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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>

<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 &lt;lwres/lwres.h&gt;</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>lwres_uint32_t <parameter>serial</parameter></paramdef>

</funcprototype>

<funcprototype>

<funcdef>

lwres_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> &mdash; typically a

lightweight resolver query packet &mdash; 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>