lwres_getaddrinfo.docbook

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<refentry>

  <refentryinfo>
    <date>Jun 30, 2000</date>
  </refentryinfo>

  <refmeta>
    <refentrytitle>lwres_getaddrinfo</refentrytitle>
    <manvolnum>3</manvolnum>
    <refmiscinfo>BIND9</refmiscinfo>
  </refmeta>

  <docinfo>
    <copyright>
      <year>2004</year>
      <year>2005</year>
      <year>2007</year>
      <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
    </copyright>
    <copyright>
      <year>2000</year>
      <year>2001</year>
      <year>2003</year>
      <holder>Internet Software Consortium.</holder>
    </copyright>
  </docinfo>

  <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 *<parameter>hostname</parameter></paramdef>
        <paramdef>const char *<parameter>servname</parameter></paramdef>
        <paramdef>const struct addrinfo *<parameter>hints</parameter></paramdef>
        <paramdef>struct addrinfo **<parameter>res</parameter></paramdef>
        </funcprototype>
<funcprototype>
        <funcdef>
void
<function>lwres_freeaddrinfo</function></funcdef>
        <paramdef>struct addrinfo *<parameter>ai</parameter></paramdef>
      </funcprototype>
</funcsynopsis>

    <para>
      If the operating system does not provide a
      <type>struct addrinfo</type>,
      the following structure is used:
    </para>
    <para><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-terminated
      strings or <type>NULL</type>.

      <parameter>hostname</parameter> is either a host name or a
      numeric host address string: a dotted decimal IPv4 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
      socket
      that 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
              the
              operating 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
              name
              of 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
              intended
              for 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 socket
              address 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 ready
              for 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 be
              set 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
              address
              and no name resolution should be attempted.
            </para>
          </listitem>
        </varlistentry>
      </variablelist>
    </para>

    <para>
      All other elements of the <type>struct addrinfo</type> passed
      via <parameter>hints</parameter> must be zero.
    </para>

    <para>
      A <parameter>hints</parameter> of <type>NULL</type> is
      treated as if
      the caller provided a <type>struct addrinfo</type> initialized to zero
      with <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 following
      the
      <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 each
      returned
      <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 socket
      address structures and canonical host name strings pointed to by the
      <constant>addrinfo</constant>structures.
      Memory allocated for the dynamically allocated structures created by
      a 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>
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