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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-07 02:04:06 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-07 02:04:06 +0000 |
| commit | 5dff2d61cc1c27747ee398e04d8e02843aabb1f8 (patch) | |
| tree | a67c336b406c8227bac912beb74a1ad3cdc55100 /docs/manual/vhosts/details.html.en | |
| parent | Initial commit. (diff) | |
| download | apache2-upstream.tar.xz apache2-upstream.zip | |
Adding upstream version 2.4.38.upstream/2.4.38upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'docs/manual/vhosts/details.html.en')
| -rw-r--r-- | docs/manual/vhosts/details.html.en | 348 |
1 files changed, 348 insertions, 0 deletions
diff --git a/docs/manual/vhosts/details.html.en b/docs/manual/vhosts/details.html.en new file mode 100644 index 0000000..7fb89cc --- /dev/null +++ b/docs/manual/vhosts/details.html.en @@ -0,0 +1,348 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head> +<meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type" /> +<!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>An In-Depth Discussion of Virtual Host Matching - Apache HTTP Server Version 2.4</title> +<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> +<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> +<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" /> +<script src="../style/scripts/prettify.min.js" type="text/javascript"> +</script> + +<link href="../images/favicon.ico" rel="shortcut icon" /></head> +<body id="manual-page"><div id="page-header"> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> +<p class="apache">Apache HTTP Server Version 2.4</p> +<img alt="" src="../images/feather.png" /></div> +<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div> +<div id="path"> +<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.4</a> > <a href="./">Virtual Hosts</a></div><div id="page-content"><div id="preamble"><h1>An In-Depth Discussion of Virtual Host Matching</h1> +<div class="toplang"> +<p><span>Available Languages: </span><a href="../en/vhosts/details.html" title="English"> en </a> | +<a href="../fr/vhosts/details.html" hreflang="fr" rel="alternate" title="Français"> fr </a> | +<a href="../ko/vhosts/details.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> | +<a href="../tr/vhosts/details.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p> +</div> + + + <p>This document attempts to explain + exactly what Apache HTTP Server does when deciding what virtual host to + serve a request from.</p> + + <p>Most users should read about <a href="name-based.html#namevip"> + Name-based vs. IP-based Virtual Hosts</a> to decide which type they + want to use, then read more about <a href="name-based.html">name-based</a> + or <a href="ip-based.html">IP-based</a> virtualhosts, and then see + <a href="examples.html">some examples</a>.</p> + + <p>If you want to understand all the details, then you can + come back to this page.</p> + +</div> +<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#configparsing">Configuration File</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#hostmatching">Virtual Host Matching</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#tips">Tips</a></li> +</ul><h3>See also</h3><ul class="seealso"><li><a href="ip-based.html">IP-based Virtual Host Support</a></li><li><a href="name-based.html">Name-based Virtual Hosts Support</a></li><li><a href="examples.html">Virtual Host examples for common setups</a></li><li><a href="mass.html">Dynamically configured mass virtual hosting</a></li><li><a href="#comments_section">Comments</a></li></ul></div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="configparsing" id="configparsing">Configuration File</a></h2> + + <p>There is a <em>main server</em> which consists of all the + definitions appearing outside of + <code><VirtualHost></code> sections.</p> + + <p>There are virtual + servers, called <em>vhosts</em>, which are defined by + <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> + sections.</p> + + <p>Each <code>VirtualHost</code> directive includes one + or more addresses and optional ports.</p> + + <p>Hostnames can be used in place of IP addresses in a virtual + host definition, but they are resolved at startup and if any name + resolutions fail, those virtual host definitions are ignored. + This is, therefore, not recommended.</p> + + <p>The address can be specified as + <code>*</code>, which will match a request if no + other vhost has the explicit address on which the request was + received. </p> + + <p>The address appearing in the <code>VirtualHost</code> + directive can have an optional port. If the port is unspecified, + it is treated as a wildcard port, which can also be indicated + explicitly using <code>*</code>. + The wildcard port matches any port.</p> + + <p>(Port numbers specified in the <code>VirtualHost</code> directive do + not influence what port numbers Apache will listen on, they only control + which <code>VirtualHost</code> will be selected to handle a request. + Use the <code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code> directive to + control the addresses and ports on which the server listens.) + </p> + + <p>Collectively the + entire set of addresses (including multiple + results from DNS lookups) are called the vhost's + <em>address set</em>.</p> + + <p>Apache automatically discriminates on the + basis of the HTTP <code>Host</code> header supplied by the client + whenever the most specific match for an IP address and port combination + is listed in multiple virtual hosts.</p> + + <p>The + <code class="directive"><a href="../mod/core.html#servername">ServerName</a></code> directive + may appear anywhere within the definition of a server. However, + each appearance overrides the previous appearance (within that + server). If no <code>ServerName</code> is specified, the server + attempts to deduce it from the server's IP address.</p> + + <p>The first name-based vhost in the configuration file for a + given IP:port pair is significant because it is used for all + requests received on that address and port for which no other + vhost for that IP:port pair has a matching ServerName or + ServerAlias. It is also used for all SSL connections if the + server does not support <a class="glossarylink" href="../glossary.html#servernameindication" title="see glossary">Server Name Indication</a>.</p> + + <p>The complete list of names in the <code>VirtualHost</code> + directive are treated just like a (non wildcard) <code>ServerAlias</code> + (but are not overridden by any <code>ServerAlias</code> statement).</p> + + <p>For every vhost various default values are set. In + particular:</p> + + <ol> + <li>If a vhost has no <code class="directive"><a href="../mod/core.html#serveradmin">ServerAdmin</a></code>, + <code class="directive"><a href="../mod/core.html#timeout">Timeout</a></code>, + <code class="directive"><a href="../mod/core.html#keepalivetimeout">KeepAliveTimeout</a></code>, + <code class="directive"><a href="../mod/core.html#keepalive">KeepAlive</a></code>, + <code class="directive"><a href="../mod/core.html#maxkeepaliverequests">MaxKeepAliveRequests</a></code>, + <code class="directive"><a href="../mod/mpm_common.html#receivebuffersize">ReceiveBufferSize</a></code>, + or <code class="directive"><a href="../mod/mpm_common.html#sendbuffersize">SendBufferSize</a></code> + directive then the respective value is inherited from the + main server. (That is, inherited from whatever the final + setting of that value is in the main server.)</li> + + <li>The "lookup defaults" that define the default directory + permissions for a vhost are merged with those of the + main server. This includes any per-directory configuration + information for any module.</li> + + <li>The per-server configs for each module from the + main server are merged into the vhost server.</li> + </ol> + + <p>Essentially, the main server is treated as "defaults" or a + "base" on which to build each vhost. But the positioning of + these main server definitions in the config file is largely + irrelevant -- the entire config of the main server has been + parsed when this final merging occurs. So even if a main server + definition appears after a vhost definition it might affect the + vhost definition.</p> + + <p>If the main server has no <code>ServerName</code> at this + point, then the hostname of the machine that <code class="program"><a href="../programs/httpd.html">httpd</a></code> + is running on is used instead. We will call the <em>main server address + set</em> those IP addresses returned by a DNS lookup on the + <code>ServerName</code> of the main server.</p> + + <p>For any undefined <code>ServerName</code> fields, a + name-based vhost defaults to the address given first in the + <code>VirtualHost</code> statement defining the vhost.</p> + + <p>Any vhost that includes the magic <code>_default_</code> + wildcard is given the same <code>ServerName</code> as the + main server.</p> + +</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="hostmatching" id="hostmatching">Virtual Host Matching</a></h2> + + <p>The server determines which vhost to use for a request as + follows:</p> + + <h3><a name="hashtable" id="hashtable">IP address lookup</a></h3> + + <p>When the connection is first received on some address and port, + the server looks for all the <code>VirtualHost</code> definitions + that have the same IP address and port.</p> + + <p>If there are no exact matches for the address and port, then + wildcard (<code>*</code>) matches are considered.</p> + + <p>If no matches are found, the request is served by the + main server.</p> + + <p>If there are <code>VirtualHost</code> definitions for + the IP address, the next step is to decide if we have to + deal with an IP-based or a name-based vhost.</p> + + + + <h3><a name="ipbased" id="ipbased">IP-based vhost</a></h3> + + <p>If there is exactly one <code>VirtualHost</code> directive + listing the IP address and port combination that was determined + to be the best match, no further actions are performed and + the request is served from the matching vhost.</p> + + + + <h3><a name="namebased" id="namebased">Name-based vhost</a></h3> + + <p>If there are multiple <code>VirtualHost</code> directives listing + the IP address and port combination that was determined to be the + best match, the "list" in the remaining steps refers to the list of vhosts + that matched, in the order they were in the configuration file.</p> + + <p>If the connection is using SSL, the server supports <a class="glossarylink" href="../glossary.html#servernameindication" title="see glossary">Server Name Indication</a>, and + the SSL client handshake includes the TLS extension with the + requested hostname, then that hostname is used below just like the + <code>Host:</code> header would be used on a non-SSL connection. + Otherwise, the first name-based vhost whose address matched is + used for SSL connections. This is significant because the + vhost determines which certificate the server will use for the + connection.</p> + + <p>If the request contains a <code>Host:</code> header field, the + list is searched for the first vhost with a matching + <code>ServerName</code> or <code>ServerAlias</code>, and the + request is served from that vhost. A <code>Host:</code> header + field can contain a port number, but Apache always ignores it and + matches against the real port to which the client sent the + request.</p> + + <p>The first vhost in the config + file with the specified IP address has the highest priority + and catches any request to an unknown server name, or a request + without a <code>Host:</code> header field (such as a HTTP/1.0 + request).</p> + + + + <h3><a name="persistent" id="persistent">Persistent connections</a></h3> + + <p>The <em>IP lookup</em> described above is only done <em>once</em> for a + particular TCP/IP session while the <em>name lookup</em> is done on + <em>every</em> request during a KeepAlive/persistent + connection. In other words, a client may request pages from + different name-based vhosts during a single persistent + connection.</p> + + + + <h3><a name="absoluteURI" id="absoluteURI">Absolute URI</a></h3> + + <p>If the URI from the request is an absolute URI, and its + hostname and port match the main server or one of the + configured virtual hosts <em>and</em> match the address and + port to which the client sent the request, then the + scheme/hostname/port prefix is stripped off and the remaining + relative URI is served by the corresponding main server or + virtual host. If it does not match, then the URI remains + untouched and the request is taken to be a proxy request.</p> + + +<h3><a name="observations" id="observations">Observations</a></h3> + + <ul> + <li>Name-based virtual hosting is a process applied after + the server has selected the best matching IP-based virtual + host.</li> + + <li>If you don't care what IP address the client has connected to, use a + "*" as the address of every virtual host, and name-based virtual hosting + is applied across all configured virtual hosts.</li> + + <li><code>ServerName</code> and <code>ServerAlias</code> + checks are never performed for an IP-based vhost.</li> + + <li>Only the ordering of + name-based vhosts for a specific address set is significant. + The one name-based vhosts that comes first in the + configuration file has the highest priority for its + corresponding address set.</li> + + <li>Any port in the <code>Host:</code> header field is never used during the + matching process. Apache always uses the real port to which + the client sent the request.</li> + + <li>If two vhosts have an address in common, those common addresses + act as name-based virtual hosts implicitly. This is new behavior as of + 2.3.11.</li> + + <li>The main server is only used to serve a request if the IP + address and port number to which the client connected + does not match any vhost (including a + <code>*</code> vhost). In other words, the main server + only catches a request for an unspecified address/port + combination (unless there is a <code>_default_</code> vhost + which matches that port).</li> + + <li>You should never specify DNS names in + <code>VirtualHost</code> directives because it will force + your server to rely on DNS to boot. Furthermore it poses a + security threat if you do not control the DNS for all the + domains listed. There's <a href="../dns-caveats.html">more + information</a> available on this and the next two + topics.</li> + + <li><code>ServerName</code> should always be set for each + vhost. Otherwise a DNS lookup is required for each + vhost.</li> + </ul> + + +</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="tips" id="tips">Tips</a></h2> + + <p>In addition to the tips on the <a href="../dns-caveats.html#tips">DNS Issues</a> page, here are + some further tips:</p> + + <ul> + <li>Place all main server definitions before any + <code>VirtualHost</code> definitions. (This is to aid the + readability of the configuration -- the post-config merging + process makes it non-obvious that definitions mixed in around + virtual hosts might affect all virtual hosts.)</li> + </ul> + +</div></div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="../en/vhosts/details.html" title="English"> en </a> | +<a href="../fr/vhosts/details.html" hreflang="fr" rel="alternate" title="Français"> fr </a> | +<a href="../ko/vhosts/details.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> | +<a href="../tr/vhosts/details.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p> +</div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div> +<script type="text/javascript"><!--//--><![CDATA[//><!-- +var comments_shortname = 'httpd'; +var comments_identifier = 'http://httpd.apache.org/docs/2.4/vhosts/details.html'; +(function(w, d) { + if (w.location.hostname.toLowerCase() == "httpd.apache.org") { + d.write('<div id="comments_thread"><\/div>'); + var s = d.createElement('script'); + s.type = 'text/javascript'; + s.async = true; + s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier; + (d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s); + } + else { + d.write('<div id="comments_thread">Comments are disabled for this page at the moment.<\/div>'); + } +})(window, document); +//--><!]]></script></div><div id="footer"> +<p class="apache">Copyright 2019 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div><script type="text/javascript"><!--//--><![CDATA[//><!-- +if (typeof(prettyPrint) !== 'undefined') { + prettyPrint(); +} +//--><!]]></script> +</body></html>
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