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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:01:30 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:01:30 +0000 |
| commit | 6beeb1b708550be0d4a53b272283e17e5e35fe17 (patch) | |
| tree | 1ce8673d4aaa948e5554000101f46536a1e4cc29 /docs/manual/developer/request.html.en | |
| parent | Initial commit. (diff) | |
| download | apache2-6beeb1b708550be0d4a53b272283e17e5e35fe17.tar.xz apache2-6beeb1b708550be0d4a53b272283e17e5e35fe17.zip | |
Adding upstream version 2.4.57.upstream/2.4.57
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'docs/manual/developer/request.html.en')
| -rw-r--r-- | docs/manual/developer/request.html.en | 248 |
1 files changed, 248 insertions, 0 deletions
diff --git a/docs/manual/developer/request.html.en b/docs/manual/developer/request.html.en new file mode 100644 index 0000000..2ea780d --- /dev/null +++ b/docs/manual/developer/request.html.en @@ -0,0 +1,248 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!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=UTF-8" http-equiv="Content-Type" /> +<!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>Request Processing in the Apache HTTP Server 2.x - 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="./">Developer Documentation</a></div><div id="page-content"><div id="preamble"><h1>Request Processing in the Apache HTTP Server 2.x</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 2.0 and above 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 + the Apache HTTP Server 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 1.3) without introducing fragile or + insecure code.</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="#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><h3>See also</h3><ul class="seealso"><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="processing" id="processing">The Request Processing Cycle</a></h2> + <p>All requests pass through <code>ap_process_request_internal()</code> + in <code>server/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 <a href="./modguide.html#hooking">hooks offered</a> to drop + out of the request cycle early, or to bypass core 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 + repercussions.</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>, as well as any trailing + <code>/.</code> or <code>/..</code> element. This helps to ensure + the path is (nearly) absolute before the request processing + continues. (See RFC 1808 section 4 for further discussion.)</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> + + <pre class="prettyprint lang-c">if ((access_status = ap_run_access_checker(r)) != 0) { + return decl_die(access_status, "check access", r); +} + +if ((access_status = ap_run_check_user_id(r)) != 0) { + return decl_die(access_status, "check user", r); +} + +if ((access_status = ap_run_auth_checker(r)) != 0) { + return decl_die(access_status, "check authorization", r); +}</pre> + +</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 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 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 Libera.chat, or sent to our <a href="https://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/developer/request.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 2023 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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