<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.1//EN"><!-- - Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC") - Copyright (C) 2001, 2003  Internet Software Consortium. - - Permission to use, copy, modify, and distribute this software for any - purpose with or without fee is hereby granted, provided that the above - copyright notice and this permission notice appear in all copies. - - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY - AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR - PERFORMANCE OF THIS SOFTWARE.--><!-- $Id: lwres_getaddrinfo.docbook,v 1.2 2004/09/20 18:00:50 mcr Exp $ --><refentry><refentryinfo><date>Jun 30, 2000</date></refentryinfo><refmeta><refentrytitle>lwres_getaddrinfo</refentrytitle><manvolnum>3</manvolnum><refmiscinfo>BIND9</refmiscinfo></refmeta><refnamediv><refname>lwres_getaddrinfo</refname><refname>lwres_freeaddrinfo</refname><refpurpose>socket address structure to host and service name</refpurpose></refnamediv><refsynopsisdiv><funcsynopsis><funcsynopsisinfo>#include &lt;lwres/netdb.h&gt;</funcsynopsisinfo><funcprototype><funcdef>int<function>lwres_getaddrinfo</function></funcdef><paramdef>const char *hostname</paramdef><paramdef>const char *servname</paramdef><paramdef>const struct addrinfo *hints</paramdef><paramdef>struct addrinfo **res</paramdef></funcprototype><funcprototype><funcdef>void<function>lwres_freeaddrinfo</function></funcdef><paramdef>struct addrinfo *ai</paramdef></funcprototype></funcsynopsis><para>If the operating system does not provide a<type>struct addrinfo</type>,the following structure is used:<programlisting>struct  addrinfo {        int             ai_flags;       /* AI_PASSIVE, AI_CANONNAME */        int             ai_family;      /* PF_xxx */        int             ai_socktype;    /* SOCK_xxx */        int             ai_protocol;    /* 0 or IPPROTO_xxx for IPv4 and IPv6 */        size_t          ai_addrlen;     /* length of ai_addr */        char            *ai_canonname;  /* canonical name for hostname */        struct sockaddr *ai_addr;       /* binary address */        struct addrinfo *ai_next;       /* next structure in linked list */};</programlisting></para></refsynopsisdiv><refsect1><title>DESCRIPTION</title><para><function>lwres_getaddrinfo()</function>is used to get a list of IP addresses and port numbers for host<parameter>hostname</parameter>and service<parameter>servname</parameter>.The function is the lightweight resolver's implementation of<function>getaddrinfo()</function>as defined in RFC2133.<parameter>hostname</parameter>and<parameter>servname</parameter>are pointers to null-terminatedstrings or<type>NULL</type>.<parameter>hostname</parameter>is either a host name or a numeric host address string: a dotted decimalIPv4 address or an IPv6 address.<parameter>servname</parameter>is either a decimal port number or a service name as listed in<filename>/etc/services</filename>.</para><para><parameter>hints</parameter>is an optional pointer to a<type>struct addrinfo</type>.This structure can be used to provide hints concerning the type of socketthat the caller supports or wishes to use.The caller can supply the following structure elements in<parameter>*hints</parameter>:<variablelist><varlistentry><term><constant>ai_family</constant></term><listitem><para>The protocol family that should be used.When<constant>ai_family</constant>is set to<type>PF_UNSPEC</type>,it means the caller will accept any protocol family supported by theoperating system.</para></listitem></varlistentry><varlistentry><term><constant>ai_socktype</constant></term><listitem><para>denotes the type of socket &mdash;<type>SOCK_STREAM</type>,<type>SOCK_DGRAM</type>or<type>SOCK_RAW</type>&mdash; that is wanted.When<constant>ai_socktype</constant>is zero the caller will accept any socket type.</para></listitem></varlistentry><varlistentry><term><constant>ai_protocol</constant></term><listitem><para>indicates which transport protocol is wanted: IPPROTO_UDP or IPPROTO_TCP.If<constant>ai_protocol</constant>is zero the caller will accept any protocol.</para></listitem></varlistentry><varlistentry><term><constant>ai_flags</constant></term><listitem><para>Flag bits.If the<type>AI_CANONNAME</type>bit is set, a successful call to<function>lwres_getaddrinfo()</function>will return a null-terminated string containing the canonical nameof the specified hostname in<constant>ai_canonname</constant>of the first<type>addrinfo</type>structure returned.Setting the<type>AI_PASSIVE</type>bit indicates that the returned socket address structure is intendedfor used in a call to<citerefentry><refentrytitle>bind</refentrytitle><manvolnum>2</manvolnum></citerefentry>.In this case, if the hostname argument is a<type>NULL</type>pointer, then the IP address portion of the socketaddress structure will be set to<type>INADDR_ANY</type>for an IPv4 address or<type>IN6ADDR_ANY_INIT</type>for an IPv6 address.</para><para>When<constant>ai_flags</constant>does not set the<type>AI_PASSIVE</type>bit, the returned socket address structure will be readyfor use in a call to<citerefentry><refentrytitle>connect</refentrytitle><manvolnum>2</manvolnum></citerefentry>for a connection-oriented protocol or<citerefentry><refentrytitle>connect</refentrytitle><manvolnum>2</manvolnum></citerefentry>,<citerefentry><refentrytitle>sendto</refentrytitle><manvolnum>2</manvolnum></citerefentry>,or<citerefentry><refentrytitle>sendmsg</refentrytitle><manvolnum>2</manvolnum></citerefentry>if a connectionless protocol was chosen.The IP address portion of the socket address structure will beset to the loopback address if<parameter>hostname</parameter>is a<type>NULL</type>pointer and<type>AI_PASSIVE</type>is not set in<constant>ai_flags</constant>.</para><para>If<constant>ai_flags</constant>is set to<type>AI_NUMERICHOST</type>it indicates that<parameter>hostname</parameter>should be treated as a numeric string defining an IPv4 or IPv6 addressand no name resolution should be attempted.</para></listitem></varlistentry></variablelist></para><para>All other elements of the <type>struct addrinfo</type> passedvia <parameter>hints</parameter> must be zero.</para><para>A <parameter>hints</parameter> of <type>NULL</type> is treated as ifthe caller provided a <type>struct addrinfo</type> initialized to zerowith <constant>ai_family</constant>set to<constant>PF_UNSPEC</constant>.</para><para>After a successful call to<function>lwres_getaddrinfo()</function>,<parameter>*res</parameter>is a pointer to a linked list of one or more<type>addrinfo</type>structures.Each<type>struct addrinfo</type>in this list cn be processed by followingthe<constant>ai_next</constant>pointer, until a<type>NULL</type>pointer is encountered.The three members<constant>ai_family</constant>,<constant>ai_socktype</constant>,and<constant>ai_protocol</constant>in eachreturned<type>addrinfo</type>structure contain the corresponding arguments for a call to<citerefentry><refentrytitle>socket</refentrytitle><manvolnum>2</manvolnum></citerefentry>.For each<type>addrinfo</type>structure in the list, the<constant>ai_addr</constant>member points to a filled-in socket address structure of length<constant>ai_addrlen</constant>.</para><para>All of the information returned by<function>lwres_getaddrinfo()</function>is dynamically allocated: the addrinfo structures, and the socketaddress structures and canonical host name strings pointed to by the<constant>addrinfo</constant>structures.Memory allocated for the dynamically allocated structures created bya successful call to<function>lwres_getaddrinfo()</function>is released by<function>lwres_freeaddrinfo()</function>.<parameter>ai</parameter>is a pointer to a<type>struct addrinfo</type>created by a call to<function>lwres_getaddrinfo()</function>.</para></refsect1><refsect1><title>RETURN VALUES</title><para><function>lwres_getaddrinfo()</function>returns zero on success or one of the error codes listed in<citerefentry><refentrytitle>gai_strerror</refentrytitle><manvolnum>3</manvolnum></citerefentry>if an error occurs.If both<parameter>hostname</parameter>and<parameter>servname</parameter>are<type>NULL</type><function>lwres_getaddrinfo()</function>returns<errorcode>EAI_NONAME</errorcode>.</para></refsect1><refsect1><title>SEE ALSO</title><para><citerefentry><refentrytitle>lwres</refentrytitle><manvolnum>3</manvolnum></citerefentry>,<citerefentry><refentrytitle>lwres_getaddrinfo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,<citerefentry><refentrytitle>lwres_freeaddrinfo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,<citerefentry><refentrytitle>lwres_gai_strerror</refentrytitle><manvolnum>3</manvolnum></citerefentry>,<citerefentry><refentrytitle>RFC2133</refentrytitle></citerefentry>,<citerefentry><refentrytitle>getservbyname</refentrytitle><manvolnum>3</manvolnum></citerefentry>,<citerefentry><refentrytitle>bind</refentrytitle><manvolnum>2</manvolnum></citerefentry>,<citerefentry><refentrytitle>connect</refentrytitle><manvolnum>2</manvolnum></citerefentry>,<citerefentry><refentrytitle>sendto</refentrytitle><manvolnum>2</manvolnum></citerefentry>,<citerefentry><refentrytitle>sendmsg</refentrytitle><manvolnum>2</manvolnum></citerefentry>,<citerefentry><refentrytitle>socket</refentrytitle><manvolnum>2</manvolnum></citerefentry>.</para></refsect1></refentry>