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
263 lines
9.8 KiB
Plaintext
263 lines
9.8 KiB
Plaintext
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
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[<!ENTITY mdash "—">]>
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<!--
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- Copyright (C) 2004, 2005, 2007, 2014 Internet Systems Consortium, Inc. ("ISC")
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- Copyright (C) 2000, 2001, 2003 Internet Software Consortium.
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-
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- Permission to use, copy, modify, and/or distribute this software for any
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- purpose with or without fee is hereby granted, provided that the above
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- copyright notice and this permission notice appear in all copies.
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-
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- THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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- AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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- OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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- PERFORMANCE OF THIS SOFTWARE.
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-->
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<refentry>
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<refentryinfo>
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<date>June 18, 2007</date>
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</refentryinfo>
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<refmeta>
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<refentrytitle>lwres_context</refentrytitle>
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<manvolnum>3</manvolnum>
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<refmiscinfo>BIND9</refmiscinfo>
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</refmeta>
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<docinfo>
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<copyright>
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<year>2004</year>
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<year>2005</year>
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<year>2007</year>
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<year>2014</year>
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<holder>Internet Systems Consortium, Inc. ("ISC")</holder>
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</copyright>
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<copyright>
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<year>2000</year>
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<year>2001</year>
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<year>2003</year>
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<holder>Internet Software Consortium.</holder>
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</copyright>
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</docinfo>
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<refnamediv>
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<refname>lwres_context_create</refname>
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<refname>lwres_context_destroy</refname>
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<refname>lwres_context_nextserial</refname>
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<refname>lwres_context_initserial</refname>
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<refname>lwres_context_freemem</refname>
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<refname>lwres_context_allocmem</refname>
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<refname>lwres_context_sendrecv</refname>
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<refpurpose>lightweight resolver context management</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <lwres/lwres.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>
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lwres_result_t
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<function>lwres_context_create</function></funcdef>
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<paramdef>lwres_context_t **<parameter>contextp</parameter></paramdef>
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<paramdef>void *<parameter>arg</parameter></paramdef>
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<paramdef>lwres_malloc_t <parameter>malloc_function</parameter></paramdef>
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<paramdef>lwres_free_t <parameter>free_function</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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lwres_result_t
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<function>lwres_context_destroy</function></funcdef>
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<paramdef>lwres_context_t **<parameter>contextp</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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void
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<function>lwres_context_initserial</function></funcdef>
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<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
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<paramdef>lwres_uint32_t <parameter>serial</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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lwres_uint32_t
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<function>lwres_context_nextserial</function></funcdef>
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<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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void
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<function>lwres_context_freemem</function></funcdef>
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<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
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<paramdef>void *<parameter>mem</parameter></paramdef>
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<paramdef>size_t <parameter>len</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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void
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<function>lwres_context_allocmem</function></funcdef>
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<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
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<paramdef>size_t <parameter>len</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>
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void *
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<function>lwres_context_sendrecv</function></funcdef>
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<paramdef>lwres_context_t *<parameter>ctx</parameter></paramdef>
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<paramdef>void *<parameter>sendbase</parameter></paramdef>
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<paramdef>int <parameter>sendlen</parameter></paramdef>
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<paramdef>void *<parameter>recvbase</parameter></paramdef>
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<paramdef>int <parameter>recvlen</parameter></paramdef>
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<paramdef>int *<parameter>recvd_len</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>DESCRIPTION</title>
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<para><function>lwres_context_create()</function>
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creates a <type>lwres_context_t</type> structure for use in
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lightweight resolver operations. It holds a socket and other
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data needed for communicating with a resolver daemon. The new
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<type>lwres_context_t</type> is returned through
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<parameter>contextp</parameter>, a pointer to a
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<type>lwres_context_t</type> pointer. This
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<type>lwres_context_t</type> pointer must initially be NULL, and
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is modified to point to the newly created
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<type>lwres_context_t</type>.
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</para>
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<para>
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When the lightweight resolver needs to perform dynamic memory
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allocation, it will call
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<parameter>malloc_function</parameter>
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to allocate memory and
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<parameter>free_function</parameter>
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to free it. If
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<parameter>malloc_function</parameter>
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and
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<parameter>free_function</parameter>
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are NULL, memory is allocated using
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<citerefentry>
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<refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>.
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and
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<citerefentry>
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<refentrytitle>free</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>.
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It is not permitted to have a NULL
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<parameter>malloc_function</parameter> and a non-NULL
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<parameter>free_function</parameter> or vice versa.
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<parameter>arg</parameter> is passed as the first parameter to
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the memory allocation functions. If
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<parameter>malloc_function</parameter> and
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<parameter>free_function</parameter> are NULL,
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<parameter>arg</parameter> is unused and should be passed as
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NULL.
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</para>
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<para>
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Once memory for the structure has been allocated,
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it is initialized using
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<citerefentry>
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<refentrytitle>lwres_conf_init</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>
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and returned via <parameter>*contextp</parameter>.
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</para>
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<para><function>lwres_context_destroy()</function>
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destroys a <type>lwres_context_t</type>, closing its socket.
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<parameter>contextp</parameter> is a pointer to a pointer to the
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context that is to be destroyed. The pointer will be set to
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NULL when the context has been destroyed.
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</para>
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<para>
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The context holds a serial number that is used to identify
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resolver request packets and associate responses with the
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corresponding requests. This serial number is controlled using
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<function>lwres_context_initserial()</function> and
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<function>lwres_context_nextserial()</function>.
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<function>lwres_context_initserial()</function> sets the serial
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number for context <parameter>*ctx</parameter> to
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<parameter>serial</parameter>.
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<function>lwres_context_nextserial()</function> increments the
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serial number and returns the previous value.
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</para>
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<para>
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Memory for a lightweight resolver context is allocated and freed
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using <function>lwres_context_allocmem()</function> and
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<function>lwres_context_freemem()</function>. These use
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whatever allocations were defined when the context was created
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with <function>lwres_context_create()</function>.
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<function>lwres_context_allocmem()</function> allocates
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<parameter>len</parameter> bytes of memory and if successful
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returns a pointer to the allocated storage.
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<function>lwres_context_freemem()</function> frees
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<parameter>len</parameter> bytes of space starting at location
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<parameter>mem</parameter>.
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</para>
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<para><function>lwres_context_sendrecv()</function>
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performs I/O for the context <parameter>ctx</parameter>. Data
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are read and written from the context's socket. It writes data
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from <parameter>sendbase</parameter> — typically a
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lightweight resolver query packet — and waits for a reply
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which is copied to the receive buffer at
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<parameter>recvbase</parameter>. The number of bytes that were
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written to this receive buffer is returned in
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<parameter>*recvd_len</parameter>.
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</para>
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</refsect1>
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<refsect1>
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<title>RETURN VALUES</title>
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<para><function>lwres_context_create()</function>
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returns <errorcode>LWRES_R_NOMEMORY</errorcode> if memory for
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the <type>struct lwres_context</type> could not be allocated,
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<errorcode>LWRES_R_SUCCESS</errorcode> otherwise.
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</para>
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<para>
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Successful calls to the memory allocator
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<function>lwres_context_allocmem()</function>
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return a pointer to the start of the allocated space.
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It returns NULL if memory could not be allocated.
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</para>
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<para><errorcode>LWRES_R_SUCCESS</errorcode>
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is returned when
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<function>lwres_context_sendrecv()</function>
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completes successfully.
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<errorcode>LWRES_R_IOERROR</errorcode>
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is returned if an I/O error occurs and
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<errorcode>LWRES_R_TIMEOUT</errorcode>
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is returned if
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<function>lwres_context_sendrecv()</function>
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times out waiting for a response.
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</para>
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</refsect1>
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<refsect1>
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<title>SEE ALSO</title>
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<para><citerefentry>
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<refentrytitle>lwres_conf_init</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>,
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<citerefentry>
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<refentrytitle>free</refentrytitle><manvolnum>3</manvolnum>
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</citerefentry>.
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</para>
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</refsect1>
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</refentry><!--
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- Local variables:
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- mode: sgml
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- End:
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-->
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