES_R_UNEXPECTEDEND</span>
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free if the buffers used for sending queries and receiving replies are too
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free<p><span class="citerefentry"><span class="refentrytitle">lwres_buffer</span>(3)</span>,
28bf548be956fa98bffa377e2caba5f28fb281adtavmjong-free <span class="citerefentry"><span class="refentrytitle">lwres_gabn</span>(3)</span>.