<!DOCTYPE html PUBLIC "XSLT-compat"> <html lang="en-GB"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <link rel="stylesheet" type="text/css" href="../../../../common.css"> <meta name="author" content="The Exim Project. <http://www.exim.org/>"> <meta name="copyright" content="Copyright ©2010 The Exim Project. All rights reserved"> <meta name="description" content="Exim is a message transfer agent (MTA) developed at the University of Cambridge for use on Unix systems connected to the Internet."> <meta name="keywords" content="exim,smtp,mta,email"> <meta name="robots" content="noodp,noydir,index,follow"> <meta name="viewport" content="width=device-width"> <title>19. The iplookup router</title> <link rel="stylesheet" type="text/css" href="../../../../doc/chapter.css"> <link rel="canonical" href="http://www.exim.org/exim-html-current/doc/html/spec_html/ch19.html"> </head> <body> <h1 id="header"><a href="../../../..">Exim Internet Mailer</a></h1> <div id="outer"> <ul id="nav_flow" class="nav"> <li><a href="../../../../index.html">Home</a></li> <li><a href="../../../../mirrors.html">Download</a></li> <li><a href="../../../../docs.html">Documentation</a></li> <li><a href="../../../../maillist.html">Mailing Lists</a></li> <li><a href="http://wiki.exim.org/">Wiki</a></li> <li><a href="http://www.exim.org/bugzilla/">Bugs</a></li> <li><a href="../../../../credits.html">Credits</a></li> <li class="search"><form action="http://www.google.com/search" method="get"> <span class="search_field_container"><input type="search" name="q" placeholder="Search Docs" class="search_field"></span><input type="hidden" name="hl" value="en"><input type="hidden" name="ie" value="UTF-8"><input type="hidden" name="as_qdr" value="all"><input type="hidden" name="q" value="site:www.exim.org"><input type="hidden" name="q" value="inurl:exim-html-current"> </form></li> </ul> <div id="inner"><div id="content"> <a class="previous_page" href="ch18.html"><-previous</a><a class="next_page" href="ch20.html">next-></a><div id="chapter" class="chapter"> <h2 id="CHID6" class="">Chapter 19 - The iplookup router</h2> <p> The <span class="docbook_command">iplookup</span> router was written to fulfil a specific requirement in Cambridge University (which in fact no longer exists). For this reason, it is not included in the binary of Exim by default. If you want to include it, you must set </p> <div class="docbook_literallayout"><pre> ROUTER_IPLOOKUP=yes </pre></div> <p> in your <span class="docbook_filename">Local/Makefile</span> configuration file. </p> <p> The <span class="docbook_command">iplookup</span> router routes an address by sending it over a TCP or UDP connection to one or more specific hosts. The host can then return the same or a different address – in effect rewriting the recipient address in the message’s envelope. The new address is then passed on to subsequent routers. If this process fails, the address can be passed on to other routers, or delivery can be deferred. Since <span class="docbook_command">iplookup</span> is just a rewriting router, a transport must not be specified for it. </p> <p> </p> <table> <tr> <td><span class="docbook_option">hosts</span></td> <td>Use: <span class="docbook_emphasis">iplookup</span> </td> <td>Type: <span class="docbook_emphasis">string</span> </td> <td>Default: <span class="docbook_emphasis">unset</span> </td> </tr> </table> <p> This option must be supplied. Its value is a colon-separated list of host names. The hosts are looked up using <span class="docbook_function">gethostbyname()</span> (or <span class="docbook_function">getipnodebyname()</span> when available) and are tried in order until one responds to the query. If none respond, what happens is controlled by <span class="docbook_option">optional</span>. </p> <p> </p> <table> <tr> <td><span class="docbook_option">optional</span></td> <td>Use: <span class="docbook_emphasis">iplookup</span> </td> <td>Type: <span class="docbook_emphasis">boolean</span> </td> <td>Default: <span class="docbook_emphasis">false</span> </td> </tr> </table> <p> If <span class="docbook_option">optional</span> is true, if no response is obtained from any host, the address is passed to the next router, overriding <span class="docbook_option">no_more</span>. If <span class="docbook_option">optional</span> is false, delivery to the address is deferred. </p> <p> </p> <table> <tr> <td><span class="docbook_option">port</span></td> <td>Use: <span class="docbook_emphasis">iplookup</span> </td> <td>Type: <span class="docbook_emphasis">integer</span> </td> <td>Default: <span class="docbook_emphasis">0</span> </td> </tr> </table> <p> This option must be supplied. It specifies the port number for the TCP or UDP call. </p> <p> </p> <table> <tr> <td><span class="docbook_option">protocol</span></td> <td>Use: <span class="docbook_emphasis">iplookup</span> </td> <td>Type: <span class="docbook_emphasis">string</span> </td> <td>Default: <span class="docbook_emphasis">udp</span> </td> </tr> </table> <p> This option can be set to “udp” or “tcp” to specify which of the two protocols is to be used. </p> <p> </p> <table> <tr> <td><span class="docbook_option">query</span></td> <td>Use: <span class="docbook_emphasis">iplookup</span> </td> <td>Type: <span class="docbook_emphasis">string</span>†<span class="docbook_emphasis"></span> </td> <td>Default: <span class="docbook_emphasis">see below</span> </td> </tr> </table> <p> This defines the content of the query that is sent to the remote hosts. The default value is: </p> <div class="docbook_literallayout"><pre> $local_part@$domain $local_part@$domain </pre></div> <p> The repetition serves as a way of checking that a response is to the correct query in the default case (see <span class="docbook_option">response_pattern</span> below). </p> <p> </p> <table> <tr> <td><span class="docbook_option">reroute</span></td> <td>Use: <span class="docbook_emphasis">iplookup</span> </td> <td>Type: <span class="docbook_emphasis">string</span>†<span class="docbook_emphasis"></span> </td> <td>Default: <span class="docbook_emphasis">unset</span> </td> </tr> </table> <p> If this option is not set, the rerouted address is precisely the byte string returned by the remote host, up to the first white space, if any. If set, the string is expanded to form the rerouted address. It can include parts matched in the response by <span class="docbook_option">response_pattern</span> by means of numeric variables such as $1, $2, etc. The variable $0 refers to the entire input string, whether or not a pattern is in use. In all cases, the rerouted address must end up in the form <span class="docbook_emphasis">local_part@domain</span>. </p> <p> </p> <table> <tr> <td><span class="docbook_option">response_pattern</span></td> <td>Use: <span class="docbook_emphasis">iplookup</span> </td> <td>Type: <span class="docbook_emphasis">string</span> </td> <td>Default: <span class="docbook_emphasis">unset</span> </td> </tr> </table> <p> This option can be set to a regular expression that is applied to the string returned from the remote host. If the pattern does not match the response, the router declines. If <span class="docbook_option">response_pattern</span> is not set, no checking of the response is done, unless the query was defaulted, in which case there is a check that the text returned after the first white space is the original address. This checks that the answer that has been received is in response to the correct question. For example, if the response is just a new domain, the following could be used: </p> <div class="docbook_literallayout"><pre> response_pattern = ^([^@]+)$ reroute = $local_part@$1 </pre></div> <p> </p> <table> <tr> <td><span class="docbook_option">timeout</span></td> <td>Use: <span class="docbook_emphasis">iplookup</span> </td> <td>Type: <span class="docbook_emphasis">time</span> </td> <td>Default: <span class="docbook_emphasis">5s</span> </td> </tr> </table> <p> This specifies the amount of time to wait for a response from the remote machine. The same timeout is used for the <span class="docbook_function">connect()</span> function for a TCP call. 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