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<div id="projectname">lwIP<span id="projectnumber">&#160;2.1.3</span>
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<div id="projectbrief">Lightweight IP stack</div>
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<a href="#func-members">Functions</a> </div>
<div class="headertitle"><div class="title">DNS<div class="ingroups"><a class="el" href="group__api.html">APIs</a> &raquo; <a class="el" href="group__callbackstyle__api.html">&quot;raw&quot; APIs</a></div></div></div>
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<tr class="heading"><td colspan="2"><h2 class="groupheader"><a id="func-members" name="func-members"></a>
Functions</h2></td></tr>
<tr class="memitem:gaf66c5d8273f83cdc2cdd8911fb68d584" id="r_gaf66c5d8273f83cdc2cdd8911fb68d584"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="#gaf66c5d8273f83cdc2cdd8911fb68d584">dns_setserver</a> (u8_t numdns, const <a class="el" href="group__ipaddr.html#ga335a8c9df66319e88a1a529047ce0a1e">ip_addr_t</a> *dnsserver)</td></tr>
<tr class="separator:gaf66c5d8273f83cdc2cdd8911fb68d584"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:gac41de226d156384ae8782cfe370284b0" id="r_gac41de226d156384ae8782cfe370284b0"><td class="memItemLeft" align="right" valign="top">const <a class="el" href="group__ipaddr.html#ga335a8c9df66319e88a1a529047ce0a1e">ip_addr_t</a> *&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="#gac41de226d156384ae8782cfe370284b0">dns_getserver</a> (u8_t numdns)</td></tr>
<tr class="separator:gac41de226d156384ae8782cfe370284b0"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:ga1e040ec38166dc9bfcc3473aab0c799f" id="r_ga1e040ec38166dc9bfcc3473aab0c799f"><td class="memItemLeft" align="right" valign="top"><a class="el" href="group__infrastructure__errors.html#gaf02d9da80fd66b4f986d2c53d7231ddb">err_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="#ga1e040ec38166dc9bfcc3473aab0c799f">dns_gethostbyname</a> (const char *hostname, <a class="el" href="group__ipaddr.html#ga335a8c9df66319e88a1a529047ce0a1e">ip_addr_t</a> *addr, <a class="el" href="dns_8h.html#ab5a9dec5b22802f91876c53e99f427ae">dns_found_callback</a> found, void *callback_arg)</td></tr>
<tr class="separator:ga1e040ec38166dc9bfcc3473aab0c799f"><td class="memSeparator" colspan="2">&#160;</td></tr>
<tr class="memitem:gae84449f60dca6b863142daca8e03ce79" id="r_gae84449f60dca6b863142daca8e03ce79"><td class="memItemLeft" align="right" valign="top"><a class="el" href="group__infrastructure__errors.html#gaf02d9da80fd66b4f986d2c53d7231ddb">err_t</a>&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="#gae84449f60dca6b863142daca8e03ce79">dns_gethostbyname_addrtype</a> (const char *hostname, <a class="el" href="group__ipaddr.html#ga335a8c9df66319e88a1a529047ce0a1e">ip_addr_t</a> *addr, <a class="el" href="dns_8h.html#ab5a9dec5b22802f91876c53e99f427ae">dns_found_callback</a> found, void *callback_arg, u8_t dns_addrtype)</td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<p>Implements a DNS host name to IP address resolver.</p>
<p>The lwIP DNS resolver functions are used to lookup a host name and map it to a numerical IP address. It maintains a list of resolved hostnames that can be queried with the dns_lookup() function. New hostnames can be resolved using the <a class="el" href="structdns__query.html">dns_query()</a> function.</p>
<p>The lwIP version of the resolver also adds a non-blocking version of gethostbyname() that will work with a raw API application. This function checks for an IP address string first and converts it if it is valid. gethostbyname() then does a dns_lookup() to see if the name is already in the table. If so, the IP is returned. If not, a query is issued and the function returns with a ERR_INPROGRESS status. The app using the dns client must then go into a waiting state.</p>
<p>Once a hostname has been resolved (or found to be non-existent), the resolver code calls a specified callback function (which must be implemented by the module that uses the resolver).</p>
<p>Multicast DNS queries are supported for names ending on ".local". However, only "One-Shot Multicast DNS Queries" are supported (RFC 6762 chapter 5.1), this is not a fully compliant implementation of continuous mDNS querying!</p>
<p>All functions must be called from TCPIP thread.</p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="group__lwip__opts__dns.html#ga9f9881c887a8aceb9765820c2dbdf292">DNS_MAX_SERVERS</a> </dd>
<dd>
<a class="el" href="group__lwip__opts__dhcp.html#ga60ccc20fbb08be24b5d5f599dd47a6a6">LWIP_DHCP_MAX_DNS_SERVERS</a> </dd>
<dd>
<a class="el" href="group__netconn__common.html">Common functions</a> for thread-safe access. </dd></dl>
<h2 class="groupheader">Function Documentation</h2>
<a id="ga1e040ec38166dc9bfcc3473aab0c799f" name="ga1e040ec38166dc9bfcc3473aab0c799f"></a>
<h2 class="memtitle"><span class="permalink"><a href="#ga1e040ec38166dc9bfcc3473aab0c799f">&#9670;&#160;</a></span>dns_gethostbyname()</h2>
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<td class="memname"><a class="el" href="group__infrastructure__errors.html#gaf02d9da80fd66b4f986d2c53d7231ddb">err_t</a> dns_gethostbyname </td>
<td>(</td>
<td class="paramtype">const char *</td> <td class="paramname"><span class="paramname"><em>hostname</em></span>, </td>
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<td class="paramkey"></td>
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<td class="paramtype"><a class="el" href="group__ipaddr.html#ga335a8c9df66319e88a1a529047ce0a1e">ip_addr_t</a> *</td> <td class="paramname"><span class="paramname"><em>addr</em></span>, </td>
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<td class="paramtype"><a class="el" href="dns_8h.html#ab5a9dec5b22802f91876c53e99f427ae">dns_found_callback</a></td> <td class="paramname"><span class="paramname"><em>found</em></span>, </td>
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<td class="paramtype">void *</td> <td class="paramname"><span class="paramname"><em>callback_arg</em></span>&#160;)</td>
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<p>Resolve a hostname (string) into an IP address. NON-BLOCKING callback version for use with raw API!!!</p>
<p>Returns immediately with one of err_t return codes:</p><ul>
<li>ERR_OK if hostname is a valid IP address string or the host name is already in the local names table.</li>
<li>ERR_INPROGRESS enqueue a request to be sent to the DNS server for resolution if no errors are present.</li>
<li>ERR_ARG: dns client not initialized or invalid hostname</li>
</ul>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">hostname</td><td>the hostname that is to be queried </td></tr>
<tr><td class="paramname">addr</td><td>pointer to a ip_addr_t where to store the address if it is already cached in the dns_table (only valid if ERR_OK is returned!) </td></tr>
<tr><td class="paramname">found</td><td>a callback function to be called on success, failure or timeout (only if ERR_INPROGRESS is returned!) </td></tr>
<tr><td class="paramname">callback_arg</td><td>argument to pass to the callback function </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>a err_t return code. </dd></dl>
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<a id="gae84449f60dca6b863142daca8e03ce79" name="gae84449f60dca6b863142daca8e03ce79"></a>
<h2 class="memtitle"><span class="permalink"><a href="#gae84449f60dca6b863142daca8e03ce79">&#9670;&#160;</a></span>dns_gethostbyname_addrtype()</h2>
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<td class="memname"><a class="el" href="group__infrastructure__errors.html#gaf02d9da80fd66b4f986d2c53d7231ddb">err_t</a> dns_gethostbyname_addrtype </td>
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<td class="paramtype">const char *</td> <td class="paramname"><span class="paramname"><em>hostname</em></span>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="group__ipaddr.html#ga335a8c9df66319e88a1a529047ce0a1e">ip_addr_t</a> *</td> <td class="paramname"><span class="paramname"><em>addr</em></span>, </td>
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<td class="paramkey"></td>
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<td class="paramtype"><a class="el" href="dns_8h.html#ab5a9dec5b22802f91876c53e99f427ae">dns_found_callback</a></td> <td class="paramname"><span class="paramname"><em>found</em></span>, </td>
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<td class="paramtype">u8_t</td> <td class="paramname"><span class="paramname"><em>dns_addrtype</em></span>&#160;)</td>
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<p>Like dns_gethostbyname, but returned address type can be controlled: </p><dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">hostname</td><td>the hostname that is to be queried </td></tr>
<tr><td class="paramname">addr</td><td>pointer to a ip_addr_t where to store the address if it is already cached in the dns_table (only valid if ERR_OK is returned!) </td></tr>
<tr><td class="paramname">found</td><td>a callback function to be called on success, failure or timeout (only if ERR_INPROGRESS is returned!) </td></tr>
<tr><td class="paramname">callback_arg</td><td>argument to pass to the callback function </td></tr>
<tr><td class="paramname">dns_addrtype</td><td>- LWIP_DNS_ADDRTYPE_IPV4_IPV6: try to resolve IPv4 first, try IPv6 if IPv4 fails only<ul>
<li>LWIP_DNS_ADDRTYPE_IPV6_IPV4: try to resolve IPv6 first, try IPv4 if IPv6 fails only</li>
<li>LWIP_DNS_ADDRTYPE_IPV4: try to resolve IPv4 only</li>
<li>LWIP_DNS_ADDRTYPE_IPV6: try to resolve IPv6 only </li>
</ul>
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<h2 class="memtitle"><span class="permalink"><a href="#gac41de226d156384ae8782cfe370284b0">&#9670;&#160;</a></span>dns_getserver()</h2>
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<td class="memname">const <a class="el" href="group__ipaddr.html#ga335a8c9df66319e88a1a529047ce0a1e">ip_addr_t</a> * dns_getserver </td>
<td>(</td>
<td class="paramtype">u8_t</td> <td class="paramname"><span class="paramname"><em>numdns</em></span></td><td>)</td>
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<p>Obtain one of the currently configured DNS server.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">numdns</td><td>the index of the DNS server </td></tr>
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<dl class="section return"><dt>Returns</dt><dd>IP address of the indexed DNS server or "ip_addr_any" if the DNS server has not been configured. </dd></dl>
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<h2 class="memtitle"><span class="permalink"><a href="#gaf66c5d8273f83cdc2cdd8911fb68d584">&#9670;&#160;</a></span>dns_setserver()</h2>
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<td class="memname">void dns_setserver </td>
<td>(</td>
<td class="paramtype">u8_t</td> <td class="paramname"><span class="paramname"><em>numdns</em></span>, </td>
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<td class="paramtype">const <a class="el" href="group__ipaddr.html#ga335a8c9df66319e88a1a529047ce0a1e">ip_addr_t</a> *</td> <td class="paramname"><span class="paramname"><em>dnsserver</em></span>&#160;)</td>
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<p>Initialize one of the DNS servers.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">numdns</td><td>the index of the DNS server to set must be &lt; DNS_MAX_SERVERS </td></tr>
<tr><td class="paramname">dnsserver</td><td>IP address of the DNS server to set </td></tr>
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</dd>
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