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| author |   hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 01:35:09 -0500 |
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| committer | hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 01:36:35 -0500 |
| commit | cc40af334e619bb549038238507407866f774f8f (patch) | |
| tree | 43ddc1974f72997a57173151eafb23e6025a13c9 /rubbos/app/apache2/manual/vhosts/details.html.en | |
| parent | 68e74fd78b2485e5914ce34a5b30f4485029e021 (diff) | |
upload apache
JIRA: BOTTLENECK-10
Change-Id: I67eae31de6dc824097dfa56ab454ba36fdd23a2c
Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
Diffstat (limited to 'rubbos/app/apache2/manual/vhosts/details.html.en')
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diff --git a/rubbos/app/apache2/manual/vhosts/details.html.en b/rubbos/app/apache2/manual/vhosts/details.html.en new file mode 100644 index 00000000..14ad0dac --- /dev/null +++ b/rubbos/app/apache2/manual/vhosts/details.html.en @@ -0,0 +1,440 @@ +<?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><!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>An In-Depth Discussion of Virtual Host Matching - Apache HTTP Server</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 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="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> +<p class="apache">Apache HTTP Server Version 2.0</p> +<img alt="" src="../images/feather.gif" /></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 2.0</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="../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>The virtual host code was completely rewritten in + <strong>Apache 1.3</strong>. This document attempts to explain + exactly what Apache does when deciding what virtual host to + serve a hit from. With the help of the new + <code class="directive"><a href="../mod/core.html#namevirtualhost">NameVirtualHost</a></code> + directive virtual host configuration should be a lot easier and + safer than with versions prior to 1.3.</p> + + <p>If you just want to <cite>make it work</cite> without + understanding how, here are <a href="examples.html">some + examples</a>.</p> + +</div> +<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#configparsing">Config File Parsing</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></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">Config File Parsing</a></h2> + + <p>There is a <em>main_server</em> which consists of all the + definitions appearing outside of + <code><VirtualHost></code> sections. 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>The directives + <code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code>, + <code class="directive"><a href="../mod/core.html#servername">ServerName</a></code>, + <code class="directive"><a href="../mod/core.html#serverpath">ServerPath</a></code>, + and <code class="directive"><a href="../mod/core.html#serveralias">ServerAlias</a></code> + can appear anywhere within the definition of a server. However, + each appearance overrides the previous appearance (within that + server).</p> + + <p>The default value of the <code>Listen</code> field for + main_server is 80. The main_server has no default + <code>ServerPath</code>, or <code>ServerAlias</code>. The + default <code>ServerName</code> is deduced from the server's IP + address.</p> + + <p>The main_server Listen directive has two functions. One + function is to determine the default network port Apache will + bind to. The second function is to specify the port number + which is used in absolute URIs during redirects.</p> + + <p>Unlike the main_server, vhost ports <em>do not</em> affect + what ports Apache listens for connections on.</p> + + <p>Each address appearing in the <code>VirtualHost</code> + directive can have an optional port. If the port is unspecified + it defaults to the value of the main_server's most recent + <code>Listen</code> statement. The special port <code>*</code> + indicates a wildcard that matches any port. Collectively the + entire set of addresses (including multiple <code>A</code> + record results from DNS lookups) are called the vhost's + <em>address set</em>.</p> + + <p>Unless a <code class="directive"><a href="../mod/core.html#namevirtualhost">NameVirtualHost</a></code> + directive is used for a specific IP address the first vhost + with that address is treated as an IP-based vhost. The IP + address can also be the wildcard <code>*</code>.</p> + + <p>If name-based vhosts should be used a + <code>NameVirtualHost</code> directive <em>must</em> appear + with the IP address set to be used for the name-based vhosts. + In other words, you must specify the IP address that holds the + hostname aliases (CNAMEs) for your name-based vhosts via a + <code>NameVirtualHost</code> directive in your configuration + file.</p> + + <p>Multiple <code>NameVirtualHost</code> directives can be used + each with a set of <code>VirtualHost</code> directives but only + one <code>NameVirtualHost</code> directive should be used for + each specific IP:port pair.</p> + + <p>The ordering of <code>NameVirtualHost</code> and + <code>VirtualHost</code> directives is not important which + makes the following two examples identical (only the order of + the <code>VirtualHost</code> directives for <em>one</em> + address set is important, see below):</p> + +<table><tr> +<td><div class="example"><p><code> + NameVirtualHost 111.22.33.44<br /> + <VirtualHost 111.22.33.44><br /> + # server A<br /> + ...<br /> + </VirtualHost><br /> + <VirtualHost 111.22.33.44><br /> + # server B<br /> + ...<br /> + </VirtualHost><br /> + <br /> + NameVirtualHost 111.22.33.55<br /> + <VirtualHost 111.22.33.55><br /> + # server C<br /> + ...<br /> + </VirtualHost><br /> + <VirtualHost 111.22.33.55><br /> + # server D<br /> + ...<br /> + </VirtualHost> +</code></p></div></td> +<td><div class="example"><p><code> + <VirtualHost 111.22.33.44><br /> + # server A<br /> + </VirtualHost><br /> + <VirtualHost 111.22.33.55><br /> + # server C<br /> + ...<br /> + </VirtualHost><br /> + <VirtualHost 111.22.33.44><br /> + # server B<br /> + ...<br /> + </VirtualHost><br /> + <VirtualHost 111.22.33.55><br /> + # server D<br /> + ...<br /> + </VirtualHost><br /> + <br /> + NameVirtualHost 111.22.33.44<br /> + NameVirtualHost 111.22.33.55<br /> + <br /> +</code></p></div></td> +</tr></table> + + + <p>(To aid the readability of your configuration you should + prefer the left variant.)</p> + + <p>After parsing the <code>VirtualHost</code> directive, the + vhost server is given a default <code>Listen</code> equal to the + port assigned to the first name in its <code>VirtualHost</code> + directive.</p> + + <p>The complete list of names in the <code>VirtualHost</code> + directive are treated just like a <code>ServerAlias</code> (but + are not overridden by any <code>ServerAlias</code> statement) + if all names resolve to the same address set. Note that + subsequent <code>Listen</code> statements for this vhost will not + affect the ports assigned in the address set.</p> + + <p>During initialization a list for each IP address is + generated and inserted into an hash table. If the IP address is + used in a <code>NameVirtualHost</code> directive the list + contains all name-based vhosts for the given IP address. If + there are no vhosts defined for that address the + <code>NameVirtualHost</code> directive is ignored and an error + is logged. For an IP-based vhost the list in the hash table is + empty.</p> + + <p>Due to a fast hashing function the overhead of hashing an IP + address during a request is minimal and almost not existent. + Additionally the table is optimized for IP addresses which vary + in the last octet.</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/core.html#receivebuffersize">ReceiveBufferSize</a></code>, + or <code class="directive"><a href="../mod/core.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">Hash table lookup</a></h3> + + <p>When the connection is first made by a client, the IP + address to which the client connected is looked up in the + internal IP hash table.</p> + + <p>If the lookup fails (the IP address wasn't found) the + request is served from the <code>_default_</code> vhost if + there is such a vhost for the port to which the client sent the + request. If there is no matching <code>_default_</code> vhost + the request is served from the main_server.</p> + + <p>If the IP address is not found in the hash table then the + match against the port number may also result in an entry + corresponding to a <code>NameVirtualHost *</code>, which is + subsequently handled like other name-based vhosts.</p> + + <p>If the lookup succeeded (a corresponding list for the IP + address was found) the next step is to decide if we have to + deal with an IP-based or a name-base vhost.</p> + + + + <h3><a name="ipbased" id="ipbased">IP-based vhost</a></h3> + + <p>If the entry we found has an empty name list then we have + found an IP-based vhost, no further actions are performed and + the request is served from that vhost.</p> + + + + <h3><a name="namebased" id="namebased">Name-based vhost</a></h3> + + <p>If the entry corresponds to a name-based vhost the name list + contains one or more vhost structures. This list contains the + vhosts in the same order as the <code>VirtualHost</code> + directives appear in the config file.</p> + + <p>The first vhost on this list (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.</p> + + <p>If the client provided a <code>Host:</code> header field the + list is searched for a matching vhost and the first hit on a + <code>ServerName</code> or <code>ServerAlias</code> is taken + and the request is served from that vhost. A <code>Host:</code> + header field can contain a port number, but Apache always + matches against the real port to which the client sent the + request.</p> + + <p>If the client submitted a HTTP/1.0 request without + <code>Host:</code> header field we don't know to what server + the client tried to connect and any existing + <code>ServerPath</code> is matched against the URI from the + request. The first matching path on the list is used and the + request is served from that vhost.</p> + + <p>If no matching vhost could be found the request is served + from the first vhost with a matching port number that is on the + list for the IP to which the client connected (as already + mentioned before).</p> + + + + <h3><a name="persistent" id="persistent">Persistent connections</a></h3> + + <p>The IP lookup described above is only done <em>once</em> for a + particular TCP/IP session while the name lookup 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>A name-based vhost can never interfere with an IP-base + vhost and vice versa. IP-based vhosts can only be reached + through an IP address of its own address set and never + through any other address. The same applies to name-based + vhosts, they can only be reached through an IP address of the + corresponding address set which must be defined with a + <code>NameVirtualHost</code> directive.</li> + + <li><code>ServerAlias</code> and <code>ServerPath</code> + checks are never performed for an IP-based vhost.</li> + + <li>The order of name-/IP-based, the <code>_default_</code> + vhost and the <code>NameVirtualHost</code> directive within + the config file is not important. 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>For security reasons the port number given in a + <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 a <code>ServerPath</code> directive exists which is a + prefix of another <code>ServerPath</code> directive that + appears later in the configuration file, then the former will + always be matched and the latter will never be matched. (That + is assuming that no <code>Host:</code> header field was + available to disambiguate the two.)</li> + + <li>If two IP-based vhosts have an address in common, the + vhost appearing first in the config file is always matched. + Such a thing might happen inadvertently. The server will give + a warning in the error logfile when it detects this.</li> + + <li>A <code>_default_</code> vhost catches a request only if + there is no other vhost with a matching IP address + <em>and</em> a matching port number for the request. The + request is only caught if the port number to which the client + sent the request matches the port number of your + <code>_default_</code> vhost which is your standard + <code>Listen</code> by default. A wildcard port can be + specified (<em>i.e.</em>, <code>_default_:*</code>) to catch + requests to any available port. This also applies to + <code>NameVirtualHost *</code> vhosts.</li> + + <li>The main_server is only used to serve a request if the IP + address and port number to which the client connected is + unspecified and does not match any other vhost (including a + <code>_default_</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>A <code>_default_</code> vhost or the main_server is + <em>never</em> matched for a request with an unknown or + missing <code>Host:</code> header field if the client + connected to an address (and port) which is used for + name-based vhosts, <em>e.g.</em>, in a + <code>NameVirtualHost</code> directive.</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> + + <li>Group corresponding <code>NameVirtualHost</code> and + <code>VirtualHost</code> definitions in your configuration to + ensure better readability.</li> + + <li>Avoid <code>ServerPaths</code> which are prefixes of + other <code>ServerPaths</code>. If you cannot avoid this then + you have to ensure that the longer (more specific) prefix + vhost appears earlier in the configuration file than the + shorter (less specific) prefix (<em>i.e.</em>, "ServerPath + /abc" should appear after "ServerPath /abc/def").</li> + </ul> + +</div></div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="../en/vhosts/details.html" title="English"> en </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 id="footer"> +<p class="apache">Copyright 2009 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="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div> +</body></html>
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