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- XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
- This file is generated from xml source: DO NOT EDIT
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-<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" />
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-<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="&lt;-" alt="&lt;-" src="../images/left.gif" /></a></div>
-<div id="path">
-<a href="http://www.apache.org/">Apache</a> &gt; <a href="http://httpd.apache.org/">HTTP Server</a> &gt; <a href="http://httpd.apache.org/docs/">Documentation</a> &gt; <a href="../">Version 2.0</a> &gt; <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">&nbsp;en&nbsp;</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">&lt;Location&gt;</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">&lt;Proxy&gt;</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">&lt;Directory&gt;</a></code> and <code class="directive"><a href="../mod/core.html#files">&lt;Files&gt;</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">&lt;Location&gt;</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">&nbsp;en&nbsp;</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>
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