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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-05 18:37:14 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-05 18:37:14 +0000
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treee2b6b1c647da68b0d4d66082835e256eb30970e8 /lib/lwres/man/lwres_gethostent.html
parentInitial commit. (diff)
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Adding upstream version 1:9.11.5.P4+dfsg.upstream/1%9.11.5.P4+dfsgupstream
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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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+<html lang="en">
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
+<title>lwres_gethostent</title>
+<meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
+</head>
+<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry">
+<a name="id-1"></a><div class="titlepage"></div>
+
+
+
+
+
+
+
+ <div class="refnamediv">
+<h2>Name</h2>
+<p>
+ lwres_gethostbyname,
+ lwres_gethostbyname2,
+ lwres_gethostbyaddr,
+ lwres_gethostent,
+ lwres_sethostent,
+ lwres_endhostent,
+ lwres_gethostbyname_r,
+ lwres_gethostbyaddr_r,
+ lwres_gethostent_r,
+ lwres_sethostent_r,
+ lwres_endhostent_r
+ &#8212; lightweight resolver get network host entry
+ </p>
+</div>
+ <div class="refsynopsisdiv">
+<h2>Synopsis</h2>
+ <div class="funcsynopsis">
+<pre class="funcsynopsisinfo">#include &lt;lwres/netdb.h&gt;</pre>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr>
+<td><code class="funcdef">
+struct hostent *
+<b class="fsfunc">lwres_gethostbyname</b>(</code></td>
+<td>const char *<var class="pdparam">name</var><code>)</code>;</td>
+</tr></table>
+<div class="funcprototype-spacer"> </div>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
+<tr>
+<td><code class="funcdef">
+struct hostent *
+<b class="fsfunc">lwres_gethostbyname2</b>(</code></td>
+<td>const char *<var class="pdparam">name</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int <var class="pdparam">af</var><code>)</code>;</td>
+</tr>
+</table>
+<div class="funcprototype-spacer"> </div>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
+<tr>
+<td><code class="funcdef">
+struct hostent *
+<b class="fsfunc">lwres_gethostbyaddr</b>(</code></td>
+<td>const char *<var class="pdparam">addr</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int <var class="pdparam">len</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int <var class="pdparam">type</var><code>)</code>;</td>
+</tr>
+</table>
+<div class="funcprototype-spacer"> </div>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr>
+<td><code class="funcdef">
+struct hostent *
+<b class="fsfunc">lwres_gethostent</b>(</code></td>
+<td>void<code>)</code>;</td>
+</tr></table>
+<div class="funcprototype-spacer"> </div>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr>
+<td><code class="funcdef">
+void
+<b class="fsfunc">lwres_sethostent</b>(</code></td>
+<td>int <var class="pdparam">stayopen</var><code>)</code>;</td>
+</tr></table>
+<div class="funcprototype-spacer"> </div>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr>
+<td><code class="funcdef">
+void
+<b class="fsfunc">lwres_endhostent</b>(</code></td>
+<td>void<code>)</code>;</td>
+</tr></table>
+<div class="funcprototype-spacer"> </div>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
+<tr>
+<td><code class="funcdef">
+struct hostent *
+<b class="fsfunc">lwres_gethostbyname_r</b>(</code></td>
+<td>const char *<var class="pdparam">name</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>struct hostent *<var class="pdparam">resbuf</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>char *<var class="pdparam">buf</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int <var class="pdparam">buflen</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int *<var class="pdparam">error</var><code>)</code>;</td>
+</tr>
+</table>
+<div class="funcprototype-spacer"> </div>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
+<tr>
+<td><code class="funcdef">
+struct hostent *
+<b class="fsfunc">lwres_gethostbyaddr_r</b>(</code></td>
+<td>const char *<var class="pdparam">addr</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int <var class="pdparam">len</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int <var class="pdparam">type</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>struct hostent *<var class="pdparam">resbuf</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>char *<var class="pdparam">buf</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int <var class="pdparam">buflen</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int *<var class="pdparam">error</var><code>)</code>;</td>
+</tr>
+</table>
+<div class="funcprototype-spacer"> </div>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;">
+<tr>
+<td><code class="funcdef">
+struct hostent *
+<b class="fsfunc">lwres_gethostent_r</b>(</code></td>
+<td>struct hostent *<var class="pdparam">resbuf</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>char *<var class="pdparam">buf</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int <var class="pdparam">buflen</var>, </td>
+</tr>
+<tr>
+<td> </td>
+<td>int *<var class="pdparam">error</var><code>)</code>;</td>
+</tr>
+</table>
+<div class="funcprototype-spacer"> </div>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr>
+<td><code class="funcdef">
+void
+<b class="fsfunc">lwres_sethostent_r</b>(</code></td>
+<td>int <var class="pdparam">stayopen</var><code>)</code>;</td>
+</tr></table>
+<div class="funcprototype-spacer"> </div>
+<table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr>
+<td><code class="funcdef">
+void
+<b class="fsfunc">lwres_endhostent_r</b>(</code></td>
+<td>void<code>)</code>;</td>
+</tr></table>
+<div class="funcprototype-spacer"> </div>
+</div>
+ </div>
+
+ <div class="refsection">
+<a name="id-1.7"></a><h2>DESCRIPTION</h2>
+
+ <p>
+ These functions provide hostname-to-address and
+ address-to-hostname lookups by means of the lightweight resolver.
+ They are similar to the standard
+ <span class="citerefentry">
+ <span class="refentrytitle">gethostent</span>(3)
+ </span>
+ functions provided by most operating systems.
+ They use a
+ <span class="type">struct hostent</span>
+ which is usually defined in
+ <code class="filename">&lt;namedb.h&gt;</code>.
+ </p>
+ <pre class="programlisting">
+struct hostent {
+ char *h_name; /* official name of host */
+ char **h_aliases; /* alias list */
+ int h_addrtype; /* host address type */
+ int h_length; /* length of address */
+ char **h_addr_list; /* list of addresses from name server */
+};
+#define h_addr h_addr_list[0] /* address, for backward compatibility */
+</pre>
+<p>
+ </p>
+ <p>
+ The members of this structure are:
+ </p>
+<div class="variablelist"><dl class="variablelist">
+<dt><span class="term"><code class="constant">h_name</code></span></dt>
+<dd>
+ <p>
+ The official (canonical) name of the host.
+ </p>
+ </dd>
+<dt><span class="term"><code class="constant">h_aliases</code></span></dt>
+<dd>
+ <p>
+ A NULL-terminated array of alternate names (nicknames) for the
+ host.
+ </p>
+ </dd>
+<dt><span class="term"><code class="constant">h_addrtype</code></span></dt>
+<dd>
+ <p>
+ The type of address being returned &#8212;
+ <span class="type">PF_INET</span>
+ or
+ <span class="type">PF_INET6</span>.
+ </p>
+ </dd>
+<dt><span class="term"><code class="constant">h_length</code></span></dt>
+<dd>
+ <p>
+ The length of the address in bytes.
+ </p>
+ </dd>
+<dt><span class="term"><code class="constant">h_addr_list</code></span></dt>
+<dd>
+ <p>
+ A <span class="type">NULL</span>
+ terminated array of network addresses for the host.
+ Host addresses are returned in network byte order.
+ </p>
+ </dd>
+</dl></div>
+<p>
+ </p>
+ <p>
+ For backward compatibility with very old software,
+ <code class="constant">h_addr</code>
+ is the first address in
+ <code class="constant">h_addr_list.</code>
+ </p>
+ <p><code class="function">lwres_gethostent()</code>,
+ <code class="function">lwres_sethostent()</code>,
+ <code class="function">lwres_endhostent()</code>,
+ <code class="function">lwres_gethostent_r()</code>,
+ <code class="function">lwres_sethostent_r()</code>
+ and
+ <code class="function">lwres_endhostent_r()</code>
+ provide iteration over the known host entries on systems that
+ provide such functionality through facilities like
+ <code class="filename">/etc/hosts</code>
+ or NIS. The lightweight resolver does not currently implement
+ these functions; it only provides them as stub functions that always
+ return failure.
+ </p>
+
+ <p><code class="function">lwres_gethostbyname()</code>
+ and <code class="function">lwres_gethostbyname2()</code> look up the
+ hostname <em class="parameter"><code>name</code></em>.
+ <code class="function">lwres_gethostbyname()</code> always looks for an
+ IPv4 address while <code class="function">lwres_gethostbyname2()</code>
+ looks for an address of protocol family
+ <em class="parameter"><code>af</code></em>: either <span class="type">PF_INET</span> or
+ <span class="type">PF_INET6</span> &#8212; IPv4 or IPV6 addresses
+ respectively. Successful calls of the functions return a
+ <span class="type">struct hostent</span>for the name that was looked up.
+ <span class="type">NULL</span> is returned if the lookups by
+ <code class="function">lwres_gethostbyname()</code> or
+ <code class="function">lwres_gethostbyname2()</code> fail.
+ </p>
+
+ <p>
+ Reverse lookups of addresses are performed by
+ <code class="function">lwres_gethostbyaddr()</code>.
+ <em class="parameter"><code>addr</code></em> is an address of length
+ <em class="parameter"><code>len</code></em> bytes and protocol family
+ <em class="parameter"><code>type</code></em> &#8212; <span class="type">PF_INET</span> or
+ <span class="type">PF_INET6</span>.
+ <code class="function">lwres_gethostbyname_r()</code> is a
+ thread-safe function
+ for forward lookups. If an error occurs, an error code is returned in
+ <em class="parameter"><code>*error</code></em>.
+ <em class="parameter"><code>resbuf</code></em> is a pointer to a
+ <span class="type">struct hostent</span> which is initialised by a successful call to
+ <code class="function">lwres_gethostbyname_r()</code>.
+ <em class="parameter"><code>buf</code></em> is a buffer of length
+ <em class="parameter"><code>len</code></em> bytes which is used to store the
+ <code class="constant">h_name</code>, <code class="constant">h_aliases</code>, and
+ <code class="constant">h_addr_list</code> elements of the
+ <span class="type">struct hostent</span> returned in <em class="parameter"><code>resbuf</code></em>.
+ Successful calls to <code class="function">lwres_gethostbyname_r()</code>
+ return <em class="parameter"><code>resbuf</code></em>,
+ which is a pointer to the <span class="type">struct hostent</span> it created.
+ </p>
+
+ <p><code class="function">lwres_gethostbyaddr_r()</code>
+ is a thread-safe function
+ that performs a reverse lookup of address <em class="parameter"><code>addr</code></em>
+ which is <em class="parameter"><code>len</code></em> bytes long and is of
+ protocol
+ family <em class="parameter"><code>type</code></em> &#8212; <span class="type">PF_INET</span> or
+ <span class="type">PF_INET6</span>. If an error occurs, the error code is returned
+ in <em class="parameter"><code>*error</code></em>. The other function
+ parameters are
+ identical to those in <code class="function">lwres_gethostbyname_r()</code>.
+ <em class="parameter"><code>resbuf</code></em> is a pointer to a
+ <span class="type">struct hostent</span> which is initialised by a successful call to
+ <code class="function">lwres_gethostbyaddr_r()</code>.
+ <em class="parameter"><code>buf</code></em> is a buffer of length
+ <em class="parameter"><code>len</code></em> bytes which is used to store the
+ <code class="constant">h_name</code>, <code class="constant">h_aliases</code>, and
+ <code class="constant">h_addr_list</code> elements of the
+ <span class="type">struct hostent</span> returned in <em class="parameter"><code>resbuf</code></em>.
+ Successful calls to <code class="function">lwres_gethostbyaddr_r()</code> return
+ <em class="parameter"><code>resbuf</code></em>, which is a pointer to the
+ <code class="function">struct hostent()</code> it created.
+ </p>
+
+ </div>
+
+ <div class="refsection">
+<a name="id-1.8"></a><h2>RETURN VALUES</h2>
+
+ <p>
+ The functions
+ <code class="function">lwres_gethostbyname()</code>,
+ <code class="function">lwres_gethostbyname2()</code>,
+ <code class="function">lwres_gethostbyaddr()</code>,
+ and
+ <code class="function">lwres_gethostent()</code>
+ return NULL to indicate an error. In this case the global variable
+ <span class="type">lwres_h_errno</span>
+ will contain one of the following error codes defined in
+ <code class="filename">&lt;lwres/netdb.h&gt;</code>:
+
+ </p>
+<div class="variablelist"><dl class="variablelist">
+<dt><span class="term"><code class="constant">HOST_NOT_FOUND</code></span></dt>
+<dd>
+ <p>
+ The host or address was not found.
+ </p>
+ </dd>
+<dt><span class="term"><code class="constant">TRY_AGAIN</code></span></dt>
+<dd>
+ <p>
+ A recoverable error occurred, e.g., a timeout.
+ Retrying the lookup may succeed.
+ </p>
+ </dd>
+<dt><span class="term"><code class="constant">NO_RECOVERY</code></span></dt>
+<dd>
+ <p>
+ A non-recoverable error occurred.
+ </p>
+ </dd>
+<dt><span class="term"><code class="constant">NO_DATA</code></span></dt>
+<dd>
+ <p>
+ The name exists, but has no address information
+ associated with it (or vice versa in the case
+ of a reverse lookup). The code NO_ADDRESS
+ is accepted as a synonym for NO_DATA for backwards
+ compatibility.
+ </p>
+ </dd>
+</dl></div>
+<p>
+ </p>
+
+ <p><span class="citerefentry">
+ <span class="refentrytitle">lwres_hstrerror</span>(3)
+ </span>
+ translates these error codes to suitable error messages.
+ </p>
+
+ <p><code class="function">lwres_gethostent()</code>
+ and <code class="function">lwres_gethostent_r()</code>
+ always return <span class="type">NULL</span>.
+ </p>
+
+ <p>
+ Successful calls to <code class="function">lwres_gethostbyname_r()</code> and
+ <code class="function">lwres_gethostbyaddr_r()</code> return
+ <em class="parameter"><code>resbuf</code></em>, a pointer to the
+ <span class="type">struct hostent</span> that was initialised by these functions. They return
+ <span class="type">NULL</span> if the lookups fail or if <em class="parameter"><code>buf</code></em>
+ was too small to hold the list of addresses and names referenced by
+ the <code class="constant">h_name</code>, <code class="constant">h_aliases</code>, and
+ <code class="constant">h_addr_list</code> elements of the
+ <span class="type">struct hostent</span>.
+ If <em class="parameter"><code>buf</code></em> was too small, both
+ <code class="function">lwres_gethostbyname_r()</code> and
+ <code class="function">lwres_gethostbyaddr_r()</code> set the global
+ variable
+ <span class="type">errno</span> to <span class="errorcode">ERANGE</span>.
+ </p>
+
+ </div>
+ <div class="refsection">
+<a name="id-1.9"></a><h2>SEE ALSO</h2>
+
+ <p><span class="citerefentry">
+ <span class="refentrytitle">gethostent</span>(3)
+ </span>,
+
+ <span class="citerefentry">
+ <span class="refentrytitle">lwres_getipnode</span>(3)
+ </span>,
+
+ <span class="citerefentry">
+ <span class="refentrytitle">lwres_hstrerror</span>(3)
+ </span>
+ </p>
+ </div>
+
+ <div class="refsection">
+<a name="id-1.10"></a><h2>BUGS</h2>
+
+ <p><code class="function">lwres_gethostbyname()</code>,
+ <code class="function">lwres_gethostbyname2()</code>,
+ <code class="function">lwres_gethostbyaddr()</code>
+ and
+ <code class="function">lwres_endhostent()</code>
+ are not thread safe; they return pointers to static data and
+ provide error codes through a global variable.
+ Thread-safe versions for name and address lookup are provided by
+ <code class="function">lwres_gethostbyname_r()</code>,
+ and
+ <code class="function">lwres_gethostbyaddr_r()</code>
+ respectively.
+ </p>
+ <p>
+ The resolver daemon does not currently support any non-DNS
+ name services such as
+ <code class="filename">/etc/hosts</code>
+ or
+ <span class="type">NIS</span>,
+ consequently the above functions don't, either.
+ </p>
+ </div>
+</div></body>
+</html>