00b67f09dd
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
323 lines
13 KiB
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323 lines
13 KiB
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<!--
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- Copyright (C) 2004, 2005, 2007, 2014 Internet Systems Consortium, Inc. ("ISC")
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>lwres_getaddrinfo</title>
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<meta name="generator" content="DocBook XSL Stylesheets V1.71.1">
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</head>
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
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<a name="id2476275"></a><div class="titlepage"></div>
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<div class="refnamediv">
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<h2>Name</h2>
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<p>lwres_getaddrinfo, lwres_freeaddrinfo — socket address structure to host and service name</p>
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</div>
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<div class="refsynopsisdiv">
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<h2>Synopsis</h2>
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<div class="funcsynopsis">
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<pre class="funcsynopsisinfo">#include <lwres/netdb.h></pre>
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<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0" style="padding-bottom: 1em">
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<tr>
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<td><code class="funcdef">
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int
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<b class="fsfunc">lwres_getaddrinfo</b>(</code></td>
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<td>const char * </td>
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<td>
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<var class="pdparam">hostname</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>const char * </td>
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<td>
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<var class="pdparam">servname</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>const struct addrinfo * </td>
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<td>
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<var class="pdparam">hints</var>, </td>
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</tr>
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<tr>
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<td> </td>
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<td>struct addrinfo ** </td>
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<td>
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<var class="pdparam">res</var><code>)</code>;</td>
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</tr>
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</table>
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<table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr>
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<td><code class="funcdef">
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void
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<b class="fsfunc">lwres_freeaddrinfo</b>(</code></td>
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<td>struct addrinfo * </td>
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<td>
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<var class="pdparam">ai</var><code>)</code>;</td>
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</tr></table>
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</div>
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<p>
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If the operating system does not provide a
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<span class="type">struct addrinfo</span>,
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the following structure is used:
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</p>
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<pre class="programlisting">
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struct addrinfo {
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int ai_flags; /* AI_PASSIVE, AI_CANONNAME */
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int ai_family; /* PF_xxx */
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int ai_socktype; /* SOCK_xxx */
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int ai_protocol; /* 0 or IPPROTO_xxx for IPv4 and IPv6 */
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size_t ai_addrlen; /* length of ai_addr */
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char *ai_canonname; /* canonical name for hostname */
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struct sockaddr *ai_addr; /* binary address */
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struct addrinfo *ai_next; /* next structure in linked list */
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};
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</pre>
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<p>
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</p>
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</div>
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<div class="refsect1" lang="en">
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<a name="id2543421"></a><h2>DESCRIPTION</h2>
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<p><code class="function">lwres_getaddrinfo()</code>
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is used to get a list of IP addresses and port numbers for host
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<em class="parameter"><code>hostname</code></em> and service
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<em class="parameter"><code>servname</code></em>.
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The function is the lightweight resolver's implementation of
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<code class="function">getaddrinfo()</code> as defined in RFC2133.
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<em class="parameter"><code>hostname</code></em> and
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<em class="parameter"><code>servname</code></em> are pointers to null-terminated
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strings or <span class="type">NULL</span>.
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<em class="parameter"><code>hostname</code></em> is either a host name or a
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numeric host address string: a dotted decimal IPv4 address or an
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IPv6 address. <em class="parameter"><code>servname</code></em> is either a
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decimal port number or a service name as listed in
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<code class="filename">/etc/services</code>.
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</p>
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<p><em class="parameter"><code>hints</code></em>
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is an optional pointer to a
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<span class="type">struct addrinfo</span>.
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This structure can be used to provide hints concerning the type of
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socket
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that the caller supports or wishes to use.
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The caller can supply the following structure elements in
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<em class="parameter"><code>*hints</code></em>:
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</p>
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<div class="variablelist"><dl>
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<dt><span class="term"><code class="constant">ai_family</code></span></dt>
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<dd><p>
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The protocol family that should be used.
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When
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<code class="constant">ai_family</code>
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is set to
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<span class="type">PF_UNSPEC</span>,
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it means the caller will accept any protocol family supported by
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the
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operating system.
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</p></dd>
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<dt><span class="term"><code class="constant">ai_socktype</code></span></dt>
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<dd><p>
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denotes the type of socket —
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<span class="type">SOCK_STREAM</span>,
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<span class="type">SOCK_DGRAM</span>
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or
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<span class="type">SOCK_RAW</span>
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— that is wanted.
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When
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<code class="constant">ai_socktype</code>
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is zero the caller will accept any socket type.
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</p></dd>
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<dt><span class="term"><code class="constant">ai_protocol</code></span></dt>
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<dd><p>
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indicates which transport protocol is wanted: IPPROTO_UDP or
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IPPROTO_TCP.
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If
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<code class="constant">ai_protocol</code>
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is zero the caller will accept any protocol.
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</p></dd>
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<dt><span class="term"><code class="constant">ai_flags</code></span></dt>
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<dd>
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<p>
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Flag bits.
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If the
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<span class="type">AI_CANONNAME</span>
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bit is set, a successful call to
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<code class="function">lwres_getaddrinfo()</code>
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will return a null-terminated string containing the canonical
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name
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of the specified hostname in
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<code class="constant">ai_canonname</code>
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of the first
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<span class="type">addrinfo</span>
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structure returned.
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Setting the
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<span class="type">AI_PASSIVE</span>
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bit indicates that the returned socket address structure is
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intended
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for used in a call to
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<span class="citerefentry"><span class="refentrytitle">bind</span>(2)</span>.
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In this case, if the hostname argument is a
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<span class="type">NULL</span>
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pointer, then the IP address portion of the socket
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address structure will be set to
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<span class="type">INADDR_ANY</span>
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for an IPv4 address or
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<span class="type">IN6ADDR_ANY_INIT</span>
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for an IPv6 address.
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</p>
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<p>
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When
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<code class="constant">ai_flags</code>
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does not set the
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<span class="type">AI_PASSIVE</span>
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bit, the returned socket address structure will be ready
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for use in a call to
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<span class="citerefentry"><span class="refentrytitle">connect</span>(2)</span>
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for a connection-oriented protocol or
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<span class="citerefentry"><span class="refentrytitle">connect</span>(2)</span>,
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<span class="citerefentry"><span class="refentrytitle">sendto</span>(2)</span>,
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or
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<span class="citerefentry"><span class="refentrytitle">sendmsg</span>(2)</span>
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if a connectionless protocol was chosen.
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The IP address portion of the socket address structure will be
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set to the loopback address if
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<em class="parameter"><code>hostname</code></em>
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is a
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<span class="type">NULL</span>
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pointer and
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<span class="type">AI_PASSIVE</span>
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is not set in
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<code class="constant">ai_flags</code>.
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</p>
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<p>
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If
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<code class="constant">ai_flags</code>
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is set to
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<span class="type">AI_NUMERICHOST</span>
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it indicates that
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<em class="parameter"><code>hostname</code></em>
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should be treated as a numeric string defining an IPv4 or IPv6
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address
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and no name resolution should be attempted.
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</p>
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</dd>
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</dl></div>
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<p>
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</p>
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<p>
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All other elements of the <span class="type">struct addrinfo</span> passed
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via <em class="parameter"><code>hints</code></em> must be zero.
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</p>
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<p>
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A <em class="parameter"><code>hints</code></em> of <span class="type">NULL</span> is
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treated as if
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the caller provided a <span class="type">struct addrinfo</span> initialized to zero
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with <code class="constant">ai_family</code>set to
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<code class="constant">PF_UNSPEC</code>.
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</p>
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<p>
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After a successful call to
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<code class="function">lwres_getaddrinfo()</code>,
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<em class="parameter"><code>*res</code></em>
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is a pointer to a linked list of one or more
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<span class="type">addrinfo</span>
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structures.
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Each
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<span class="type">struct addrinfo</span>
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in this list cn be processed by following
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the
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<code class="constant">ai_next</code>
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pointer, until a
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<span class="type">NULL</span>
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pointer is encountered.
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The three members
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<code class="constant">ai_family</code>,
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<code class="constant">ai_socktype</code>,
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and
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<code class="constant">ai_protocol</code>
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in each
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returned
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<span class="type">addrinfo</span>
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structure contain the corresponding arguments for a call to
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<span class="citerefentry"><span class="refentrytitle">socket</span>(2)</span>.
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For each
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<span class="type">addrinfo</span>
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structure in the list, the
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<code class="constant">ai_addr</code>
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member points to a filled-in socket address structure of length
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<code class="constant">ai_addrlen</code>.
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</p>
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<p>
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All of the information returned by
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<code class="function">lwres_getaddrinfo()</code>
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is dynamically allocated: the addrinfo structures, and the socket
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address structures and canonical host name strings pointed to by the
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<code class="constant">addrinfo</code>structures.
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Memory allocated for the dynamically allocated structures created by
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a successful call to
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<code class="function">lwres_getaddrinfo()</code>
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is released by
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<code class="function">lwres_freeaddrinfo()</code>.
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<em class="parameter"><code>ai</code></em>
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is a pointer to a
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<span class="type">struct addrinfo</span>
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created by a call to
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<code class="function">lwres_getaddrinfo()</code>.
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</p>
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</div>
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<div class="refsect1" lang="en">
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<a name="id2543799"></a><h2>RETURN VALUES</h2>
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<p><code class="function">lwres_getaddrinfo()</code>
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returns zero on success or one of the error codes listed in
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<span class="citerefentry"><span class="refentrytitle">gai_strerror</span>(3)</span>
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if an error occurs. If both <em class="parameter"><code>hostname</code></em> and
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<em class="parameter"><code>servname</code></em> are <span class="type">NULL</span>
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<code class="function">lwres_getaddrinfo()</code> returns
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<span class="errorcode">EAI_NONAME</span>.
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</p>
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</div>
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<div class="refsect1" lang="en">
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<a name="id2543836"></a><h2>SEE ALSO</h2>
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<p><span class="citerefentry"><span class="refentrytitle">lwres</span>(3)</span>,
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<span class="citerefentry"><span class="refentrytitle">lwres_getaddrinfo</span>(3)</span>,
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<span class="citerefentry"><span class="refentrytitle">lwres_freeaddrinfo</span>(3)</span>,
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<span class="citerefentry"><span class="refentrytitle">lwres_gai_strerror</span>(3)</span>,
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<span class="citerefentry"><span class="refentrytitle">RFC2133</span></span>,
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<span class="citerefentry"><span class="refentrytitle">getservbyname</span>(3)</span>,
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<span class="citerefentry"><span class="refentrytitle">bind</span>(2)</span>,
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<span class="citerefentry"><span class="refentrytitle">connect</span>(2)</span>,
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<span class="citerefentry"><span class="refentrytitle">sendto</span>(2)</span>,
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<span class="citerefentry"><span class="refentrytitle">sendmsg</span>(2)</span>,
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<span class="citerefentry"><span class="refentrytitle">socket</span>(2)</span>.
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</p>
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</div>
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</div></body>
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</html>
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