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<?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>Request Processing in Apache 2.0 - 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-project/">Documentation</a> > <a href="../">Version 2.0</a> > <a href="./">Developer Documentation</a></div><div id="page-content"><div id="preamble"><h1>Request Processing in Apache 2.0</h1><div class="toplang"><p><span>Available Languages: </span><a href="../en/developer/request.html" title="English"> en </a></p></div> <div class="warning"><h3>Warning</h3> <p>Warning - this is a first (fast) draft that needs further revision!</p> </div> <p>Several changes in Apache 2.0 affect the internal request processing mechanics. Module authors need to be aware of these changes so they may take advantage of the optimizations and security enhancements.</p> <p>The first major change is to the subrequest and redirect mechanisms. There were a number of different code paths in Apache 1.3 to attempt to optimize subrequest or redirect behavior. As patches were introduced to 2.0, these optimizations (and the server behavior) were quickly broken due to this duplication of code. All duplicate code has been folded back into <code>ap_process_request_internal()</code> to prevent the code from falling out of sync again.</p> <p>This means that much of the existing code was 'unoptimized'. It is the Apache HTTP Project's first goal to create a robust and correct implementation of the HTTP server RFC. Additional goals include security, scalability and optimization. New methods were sought to optimize the server (beyond the performance of Apache 1.3) without introducing fragile or insecure code.</p></div><div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#processing">The Request Processing Cycle</a></li><li><img alt="" src="../images/down.gif" /> <a href="#parsing">The Request Parsing Phase</a></li><li><img alt="" src="../images/down.gif" /> <a href="#security">The Security Phase</a></li><li><img alt="" src="../images/down.gif" /> <a href="#preparation">The Preparation Phase</a></li><li><img alt="" src="../images/down.gif" /> <a href="#handler">The Handler Phase</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="processing" id="processing">The Request Processing Cycle</a></h2> <p>All requests pass through <code>ap_process_request_internal()</code> in <code>request.c</code>, including subrequests and redirects. If a module doesn't pass generated requests through this code, the author is cautioned that the module may be broken by future changes to request processing.</p> <p>To streamline requests, the module author can take advantage of the hooks offered to drop out of the request cycle early, or to bypass core Apache hooks which are irrelevant (and costly in terms of CPU.)</p></div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div><div class="section"><h2><a name="parsing" id="parsing">The Request Parsing Phase</a></h2> <h3><a name="unescape" id="unescape">Unescapes the URL</a></h3> <p>The request's <code>parsed_uri</code> path is unescaped, once and only once, at the beginning of internal request processing.</p> <p>This step is bypassed if the proxyreq flag is set, or the <code>parsed_uri.path</code> element is unset. The module has no further control of this one-time unescape operation, either failing to unescape or multiply unescaping the URL leads to security reprecussions.</p> <h3><a name="strip" id="strip">Strips Parent and This Elements from the URI</a></h3> <p>All <code>/../</code> and <code>/./</code> elements are removed by <code>ap_getparents()</code>. This helps to ensure the path is (nearly) absolute before the request processing continues.</p> <p>This step cannot be bypassed.</p> <h3><a name="inital-location-walk" id="inital-location-walk">Initial URI Location Walk</a></h3> <p>Every request is subject to an <code>ap_location_walk()</code> call. This ensures that <code class="directive"><a href="../mod/core.html#location"><Location></a></code> sections are consistently enforced for all requests. If the request is an internal redirect or a sub-request, it may borrow some or all of the processing from the previous or parent request's ap_location_walk, so this step is generally very efficient after processing the main request.</p> <h3><a name="translate_name" id="translate_name">translate_name</a></h3> <p>Modules can determine the file name, or alter the given URI in this step. For example, <code class="module"><a href="../mod/mod_vhost_alias.html">mod_vhost_alias</a></code> will translate the URI's path into the configured virtual host, <code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> will translate the path to an alias path, and if the request falls back on the core, the <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code> is prepended to the request resource.</p> <p>If all modules <code>DECLINE</code> this phase, an error 500 is returned to the browser, and a "couldn't translate name" error is logged automatically.</p> <h3><a name="map_to_storage" id="map_to_storage">Hook: map_to_storage</a></h3> <p>After the file or correct URI was determined, the appropriate per-dir configurations are merged together. For example, <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code> compares and merges the appropriate <code class="directive"><a href="../mod/mod_proxy.html#proxy"><Proxy></a></code> sections. If the URI is nothing more than a local (non-proxy) <code>TRACE</code> request, the core handles the request and returns <code>DONE</code>. If no module answers this hook with <code>OK</code> or <code>DONE</code>, the core will run the request filename against the <code class="directive"><a href="../mod/core.html#directory"><Directory></a></code> and <code class="directive"><a href="../mod/core.html#files"><Files></a></code> sections. If the request 'filename' isn't an absolute, legal filename, a note is set for later termination.</p> <h3><a name="location-walk" id="location-walk">URI Location Walk</a></h3> <p>Every request is hardened by a second <code>ap_location_walk()</code> call. This reassures that a translated request is still subjected to the configured <code class="directive"><a href="../mod/core.html#location"><Location></a></code> sections. The request again borrows some or all of the processing from its previous <code>location_walk</code> above, so this step is almost always very efficient unless the translated URI mapped to a substantially different path or Virtual Host.</p> <h3><a name="header_parser" id="header_parser">Hook: header_parser</a></h3> <p>The main request then parses the client's headers. This prepares the remaining request processing steps to better serve the client's request.</p> </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div><div class="section"><h2><a name="security" id="security">The Security Phase</a></h2> <p>Needs Documentation. Code is:</p> <div class="example"><pre>switch (ap_satisfies(r)) {case SATISFY_ALL:case SATISFY_NOSPEC: if ((access_status = ap_run_access_checker(r)) != 0) { return decl_die(access_status, "check access", r); } if (ap_some_auth_required(r)) { if (((access_status = ap_run_check_user_id(r)) != 0) || !ap_auth_type(r)) { return decl_die(access_status, ap_auth_type(r) ? "check user. No user file?" : "perform authentication. AuthType not set!", r); } if (((access_status = ap_run_auth_checker(r)) != 0) || !ap_auth_type(r)) { return decl_die(access_status, ap_auth_type(r) ? "check access. No groups file?" : "perform authentication. AuthType not set!", r); } } break;case SATISFY_ANY: if (((access_status = ap_run_access_checker(r)) != 0)) { if (!ap_some_auth_required(r)) { return decl_die(access_status, "check access", r); } if (((access_status = ap_run_check_user_id(r)) != 0) || !ap_auth_type(r)) { return decl_die(access_status, ap_auth_type(r) ? "check user. No user file?" : "perform authentication. AuthType not set!", r); } if (((access_status = ap_run_auth_checker(r)) != 0) || !ap_auth_type(r)) { return decl_die(access_status, ap_auth_type(r) ? "check access. No groups file?" : "perform authentication. AuthType not set!", r); } } break;}</pre></div></div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div><div class="section"><h2><a name="preparation" id="preparation">The Preparation Phase</a></h2> <h3><a name="type_checker" id="type_checker">Hook: type_checker</a></h3> <p>The modules have an opportunity to test the URI or filename against the target resource, and set mime information for the request. Both <code class="module"><a href="../mod/mod_mime.html">mod_mime</a></code> and <code class="module"><a href="../mod/mod_mime_magic.html">mod_mime_magic</a></code> use this phase to compare the file name or contents against the administrator's configuration and set the content type, language, character set and request handler. Some modules may set up their filters or other request handling parameters at this time.</p> <p>If all modules <code>DECLINE</code> this phase, an error 500 is returned to the browser, and a "couldn't find types" error is logged automatically.</p> <h3><a name="fixups" id="fixups">Hook: fixups</a></h3> <p>Many modules are 'trounced' by some phase above. The fixups phase is used by modules to 'reassert' their ownership or force the request's fields to their appropriate values. It isn't always the cleanest mechanism, but occasionally it's the only option.</p> </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div><div class="section"><h2><a name="handler" id="handler">The Handler Phase</a></h2> <p>This phase is <strong>not</strong> part of the processing in <code>ap_process_request_internal()</code>. Many modules prepare one or more subrequests prior to creating any content at all. After the core, or a module calls <code>ap_process_request_internal()</code> it then calls <code>ap_invoke_handler()</code> to generate the request.</p> <h3><a name="insert_filter" id="insert_filter">Hook: insert_filter</a></h3> <p>Modules that transform the content in some way can insert their values and override existing filters, such that if the user configured a more advanced filter out-of-order, then the module can move its order as need be. There is no result code, so actions in this hook better be trusted to always succeed.</p> <h3><a name="hook_handler" id="hook_handler">Hook: handler</a></h3> <p>The module finally has a chance to serve the request in its handler hook. Note that not every prepared request is sent to the handler hook. Many modules, such as <code class="module"><a href="../mod/mod_autoindex.html">mod_autoindex</a></code>, will create subrequests for a given URI, and then never serve the subrequest, but simply lists it for the user. Remember not to put required teardown from the hooks above into this module, but register pool cleanups against the request pool to free resources as required.</p> </div></div><div class="bottomlang"><p><span>Available Languages: </span><a href="../en/developer/request.html" title="English"> en </a></p></div><div id="footer"><p class="apache">Copyright 1995-2005 The Apache Software Foundation or its licensors, as applicable.<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>⌨️ 快捷键说明
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