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 - Copyright (C) Internet Systems Consortium, Inc. ("ISC")

 -

 - This Source Code Form is subject to the terms of the Mozilla Public

 - License, v. 2.0. If a copy of the MPL was not distributed with this

 - file, You can obtain one at http://mozilla.org/MPL/2.0/.

 -

 - See the COPYRIGHT file distributed with this work for additional

 - information regarding copyright ownership.

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<refentry xmlns:db="http://docbook.org/ns/docbook" version="5.0">

  <info>

    <date>2007-06-18</date>

  </info>

  <refentryinfo>

    <corpname>ISC</corpname>

    <corpauthor>Internet Systems Consortium, Inc.</corpauthor>

  </refentryinfo>

  <refmeta>

    <refentrytitle>lwres_context</refentrytitle>

    <manvolnum>3</manvolnum>

    <refmiscinfo>BIND9</refmiscinfo>

  </refmeta>

  <docinfo>

    <copyright>

      <year>2000</year>

      <year>2001</year>

      <year>2003</year>

      <year>2004</year>

      <year>2005</year>

      <year>2007</year>

      <year>2014</year>

      <year>2015</year>

      <year>2016</year>

      <year>2018</year>

      <year>2019</year>

      <year>2020</year>

      <holder>Internet Systems Consortium, Inc. ("ISC")</holder>

    </copyright>

  </docinfo>

  <refnamediv>

    <refname>lwres_context_create</refname>

    <refname>lwres_context_destroy</refname>

    <refname>lwres_context_nextserial</refname>

    <refname>lwres_context_initserial</refname>

    <refname>lwres_context_freemem</refname>

    <refname>lwres_context_allocmem</refname>

    <refname>lwres_context_sendrecv</refname>

    <refpurpose>lightweight resolver context management</refpurpose>

  </refnamediv>

  <refsynopsisdiv>

    <funcsynopsis>

<funcsynopsisinfo>#include <lwres/lwres.h></funcsynopsisinfo>

<funcprototype>

        <funcdef>

lwres_result_t

<function>lwres_context_create</function></funcdef>

        <paramdef>lwres_context_t **<parameter>contextp</parameter></paramdef>

        <paramdef>void *<parameter>arg</parameter></paramdef>

        <paramdef>lwres_malloc_t <parameter>malloc_function</parameter></paramdef>

        <paramdef>lwres_free_t <parameter>free_function</parameter></paramdef>

        </funcprototype>

<funcprototype>

        <funcdef>

lwres_result_t

<function>lwres_context_destroy</function></funcdef>

        <paramdef>lwres_context_t **<parameter>contextp</parameter></paramdef>

        </funcprototype>

<funcprototype>

        <funcdef>

void

<function>lwres_context_initserial</function></funcdef>

        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>

        <paramdef>uint32_t <parameter>serial</parameter></paramdef>

        </funcprototype>

<funcprototype>

        <funcdef>

uint32_t

<function>lwres_context_nextserial</function></funcdef>

        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>

        </funcprototype>

<funcprototype>

        <funcdef>

void

<function>lwres_context_freemem</function></funcdef>

        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>

        <paramdef>void *<parameter>mem</parameter></paramdef>

        <paramdef>size_t <parameter>len</parameter></paramdef>

        </funcprototype>

<funcprototype>

        <funcdef>

void

<function>lwres_context_allocmem</function></funcdef>

        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>

        <paramdef>size_t <parameter>len</parameter></paramdef>

        </funcprototype>

<funcprototype>

        <funcdef>

void *

<function>lwres_context_sendrecv</function></funcdef>

        <paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>

        <paramdef>void *<parameter>sendbase</parameter></paramdef>

        <paramdef>int <parameter>sendlen</parameter></paramdef>

        <paramdef>void *<parameter>recvbase</parameter></paramdef>

        <paramdef>int <parameter>recvlen</parameter></paramdef>

        <paramdef>int *<parameter>recvd_len</parameter></paramdef>

      </funcprototype>

</funcsynopsis>

  </refsynopsisdiv>

  <refsection><info><title>DESCRIPTION</title></info>

    <para><function>lwres_context_create()</function>

      creates a <type>lwres_context_t</type> structure for use in

      lightweight resolver operations.  It holds a socket and other

      data needed for communicating with a resolver daemon.  The new

      <type>lwres_context_t</type> is returned through

      <parameter>contextp</parameter>, a pointer to a

      <type>lwres_context_t</type> pointer.  This

      <type>lwres_context_t</type> pointer must initially be NULL, and

      is modified to point to the newly created

      <type>lwres_context_t</type>.

    </para>

    <para>

      When the lightweight resolver needs to perform dynamic memory

      allocation, it will call

      <parameter>malloc_function</parameter>

      to allocate memory and

      <parameter>free_function</parameter>

      to free it.  If

      <parameter>malloc_function</parameter>

      and

      <parameter>free_function</parameter>

      are NULL, memory is allocated using

      <citerefentry>

        <refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum>

      </citerefentry>.

      and

      <citerefentry>

        <refentrytitle>free</refentrytitle><manvolnum>3</manvolnum>

      </citerefentry>.

      It is not permitted to have a NULL

      <parameter>malloc_function</parameter> and a non-NULL

      <parameter>free_function</parameter> or vice versa.

      <parameter>arg</parameter> is passed as the first parameter to

      the memory allocation functions.  If

      <parameter>malloc_function</parameter> and

      <parameter>free_function</parameter> are NULL,

      <parameter>arg</parameter> is unused and should be passed as

      NULL.

    </para>

    <para>

      Once memory for the structure has been allocated,

      it is initialized using

      <citerefentry>

        <refentrytitle>lwres_conf_init</refentrytitle><manvolnum>3</manvolnum>

      </citerefentry>

      and returned via <parameter>*contextp</parameter>.

    </para>

    <para><function>lwres_context_destroy()</function>

      destroys a <type>lwres_context_t</type>, closing its socket.

      <parameter>contextp</parameter> is a pointer to a pointer to the

      context that is to be destroyed.  The pointer will be set to

      NULL when the context has been destroyed.

    </para>

    <para>

      The context holds a serial number that is used to identify

      resolver request packets and associate responses with the

      corresponding requests.  This serial number is controlled using

      <function>lwres_context_initserial()</function> and

      <function>lwres_context_nextserial()</function>.

      <function>lwres_context_initserial()</function> sets the serial

      number for context <parameter>*ctx</parameter> to

      <parameter>serial</parameter>.

      <function>lwres_context_nextserial()</function> increments the

      serial number and returns the previous value.

    </para>

    <para>

      Memory for a lightweight resolver context is allocated and freed

      using <function>lwres_context_allocmem()</function> and

      <function>lwres_context_freemem()</function>.  These use

      whatever allocations were defined when the context was created

      with <function>lwres_context_create()</function>.

      <function>lwres_context_allocmem()</function> allocates

      <parameter>len</parameter> bytes of memory and if successful

      returns a pointer to the allocated storage.

      <function>lwres_context_freemem()</function> frees

      <parameter>len</parameter> bytes of space starting at location

      <parameter>mem</parameter>.

    </para>

    <para><function>lwres_context_sendrecv()</function>

      performs I/O for the context <parameter>ctx</parameter>.  Data

      are read and written from the context's socket.  It writes data

      from <parameter>sendbase</parameter> — typically a

      lightweight resolver query packet — and waits for a reply

      which is copied to the receive buffer at

      <parameter>recvbase</parameter>.  The number of bytes that were

      written to this receive buffer is returned in

      <parameter>*recvd_len</parameter>.

    </para>

  </refsection>

  <refsection><info><title>RETURN VALUES</title></info>

    <para><function>lwres_context_create()</function>

      returns <errorcode>LWRES_R_NOMEMORY</errorcode> if memory for

      the <type>struct lwres_context</type> could not be allocated,

      <errorcode>LWRES_R_SUCCESS</errorcode> otherwise.

    </para>

    <para>

      Successful calls to the memory allocator

      <function>lwres_context_allocmem()</function>

      return a pointer to the start of the allocated space.

      It returns NULL if memory could not be allocated.

    </para>

    <para><errorcode>LWRES_R_SUCCESS</errorcode>

      is returned when

      <function>lwres_context_sendrecv()</function>

      completes successfully.

      <errorcode>LWRES_R_IOERROR</errorcode>

      is returned if an I/O error occurs and

      <errorcode>LWRES_R_TIMEOUT</errorcode>

      is returned if

      <function>lwres_context_sendrecv()</function>

      times out waiting for a response.

    </para>

  </refsection>

  <refsection><info><title>SEE ALSO</title></info>

    <para><citerefentry>

        <refentrytitle>lwres_conf_init</refentrytitle><manvolnum>3</manvolnum>

      </citerefentry>,

      <citerefentry>

        <refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum>

      </citerefentry>,

      <citerefentry>

        <refentrytitle>free</refentrytitle><manvolnum>3</manvolnum>

      </citerefentry>.

    </para>

  </refsection>

</refentry>