ibm-information-center/dist/eclipse/plugins/i5OS.ic.apis_5.4.0.1/resninit.htm

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<title>res_ninit()--Initialize res Structure</title>
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<h2>res_ninit()--Initialize res Structure</h2>
<div class="box" style="width: 60%;">
<br>
&nbsp;&nbsp;Syntax<br>
<pre>
#include &lt;sys/types.h&gt;
#include &lt;netinet/in.h&gt;
#include &lt;arpa/nameser.h&gt;
#include &lt;resolv.h&gt;
int res_ninit(state* <em>res</em>)
</pre>
<br>
&nbsp;&nbsp;Service Program Name: QSOSRV2&nbsp;&nbsp;<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Default Public Authority: *USE<br>
<!-- iddvc RMBR -->
<br>
&nbsp;&nbsp;Threadsafe: Yes<br>
<!-- iddvc RMBR -->
<br>
</div>
<p>The <em>res_ninit()</em> function is similar to <em>res_init()</em> but it
uses a user-declared <strong>res</strong> pointer instead of the shared
<strong>_res</strong>.</p>
<p>For a description of this function and more information on the parameters,
authorities required, return values, error conditions, error messages, usage
notes, and related information, see <a href="resini.htm">res_init()</a>--Initialize
_res Structure.</p>
<h3>Parameters</h3>
<dl>
<dt><strong>res</strong></dt>
<dd>(Input/Output) The pointer to the <strong>state</strong> structure.</dd>
</dl>
<p>The RES_INIT and RES_XINIT options flags must be initialized to zero before
the first call to any resolver API or the <strong>res</strong> structure will
not be properly initialized. For example:</p>
<pre>
state res;
res.options &amp;= ~ (RES_INIT | RES_XINIT);
int n = res_ninit(&amp;res);
</pre>
<br>
<h3>Return Value</h3>
<p><em>res_ninit()</em> returns an integer. Possible values are:</p>
<ul>
<li>-1 (unsuccessful)</li>
<li>0 (successful)</li>
</ul>
<br>
<h3>Error Conditions</h3>
<p>When the <em>res_ninit()</em> function fails, <em>errno</em> can be set to
one of the following:</p>
<dl>
<dt><em>[EFAULT]</em></dt>
<dd><p>The system detected a pointer that was invalid
while attempting to access an input pointer.</p></dd>
<dt><em>[EINVAL]</em></dt>
<dd><p>The <strong>res</strong> appears to have been
previously initialized but the reserved field is not set to zeros.</p></dd>
</dl>
<br>
<br>
<h3>Related Information</h3>
<ul>
<li><a href="hstrerror.htm">hstrerror()</a>--Retrieve Resolver Error
Message<br>
<br>
</li>
<li><a href="resini.htm">res_init()</a>--Initialize _res Structure<br>
<br>
</li>
<li><a href="resfindzonecut.htm">res_findzonecut()</a>--Find the Enclosing Zone and
Servers<br>
<br>
</li>
<li><a href="reshostalias.htm">res_hostalias()</a>--Retrieve the host alias<br>
<br>
</li>
<li><a href="resnclose.htm">res_nclose()</a>--Close Socket and Reset res
Structure<br>
<br>
</li>
<li><a href="resnmkquery.htm">res_nmkquery()</a>--Place Domain Query in
Buffer<br>
<br>
</li>
<li><a href="resnquery.htm">res_nquery()</a>--Send Domain Query<br>
<br>
</li>
<li><a href="resnsearch.htm">res_nsearch()</a>--Search for Domain Name<br>
<br>
</li>
<li><a href="resnsend.htm">res_nsend()</a>--Send Buffered Domain Query<br>
<br>
</li>
<li><a href="resxlt.htm">res_xlate()</a>--Translate DNS Packets</li>
</ul>
<br>
<h3>Example</h3>
<p>See <a href="../apiref/aboutapis.htm#codedisclaimer">Code disclaimer information</a>
for information pertaining to code examples.</p>
<p>The following example shows how <strong>res_ninit()</strong> is used and how
initialization defaults can be changed after initialization:</p>
<pre>
#include &lt;stdio.h&gt;
#include &lt;errno.h&gt;
#include &lt;netinet/in.h&gt;
#include &lt;arpa/nameser.h&gt;
#include &lt;resolv.h&gt;
#include &lt;netdb.h&gt;
/* Declare update records - a zone record, a pre-requisite record, and
an update record */
ns_updrec update_records[] =
{
{
{NULL,NULL},
{NULL,&amp;update_records[1]},
ns_s_zn, /* a zone record */
&quot;mydomain.ibm.com.&quot;,
ns_c_in,
ns_t_soa,
0,
NULL,
0,
0,
NULL,
NULL,
0
},
{
{NULL,NULL},
{&amp;update_records[0],&amp;update_records[2]},
ns_s_pr, /* pre-req record */
&quot;mypc.mydomain.ibm.com.&quot;,
ns_c_in,
ns_t_a,
0,
NULL,
0,
ns_r_nxdomain, /* record must not exist */
NULL,
NULL,
0
},
{
{NULL,NULL},
{&amp;update_records[1],NULL},
ns_s_ud, /* update record */
&quot;mypc.mydomain.ibm.com.&quot;,
ns_c_in,
ns_t_a,
10,
(unsigned char *)&quot;10.10.10.10&quot;,
11,
ns_uop_add, /* to be added */
NULL,
NULL,
0
}
};
void main()
{
struct state res;
int result;
unsigned char update_buffer[2048];
int buffer_length = sizeof update_buffer;
unsigned char answer_buffer[2048];
/* Turn off the init flags so that the structure will be initialized
*/
res.options &amp;= ~ (RES_INIT | RES_XINIT);
result = res_ninit(&amp;res);
/* Put processing here to check the result and handle errors
*/
/* We choose to use TCP and not UDP, so set the appropriate option now
that the res variable has been initialized.
*/
res.options |= RES_USEVC;
/* Send a query for mypc.mydomain.ibm.com address records
*/
result = res_nquerydomain(&amp;res,&quot;mypc&quot;, &quot;mydomain.ibm.com.&quot;, ns_c_in, ns_t_a,
update_buffer, buffer_length);
/* Sample error handling and printing errors
*/
if (result == -1)
{
printf(&quot;\nquery domain failed. result = %d \nerrno: %d: %s \nh_errno: %d: %s&quot;,
result,
errno, strerror(errno),
h_errno, hstrerror(h_errno));
return;
}
/* The output on a failure will be:
query domain failed. result = -1
errno: 0: There is no error.
h_errno: 5: Unknown host
*/
{
/* Build an update buffer (packet to be sent) from the update records
*/
result = res_nmkupdate(&amp;res, update_records, update_buffer, buffer_length);
/* Put processing here to check the result and handle errors
*/
}
{
char zone_name[NS_MAXDNAME];
size_t zone_name_size = sizeof zone_name;
struct sockaddr_in s_address;
struct in_addr addresses[1];
int number_addresses = 1;
/* Find the DNS server that is authoritative for the domain
that we want to update
*/
result = res_findzonecut(&amp;res, &quot;mypc.mydomain.ibm.com&quot;, ns_c_in, 0,
zone_name, zone_name_size,
addresses, number_addresses);
/* Put processing here to check the result and handle errors
*/
/* Check if the DNS server found is one of our regular
DNS addresses
*/
s_address.sin_addr = addresses[0];
s_address.sin_family = res.nsaddr_list[0].sin_family;
s_address.sin_port = res.nsaddr_list[0].sin_port;
memset(s_address.sin_zero, 0x00, 8);
result = res_nisourserver(&amp;res, &amp;s_address);
/* Put processing here to check the result and handle errors
*/
/* Set the DNS address found with res_findzonecut into the res
structure. We will send the (TSIG signed) update to that DNS.
*/
res.nscount = 1;
res.nsaddr_list[0] = s_address;
}
{
ns_tsig_key my_key = {
&quot;my-long-key&quot;, /* This key must exist on the DNS */
NS_TSIG_ALG_HMAC_MD5,
(unsigned char*) &quot;abcdefghijklmnopqrstuvwx&quot;,
24
};
/* Send a TSIG signed update to the DNS
*/
result = res_nsendsigned(&amp;res, update_buffer, result,
&amp;my_key,
answer_buffer, sizeof answer_buffer);
/* Put processing here to check the result and handle errors
*/
}
/* The res_findzonecut(), res_nmkupdate(), and res_nsendsigned() could
be replaced with one call to res_nupdate() using update_records[1]
to skip the zone record::
result = res_nupdate(&amp;res, &amp;update_records[1], &amp;my_key);
*/
return;
}
</pre>
<br>
<hr>
API introduced: V5R1
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