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diff --git a/doc/index.html b/doc/index.html new file mode 100644 index 0000000..839d364 --- /dev/null +++ b/doc/index.html @@ -0,0 +1,2751 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<html> +<head> + <title>mod_qos</title> +<meta http-equiv="content-type" content="text/html; charset=ISO-8859-1" /> +<meta name="author" content="Pascal Buchbinder" /> +<meta name="KeyWords" content="mod_qos, Quality of Service, Apache Web Server, Throttling, Web application security, WAF, Open Source Software, Secure Reverse Proxy, Denial of Service Prevention, DoS, DDoS" /> +<link rel="shortcut icon" href="favicon.ico" /> +<style TYPE="text/css"> +<!-- + body { + background-color: white; + color: black; + font-family: sans-serif, arial, verdana; + font-weight: normal; + text-align: left; + } + a:link { color:#00673F; text-decoration:none; } + a:visited { color:#00673F; text-decoration:none; } + a:focus { color:black; text-decoration:underline; } + a:hover { color:black; text-decoration:underline; } + a:active { color:black; text-decoration:underline; } + li { margin: 4px 0; } + syntax { font-family: monospace; font-size: 14; line-height: 1.8; } + .btable { font-size:0.75em; } + .prept { font-size:0.75em; } +--> +</style> +</head> +<body> +<!-- + + Quality of service module for Apache Web Server. + + See http://mod-qos.sourceforge.net/ for further details. + + Copyright (C) 2023 Pascal Buchbinder + + Licensed to the Apache Software Foundation (ASF) under one or more + contributor license agreements. See the NOTICE file distributed with + this work for additional information regarding copyright ownership. + The ASF licenses this file to You under the Apache License, Version 2.0 + (the "License"); you may not use this file except in compliance with + the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. + +--> +<table> +<tbody> +<tr><td><img src="images/mod_qos.gif" alt="mod_qos" title="mod_qos" /></td> + <td style="vertical-align: bottom;"><h1>mod_qos</h1></td> +</tr> +<tr><td> </td> + <td> +<p> +In computer networking, the term quality of service (QoS) describes +resource management rather than the quality of a service. +Quality of service implements control mechanisms to provide +different priority to different users, applications, and data +connections. It is used to guarantee a certain level of performance +to data resources. The term quality of service is often used +in the field of wide area network protocols (e.g. ATM) and +telephony (e.g. VoIP), but rarely in conjunction with web applications. +<b>mod_qos is a quality of service module for the Apache web server</b> +implementing control mechanisms that can provide different levels of +priority to different HTTP requests. +</p> +<p> +But why do you need quality of service for a web application? Well, +web servers require threads and processes to serve HTTP requests. +Each TCP connection to the web server occupies one of these threads +respectively processes. Sometimes a server gets too busy to serve +every request due to the lack of free processes or threads. Another +parameter requiring control by mod_qos is the available bandwidth: +all clients communicate to the server over a network link with +limited bandwidth. Overfilling the link results in network +congestion and poor performance. +</p> +<p> +Example situations where web applications require QoS: +<ul> +<li> +More resources are consumed if request processing by an application +takes a long time, e.g. when request processing includes +time consuming database queries. +</li> +<li> +Oversubscription of link capabilities due to many concurrent +clients uploading or downloading data. +</li> +<li> +Penetration of the web server by attackers (DoS).<!-- line is a MARKER --> +</li> +</ul> +</p> +<p> +mod_qos may be used to determine which requests should be served and +which shouldn't in order to avoid resource oversubscription. The +module collects different attributes such as the request URL, +HTTP request and response headers, the IP source address, country codes, +the HTTP response code, history data (based on user session and source +IP address), the number of concurrent requests to the +server (total or requests having similar attributes), the number +of concurrent TCP connections (total or from a single source IP), +and so forth.</p> +<p> +<a name="rules"></a> +The <u><a href="glossary.html#rules">rules</a></u> you want to configure +are defined by the +<u><a href="glossary.html#directives">module's directives</a></u>. Every rule +reads attributes from different sources and using its own counters to +store their status. +</p> +<p> +Counteractive measures to enforce the defined rules are: request +blocking, dynamic timeout adjustment, request delay, response +throttling, and dropping of TCP connections. +</p> +<p> +The <a title="change log" href="CHANGES.txt">current release</a> of the mod_qos +module implements various control mechanisms: +<ul> +<li type=square> +The maximum number of <a href="glossary.html#concurrency">concurrent</a> +requests to a location/resource (URL) +or virtual host. +</li> +<li type=square> +Limitation of the <a href="glossary.html#throughput">bandwidth</a> such as the maximum +allowed number of requests per second to an URL or the maximum/minimum of downloaded +kbytes per second. +</li> +<li type=square> +Limits the number of request <a href="glossary.html#requestPerSecond">events per second</a> (special request conditions). +</li> +<li type=square> +Limits the number of request <a href="glossary.html#repeat">events within a defined +period of time</a>. +</li> +<li type=square> +It can also detect very important persons (VIP) which may access the +web server without or with fewer restrictions. +</li> +<li type=square> +Generic request line and header filter to deny unauthorized operations. +</li> +<li type=square> +Request body data limitation and filtering (requires +<a href="http://parp.sourceforge.net">mod_parp <img src="images/link.png"/></a>). +</li> +<li type=square> +Limits the number of request events for individual clients (IP). +</li> +<li type=square> +Limitations on the TCP connection level, e.g., the maximum number of +allowed connections from a single IP source address or dynamic +keep-alive control. +</li> +<li type=square> +Prefers known IP addresses when server runs out of free TCP connections. +</li> +<li type=square> +Serialization of requests. +</li> +</ul> +</p> +<hr> +</td></tr> +<tr><td> </td><td style="background-color: #E2EDE2"> +<p align="center"> +<br> +mod_qos is an open source software licensed under the +<a href="LICENSE.txt">Apache License</a>. You can download the latest release at +<a href="https://sourceforge.net/projects/mod-qos/files/">SourceForge.net</a>. +<br><br> +</p> +</td></tr> +<tr><td> </td><td> +<hr> +<p> +More information about mod_qos: +<ul> +<li><a href="#build">Build</a></li> +<!-- DIST START --> +<li><a href="#source">Source Code</a></li> +<li><a href="CHANGES.txt">Changes</a></li> +<!-- DIST END --> +<li><a href="#configuration">Configuration</a></li> +<ul> +<li><a href="#requestlevelcontrol">Request Level Control</a></li> +<li><a href="#statuscode">Status Code and Error Page</a></li> +<li><a href="#privilegedusers">Privileged Users</a></li> +<li><a href="#variables">Variables</a></li> +<li><a href="#conditionalrules">Conditional Rules</a></li> +<li><a href="#eventcontrol">Events</a></li> +<li><a href="#filter">Request Level, Generic Filter</a></li> +<li><a href="#connectionlevelcontrol">Connection Level Control</a></li> +<li><a href="#clientlevelcontrol">Client Level Control</a></li> +</ul> +<li><a href="#messages">Log Messages</a></li> +<ul> +<li><a href="#errorlog">Error Log</a></li> +<li><a href="#accesslog">Access Log</a></li> +<li><a href="#requeststatistics">Request Statistics</a></li> +<li><a href="#statusviewer">Status Viewer</a></li> +<li><a href="#webconsole">Web Console</a></li> +<li><a href="#utilities">Utilities</a></li> +</ul> +<li><a href="#usecases">Sample Use Cases</a></li> +</ul> +</p> + +<hr> +<a name="build"></a> +<h2>Build</h2> +<p> +mod_qos requires OpenSSL, PCRE, threading and shared memory support. +mod_qos is designed to be used with Apache's +<a href="http://httpd.apache.org/docs/current/mod/worker.html">MPM worker <img src="images/link.png"/></a> +binaries but works, with some restrictions, also with other Apache 2.4 multi-processing modules. +The module is optimized to be used in a +<a href="http://httpd.apache.org/docs/current/mod/mod_proxy.html">reverse proxy +<img src="images/link.png"/></a> server.<p> +<p> +<small><i>Notes:<br> You should choose the <a href="https://httpd.apache.org/docs/current/mod/worker.html">worker MPM <img src="images/link.png"/></a> +if you intend to use any <a href="#connectionlevelcontrol">connection level control</a> directive. <br> + If you decide to use <a href="https://httpd.apache.org/docs/current/howto/http2.html">HTTP/2 <img src="images/link.png"/></a>, +you should only use the <a href="#requestlevelcontrol">request level control</a> directives +as mod_qos works for the hypertext transfer protocol +version 1.0 and 1.1 (RFC1945/RFC2616) only. +</i></small> +</p> +<p> +You can compile the module using +<code><a href="http://httpd.apache.org/docs/current/programs/apxs.html">apxs <img src="images/link.png"/></a></code>. +Your httpd binary must support dynamically loaded objects +(DSO). Verify this by checking the availability of mod_so: The command +<code>httpd -l</code> must list the mod_so.c module. +The following command compiles the module and installs mod_qos into the +server's modules directory. +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +cd mod_qos-11.74/apache2 +apxs -i -c mod_qos.c -lcrypto -lpcre2-8 +cd ../.. +</pre> +</td></tr> +</table> +If the necessary header files of OpenSSL, PCRE, etc. cannot be found, add +the <code>-I</code> option to the <code>apxs</code> command to specify +the directory where header files can be found and if any of the required +libraries cannot be found (may happen if you use mod_qos without mod_ssl), +add the <code>-L</code> option to specify the directory where libraries +can be found. +<br> +<small><i>Note: you may customize the code using the following preprocessor directives:</i></small> +<table class="prept" width="780px"> +<tr> + <td> </td> + <td bgcolor="#E2EDE2">Name</td> + <td bgcolor="#E2EDE2">Description</td> + <td bgcolor="#E2EDE2">Default</td> +</tr> +<tr> + <td> </td> + <td>QS_MOD_EXT_HOOKS</td> + <td>Enables the optional hooks defined in mod_qos.h</td> + <td><i>not set</i></td> +</tr> +<tr> + <td> </td> + <td>QSLOG_CLID</td> + <td>Defines the environment variable which shall be used for the "user tracking id" (U) +within the format string used by the <a href="#QSLog"><code>QSLog</code></a> directive.</td> + <td>mod_qos_user_id</td> +</tr> +<tr> + <td> </td> + <td>QSLOG_EVENT</td> + <td>Defines the environment variable which shall be used for the "event" (Q) +within the format string used by the <a href="#QSLog"><code>QSLog</code></a> directive.</td> + <td>Event</td> +</tr> +<tr> + <td> </td> + <td>QSLOG_AVERAGE</td> + <td>Defines the environment variable which shall be used for the "average" (a) +within the format string used by the <a href="#QSLog"><code>QSLog</code></a> directive.</td> + <td>QS_AllConn</td> +</tr> +<tr> + <td> </td> + <td>QS_LOG_REPEAT</td> + <td>Counter used to define how many repetitive messages are summarized.</td> + <td>20</td> +</tr> +<tr> + <td> </td> + <td>QS_REQ_RATE_TM</td> + <td>Default for the <a href="#QS_SrvSampleRate"><code>QS_SrvSampleRate</code></a> directive.</td> + <td>5</td> +</tr> +<tr> + <td> </td> + <td>QS_EXTRA_MATCH_LIMIT</td> + <td>Match limit field used for PCRE data processing.</td> + <td>1500</td> +</tr> +</table> +</p> +<p> +The <a href="#utilities">support tools</a> may be built (at least on some +Linux platforms) using the GNU autotools. Some of these +utilities require third-party libraries such as apr, apr-util, PCRE2, +libpng, and OpenSSL. +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +cd mod_qos-11.74/tools +./configure +make +</pre> +</td></tr> +</table> +<!-- +<small><i>Note: +If you have a different version of <code>aclocal</code> or +<code>automake</code> on your system (you get a message like +"aclocal-x.y is missing on your system"), edit the configure +script and change the <code>am__api_version</code> variable +to match the version you have installed (<code>aclocal --versions</code> +shows you which version this is). +</i></small> +--> +</p> + +<!-- DIST START --> + +<a name="source"></a> +<h2>Source Code</h2> +<p> +<a href="../apache2">mod_qos</a> is available for Apache version 2.4. +</p> + +<!-- DIST END --> +<!-- CONFIGURATION --> + +<a name="configuration"></a> +<h2>Configuration</h2> +<p>Configuration is mostly done on a per-server basis (except the +<a href="#filter">generic request</a> filter and a few other directives). +<a href="glossary.html#directives">Directives</a> within a virtual +host are merged with the settings in the global configuration. +</p> +<p> +The <code><a href="#QS_SrvMinDataRate">QS_SrvMinDataRate</a></code>, +<code><a href="#QS_SrvRequestRate">QS_SrvRequestRate</a></code>, +<code><a href="#QS_RequestHeaderFilterRule">QS_RequestHeaderFilterRule</a></code>, +<code><a href="#QS_ResponseHeaderFilterRule">QS_ResponseHeaderFilterRule</a></code>, +and all <code><a href="#clientlevelcontrol">QS_Client*</a></code> +directives may be used outside of virtual host configurations only. +</p> +<p> +<a name="QS_LogOnly"></a> +The <code>QS_LogOnly on</code> directive may be used to put mod_qos +into a permissive mode where rule violations are logged only but +requests/connections are not blocked. This may be used for test purposes.<br> +Should not be activated if you are using any +<a href="glossary.html#throughput">throughput control</a> +directive (open loop). +</p> + +<p> +<a name="requestlevelcontrol"></a> +<h3>Request Level Control</h3> +The module features directives to control server access +on a per-URL level - basically the main function of mod_qos. <br> +Only one <code>QS_Loc*</code> rule (URL string or +regular expression) of each type is evaluated per request where +regular expression rules (*Match) have higher priority +than the rules using a literal URL-string. A +<code>QS_LocRequestLimit*</code> rule may be used in parallel to a +<code>QS_LocRequestPerSecLimit*</code> and/or +<code>QS_LocKBytesPerSecLimit*</code> rule if they use the very +same URL string or regular expression. +<ul> +<li> +<a name="QS_LocRequestLimitMatch"></a> +<syntax>QS_LocRequestLimitMatch <regex> <number></syntax><br> +Defines the number of <a href="glossary.html#concurrency">concurrent</a> +requests for the specified request pattern (path and query). +The rule with the lowest number of allowed concurrent connections has the +highest priority if multiple expressions match the request. +By default, no limitations are active. +</li> +<li> +<a name="QS_LocRequestPerSecLimitMatch"></a> +<syntax>QS_LocRequestPerSecLimitMatch <regex> <number></syntax><br> +Defines the allowed number of <a href="glossary.html#requestPerSecond">requests per second</a> +to the URL (path and query) pattern. Requests are limited by +adding a delay to each request (linear). The delay calculation is based on +an average request rate measurement using a sampling rate of 10 seconds. +By default, no limitation is active. This directive should be used in +conjunction with <code><a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a></code> +only (you must use the very same regex pattern with the +<code><a href="#QS_LocRequestPerSecLimitMatch">QS_LocRequestPerSecLimitMatch</a></code> +and <code><a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a></code> +directive) to avoid too many concurrent requests. +</li> +<li> +<a name="QS_LocKBytesPerSecLimitMatch"></a> +<syntax>QS_LocKBytesPerSecLimitMatch <regex> <number></syntax><br> +Defines the allowed download <a href="glossary.html#throughput">bandwidth</a> to the location +matching the defined URL (path and query) pattern. Responses are slowed down by +adding a delay to each response (every 8kbytes). Bandwidth calculation +is based on measuring the transferred data. +By default, no limitation is active. This directive should be used +in conjunction with <code><a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a></code> +only (you must use the very same regex pattern with the +<code><a href="#QS_LocKBytesPerSecLimitMatch">QS_LocKBytesPerSecLimitMatch</a></code> and +<code><a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a></code> directive) +to avoid too many concurrent requests. +</li> +<li> +<a name="QS_LocRequestLimit"></a> +<syntax>QS_LocRequestLimit <location> <number></syntax><br> +Defines the number of <a href="glossary.html#concurrency">concurrent</a> +requests for the specified location (applied to the parsed path). +By default, no limitations are active for locations. Has lower priority than +<code><a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a></code> +directives. +</li> +<li> +<a name="QS_LocRequestLimitDefault"></a> +<syntax>QS_LocRequestLimitDefault <number></syntax><br>Defines the +default limitation for the maximum of concurrent requests per-location +for those locations not defined by any +<code><a href="#QS_LocRequestLimit">QS_LocRequestLimit</a></code> +directive. It could also be used to limit the number of concurrent +requests to a virtual host. +</li> +<li> +<a name="QS_LocRequestPerSecLimit"></a> +<syntax>QS_LocRequestPerSecLimit <location> <number></syntax><br> +Defines the allowed number of <a href="glossary.html#requestPerSecond">requests per second</a> +to a location, similar to the +<a href="#QS_LocRequestPerSecLimitMatch"><code>QS_LocRequestPerSecLimitMatch</code></a> +directive. The maximum number of requests is limited by adding a delay to +each request (linear, each request gets the same delay). By default, +no limitation is active. +This directive should be used in conjunction with +<code><a href="#QS_LocRequestLimit">QS_LocRequestLimit</a></code> only (you +must use the same location for both directives) to avoid too many +concurrent requests.. Has lower priority than +<code><a href="#QS_LocRequestPerSecLimitMatch">QS_LocRequestPerSecLimitMatch</a></code>. +</li> +<li> +<a name="QS_LocKBytesPerSecLimit"></a> +<syntax>QS_LocKBytesPerSecLimit <location> <number></syntax><br> +Throttles the download <a href="glossary.html#throughput">bandwidth</a> to the defined +kbytes per second. Works similar as the +<a href="#QS_LocKBytesPerSecLimitMatch"><code>QS_LocKBytesPerSecLimitMatch</code></a> +directive slowing down HTTP responses by adding a delay to each response. +By default, no limitation is active. This directive should be used in +conjunction with <code><a href="#QS_LocRequestLimit">QS_LocRequestLimit</a></code> only +(you must use the same location for both directives) to avoid too many +concurrent requests.. Has lower priority than +<code><a href="#QS_LocKBytesPerSecLimitMatch">QS_LocKBytesPerSecLimitMatch</a></code>. +</li> +</ul> + +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample configuration:<br> +<pre> +# maximum number of active TCP connections is limited to 512 +MaxClients 512 + +# limits concurrent requests to the locations: +# - /app/a max. 200 concurrent requests +# - /app/b and /app/c (together) max. 300 concurrent requests +# - /images max. 100 concurrent requests +<a href="#QS_LocRequestLimit">QS_LocRequestLimit</a> /app/a 200 +<a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a> ^(/app/b/|/app/c/).*$ 300 +<a href="#QS_LocRequestLimit">QS_LocRequestLimit</a> /images 100 +# limits download bandwidth to 5Mbit/sec (resp. 640kbytes/sec) +# for downloads from /app/a: +<a href="#QS_LocKBytesPerSecLimit">QS_LocKBytesPerSecLimit</a> /app/a 640 +</pre> +</td></tr> +</table> +<br> + + +<a name="statuscode"></a> +<h3>Status Code and Error Page</h3> +The <code>QS_Error*</code> directives are used to control the response +given to clients whose requests have been denied. +<ul> +<li> +<a name="QS_ErrorPage"></a> +<syntax>QS_ErrorPage <URL></syntax><br>Defines an error page to be +returned when a request is denied. The defined URL must be a (S)HTML +document accessible by the client. +You may enable <a href="glossary.html#ssi">server-side includes (SSI)</a> +in order to present detailed error messages based on the +<a href="#errorlog">error codes</a> provided by mod_qos.<br> +Alternatively, a HTTP redirect (302) to a dedicated error page may be +defined using an absolute URL defining schema, hostname, and path. +</li> +<li> +<a name="QS_ErrorResponseCode"></a> +<syntax>QS_ErrorResponseCode <code></syntax><br>Defines the HTTP +response code which is used when a request is denied. Requests denied +at connection level usually get a HTTP 500 response code (ignoring +the settings of the <code>QS_ErrorResponseCode</code> and +<code><a href="#QS_ErrorPage">QS_ErrorPage</a></code> directives).<br> +Default (no custom error code or page defined) codes are:<br> + 400: if a request has no valid URL.<br> + 403: for requests denied by a <code><a href="#filter">QS_Deny*</a></code>, +<code><a href="#filter">QS_Permit*</a></code> or +<code><a href="#QS_RequestHeaderFilter">QS_RequestHeaderFilter</a></code> +directive.<br> + 413: when limiting the max. body data length by the +<code><a href="#QS_LimitRequestBody">QS_LimitRequestBody</a></code> directive.<br> + 500: for requests denied by any other directive.<br> +</li> +</ul> + +<a name="privilegedusers"></a> +<h3>Privileged Users</h3> +Additional directives are used to identify VIPs (very important persons) +and to control the session life time and its cookie format. VIP users have +privileged access and less QoS restrictions than ordinary users. <br><br> +VIP information is stored and evaluated at different levels: +<ul> +<li> +Session: VIP identification is stored using a HTTP +session cookie. mod_qos starts a new session when detecting a HTTP +response header (the header name is defined by the +<code><a href="#QS_VipHeaderName">QS_VipHeaderName</a></code> +directive). Alternatively, a new session is started when detecting an +authenticated user, see <code><a href="#QS_VipUser">QS_VipUser</a></code>. +The <code><a href="#QS_Session">QS_Session*</a></code> +directives are used to set session attributes. +</li> +<li> +Request: The <code><a href="#QS_VipRequest">QS_VipRequest</a></code> +process environment may be evaluated by mod_qos rules. This +variable is set automatically when receiving a valid mod_qos +session cookie. The <code><a href="#QS_VipRequest">QS_VipRequest</a></code> +variable may also be set by configuration using a <code><a href="#QS_SetEnvIf">QS_SetEnvIf*</a></code> +or <code><a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html#setenvif">SetEnvIf <img src="images/link.png"/></a></code> +directive. VIP status lasts for the particular +request only. +</li> +<li> +Client IP address: VIP identification may be stored at the server side +on a per-client IP address basis. +The <code><a href="#QS_VipIPHeaderName">QS_VipIPHeaderName</a></code>, +<code><a href="#QS_VipHeaderName">QS_VipHeaderName</a></code>, +<code><a href="#QS_VipIPUser">QS_VipIPUser</a></code>, and +<code><a href="#QS_VipUser">QS_VipUser</a></code> directives are used +to define when an IP address should be marked as a VIP user. +</li> +</ul> + +Directives: + +<ul> +<li> +<a name="QS_VipHeaderName"></a> +<syntax>QS_VipHeaderName <header name>[=<regex>] [drop]</syntax><br> +Defines an HTTP response header which marks a user as a VIP. mod_qos creates +a session for this user by setting a cookie, e.g., after successful user +authentication. +Tests optionally its value against the provided regular expression. +Specify the action 'drop' if you want mod_qos to remove this +control header from the HTTP response. +</li> +<li> +<a name="QS_VipIPHeaderName"></a> +<syntax>QS_VipIPHeaderName <header name>[=<regex>] [drop]</syntax><br> +Defines an HTTP response header which marks a client source IP address as +a VIP. +Tests optionally its value against the provided regular expression. +Specify the action 'drop' if you want mod_qos to remove this +control header from the HTTP response. +</li> +<li> +<a name="QS_VipUser"></a> +<syntax>QS_VipUser</syntax><br> +Creates a VIP session for users which have been authenticated by the +Apache server, e.g., by the standard mod_auth* modules. +It works similar to the <code><a href="#QS_VipHeaderName">QS_VipHeaderName</a></code> directive. +</li> +<li> +<a name="QS_VipIPUser"></a> +<syntax>QS_VipIPUser</syntax><br> +Marks a source IP address as a VIP if the user has been authenticated by the +Apache server, e.g. by the standard mod_auth* modules. It works similar to +the <code><a href="#QS_VipIPHeaderName">QS_VipIPHeaderName</a></code> directive. +</li> +<li> +<a name="QS_Session"></a> +<a name="QS_SessionTimeout"></a> +<syntax>QS_SessionTimeout <seconds></syntax><br> +Defines the session life time for a VIP. It is only used for session +based (cookie) VIP identification (not for IP based). +Default is 3600 seconds. +</li> +<a name="QS_SessionCookieName"></a> +<li> +<syntax>QS_SessionCookieName <name></syntax><br> +A cookie is used to identify requests coming from a user which has +been identified as a VIP. This directive defines a custom cookie name +for the mod_qos session cookie. Default is MODQOS. +</li> +<li> +<a name="QS_SessionCookiePath"></a> +<syntax>QS_SessionCookiePath <path></syntax><br> +Defines the cookie path. Default is "/". +</li> +<li> +<a name="QS_SessionKey"></a> +<syntax>QS_SessionKey <string></syntax><br> +Secret key used for cookie encryption. This key must be defined +when using the same session cookie for multiple web servers +(load balancing) or the sessions should survive a server restart. +By default, a random key is used which changes every server restart. +</li> +</ul> + +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample configuration:<br> +<pre> +<a href="#QS_ErrorPage">QS_ErrorPage</a> /error-docs/qs_error.html + +# restricts max concurrent requests for any location which has no +# individual rule: +<a href="#QS_LocRequestLimitDefault">QS_LocRequestLimitDefault</a> 200 + +# limits access to *.gif files to 100 concurrent requests: +<a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a> "^.*\.gif$" 100 + +# limits concurrent requests to the locations /images and /app/a: +<a href="#QS_LocRequestLimit">QS_LocRequestLimit</a> /images 100 +<a href="#QS_LocRequestLimit">QS_LocRequestLimit</a> /app/a 300 +# limits download bandwidth to 5Mbit/sec: +<a href="#QS_LocKBytesPerSecLimit">QS_LocKBytesPerSecLimit</a> /app/a 640 + +# two locations (/app/b and /app/c) representing a single application: +<a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a> "^(/app/b/|/app/c/).*$" 300 + + +# allows the application to nominate VIP users by sending a +# "mod-qos-vip" HTTP response header: +<a href="#QS_VipHeaderName">QS_VipHeaderName</a> mod-qos-vip +<a href="#QS_SessionKey">QS_SessionKey</a> na&5san-sB.F4_0a=%VBEBahXT1 +</pre> +</td></tr> +</table> +<br> + +<a name="privilegedusers_list"></a> +The following table shows if a rules may be deactivated for VIPs: +<table class="btable" width="280px"> +<tr><td>QS_ClientEventBlockCount</td><td>no</td></tr> +<tr><td>QS_ClientEventLimitCount</td><td>no</td></tr> +<tr><td>QS_ClientEventPerSecLimit</td><td>no</td></tr> +<tr><td>QS_ClientEventRequestLimit</td><td>no</td></tr> +<tr><td>QS_ClientPrefer</td><td>yes</td></tr> +<tr><td>QS_ClientSerialize</td><td>no</td></tr> +<tr><td>QS_ClientGeoCountryPriv</td><td>no</td></tr> +<tr><td>QS_CondLocRequestLimitMatch</td><td>yes</td></tr> +<tr><td>QS_CondEventLimitCount</td><td>no</td></tr> +<tr><td>QS_CondClientEventLimitCount</td><td>no</td></tr> +<tr><td>QS_DenyQueryBody</td><td>no</td></tr> +<tr><td>QS_PermitUriBody</td><td>no</td></tr> +<tr><td>QS_DenyEvent</td><td>no</td></tr> +<tr><td>QS_DenyPath</td><td>no</td></tr> +<tr><td>QS_DenyQuery</td><td>no</td></tr> +<tr><td>QS_DenyRequestLine</td><td>no</td></tr> +<tr><td>QS_EventKBytesPerSecLimit</td><td>yes</td></tr> +<tr><td>QS_EventPerSecLimit</td><td>yes</td></tr> +<tr><td>QS_EventRequestLimit</td><td>no</td></tr> +<tr><td>QS_EventLimitCount</td><td>no</td></tr> +<tr><td>QS_InvalidUrlEncoding</td><td>no</td></tr> +<tr><td>QS_LimitRequestBody</td><td>no</td></tr> +<tr><td>QS_LocKBytesPerSecLimit(Match)</td><td>yes</td></tr> +<tr><td>QS_LocRequestLimit(Match)</td><td>yes</td></tr> +<tr><td>QS_LocRequestPerSecLimit(Match)</td><td>yes</td></tr> +<tr><td>QS_MileStone</td><td>no</td></tr> +<tr><td>QS_RedirectIf</td><td>no</td></tr> +<tr><td>QS_PermitUri</td><td>no</td></tr> +<tr><td>QS_RequestHeaderFilter</td><td>no</td></tr> +<tr><td>QS_ResponseHeaderFilter</td><td>no</td></tr> +<tr><td>QS_SrvMaxConn</td><td>yes</td></tr> +<tr><td>QS_SrvMaxConnClose</td><td>no</td></tr> +<tr><td>QS_SrvMaxConnPerIP</td><td>yes*</td></tr> +<tr><td>QS_SrvMinDataRate</td><td>yes*</td></tr> +<tr><td>QS_SrvSerialize</td><td>no</td></tr> +<tr><td> </td><td> </td></tr> +</table> +<small><i>Notes:<br> + Directives marked by "*" allow you to disable VIP support.<br> + Event based or conditional rules may evaluate the +<a href="#QS_VipRequest">QS_VipRequest</a> and +<a href="#QS_IsVipRequest">QS_IsVipRequest</a> variables to decide +if the rule should be applied.</i></small> +<br> +<a name="variables"></a> +<h3>Variables</h3> +<a href="glossary.html#variables">Environment variables</a> are used on a per +request level and implement additional control mechanisms. Variables may be set +using the standard Apache module +<a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html">mod_setenvif <img src="images/link.png"/></a> or +<a href="http://modsetenvifplus.sourceforge.net/">mod_setenvifplus <img src="images/link.png"/></a>. +See also the <a href="#eventcontrol"> +<code><a href="#QS_SetEnvIf">QS_SetEnvIf*</a></code></a> directives in order to combine multiple +variables to form new variables interpreted by mod_qos rules. <br> +<br> +These are the variables recognized by mod_qos: +<ul> +<li> +<a name="QS_ErrorPage_Var"></a> +<syntax>QS_ErrorPage=<URL></syntax><br> +Defines the error page overriding the setting made by the +<code><a href="#QS_ErrorPage">QS_ErrorPage</a></code> directive. +</li> +<li> +<a name="QS_VipRequest"></a> +<syntax>QS_VipRequest=yes</syntax><br> +Disables some restrictions for this request (see <a href="#privilegedusers">privileged Users</a>). +Requires the definition of a VIP header using the +<code><a href="#QS_VipHeaderName">QS_VipHeaderName</a></code> directive +(this activates VIP verification). However, such an event does +not create a VIP session. The user has the VIP status only for +a single request. <br>The variable is set by mod_qos when +receiving a valid VIP <a href="#QS_SessionCookieName">session cookie</a>. +</li> +<li> +<a name="QS_KeepAliveTimeout"></a> +<syntax>QS_KeepAliveTimeout=<seconds></syntax><br> +Applies dynamic connection keep-alive settings overriding the Apache +<code><a href="http://httpd.apache.org/docs/current/mod/core.html#keepalivetimeout">KeepAliveTimeout <img src="images/link.png"/></a></code> directive settings. +</li> +<li> +<a name="QS_MaxKeepAliveRequests"></a> +<syntax>QS_MaxKeepAliveRequests=<number></syntax><br> +Applies dynamic connection keep-alive settings overriding the Apache +<code><a href="http://httpd.apache.org/docs/current/mod/core.html#maxkeepaliverequests">MaxKeepAliveRequests <img src="images/link.png"/></a></code> directive settings. +</li> +<li> +<a name="QS_Timeout"></a> +<syntax>QS_Timeout=<seconds></syntax><br> +Alters the I/O timeout (while reading the request body / writing the response) +of the current request overriding the Apache +<code><a href="http://httpd.apache.org/docs/current/mod/core.html#timeout">TimeOut <img src="images/link.png"/></a></code> +directive settings. +</li> +<li> +<a name="QS_Set_DSCP"></a> +<syntax>QS_Set_DSCP=<value></syntax><br> +Variable used to set the IP differentiated services code points +(DiffServ / RFC 2474). This allows you to classify the network +traffic when sending the response data to the client. "value" +represents the 6-bit DSCP field as a decimal number (0 to 63).<br> +Commonly used values: +<small> +<table class="btable"> +<tr><td>DSCP</td><td>Class</td><td> </td> <td>DSCP</td><td>Class</td></tr> +<tr><td>0</td><td>none</td><td> </td> <td>8</td><td>Class selector 1</td></tr> +<tr><td>10</td><td>Assured forwarding 11</td><td> </td> <td>12</td><td>Assured forwarding 12</td></tr> +<tr><td>14</td><td>Assured forwarding 13</td><td> </td> <td>16</td><td>Class selector 2</td></tr> +<tr><td>18</td><td>Assured forwarding 21</td><td> </td> <td>20</td><td>Assured forwarding 22</td></tr> +<tr><td>22</td><td>Assured forwarding 23</td><td> </td> <td>24</td><td>Class selector 3</td></tr> +<tr><td>26</td><td>Assured forwarding 31</td><td> </td> <td>28</td><td>Assured forwarding 32</td></tr> +<tr><td>30</td><td>Assured forwarding 33</td><td> </td> <td>32</td><td>Class selector 4</td></tr> +<tr><td>34</td><td>Assured forwarding 41</td><td> </td> <td>36</td><td>Assured forwarding 42</td></tr> +<tr><td>38</td><td>Assured forwarding 43</td><td> </td> <td>40</td><td>Class selector 5</td></tr> +<tr><td>44</td><td>Voice admit</td><td> </td> <td>46</td><td>Expedited forwarding</td></tr> +<tr><td>48</td><td>Class selector 6</td><td> </td> <td>56</td><td>Class selector 7</td></tr> +</table> +</small> +</li> +<li> +<a name="QS_Delay"></a> +<syntax>QS_Delay=<milliseconds></syntax><br> +Defines a number of milliseconds to delay the request processing. +</li> +<li> +<a name="QS_Event"></a> +<syntax>QS_Event</syntax><br> +The variable processed by the <code><a href="#QS_ClientEventPerSecLimit">QS_ClientEventPerSecLimit</a></code> directive. +</li> +<li> +<a name="QS_Block"></a> +<syntax>QS_Block[=<number>]</syntax><br> +Variable processed by the <code><a href="#QS_ClientEventBlockCount">QS_ClientEventBlockCount</a></code> +directive.<br> +The optional <code>number</code> value defines the penalty points to +increase the counter (default is 1). +</li> +<li> +<a name="QS_Limit"></a> +<syntax>QS_Limit[=<number>]</syntax><br> +(Default) variable processed by the +<code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code> +directive.<br> +The optional <code>number</code> value defines the penalty points to +increase the counter (default is 1). +</li> +<li> +<a name="_Clear"></a> +<syntax>*_Clear</syntax><br> +The counter of the variable processed by the +<code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code> +directive is reset if you set the same variable suffixed by <code>_Clear</code>, +e.g. <code>QS_Limit_Clear</code>. +</li> +<li> +<a name="_Decrement"></a> +<syntax>*_Decrement</syntax><br> +The counter of the variable processed by the +<code><a href="#QS_EventLimitCount">QS_EventLimitCount</a></code>, +<code><a href="#QS_CondEventLimitCount">QS_CondEventLimitCount</a></code>, +<code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code>, +<code><a href="#QS_CondClientEventLimitCount">QS_CondClientEventLimitCount</a></code>, and +<code><a href="#QS_ClientEventBlockCount">QS_ClientEventBlockCount</a></code> +directives +is decremented by the value set in the same variable suffixed by <code>_Decrement</code>, +e.g. <code>QS_Limit_Decrement=1</code> decrements the value of the <code>QS_Limit</code> +variable of the corresponding +<code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code> +rule by 1. The variable is evaluated at the end of the request processing. +</li> +<li> +<a name="QS_Serialize"></a> +<syntax>QS_Serialize</syntax><br> +Variable processed by the <code><a href="#QS_ClientSerialize">QS_ClientSerialize</a></code> +directive. +</li> +<li> +<a name="QS_SrvSerialize_var"></a> +<syntax>QS_SrvSerialize</syntax><br> +Variable processed by the <code><a href="#QS_SrvSerialize">QS_SrvSerialize</a></code> +directive. +</li> +<li> +<a name="QS_Cond"></a> +<syntax>QS_Cond</syntax><br> +Variable processed by the <code><a href="#QS_CondLocRequestLimitMatch">QS_CondLocRequestLimitMatch</a></code>, +<code><a href="#QS_CondEventLimitCount">QS_CondEventLimitCount</a></code>, and +<code><a href="#QS_CondClientEventLimitCount">QS_CondClientEventLimitCount</a></code> directives. +</li> +<li> +<a name="QS_EventRequest"></a> +<syntax>QS_EventRequest</syntax><br> +Variable processed by the <code><a href="#QS_ClientEventRequestLimit">QS_ClientEventRequestLimit</a></code> directive. +</li> +</ul> + +Variables set by mod_qos which may be processed by conditional or event based +rules, e.g., +<code><a href="#QS_CondLocRequestLimitMatch">QS_CondLocRequestLimitMatch</a></code>: +<ul> +<li> +<a name="QS_SrvConn"></a> +<syntax>QS_SrvConn</syntax><br> +Number of <a href="glossary.html#concurrency">concurrent</a> +connections for this server/virtual host. Value is set +when using either the <code><a href="#QS_SrvMaxConn">QS_SrvMaxConn</a></code>, +<code><a href="#QS_SrvMinDataRate">QS_SrvMinDataRate</a></code>, +<code><a href="#QS_SrvMaxConnClose">QS_SrvMaxConnClose</a></code>, or +<code><a href="#QS_ClientGeoCountryDB">QS_ClientGeoCountryDB</a></code> +directive. <br> +<small><i>Note: value is calulcated when the client establishes the connection +and remains the same for all HTTP requests performed on this connection.</i></small> +</li> +<li> +<a name="QS_AllConn"></a> +<syntax>QS_AllConn</syntax><br> +Number of all concurrent connections for this Apache instance. Value is set +when using either the <code><a href="#QS_SrvMaxConn">QS_SrvMaxConn</a></code>, +<code><a href="#QS_SrvMinDataRate">QS_SrvMinDataRate</a></code>, +<code><a href="#QS_SrvMaxConnClose">QS_SrvMaxConnClose</a></code>, or +<code><a href="#QS_ClientGeoCountryDB">QS_ClientGeoCountryDB</a></code> +directive. <br> +<small><i>Note: value is calulcated when the client establishes the connection +and remains the same for all HTTP requests performed on this connection.</i></small> +</li> +<li> +<a name="QS_IPConn"></a> +<syntax>QS_IPConn</syntax><br> +Number of IP connections open from the current IP address. Variable is +available when using the <code><a href="#QS_SrvMaxConnPerIP">QS_SrvMaxConnPerIP</a></code> +directive. <br> +<small><i>Note: value is calulcated when the client establishes the connection +and remains the same for all HTTP requests performed on this connection.</i></small> +</li> +<li> +<a name="QS_ClientLowPrio"></a> +<syntax>QS_ClientLowPrio</syntax><br> +The variable is set for connections by clients which have been marked to be +processed with low priority, see <code><a href="#QS_ClientPrefer">QS_ClientPrefer</a></code>. +The variable's value is determined when the client opens a new connection and +its value represents the status flag of the tracked client attributes +(hexadecimal). <a href="#privilegedusers">VIP</a> status is ignored and +the variable is always set even the IP has been marked as being VIP. +</li> +<li> +<a name="QS_IsVipRequest"></a> +<syntax>QS_IsVipRequest</syntax><br> +Variable is set when detecting a <a href="#privilegedusers">VIP</a> request +(either by cookie, IP address status, valid user, etc.). May be used by +various event based directives. +</li> +<li> +<a name="_Counter"></a> +<syntax>*_Counter</syntax><br> +The counter values of the variables used by the +<code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code> +and <code><a href="#QS_EventLimitCount">QS_EventLimitCount</a></code> +directive are stored within the variable whose name is suffixed by +<code>_Counter</code>, e.g. <code>QS_Limit_Counter</code> when limiting +<code><a href="#QS_Limit">QS_Limit</a></code> events. +</li> +<li> +<a name="QS_ErrorNotes"></a> +<syntax>QS_ErrorNotes</syntax><br> +The error code (number only) of a mod_qos <a href="#errorlog">log message</a> +that has occurred during a request. +</li> +<li> +<a name="QS_Country"></a> +<syntax>QS_Country</syntax><br> +ISO 3166 country code of client IPv4 address. Only available if the +<a href="#QS_ClientGeoCountryDB">geographical database</a> file has been loaded.<br> +<small><i>Note: You may use the <code>QS_ClientIpFromHeader <header></code> +directive to override the client's IP address based on the value within the defined +HTTP request header (e.g., X-Forwarded-For) instead of taking the IP address of +the client which has opened the TCP connection.</i></small> +</li> +<!--<li> +<syntax>QS_RuleId</syntax><br> +ID of the matching <code>QS_Deny*</code> rule. +</li>--> +</ul> + +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample of variable usage:<br> +<pre> +# privileged access for curl clients: +BrowserMatch "curl" <a href="#QS_VipRequest">QS_VipRequest</a>=yes + +# allows privileged access to a single resource: +SetEnvIf Request_URI /app/start.html <a href="#QS_VipRequest">QS_VipRequest</a>=yes + +# allows privileged access from a specified source address +# or source address range: +SetEnvIf Remote_Addr 172.18.3.32 <a href="#QS_VipRequest">QS_VipRequest</a>=yes +SetEnvIf Remote_Addr 192.168.10. <a href="#QS_VipRequest">QS_VipRequest</a>=yes + +# set keep-alive timeout for MSIE version 5.x browser to 65 seconds: +BrowserMatch "(MSIE 5\.)" <a href="#QS_KeepAliveTimeout">QS_KeepAliveTimeout</a>=65 + +# dynamic error page URL (per host error page): +SetEnvIf Host ^([a-zA-Z0-9_\.\-]+) <a href="#QS_ErrorPage">QS_ErrorPage</a>=/error-docs/$1.html +# external redirect to a sever hosting the error page: +SetEnvIf Request_URI /app <a href="#QS_ErrorPage">QS_ErrorPage</a>=http://your.server.name/error.html +</pre> +</td></tr> +</table> +<a name="QS_LogEnv"></a> +<small><i>Note: The <code>QS_LogEnv</code> directive can be used to enable environment variable logging. mod_qos +writes all environment variables which are set when entering a <a href="glossary.html#directives">handler</a> +to the log.</i></small> +<br> + +<a name="conditionalrules"></a> +<h3>Conditional Rules</h3> +Conditional rules are only enforced if the <code><a href="#QS_Cond">QS_Cond</a></code> +variable matches the specified pattern. +<ul> +<li> +<a name="QS_CondLocRequestLimitMatch"></a> +<syntax>QS_CondLocRequestLimitMatch <regex> <number> <condition></syntax><br> +Rule works similar to <a href="#QS_LocRequestLimitMatch"><code>QS_LocRequestLimitMatch</code></a> +but it is only enforced for requests whose <code><a href="#QS_Cond">QS_Cond</a></code> +variable matches the specified condition (regular expression). Every request +matching the defined pattern is counted, but the defined limitation is only +enforced for those requests matching the specified condition. <br> +Only one <code>QS_CondLocRequestLimitMatch</code> rule is evaluated per request. +</li> +<li> +<a name="QS_CondEventLimitCount"></a> +<syntax>QS_CondEventLimitCount <env-variable> <number> <seconds> <pattern></syntax><br> +Same as <code><a href="#QS_EventLimitCount">QS_EventLimitCount</a></code> but +requests are only blocked if the value of the +<code><a href="#QS_Cond">QS_Cond</a></code> +variable matches the defined pattern (regex). +</li> +<li> +<a name="QS_CondClientEventLimitCount"></a> +<syntax>QS_CondClientEventLimitCount <number> <seconds> <variable> <pattern></syntax><br> +Defines the maximum number of the specified environment variable +allowed within the defined time. Directive works similar as +<a href="#QS_ClientEventLimitCount"><code>QS_ClientEventLimitCount</code></a> +but requests are only blocked if the value of the <code><a href="#QS_Cond">QS_Cond</a></code> +variable matches the defined pattern (regex). Directive is allowed +in global server context only. <br> +</li> +</ul> + +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample of conditional rules:<br> +<pre> +# set the conditional variable to spider if detecting a +# "slurp" or "googlebot" search engine: +BrowserMatch "slurp" <a href="#QS_Cond">QS_Cond</a>=spider +BrowserMatch "googlebot" <a href="#QS_Cond">QS_Cond</a>=spider + +# limits the number of concurrent requests to two applications +# (/app/b and /app/c) to 300 but does not allow access by a "spider" +# if the number of concurrent requests exceeds the limit of 10: +<a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a> "^(/app/b/|/app/c/).*$" 300 +<a href="#QS_LocRequestLimitMatch">QS_CondLocRequestLimitMatch</a> "^(/app/b/|/app/c/).*$" 10 spider +</pre> +</td></tr> +</table> + +<a name="eventcontrol"></a> +<h3>Events</h3> +mod_qos may control the frequency of "events". An event may be any +request attribute which can be represented by an +<a href="glossary.html#variables">environment variable</a>. +Such variables may be set by +<a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html">mod_setenvif <img src="images/link.png"/></a>, +<a href="http://modsetenvifplus.sourceforge.net/">mod_setenvifplus <img src="images/link.png"/></a>, or +by other Apache modules. +Please consider the <a href="glossary.html#directives">order of command execution</a> +to ensure that the necessary variables are set. + +<ul> +<li> +<a name="QS_EventRequestLimit"></a> +<syntax>QS_EventRequestLimit <env-variable>[=<regex>] <number></syntax><br> +Defines the number of <a href="glossary.html#concurrency">concurrent</a> events. +Directive works similar to +<code><a href="#QS_LocRequestLimit">QS_LocRequestLimit</a></code>, but +counts the requests having the same environment variable (and optionally +matching its value, too) rather than those that have the same URL pattern. +<br><small><i>Note: The counter's value is stored in the environment variable +QS_EventRequestLimit_<env-variable>_Counter. +</i></small> +</li> +<li> +<a name="QS_EventPerSecLimit"></a> +<syntax>QS_EventPerSecLimit [!]<env-variable> <number></syntax><br> +Defines how often requests may have the defined environment variable +(literal string) set. It measures the occurrences of the defined +environment variable on a <a href="glossary.html#requestPerSecond">request per seconds</a> +level and tries to limit this occurrence to the defined number. It works similar as +<a href="#QS_LocRequestPerSecLimit"><code>QS_LocRequestPerSecLimit</code></a>, +but counts only the requests with the specified variable (or without it +if the variable name is prefixed by a "!"). If a request matches +multiple events, the rule with the lowest bandwidth is applied. +Events are limited by adding a delay to each request causing an +event. +</li> +<li> +<a name="QS_EventKBytesPerSecLimit"></a> +<syntax>QS_EventKBytesPerSecLimit [!]<env-variable> <number></syntax><br> +Throttles the download <a href="glossary.html#throughput">bandwidth</a> +of all requests having the defined variable set to the defined +kbytes per second. Responses are slowed by adding a delay to each +response (every 8kbytes). The delay calculation +is based on an average request rate measurement. +By default, no limitation is active. +This directive should be used in conjunction with +<code><a href="#QS_EventRequestLimit">QS_EventRequestLimit</a></code> +only (you must use the same variable name for both directives) to avoid too many +concurrent requests. +</li> +<li> +<a name="QS_EventLimitCount"></a> +<syntax>QS_EventLimitCount <env-variable> <number> <seconds></syntax><br> +Defines the maximum <a href="glossary.html#repeat">number of events allowed within the defined time</a>. +Requests causing the event are denied when reaching this limitation for the specified time +(blocked at request level).<br> +<small><i>Notes:<ul> +<li>The current counter value is propagated to the process environment within +the variable <code><env-variable><a href="#_Counter">_Counter</a></code>.</li> +<li>See also <a href="#QS_CondEventLimitCount"><code>QS_CondEventLimitCount</code></a> +if you want to enforce a rule under certain conditions only.</li> +<li>The event counter can be decremented by setting the environment +<code><env-variable><a href="#_Decrement">_Decrement</a></code>.</li> +</ul> +</i></small> +</li> +</ul> +Mulpiple built-in directives may be used to set or detect events (additional +event variable processing could be configured using +<a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html">mod_setenvif <img src="images/link.png"/></a> or +<a href="http://modsetenvifplus.sourceforge.net/">mod_setenvifplus <img src="images/link.png"/></a>). +<ul> +<li> +<a name="QS_SetEnvIf"></a> +<syntax>QS_SetEnvIf [!]<env-variable1> [!]<env-variable2> [!]<env-variable=value></syntax><br> +Sets (or unsets) the environment "variable=value" (literal string) if variable1 (literal +string) AND variable2 (literal string) are set in the request environment +variable list (not case sensitive). This is used to combine multiple +variables to a new event type.<br> +This directive may be used on a per-server or +<a href="http://httpd.apache.org/docs/current/mod/core.html.en#location">location <img src="images/link.png"/></a> +basis. +</li> +<li> +<a name="QS_SetEnvIfMatch"></a> +<syntax>QS_SetEnvIf <env-variable1>=<regex> [!]<env-variable>=<value></syntax><br> +Sets the environment variable if the environment variable1's value +matches the defined regular expression. <code>$1</code>..<code>$9</code> +within the value and are replaced by parenthesized subexpressions +of the regular expression.<br> +This directive may be used on a per-server or +<a href="http://httpd.apache.org/docs/current/mod/core.html.en#location">location <img src="images/link.png"/></a> +basis. +</li> +<li> +<a name="QS_SetEnv"></a> +<syntax>QS_SetEnv <env-variable> <value></syntax><br> +Sets the defined variable with the value where the value string may contain +other environment variables surrounded by "${" and "}". The variable is only +set if all defined variables within the value have been resolved. +</li> +<li> +<a name="QS_SetEnvIfQuery"></a> +<syntax>QS_SetEnvIfQuery <regex> [!]<env-variable>[=<value>]</syntax><br> +Directive works quite similar to the +<code><a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html#setenvif">SetEnvIf <img src="images/link.png"/></a></code> +directive of the Apache module +<a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html">mod_setenvif <img src="images/link.png"/></a>, +but the specified regex is applied against the query string +portion of the request line. The directive recognizes +the occurrences of $1..$9 within value and replaces them +by the sub-expressions of the defined regex pattern.<br> +This directive may be used on a per-server or +<a href="http://httpd.apache.org/docs/current/mod/core.html.en#location">location <img src="images/link.png"/></a> +basis. +</li> +<a name="QS_SetEnvIfCmp"></a> +<li> +<syntax>QS_SetEnvIfCmp <env-variable1> eq|ne|gt|lt <env-variable2> [!]<env-variable>[=<value>]</syntax><br> +Sets the defined environment variable if the specified env-variables[1|2] +are numerical or alphabetically (case insensitive) equal (<code>eq</code>), +not equal (<code>ne</code>) greater (<code>gt</code>), or less (<code>lt</code>).<br> +This directive may be used on a per-<a href="http://httpd.apache.org/docs/current/mod/core.html.en#location">location <img src="images/link.png"/></a> +basis only.</li> +<li> +<a name="QS_SetEnvIfParp"></a> +<syntax>QS_SetEnvIfParp <regex> [!]<env-variable>[=<value>]</syntax><br> +Directive parsing the request payload using the Apache module +<a href="http://parp.sourceforge.net">mod_parp <img src="images/link.png"/></a>. It matches +the request URL query and the HTTP request message body data as well +(<code>application/x-www-form-urlencoded</code>, +<code>multipart/form-data</code>, and <code>multipart/mixed</code>) +and sets the defined process variable (quite similar to the +<code><a href="#QS_SetEnvIfQuery">QS_SetEnvIfQuery</a></code> directive). +The directive recognizes the occurrences of $1..$9 within +value and replaces them by the sub-expressions +of the defined regex pattern. This directive activates +mod_parp for every request to the virtual host. +You may deactivate mod_parp for selected requests using the +<code><a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html#setenvif">SetEnvIf <img src="images/link.png"/></a></code> +or <code><a href="http://modsetenvifplus.sourceforge.net/#SetEnvIfPlus">SetEnvIfPlus <img src="images/link.png"/></a></code> +directive: unset the variable "parp" to do so. +Important: request message body processing requires that the server +loads the whole request into its memory (at least twice the length +of the message). You should limit the allowed size of the HTTP +request message body using the <code><a href="#QS_LimitRequestBody">QS_LimitRequestBody</a></code> directive +when using <code><a href="#QS_SetEnvIfParp">QS_SetEnvIfParp</a></code>! +</li> +<li> +<a name="QS_SetEnvIfBody"></a> +<syntax>QS_SetEnvIfBody <regex> [!]<env-variable>[=<value>]</syntax><br> +Directive parsing the request body using the Apache module +<a href="http://parp.sourceforge.net">mod_parp <img src="images/link.png"/></a>. Specify the content +types to process using the mod_parp directive +<code><a href="http://parp.sourceforge.net/#PARP_BodyData">PARP_BodyData <img src="images/link.png"/></a></code> +and ensure that mod_parp is enabled using the +<code><a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html#setenvif">SetEnvIf <img src="images/link.png"/></a></code> +or <code><a href="http://modsetenvifplus.sourceforge.net/#SetEnvIfPlus">SetEnvIfPlus <img src="images/link.png"/></a></code> +directive. +You should limit the allowed size of HTTP requests message body +using the <code><a href="#QS_LimitRequestBody">QS_LimitRequestBody</a></code> +directive when using mod_parp. The directive recognizes the occurrence of $1 +within the variable value and replaces it by the sub-expressions of the +defined regex pattern. The regular expressions is case insensitive. +</li> +<li> +<a name="QS_SetEnvIfStatus"></a> +<syntax>QS_SetEnvIfStatus <code> <env-variable>[=<value>]</syntax><br> +Sets the defined variable in the request environment if the HTTP +response status code matches the defined code. Default value is the status code, but +you might override this by any other value. +Directive may be used on a per-server or per-location basis. <br> +A possible use case for this directive is the prevention of +repetitive occurrence of unwanted response status codes in +conjunction with the +<code><a href="#QS_ClientEventBlockCount">QS_ClientEventBlockCount</a></code> or +<code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code> +directive. <br> +When using the special variable <code><a href="#QS_Block">QS_Block</a></code>, its +value is set to "1" by default. There are also four "special codes" available to +set the <code><a href="#QS_Block">QS_Block</a></code> event: +<ul> +<li><a name="QS_SrvMinDataRate_var"></a> +<code><a href="#QS_SrvMinDataRate">QS_SrvMinDataRate</a></code> may be used +to set <code><a href="#QS_Block">QS_Block</a></code> events in order to limit the +allowed number of <a href="#QS_SrvMinDataRate"><code>QS_SrvMinDataRate</code></a> +rule violations.</li> +<li><a name="QS_SrvMaxConnPerIP_var"></a> +<code><a href="#QS_SrvMaxConnPerIP">QS_SrvMaxConnPerIP</a></code> may be used +to increment the <code><a href="#QS_Block">QS_Block</a></code> +event when closing connections due to the reach of the limitation configured +by the <a href="#QS_SrvMaxConnPerIP"><code>QS_SrvMaxConnPerIP</code></a> directive.</li> +<li><a name="NullConnection"></a> +<code>NullConnection</code> detects connections +which are closed even no HTTP request has been received. <br> +<small><i>Note: The <code>NullConnection</code> event may happen silently (no log +message) expect when using <code><a href="http://httpd.apache.org/docs/current/mod/core.html#loglevel">LogLevel <img src="images/link.png"/></a></code> "debug". +The parameter may be used to defend against SSL DoS attacks. <!-- "defend against SSL DoS attacks" is a MARKER --> +Please pay attention to the fact that unused speculative TCP pre-connections of +browsers may unintentionally cause this event as well.</i></small></li> +<li><a name="BrokenConnection"></a> +<code>BrokenConnection</code> may be used +to mark clients aborting the TCP connection before reading the whole HTTP +response.<br> +<small><i>Note: Connections may also be aborted by mod_qos if client reads +the response too slow.</i></small></li> +</ul> +</li> +<li> +<a name="QS_SetEnvIfResBody"></a> +<syntax>QS_SetEnvIfResBody <string> [!]<env-variable></syntax><br> +Adds the defined environment variable (e.g., <code><a href="#QS_Block">QS_Block</a></code>) +if the response body contains the defined literal string. Used on a per- +<a href="http://httpd.apache.org/docs/current/mod/core.html.en#location">location <img src="images/link.png"/></a> +level. Only one directive may be defined per-location +(one search string per response). Prefixing the variably by a "!" +lets the variable being removed (unset). You may set the <code>QS_SetEnvIfResBodyIgnore</code> +environment variable if you want mod_qos to skip (not parsing) a request's response +body. +</li> +<li> +<a name="QS_SetEnvRes"></a> +<syntax>QS_SetEnvRes <env-variable> <regex> <env-variable2>[=<value>]</syntax><br> +Sets the environment variable (env-variable2) if the regular expression (regex) matches +against the value of the environment variable (env-variable). Occurrences of $1..$9 within +the value are replaced by parenthesized subexpressions of the regular expression. +</li> +<li> +<a name="QS_SetReqHeader"></a> +<syntax>QS_SetReqHeader [!]<header name> <env-variable> [late]</syntax><br> +Sets the defined HTTP request header with the value of the specified +environment variable if the variable is available.<br> +The header is unset (removed from the request) if the header name is prefixed by a "!". +</li> +<li> +<a name="QS_SetEnvResHeader"></a> +<syntax>QS_SetEnvResHeader <header name> [drop]</syntax><br> +Sets the defined HTTP response header (name and value) to the request environment variables. +Deletes the specified header if the action 'drop' has been specified. +</li> +<li> +<a name="QS_SetEnvResHeaderMatch"></a> +<syntax>QS_SetEnvResHeaderMatch <header name> <regex></syntax><br> +Sets the defined HTTP response header (name and value) to the request environment variables if +the specified regular expression (pcre, not case sensitive) matches +the header value. +</li> +<li> +<a name="QS_UnsetReqHeader"></a> +<syntax>QS_UnsetReqHeader <header name></syntax><br> +The request header of this name is removed. +</li> +<li> +<a name="QS_UnsetResHeader"></a> +<syntax>QS_UnsetResHeader <header name></syntax><br> +The response header of this name is removed. +</li> +<li> +<a name="QS_RedirectIf"></a> +<syntax>QS_RedirectIf <variable> <regex> [<code>:]<url></syntax><br> +Redirects the client to the configured url if the regular expression (case insensitive) +matches the value of the the environment variable. Occurrences of $1..$9 +within the url are replaced by parenthesized subexpressions of the +regular expression. The default status code used by this directive is 302 +but you may prefix the url parameter by <i>307:</i> or <i>301:</i> to change +it to a "307 Temporary Redirect" or "301 Moved Permanently" response. +Directive may be used on a per-server or per-location basis. +</li> +</ul> + +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample of event rules:<br> +<pre> +# marks clients coming from the internal network: +SetEnvIf Remote_Addr ^192\.168\. QS_Intra + +# marks clients neither coming from the internal network +# nor are VIP clients as low priority clients: +<a href="#QS_SetEnvIf">QS_SetEnvIf</a> !<a href="#QS_VipRequest">QS_VipRequest</a> !QS_Intra QS_LowPrio=1 + +# limits the request rate for low priority (neither VIP nor internal) +# clients (and no more than 400 concurrent requests for them): +<a href="#QS_EventPerSecLimit">QS_EventPerSecLimit</a> QS_LowPrio 100 +<a href="#QS_EventRequestLimit">QS_EventRequestLimit</a> QS_LowPrio 400 + +# detects the variable "file" within the query portion of the URL: +<a href="#QS_SetEnvIfQuery">QS_SetEnvIfQuery</a> file=([a-zA-Z]*) QS_LowPrio=$1 + +# combine variables and propagate them to the application via HTTP header: +SetEnvIf Content-Length ([0-9]*) QS_Length=$1 +<a href="#QS_SetEnv">QS_SetEnv</a> QS_Type "length=${QS_Length}; file=${QS_LowPrio}" +<a href="#QS_SetReqHeader">QS_SetReqHeader</a> X-File QS_Type + +# limit the max. body size since mod_parp loads the whole message into +# the memory servers's: +<a href="#QS_LimitRequestBody">QS_LimitRequestBody</a> 131072 + +# body pattern detection, example limits the maximum number of concurrent +# requests posting "id=1234" to ten: +<a href="#QS_SetEnvIfParp">QS_SetEnvIfParp</a> id=([0-9]*) PARP_PATTERN=$1 +<a href="#QS_EventRequestLimit">QS_EventRequestLimit</a> PARP_PATTERN=1234 10 +# but ignore requests to the location /main/ (any sub-locations): +SetEnvIf Request_URI /main/.* !parp +</pre> +</td></tr> +</table> + +<a name="filter"></a> +<h3>Request Level, Generic Filter</h3> +These filters are defined on a per- +<a href="http://httpd.apache.org/docs/current/mod/core.html.en#location">location <img src="images/link.png"/></a> +level and are used to restrict access to resources in +general, independent of server resource availability. +New rules are added by defining a rule id prefixed by a '+'. Rules are merged +to sub-locations. If a rule should not be active for a sub-location, the +very same rule must be defined, but instead, the rule id must be prefixed with a '-'. The filter rules are implemented as Perl-compatible regular expressions +(pcre) and are applied to the decoded URL components (un-escaped characters, +e.g., %20 is a space). The generic request filter ignores the +<a href="#privilegedusers">VIP</a> status of a client.<br> +<small><i>Note: Compile mod_qos with the preprocessor definition +<code>-DQS_MOD_EXT_HOOKS</code> to enable the decoding hooks defined +in <code>mod_qos.h</code> if you intend to implement additional +decodings by other Apache modules.</i></small> +<ul> +<li> +<a name="QS_DenyRequestLine"></a> +<syntax>QS_DenyRequestLine '+'|'-'<id> 'log'|'deny' <pcre></syntax><br> +Generic request line (method, path, query, and protocol) filter used to +deny access for requests matching the defined expression (pcre, case insensitive). +The action taken for matching rules is either 'log' (access is granted but the rule +match is logged) or 'deny' (access is denied). +</li> +<li> +<a name="QS_DenyPath"></a> +<syntax>QS_DenyPath '+'|'-'<id> 'log'|'deny' <pcre></syntax><br> +Generic abs_path (see RFC 2616 section 3.2.2) filter used to deny access +for requests matching the defined expression (pcre, case insensitive). +The action taken for matching rules is either 'log' (access is granted +but the rule match is logged) or 'deny' (access is denied). +</li> +<li> +<a name="QS_DenyQuery"></a> +<syntax>QS_DenyQuery '+'|'-'<id> 'log'|'deny' <pcre></syntax><br> +Generic query (see RFC 2616 section 3.2.2) filter used to deny access for +requests matching the defined expression (pcre, case insensitive). +The action taken for matching rules is either 'log' (access is granted +but the rule match is logged) or 'deny' (access is denied). +</li> +<li> +<a name="QS_InvalidUrlEncoding"></a> +<syntax>QS_InvalidUrlEncoding 'log'|'deny'|'off'</syntax><br> +Enforces correct URL decoding in conjunction with the +<code><a href="#QS_DenyRequestLine">QS_DenyRequestLine</a></code>, +<code><a href="#QS_DenyPath">QS_DenyPath</a></code>, and +<code><a href="#QS_DenyQuery">QS_DenyQuery</a></code> directives. +Default is "off" which means that an incorrect encoding does stop +request processing. +</li> +<li> +<a name="QS_Decoding"></a> +<syntax>QS_Decoding 'uni'</syntax><br> +Enables additional string decoding functions which are applied before +matching <code>QS_Deny*</code> and <code>QS_Permit*</code> directives. +Default is URL decoding (%xx, \\xHH, '+'). <br>Available additional decodings: +<ul> +<li><code>uni</code>: unicode decoding for MS IIS (%uXXXX and \uXXXX) encoded characters. +</li> +</ul> +</li> +<li> +<a name="QS_DenyEvent"></a> +<syntax>QS_DenyEvent '+'|'-'<id> 'log'|'deny' [!]<env-variable></syntax><br> +Rule matching requests having the defined process environment variable set +(or NOT set if prefixed by a '!'). +The action taken for matching rules is either 'log' (access is granted +but the rule match is logged) or 'deny' (access is denied). +</li> +<li> +<a name="QS_PermitUri"></a> +<syntax>QS_PermitUri '+'|'-'<id> 'log'|'deny' <pcre></syntax><br> +Generic URL (path and query) filter implementing a request pattern +allow list. Only requests matching at least one <code>QS_PermitUri</code> +pattern are allowed. If a <code>QS_PermitUri</code> pattern has +been defined and the request does not match any rule, the request +is denied. +All rules must define the same action. pcre is case sensitive. +You may use the <code><a href="qsfilter2.1.html">qsfilter2</a></code> +utility to generate rules based on access log files. +</li> +<li> +<a name="QS_DenyInheritanceOff"></a> +<syntax>QS_DenyInheritanceOff</syntax><br> +Disables inheritance of <code>QS_Deny*</code> and <code>QS_Permit*</code> +directives (pattern definitions) to a location. +</li> +<li> +<a name="QS_RequestHeaderFilter"></a> +<syntax>QS_RequestHeaderFilter 'on'|'off'|'size'</syntax><br> +Filters request headers using validation rules <a href="headerfilterrules.txt">provided by mod_qos</a>. +Suspicious headers (not matching the pattern or those which are too long) are normally +dropped (removed from the request). Abnormal <code>content-*</code> headers cause +request blocking. Only the defined headers are allowed (allow list). Custom +rules (additional headers or different pattern/size definitions) may be +added using the +<code><a href="#QS_RequestHeaderFilterRule">QS_RequestHeaderFilterRule</a></code> +directive.<br> +This directive has three different operation modes: 'on' (activated), 'off' (disabled), +and 'size' (activated). The operation mode enabled by 'size' does not check the header +values against the patterns but limits the maximum length of request header +values only (similar to the Apache directive <code>LimitRequestFieldsize</code> +but with an individual rule for each header field). +This directive may be used on a per-server or per-location level.<br> +<small><i>Notes:<ul><li>Header validation is also useful to avoid bypassing of +<code><a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html#setenvif">SetEnvIf <img src="images/link.png"/></a></code> / +<code><a href="http://modsetenvifplus.sourceforge.net/#SetEnvIfPlus">SetEnvIfPlus <img src="images/link.png"/></a></code> +(if configured on a per-location level) directive settings as request headers have higher priority than +<a href="glossary.html#variables">environment variables</a> for those +directives and therefore a header sent a by client +can override an environment variable having the same name.</li> +<li> +You might also configure deny list rules (delete unwanted headers) using the +<code><a href="#QS_UnsetReqHeader">QS_UnsetReqHeader</a></code> or +<code><a href="#QS_UnsetResHeader">QS_UnsetResHeader</a></code> directive. +</li> +</ul></i></small> +</li> +<li> +<a name="QS_RequestHeaderFilterRule"></a> +<syntax>QS_RequestHeaderFilterRule <header name> 'drop'|'deny' <pcre> <size></syntax><br> +Used to add custom request header filter rules, e.g., to override the +<a href="headerfilterrules.txt">internal rules</a> (different pcre or size) +or to add additional headers which should be allowed. +Definitions are made globally (outside VirtualHost). The list of all loaded rules +is shown at server startup when using <code><a href="http://httpd.apache.org/docs/current/mod/core.html#loglevel">LogLevel <img src="images/link.png"/></a></code> "debug". pcre is +case sensitive. The size parameter defines the maximum length of a header value. +The action 'drop' removes a header not matching the pcre, the action 'deny' +rejects a request including such a header not matching the pcre. +</li> +<li> +<a name="QS_ResponseHeaderFilter"></a> +<syntax>QS_ResponseHeaderFilter 'on'|'silent'|'off'</syntax><br> +Filters response headers using validation rules <a href="headerfilterrules.txt">provided by mod_qos</a>. +Suspicious headers (not matching the pattern or those which are too long) are removed +from the response. Only the defined headers are allowed. Filter +is activated ('on' or 'silent') or deactivated ('off'). +</li> +<li> +<a name="QS_ResponseHeaderFilterRule"></a> +<syntax>QS_ResponseHeaderFilterRule <header name> <pcre> <size></syntax><br> +Used to add custom response header filter rules, e.g., to override the +<a href="headerfilterrules.txt">internal rules</a> +(different pcre or size) or to add additional headers which should be allowed. +Definitions are made globally (outside VirtualHost). A list of all loaded rules +is shown at server startup when using <code><a href="http://httpd.apache.org/docs/current/mod/core.html#loglevel">LogLevel <img src="images/link.png"/></a></code> "debug". pcre is +case sensitive. The size parameter defines the maximum length of a header value. +</li> +</ul> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample configuration:<br> +<pre> +<a href="#QS_ErrorPage">QS_ErrorPage</a> /error-docs/qs_error.html + +# add a custom request header rule: +<a href="#QS_RequestHeaderFilterRule">QS_RequestHeaderFilterRule</a> UA-CPU drop "^[a-zA-Z0-9]+$" 20 + +# enable header validation: +<a href="#QS_RequestHeaderFilter">QS_RequestHeaderFilter</a> on + +<Location /> + # don't allow access to the path /app/admin.jsp: + <a href="#QS_DenyPath">QS_DenyPath</a> +admin deny "^/app/admin.jsp$" + + # allow printable characters only within the request line: + <a href="#QS_DenyRequestLine">QS_DenyRequestLine</a> +printable deny ".*[\x00-\x19].*" +</Location> +</pre> +</td></tr> +</table> +</p> +<p> +Body data filtering requires <a href="http://parp.sourceforge.net">mod_parp <img src="images/link.png"/></a> +which processes the request's message body of the following HTTP request content types: +<code>application/x-www-form-urlencoded</code>, +<code>multipart/form-data</code>, and <code>multipart/mixed</code>. The content type +<code>application/json</code> may be processed by the built-in JSON parser of mod_qos. The body +data is transformed into a request query and may be filtered using the +<code><a href="#QS_DenyQuery">QS_DenyQuery</a></code> and +<code><a href="#QS_PermitUri">QS_PermitUri</a></code> directives. +<ul> +<li> +<a name="QS_DenyQueryBody"></a> +<syntax>QS_DenyQueryBody 'on|'off'</syntax><br> +Enables request body data filtering for the +<code><a href="#QS_DenyQuery">QS_DenyQuery</a></code> directive. +</li> +<li> +<a name="QS_PermitUriBody"></a> +<syntax>QS_PermitUriBody 'on|'off'</syntax><br> +Enables request body data filtering for the +<code><a href="#QS_PermitUri">QS_PermitUri</a></code> directive. +</li> +<li> +<a name="QS_LimitRequestBody"></a> +<syntax>QS_LimitRequestBody <bytes></syntax><br> +Limits the allowed size of an HTTP request message body. This directive may +be placed anywhere in the configuration. Alternatively, the limitation +may be set as an environment variable using +<a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html">mod_setenvif <img src="images/link.png"/></a> +(overriding the directive settings). +</li> +</ul> + +<a name="QS_DeflateReqBody"></a> +Set the <code>QS_DeflateReqBody</code> variable if the request body data has to +be deflated (compressed data) using +<a href="http://httpd.apache.org/docs/current/mod/mod_deflate.html">mod_deflate <img src="images/link.png"/></a>. + +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample configuration:<br><a name="qsfiltersample"></a> +<pre> +# configure the audit log writing the request body data to a file +# (use this log to generate allow list rules using <a href="qsfilter2.1.html">qsfilter2</a> +# when <a href="#QS_PermitUriBody">QS_PermitUriBody</a> has been enabled) +# format: +# %h: +# The remote host (used to filter by IP address). +# %>s: +# The HTTP response status code. +# %{qos-loc}n +# The matching Location to generate the rules for. +# %{qos-path}n%{qos-query}n +# The request data required by qsfilter2 to generate rules. +CustomLog logs/qsaudit_log "%h %>s %{qos-loc}n %{qos-path}n%{qos-query}n" + +# enable json parser +PARP_BodyData application/json + +<a href="#QS_RequestHeaderFilter">QS_RequestHeaderFilter</a> on + +# limit the max. body size since mod_parp loads the whole message into the +# servers's memory: +SetEnvIfNoCase Content-Type application/x-www-form-urlencoded <a href="#QS_LimitRequestBody">QS_LimitRequestBody</a>=131072 +SetEnvIfNoCase Content-Type multipart/form-data <a href="#QS_LimitRequestBody">QS_LimitRequestBody</a>=131072 +SetEnvIfNoCase Content-Type multipart/mixed <a href="#QS_LimitRequestBody">QS_LimitRequestBody</a>=131072 +SetEnvIfNoCase Content-Type application/json <a href="#QS_LimitRequestBody">QS_LimitRequestBody</a>=65536 + +# enable mod_deflate input filter for compressed request body data: +SetEnvIfNoCase Content-Encoding (gzip|compress|deflate) <a href="#QS_DeflateReqBody">QS_DeflateReqBody</a> + +<Location /app> + # don't allow a certain string pattern within the request query or + # the request message body data: + <a href="#QS_DenyQueryBody">QS_DenyQueryBody</a> on + <a href="#QS_DenyQuery">QS_DenyQuery</a> +s01 deny "(EXEC|SELECT|INSERT|UPDATE|DELETE)" +</Location> +</pre> +</td></tr> +</table> +You may enable request body filtering for arbitrary content types: +<ul> +<li>Register the <a href="http://parp.sourceforge.net">mod_parp <img src="images/link.png"/></a> raw parser using the +<code><a href="http://parp.sourceforge.net/#PARP_BodyData">PARP_BodyData <img src="images/link.png"/></a></code> directive.</li> +<li>Enable mod_parp for the content type using the +<code><a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html#setenvifnocase">SetEnvIfNoCase <img src="images/link.png"/></a></code> directive.</li> +<li>Use <code><a href="#QS_SetEnvIfBody">QS_SetEnvIfBody</a></code> to detect patterns within the HTTP request body.</li> +<li>The <code><a href="#QS_DenyEvent">QS_DenyEvent</a></code> directive denies access for the request.</li> +</ul> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample configuration:<br> +<pre> +# sample (using the raw body parser of mod_parp) which denies XML documents +# containing the pattern "<code>delete</code>": +PARP_BodyData text/xml +SetEnvIfNoCase Content-Type text/xml.* parp +SetEnvIfNoCase Content-Type application/xml <a href="#QS_LimitRequestBody">QS_LimitRequestBody</a>=65536 +<a href="#QS_SetEnvIfBody">QS_SetEnvIfBody</a> <code>delete</code> DENYACTION +<Location /app/web> + <a href="#QS_DenyEvent">QS_DenyEvent</a> +BADCODE deny DENYACTION +</Location> +</pre> +</td></tr> +</table> +</p> +<p> +<a name="QS_MileStone"></a> +<h4>Milestones</h4> +You may define a number of resources (request line patterns) as milestones. A +client must access these resources in the correct order as they are defined within +the server configuration. A client is not allowed to skip these milestones (but may access +any other resource not covered by a milestone in between requests to milestones). +<ul> +<li> +<syntax>QS_MileStone 'log'|'deny' <pattern> [<thinktime>]</syntax><br> +Defines request line patterns a client must access in the defined order as +they are defined in the configuration file. The optional 'thinktime' parameter +defines the minimal elapse time (in seconds) between two milestones. +Milestones are defined on a per-server basis, outside +<a href="http://httpd.apache.org/docs/current/mod/core.html.en#location">location <img src="images/link.png"/></a>. +Access to milestones is tracked by a dedicated +<a href="#QS_SessionKey">session cookie</a> (QSSCD). +</li> +<li> +<a name="QS_MileStoneTimeout"></a> +<syntax>QS_MileStoneTimeout <seconds></syntax><br> +Defines the time in seconds within which a client must reach the next +milestone. Default are 3600 seconds. +</li> +</ul> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample configuration:<br> +<pre> +# four milestones: +# 1) client must start with /app/index.html +# 2) and then read some images (e.g. media used within the first page) +# 3) before posting data to /app/register +# 4) afterwards, the user may download zip files +<a href="#QS_MileStone">QS_MileStone</a> deny "^GET /app/index.html" +<a href="#QS_MileStone">QS_MileStone</a> deny "^GET /app/images/.*" +<a href="#QS_MileStone">QS_MileStone</a> deny "^POST /app/register*" +<a href="#QS_MileStone">QS_MileStone</a> deny "^GET /app/.*\.zip HTTP/..." +</pre> +</td></tr> +</table> +</p> + +<a name="connectionlevelcontrol"></a> +<h3>Connection Level Control</h3> +<p> +The module features the following directives to control server access on a per-server +(TCP connection) level. These directives must only be used in the global server context +and for port based virtual hosts. +Virtual hosts neither defining <code>QS_SrvMaxConn</code>, <code>QS_SrvMaxConnClose</code>, +nor <code>QS_SrvMaxConnPerIP</code> are using the base server's settings and counters. +And do not use these three directives for name based virtual hosts! +<ul> +<li> +<a name="QS_SrvMaxConn"></a> +<syntax>QS_SrvMaxConn <number></syntax><br> +Defines the maximum allowed number of <a href="glossary.html#concurrency">concurrent</a> +TCP connections for this server (virtual host). +</li> +<li> +<a name="QS_SrvMaxConnClose"></a> +<syntax>QS_SrvMaxConnClose <number>[%]</syntax><br> +Defines the maximum number of connections for this server (virtual host) supporting +HTTP keep-alive. If the number of <a href="glossary.html#concurrency">concurrent</a> +connections exceeds this threshold, the TCP connections +gets closed after each request. You may specify the number of +connections as a percentage of <a href="http://httpd.apache.org/docs/current/mod/mpm_common.html#maxrequestworkers"><code>MaxClients</code> <img src="images/link.png"/></a> if adding the suffix '%' to the +specified value.<br> +<small><i>Note: It's also possible to control the Keep-Alive settings dynamically using +the <code><a href="#QS_KeepAliveTimeout">QS_KeepAliveTimeout</a></code> +and <code><a href="#QS_MaxKeepAliveRequests">QS_MaxKeepAliveRequests</a></code> +environment <a href="glossary.html#variables">variables</a>.</i></small> +</li> +<li> +<a name="QS_SrvMaxConnPerIP"></a> +<syntax>QS_SrvMaxConnPerIP <number> [<connections>]</syntax><br> +Defines the maximum number of connections per source IP address for this server (virtual host). +The "connections" argument defines the number of busy connections of the server +(all virtual hosts) to enable this limitation, default is 0 (which means that the limitation +is always enabled, even the server is idle). +</li> +<li> +<a name="QS_SrvMaxConnExcludeIP"></a> +<syntax>QS_SrvMaxConnExcludeIP <address></syntax><br> +Defines an IP address or address range to be excluded from connection +level control restrictions (trusted proxy servers). An address range +must end with a "." or ":". +</li> +<li> +<a name="QS_SrvMaxConnPerIPIgnoreVIP"></a> +<syntax>QS_SrvMaxConnPerIPIgnoreVIP 'on'|'off'</syntax><br> +Tells the <a href="#QS_SrvMaxConnPerIP"><code>QS_SrvMaxConnPerIP</code></a> directive +to ignore (if set to "on") the <a href="#privilegedusers">VIP</a> status of +clients. Default is "off", which means that <code>QS_SrvMaxConnPerIP</code> gets +disabled for VIPs. +</li> +<li> +<a name="QS_SrvMinDataRate"></a> +<syntax>QS_SrvMinDataRate <bytes per second> [<max bytes per second> [<connections>]]</syntax><br> +Defines the minimum upload/download throughput a client must generate (the bytes +sent/received by the client per seconds). This bandwidth is measured while +receiving request data (<i>in</i>: request line, header fields, or body), sending response data +(<i>out</i>: header fields, body) and during keep-alive (<i>enforce keep-alive</i>). +The client connection is closed if the client does not fulfill this required minimal +data rate and the IP address of the causing client is marked in order to be handled +with low priority (see the <code><a href="#QS_ClientPrefer">QS_ClientPrefer</a></code> directive). +The "max bytes per second" activates <u><a href="images/SrvMinDataRate.png">dynamic minimum throughput control</a></u>: +The required minimal throughput is increased in parallel to the number of concurrent clients +sending/receiving data (starts increasing when reaching the "connections" threshold) +as a percentage of the "max bytes per second" which maximum is reached when the number of +sending/receiving clients is equal to the <code>MaxClients</code> setting. +The "connections" argument is used to specify the number of busy TCP connections a +server must have to enable this feature (used to disable the +<code>QS_SrvMinDataRate</code> rule enforcement on idle servers).<br> +This directives must only be used in the global server context. +</li> +<li> +<a name="QS_SrvRequestRate"></a> +<syntax>QS_SrvRequestRate <bytes per second> [<max bytes per second>]</syntax><br> +Same as <code><a href="#QS_SrvMinDataRate">QS_SrvMinDataRate</a></code> but enforcing a +minimal upload (reading request) throughput only. +</li> +<li> +<a name="QS_SrvDataRateOff"></a> +<syntax>QS_SrvDataRateOff</syntax><br> +Disables the <code><a href="#QS_SrvMinDataRate">QS_SrvMinDataRate</a></code> or +<code><a href="#QS_SrvRequestRate">QS_SrvRequestRate</a></code> enforcement +for a virtual host. +</li> +<li> +<a name="QS_SrvMinDataRateOffEvent"></a> +<syntax>QS_SrvMinDataRateOffEvent '+'|'-'<env-variable></syntax><br> +Disables the <code><a href="#QS_SrvMinDataRate">QS_SrvMinDataRate</a></code> or +<code><a href="#QS_SrvRequestRate">QS_SrvRequestRate</a></code> enforcement +for a connection when the defined process environment variable is set. +The '+' prefix is used to add a variable to the configuration while the '-' prefix +is used to remove a variable. Directive may be used on a per-server or a +per-<a href="http://httpd.apache.org/docs/current/mod/core.html.en#location">location <img src="images/link.png"/></a> basis. +</li> +<li> +<a name="QS_SrvSampleRate"></a> +<syntax>QS_SrvSampleRate <seconds></syntax><br> +Defines the sampling rate used to measure the data throughput. +Default is 5 seconds or the value you have used for +<code>QS_REQ_RATE_TM</code> while compiling the module. +Increase this value if you want to compensate bandwidth +variations.<br> +This directives must only be used in the global server context.<br> +<small><i>Note: It might also be increased to avoid too many error messages generated by a +<code>QS_SrvMinDataRate</code> rule for clients opening unused TCP pre-connections +which might happen if Apache's +<code><a href="http://httpd.apache.org/docs/current/mod/core.html#timeout">TimeOut <img src="images/link.png"/></a></code> directive is set to higher value than this sample rate. +</i></small> +</li> +<li> +<a name="QS_SrvMinDataRateIgnoreVIP"></a> +<syntax>QS_SrvMinDataRateIgnoreVIP 'on'|'off'</syntax><br> +Tells the <a href="#QS_SrvMinDataRate"><code>QS_SrvMinDataRate</code></a> directive +to ignore (if set to "on") the <a href="#privilegedusers">VIP</a> status of +clients. Default is "off", which means that <code>QS_SrvMinDataRate</code> gets +disabled for VIPs. +</li> +<li> +<a name="QS_SrvSerialize"></a> +<syntax>QS_SrvSerialize 'on'|'off' [<timeout>]</syntax><br> +Ensures that not more than one request having the +<a href="#QS_SrvSerialize_var"><code>QS_SrvSerialize</code></a> +variable set is processed at the same time by +<a href="glossary.html#serialization">serializing</a> them +(process one request after each other). Default is "off".<br> +<small><i>Note: Maximum wait time for a request is defined by the +optional timeout parameter (in seconds). The default is 300 seconds. +</i></small> +</li> +<li> +Throttling the download bandwidth: +mod_qos does not support bandwidth limitation on a per connection +basis but you might use the <code>RATE_LIMIT</code> filter +provided by the Apache module +<a href="https://httpd.apache.org/docs/2.4/mod/mod_ratelimit.html">mod_ratelimit <img src="images/link.png"/></a> +to implement a bandwidth rate limitation for connections. +</li> +</ul> + +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample configuration:<br> +<pre> +# minimum data rate (bytes/sec) when the server +# has 150 or more open TCP connections: +<a href="#QS_SrvMinDataRate">QS_SrvMinDataRate</a> 64 256 150 + +# limits the connections for this virtual host: +<a href="#QS_SrvMaxConn">QS_SrvMaxConn</a> 800 + +# allows keep-alive support till the server reaches 600 connections: +<a href="#QS_SrvMaxConnClose">QS_SrvMaxConnClose</a> 600 + +# allows max 50 connections from a single ip address: +<a href="#QS_SrvMaxConnPerIP">QS_SrvMaxConnPerIP</a> 50 + +# disables connection restrictions for certain clients: +<a href="#QS_SrvMaxConnExcludeIP">QS_SrvMaxConnExcludeIP</a> 172.18.3.32 +<a href="#QS_SrvMaxConnExcludeIP">QS_SrvMaxConnExcludeIP</a> 192.168.10. +</pre> +</td></tr> +</table> +</p> + +<a name="clientlevelcontrol"></a> +<h3>Client Level Control</h3> +<p> +Client level control rules are applied per client (IP source address). +These directives must only be used in the global server context. +<ul> +<li> +<a name="QS_ClientEntries"></a> +<syntax>QS_ClientEntries <number></syntax><br> +Defines the number of individual clients managed by mod_qos. +Default is 50'000 concurrent IP addresses. Each client requires +about 150 bytes memory on a 64bit system (depending on how many +<code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code> +events you have configured). Client IP source address store +survives graceful server restart. The maximum value is 10'000'000. +</li> +<li> +<a name="QS_ClientEventRequestLimit"></a> +<syntax>QS_ClientEventRequestLimit <number></syntax><br> +Defines the allowed number of <a href="glossary.html#concurrency">concurrent</a> +requests coming from the same client source IP address having the +<code><a href="#QS_EventRequest">QS_EventRequest</a></code> variable set.<br> +<small><i>Note: You may use the <code>QS_ClientIpFromHeader <header></code> +directive to override the client's IP address based on the value within the defined +HTTP request header (e.g., X-Forwarded-For) instead of taking the IP address of +the client which has opened the TCP connection.</i></small> +</li> +<li> +<a name="QS_ClientEventPerSecLimit"></a> +<syntax>QS_ClientEventPerSecLimit <number></syntax><br> +Defines how often a client may cause a +<code><a href="#QS_Event">QS_Event</a></code> +<a href="glossary.html#requestPerSecond">per second</a>. Such events are requests having the +<code><a href="#QS_Event">QS_Event</a></code> variable set, e.g., defined by +using the <code><a href="http://httpd.apache.org/docs/current/mod/mod_setenvif.html#setenvif">SetEnvIf <img src="images/link.png"/></a></code> directive. +The rule is enforced by adding a delay to requests causing +the event (similar to the <code><a href="#QS_LocRequestPerSecLimit">QS_LocRequestPerSecLimit</a></code> +directive). +</li> +<li> +<a name="QS_ClientEventBlockCount"></a> +<a name="QS_ClientEventBlockExcludeIP"></a> +<syntax>QS_ClientEventBlockCount <number> [<seconds>]</syntax><br> +Defines the <a href="glossary.html#repeat">maximum number</a> of <code><a href="#QS_Block">QS_Block</a></code> +events allowed within the defined time (default is 600 seconds). +Client IP is blocked when reaching this counter for the specified +time (blocked at connection level: user might not always get a +user friendly error response).<br/> +<small><i>Notes: +<ul> +<li> +You may use <code>QS_ClientEventBlockExcludeIP <addr></code> +to exclude an IP address from being processed by this limitation +(e.g. for trusted clients connecting via a proxy server). An address +range must end with a "." or ":". +</li> +<li>The counter can be decremented by setting the environment +variable <code><a href="#_Decrement">QS_Block_Decrement</a></code>. +</li> +</ul></i></small> +</li> +<li> +<a name="QS_ClientEventLimitCount"></a> +<syntax>QS_ClientEventLimitCount <number> [<seconds> [<variable>]]</syntax><br> +Defines the <a href="glossary.html#repeat">maximum number</a> of requests +having the defined environment variables +(<code><a href="#QS_Limit">QS_Limit</a></code> by default) set allowed within +the defined time (default is 600 seconds). Requests from client IP's reaching +this limitation are denied for the specified time (blocked at request level). <br/> +<small><i>Notes: +<ul> +<li>The value of the variable defines the penalty points by which the counters +are increased. Default (empty or non-numeric value) is 1 (increment per request).</li> +<li><a name="QS_ClientIpFromHeader"></a> +You may use the <code>QS_ClientIpFromHeader <header></code> +directive to determine the client's IP address based on the defined HTTP +request header (e.g., X-Forwarded-For) instead of taking the IP address +of the client which has opened the TCP connection. The header must only +contain a single IP address.<br> +You might also use a pseudo IP address by creating a hash from the +header's value if you prefix the header name by a '#', +e.g. <code>#Authorization</code> to use the HTTP basic auth header. +as the pseudo IP address. The special name <code>#SSL_CLIENT_S_DN</code> +creates a pseudo IP from the SSL client certificate's subject and issuer DN. +</li> +<li>The current value of this counter is stored within the variable suffixed +by <code><a href="#_Counter">_Counter</a></code>, e.g. <code>QS_Limit_Counter</code> for further +processing by other rules. </li> +<a name="QS_Limit_Remaining"></a> +<li>The remaining time (in seconds) is stored within the variabled suffixed +by <code>_Remaining</code>, e.g. <code>QS_Limit_Remaining</code> to be +used within <a href="glossary.html#ssi">SSI</a> error pages.</li> +<li>The counter can be reset by setting the environment variable which name is +suffixed by <code><a href="#_Clear">_Clear</a></code>, e.g. <code>QS_Limit_Clear</code>. +<li>The counter can be decremented by setting the environment variable which name is +suffixed by <code><a href="#_Decrement">_Decrement</a></code>, e.g. <code>QS_Limit_Decrement</code>. +<li>Adding/removing events (configuration changes) require a server restart +(graceful restart is not supported).</li> +<li>Only the default rule (<code><a href="#QS_Limit">QS_Limit</a></code>) is accessibly by the +<a href="#statusviewer">status viewer</a> (you may use the +<a href="#webconsole">console</a> to view other variables alternatively).</li> +<li>See also <a href="#QS_CondClientEventLimitCount"><code>QS_CondClientEventLimitCount</code></a> +if you want to enforce a rule under certain conditions only.</li> +</ul></i></small> +</li> +<li> +<a name="QS_ClientSerialize"></a> +<syntax>QS_ClientSerialize</syntax><br> +<a href="glossary.html#serialization">Serializes</a> requests having the +<a href="#QS_Serialize"><code>QS_Serialize</code></a> +variable set if they are coming from the same IP address.<br> +<small><i>Notes: +<ul> +<li>You may use the <code>QS_ClientIpFromHeader <header></code> directive to +override the client's IP address based on the value within the defined HTTP request +header (e.g., X-Forwarded-For) instead of taking the IP address of the client which has opened +the TCP connection. +</li> +<li>Maximum wait time for a request is 5 minutes. +</li> +</ul></i></small> +</li> +<li> +<a name="QS_ClientPrefer"></a> +<syntax>QS_ClientPrefer [<percent>]</syntax><br> +Accepts only <a href="#privilegedusers">VIP</a> +and high priority clients when the server has less than 80% +(or the defined percentage) of free TCP connections. The server +<u><a href="images/ClientPrefer.png">continues dropping more and more clients</a></u> +(also those with few penalty points) the higher the number of connections +grows. +<br>Use the +<code><a href="#QS_VipHeaderName">QS_VipHeaderName</a></code> or +<code><a href="#QS_VipIPHeaderName">QS_VipIPHeaderName</a></code> +directive in order to identify <a href="#privilegedusers">VIP</a> clients.<br> +The distinction between high and low priority clients is made +based on penalty points which are calculated based of these attributes: +<ul> +<li>Data transfer behavior (clients sending data slowly / their transfer rate) (0x01).</li> +<li>Accessing "unusual" content types (see <code><a href="#QS_ClientTolerance">QS_ClientTolerance</a></code> +and <code><a href="#QS_ClientContentTypes">QS_ClientContentTypes</a></code>) +(0x00 unknown / 0x02 normal / 0x04 unusual).</li> +<li>Causing events <a href="#QS_ClientEventBlockCount">blocking</a> / +<a href="#QS_ClientEventLimitCount">limiting</a> them (0x08 block / 0x10 limit).</li> +<li>If their connections get closed due to timeouts (0x20).</li> +</ul> +HTTP requests causing a client to get marked as "low priority" have the +"r;" event within the <a href="#mod_qos_ev">mod_qos_ev</a> variable set. +You may use the <a href="#statusviewer">status viewer</a> to determine +which client addresses are identified as low priority clients. Feature is +disabled if directive is not set.<br> +A low priority flag is cleared after 24h hours. Clients identified by +<code><a href="#QS_SrvMaxConnExcludeIP">QS_SrvMaxConnExcludeIP</a></code> +are excluded from connection restrictions. Filter is applied on connection level +blocking clients even before the server starts reading the HTTP request data. +</li> +<li> +<a name="QS_ClientTolerance"></a> +<syntax>QS_ClientTolerance <percent></syntax><br> +Defines the allowed variation from a "normal" client (average) behavior when enabling +the <code><a href="#QS_ClientPrefer">QS_ClientPrefer</a></code> directive. Default is 20%. +</li> +<li> +<a name="QS_ClientContentTypes"></a> +<syntax>QS_ClientContentTypes <html> <css/js> <images> <other> <304></syntax><br> +Defines the distribution of HTTP response content types a client normally +receives when accessing the server. Can only be used in conjunction with the +<code><a href="#QS_ClientPrefer">QS_ClientPrefer</a></code> directive. +<code><a href="#QS_ClientTolerance">QS_ClientTolerance</a></code> defines +the allowed deviation from these values. mod_qos normally learns the average +behavior automatically by default (you can see the learned values within +the <a href="#statusviewer">status viewer</a> or by enabling the +<a href="#QS_Status"><code>QS_Status</code></a> log messages) but +you may specify a static configuration using this directive in order +to avoid influences by a high number of abnormal clients. Default is +automatic self-learning. +</li> +<li> +<a name="QS_ClientGeoCountryDB"></a> +<syntax>QS_ClientGeoCountryDB <path></syntax><br> +Defines the path to the geographical database file. +The file is a Comma Separated Value (CSV) format file +(<a href="https://sourceforge.net/p/mod-qos/source/HEAD/tree/trunk/test/conf/GeoIPCountryWhois.csv?format=raw">example</a>). +Each line contains the following fields: +<ul> +<li> +Double quoted beginning <i><id title="where w.x.y.z results in 16777216*w + 65536*x + 256*y + z">IPv4 number</id></i> of the address range, e.g. "1052272128" for 62.184.102.0 +</li> +<li> +Double quoted ending <i><id title="where w.x.y.z results in 16777216*w + 65536*x + 256*y + z">IPv4 number</id></i> of the address range, e.g. "1052272543" for 62.184.103.159. +</li> +<li> +Double quoted ISO 3166 country code, e.g. "FR" for France. +</li> +</ul> +The <a href="#QS_Country"><code>QS_Country</code></a> variable contains +the country code for the client's IP address. <br> +<small><i>Note: You may use the <code>QS_ClientIpFromHeader <header></code> directive to +override the client's IP address based on the value within the defined HTTP request +header (e.g., X-Forwarded-For) instead of taking the IP address of the client which has opened +the TCP connection to evaluate this variable.</i></small> +</li> +<li> +<a name="QS_ClientGeoCountryPriv"></a> +<syntax>QS_ClientGeoCountryPriv <list> <connections> ['excludeUnknown']</syntax><br> +Defines a comma separated list of country codes for origin client IPv4 address +which are allowed to access the server even if the number of busy TCP +connections reaches the defined number of connections.<br> +Uses the geographical database loaded by +<a href="#QS_ClientGeoCountryDB"><code>QS_ClientGeoCountryDB</code></a>. +<br>Clients whose IP can't be mapped to a country code can be excluded +from the limitation by configuring the 'excludeUnknown' argument. +</li> +</ul> + +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample configuration:<br> +<pre> +# allows not more than 20 events/penalty points per 10 minutes: +<a href="#QS_ClientEventBlockCount">QS_ClientEventBlockCount</a> 20 + +# don't allow a client to access /app/start.html more than +# 20 times within 10 minutes: +SetEnvIf Request_URI /app/start.html <a href="#QS_Block">QS_Block</a>=1 + +# don't allow more than 4 "403" status code responses +# (forbidden) for a client within 10 minutes: +<a href="#QS_SetEnvIfStatus">QS_SetEnvIfStatus</a> 403 <a href="#QS_Block">QS_Block</a>=5 +</pre> +</td></tr> +</table> +</p> + +<a name="messages"></a> +<h2>Log Messages</h2> +<a name="errorlog"></a> +<h3>Error Log</h3> +<p> +mod_qos writes <a href="MESSAGES.txt">messages</a> to Apache's error log when +detecting a rule violation. Each error message is prefixed by an id: +<code>mod_qos(<number>)</code>. These error codes (number only) +are also written to the error notes (Apache's <code>error-notes</code> note +as well as the <a href="#QS_ErrorNotes"><code>QS_ErrorNotes</code></a> +variable) in order to be processed within error pages using +<a href="glossary.html#ssi">server-side includes (SSI)</a>. +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +mod_qos(00x): initialisation event +mod_qos(01x): request level control event +mod_qos(08x): request level control event +mod_qos(02x): vip session event +mod_qos(03x): connection level event +mod_qos(04x): generic filter event +mod_qos(14x): generic filter event +mod_qos(05x): bandwidth limitation event +mod_qos(06x): client control event +mod_qos(16x): client control event +mod_qos(07x): console errors +mod_qos(08x): initialisation/resource errors +mod_qos(10x): geo errors +</pre> +</td></tr> +</table> +</p> + +<a name="accesslog"></a> +<h3>Access Log</h3> +<p> +mod_qos adds event variables to the request record which may be added +to access log messages. +<ul> +<li> +<a name="mod_qos_ev"></a> +<syntax>mod_qos_ev</syntax> <br> Status event message of mod_qos. It's a +single letter which is used to signalize an event: "D"=denied, "S"=pass +due to an available <a href="#privilegedusers">VIP</a> session, +"V"=create VIP session (cookie), "v"=marks an IP as VIP, +"K"=connection closed (no keep-alive), "T"=dynamic keep-alive, +"r"=IP is marked as a slow/bad client, "L"=means a request slowdown, +"u"=request without a <a href="#QS_UserTrackingCookieName">user tracking cookie</a>, +and "s" is used for serialized requests. The letter "A" for connection abort +is set if the status code detection +<a href="#BrokenConnection"><code>BrokenConnection</code></a> +has been configured. +</li> +<li> +<a name="mod_qos_cr"></a> +<syntax>mod_qos_cr</syntax> <br> The number of concurrent requests to a +location matching the <code><a href="#QS_LocRequestLimit">QS_LocRequestLimit</a></code>, +<code><a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a></code>, +<code><a href="#QS_LocRequestPerSecLimit">QS_LocRequestPerSecLimit</a></code>, +<code><a href="#QS_LocRequestPerSecLimitMatch">QS_LocRequestPerSecLimitMatch</a></code>, +<code><a href="#QS_LocKBytesPerSecLimit">QS_LocKBytesPerSecLimit</a></code>, +<code><a href="#QS_LocKBytesPerSecLimitMatch">QS_LocKBytesPerSecLimitMatch</a></code>, +<code><a href="#QS_CondLocRequestLimitMatch">QS_CondLocRequestLimitMatch</a></code>, +or <code><a href="#QS_EventRequestLimit">QS_EventRequestLimit</a></code> directive. +</li> +<li> +<a name="mod_qos_con"></a> +<syntax>mod_qos_con</syntax> <br> This event shows the number of +concurrent connections to this server. Only available if the directive +<a href="#QS_SrvMaxConn"><code>QS_SrvMaxConn</code></a> +is used. +</li> +<li> +<a name="mod_qos_user_id"></a> +<a name="QS_UserTrackingCookieName"></a> +<syntax>mod_qos_user_id</syntax> <br> The user id which is available when +enabling <a href="glossary.html#UserTracking">user tracking</a>.<br> +<a href="glossary.html#UserTracking">User tracking</a> is based on a unique identifier generated by +<a href="https://httpd.apache.org/docs/current/mod/mod_unique_id.html">mod_unique_id <img src="images/link.png"/></a>. +This unique identifier is stored as a cookie. The user tracking +feature is enabled by setting the +<code>QS_UserTrackingCookieName <name> [<path>] [<domain>] ['session'] ['jsredirect']</code> +directive.<br> +Options of the <code>QS_UserTrackingCookieName</code> directive are: +<ul> +<li>The <code>name</code> argument defining the name of the +user tracking cookie.</li> +<li>The <code>path</code> specifies a local error document +which is shown if a user does not accept the cookie (enforcement). +<br> +You may disable this enforcement for certain clients by setting the +<code>DISABLE_UTC_ENFORCEMENT</code> environment variable at server +level (outside Location), e.g., to allow crawlers not supporting +cookies to access your site.<br/> +This option can be used to ensure whether a client/browser accepts cookies +at all which might be a requirement of your application.</li> +<li><code>domain</code> defines optionally the domain attribute for +the Set-Cookie header.</li> +<li>The <code>session</code> flag indicates that a short lived (per +session) cookie shall be created which won't be stored by the browser +permanently.</li> +<li>When using the additional option <code>'jsredirect'</code>, +the client (browser) has to interpret Javascript used within the +<a href="http://mod-qos.sourceforge.net/cookie-ir.shtml">cookie check page</a> +to fetch the cookie and to execute the redirect back to the initially +requested page (adding Javascript to the cookie challenge).<br> +The following <a href="glossary.html#ssi">SSI variables</a> can be used:<ul> +<li><code>QS_UT_QUERY</code>: Query string to call (ajax) the cookie +page again to obtain the cookie.</li> +<li><code>QS_UT_NAME</code>: Name of the cookie.</li> +<li><code>QS_UT_INITIAL_URI</code>: Initial page to redirect to.</li> +</ul> +</ul> +<small><i> +Notes: +<ul> +<li><code>QS_UserTrackingCookieName</code> ignores the +<code><a href="#QS_LogOnly">QS_LogOnly</a></code> +directive.</li> +<li>The cookie is secured by the <code><a href="#QS_SessionKey">QS_SessionKey</a></code> +and you should set this directive to have a constant key.</li> +</ul> +</li> +</i></small> +<li> +<a name="UNIQUE_ID"></a> +<syntax>UNIQUE_ID</syntax> <br> This is a unique request id generated by +mod_unique_id. mod_qos uses this id to mark messages written to the +error log. So it might be useful to log the <code>UNIQUE_ID</code> +environment variable as well, in order to correlate errors +to access log messages. +</li> +<li> +<a name="QS_ConnectionId"></a> +<syntax>QS_ConnectionId</syntax> <br> Connection correlation id used to +mark all messages belonging to the same TCP connection. +</li> +</ul> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +Sample configuration:<br> +<pre> +LogFormat "%h %u %t \"%r\" %>s %b %T \"%{content-length}i\" %k \"%{User-Agent}i\" \ + %{mod_qos_cr}e %{mod_qos_ev}e %{mod_qos_con}e %{QS_SrvConn}e %{QS_AllConn}e \ + id=%{UNIQUE_ID}e %{QS_ConnectionId}e %{mod_qos_user_id}e %{QS_Country}e #%P" +</pre> +</td></tr> +</table> +</p> + +<a name="requeststatistics"></a> +<h3>Request Statistics</h3> +<p> +The <code><a href="qslog.1.html">qslog</a></code> tool, which is part of +the support utilities of mod_qos, may be used to gather request +statistics from Apache's access log data. This includes data such +as the number of denied requests or new VIP session creations per +minute but also total requests per second and other data. Refer +to the usage text of the <code><a href="qslog.1.html">qslog</a></code> +utility and read <a href="glossary.html#RequestStatistics">"Request Statistics Using qslog"</a> +for further details. +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +CustomLog "|/usr/bin/qslog -o logs/qslog.csv -x -f ISBDQkU" \ + "%h %>s %b %D %{mod_qos_ev}e %k %{mod_qos_user_id}e" +</pre> +</td></tr> +</table> +</p> +<p> +<a name="QSLog"></a> +Instead of using the standard Apache log <code>CustomLog</code> directive, +you may use the <code>QSLog</code> directive of mod_qos alternatively. This +allows you to configure a single log file for your Apache instance (globally, +not per virtual host) and you don't have to specify the format (-f) option. +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +QSLog "|/usr/bin/qslog -o /var/log/apache/qslog.csv" +</pre> +</td></tr> +</table> +</p> + +<a name="statusviewer"></a> +<h3>Status Viewer</h3> +<p> +mod_qos features a handler showing the current connection and request status. +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +<Location /qos> + SetHandler qos-viewer +</Location> +</pre> +</td></tr> +</table> +A machine-readable version of the status information is available when using +the request query string <code>auto</code>, e.g., +<code>http://your.server.name/qos?auto</code>. The page updates itself +automatically every 10 seconds if you add the request +query string <code>refresh</code>, e.g., +<code>http://your.server.name/qos?refresh</code>.<br> +<a name="QS_EventCount"></a> +<small><i>Note: This view also shows you the <a href="#errorlog">error log event</a> +counters if you enable event (errors and warnings) counting by +configuring <code>QS_EventCount on</code> and are using any +<a href="#clientlevelcontrol">client level limitation</a> using +<code>QS_Client*</code> directives.</i></small> +</p> +<p> +The status information is also provided on the server status page of +<a href="http://httpd.apache.org/docs/current/mod/mod_status.html">mod_status <img src="images/link.png"/></a> +(although in a reduced scope).<br> +<small><i>Note: Compile mod_qos with the preprocessor definition +<code>-DQS_NO_STATUS_HOOK</code> to disable its registration to +the status page rendered by mod_status.</i></small> +</p> +<p> +<a name="QS_DisableHandler"></a> +Use the directive <code>QS_DisableHandler on</code> to disable the qos-viewer and qos-console for +a virtual host in order to prevent accidental activation of these functions, including by configuration +settings of per-directory files (e.g., .htaccess). +</p> +<p> +<a name="QS_Status"></a> +The directive <code>QS_Status 'on'|'off'</code> may be used to enable a +status log message (<i>mod_qos(200)</i>) written to the Apache server's +<code>ErrorLog</code>. This message contains information about the server's +scoreboard. The message is written once every minute. +</p> + +<a name="webconsole"></a> +<h3>Web Console</h3> +<p> +mod_qos implements an Apache handler which acts as a web console for setting attributes via HTTP requests. +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +<Location /qos/console> + SetHandler qos-console +</Location> +</pre> +</td></tr> +</table> +Access a location where you have enabled the <code>qos-console</code> handler +with a web client and use the following request query parameter to modify +the status of a client (may only be used if <a href="#clientlevelcontrol">client level control</a> +has been enabled). +<ul> +<li> +<syntax>address=<IP address></syntax><br>Specifies the IP address of the client to modify. +</li> +<li> +<syntax>action='block'|'unblock'|'limit'|'unlimit'|'inclimit'|'setvip'|'unsetvip'|'setlowprio'|'unsetlowprio'|'search'</syntax><br>Defines the command to be executed, or the attribute to be changed. +<ul> +<li><code>block</code>: <a href="#QS_ClientEventBlockCount">blocks</a> the client for the configured period of time, +see also <code><a href="#QS_ClientEventBlockCount">QS_ClientEventBlockCount</a></code>.</li> +<li><code>unblock</code>: clears the <a href="#QS_ClientEventBlockCount">block</a> attribute of the client.</li> +<li><code>limit</code>: <a href="#QS_ClientEventLimitCount">denies requests</a> +from the client IP for the configured period of time, see also +<code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code>.</li> +<li><code>unlimit</code>: clears the <a href="#QS_ClientEventLimitCount">limit</a> +attribute of the client.</li> +<li><code>inclimit</code>: increments the client's <a href="#QS_ClientEventLimitCount">limit</a> counter.</li> +<li><code>setvip</code>: sets the client status to <a href="#privilegedusers">VIP</a>.</li> +<li><code>unsetvip</code>: clears the <a href="#privilegedusers">VIP</a> status for a client.</li> +<li><code>setlowprio</code>: sets the client's <a href="#QS_ClientPrefer">priority</a> to 'low'.</li> +<li><code>unsetlowprio</code>: clears the 'low' <a href="#QS_ClientPrefer">priority</a> +attribute of the client.</li> +<li><code>search</code>: verifies the availability of a client IP address. <br/>Use the asterisk (*) +for the <code>address</code> parameter in order to get a list of all available clients (dump).</li> +</ul> +</li> +<li><syntax>event=<name></syntax><br>Specifies the event name of the +<code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code> +directive <a href="glossary.html#repeat">counter</a> which shall be +shown or modified (used in conjunction with the <code>limit</code>, +<code>unlimit</code>, <code>inclimit</code>, and <code>search</code> action). +Default is <code><a href="#QS_Limit">QS_Limit</a></code>.</li> +</ul> +</p> +<p> +The output (which is plain text) contains the following fields: +<ul> + <li>IP address</li> + <li><a href="#privilegedusers">VIP</a> status</li> + <li>low <a href="#QS_ClientPrefer">priority</a> status</li> + <li><code><a href="#QS_ClientEventBlockCount">QS_ClientEventBlockCount</a></code> + counter (<a href="glossary.html#repeat">Cr</a>) and + remaining time (<a href="glossary.html#repeat">Td</a>)</li> + <li><code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code> + counter (<a href="glossary.html#repeat">Cr</a>) and + remaining time (<a href="glossary.html#repeat">Td</a>)</li> +</ul> +The wildcard search (<code>address=*</code>) generates a by a newline separated list of +all client IP entries. Each line is prefixed by an index and terminated +by the time of the last entry update (seconds since epoch). +</p> +<p> +The console may be used to manually update the status of a client (IP) or +for automated actions. <br/>Examples: +<ul> +<li>To unlock a client which got blocked by mistake.</li> +<li>To synchronize events within multiple Apache instances. <br/> +An example using <code><a href="qsexec.1.html">qsexec</a></code> +is available within the +<a href="https://sourceforge.net/p/mod-qos/source/HEAD/tree/trunk/test/sync.sh?format=raw">source code repository</a>.</li> +<li><a href="https://sourceforge.net/p/mod-qos/source/HEAD/tree/trunk/tools/cc_sync_2k.sh?format=raw">Download/upload</a> client status from one +Apache instance to another (or to the same instance, +e.g., when restarting an instance).</li> +</ul> +</p> +<p> +Examples to access the console: +<ul> +<li>Sets VIP status for the IP 194.31.217.21:<br> +<code>http://your.server.name/qos/console?action=setvip&address=194.31.217.21</code></li> +<li>Clears the QS_Limit counter for the IP 194.31.217.21:<br> +<code>http://your.server.name/qos/console?action=unlimit&address=194.31.217.21&event=QS_Limit</code></li> +</ul> +</p> +<p> +The <a href="#statusviewer">status viewer</a> may be used as well to +verify the status of the client. Example: <br/> +<code>http://your.server.name/qos?action=search&address=194.31.217.21</code> +</p> + +<a name="utilities"></a> +<h3>Utilities</h3> +<p> +mod_qos provides optional tools for log data processing and analysis: +<ul> +<a name="qsdt"></a> +<li><syntax><a href="qsdt.1.html">qsdt</a></syntax><br>Simple tool +to measure the elapse time between related log messages.</li> +<a name="qsexec"></a> +<li><syntax><a href="qsexec.1.html">qsexec</a></syntax><br>Command execution +triggered by patterns within log files.</li> +<a name="qsfilter2"></a> +<li><syntax><a href="qsfilter2.1.html">qsfilter2</a></syntax><br> +Rule generator. Creates <code><a href="#filter">QS_Permit*</a></code> directives and rule patterns +from audit log files.</li> +<a name="qsgeo"></a> +<li><syntax><a href="qsgeo.1.html">qsgeo</a></syntax><br>Adds the country code +for the client IP address within a log file.</li> +<a name="qsgrep"></a> +<li><syntax><a href="qsgrep.1.html">qsgrep</a></syntax><br>Searches a file for a +pattern and prints the data in a new format.</li> +<a name="qslog"></a> +<li><syntax><a href="qslog.1.html">qslog</a></syntax><br>A real time +<code><a href="http://httpd.apache.org/docs/current/mod/mod_log_config.html">TransferLog/CustomLog <img src="images/link.png"/></a></code> +data analyzer. It reads the per request log data from stdin and generates +statistic records every minute.</li> +<a name="qslogger"></a> +<li><syntax><a href="qslogger.1.html">qslogger</a></syntax><br>Shell command +interface to the syslog(3) system log module.</li> +<a name="qspng"></a> +<li><syntax><a href="qspng.1.html">qspng</a></syntax><br>Creates graphics (png +images) from the output of <code>qslog</code>.</li> +<a name="qsre"></a> +<li><syntax><a href="qsre.1.html">qsre</a></syntax><br>Regular expression (pcre) +pattern match test tool.</li> +<a name="qsrespeed"></a> +<li><syntax><a href="qsrespeed.1.html">qsrespeed</a></syntax><br>Compares the +expected processing time per regular expression.</li> +<a name="qsrotate"></a> +<li><syntax><a href="qsrotate.1.html">qsrotate</a></syntax><br>Log rotation tool +similar to Apache's <code>rotatelogs</code>.</li> +<a name="qssign"></a> +<li><syntax><a href="qssign.1.html">qssign</a></syntax><br>A log data integrity +check tool. It reads log data from stdin (pipe) and writes the signed data +to stdout adding a sequence number and signature to ever log line.<br> +<a href="https://sourceforge.net/p/mod-qos/source/HEAD/tree/trunk/tools/logstash-filter-qssign/lib/logstash/filters/qssign.rb?format=raw"><code>qssign.rb</code></a> is a <a href="http://www.logstash.net/">Logstash <img src="images/link.png"/></a> filter +plugin which may be used to verify the signatures of log messages in real time.</li> +<a name="qstail"></a> +<li><syntax><a href="qstail.1.html">qstail</a></syntax><br>Shows the end of a log +file beginning at a defined pattern.</li> +</ul> + +</p> + + +<a name="usecases"></a> +<h2>Sample Use Cases</h2> + +The following use cases may give you an idea about how to use mod_qos. +<a name="Slow_Application"></a> +<h3>Slow Application</h3> +<p> +In case of a very slow application (e.g., at location /ccc), requests wait +until a timeout occurs. Due to many waiting requests, there are no free TCP +connections left and the web sever is not able to process other requests +to applications still working fine, e.g., to /aaa, /bbb /dd1, and /dd2. +mod_qos limits the number of <a href="glossary.html#concurrency">concurrent</a> +requests to an application in order to +assure the availability of other resources. +<br><br>Example:<br> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +# maximum number of active TCP connections is limited to 256 (limited +# by the available memory, adjust the settings according to the +# used hardware): +MaxClients 256 + +# limits the maximum of concurrent requests per application to 100: +<a href="#QS_LocRequestLimit">QS_LocRequestLimit</a> /aaa 100 +<a href="#QS_LocRequestLimit">QS_LocRequestLimit</a> /bbb 100 +<a href="#QS_LocRequestLimit">QS_LocRequestLimit</a> /ccc 100 +<a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a> "^(/dd1/|/dd2/).*$" 100 +</pre> +</td></tr> +</table> +The <code><a href="qslog.1.html">qslog</a></code> tool may be used +to analyze your log files in order to identify "slow" resources by +using the <code>-pu</code>, <code>-puc</code>, or <code>-c</code> option. +</p> + +<a name="HTTP_Keep-Alive"></a> +<h3>HTTP Keep-Alive</h3> +<p> +The keep-alive extension of HTTP 1.1 allows persistent TCP connections for +multiple requests/responses. This accelerates access to the web server due to less and optimized network traffic. The disadvantage of these persistent +connections is that server resources are blocked even when no data is exchanged +between client and server. mod_qos allows a server to support keep-alive +as long as sufficient connections are available, but stops the keep-alive +support when it reaches a defined connection threshold. +<br><br>Example:<br> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +# maximum number of active TCP connections is limited to 256 (limited +# by the available memory, adjust the settings according to the +# used hardware): +MaxClients 256 + +# disables keep-alive when 70% of the TCP connections are occupied: +<a href="#QS_SrvMaxConnClose">QS_SrvMaxConnClose</a> 70% +</pre> +</td></tr> +</table> +</p> + +<a name="Client_Opens_Many_Concurrent_Connections"></a> +<h3>Client Opens Many Concurrent Connections</h3> +<p> +A single client may open many TCP connections simultaneously in order to +download different content from the web server. So the client gets many +connections while other users may not be able to access the server because +no free connections remain for them. mod_qos can limit the number +of concurrent connections for a single IP source address. +<br><br>Example:<br> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +# maximum number of active TCP connections is limited to 896 +# (limited by the available memory, adjust the settings according to the +# used hardware): +MaxClients 896 + +# don't allow a single client to open more than 50 TCP connections if +# the server has not more than 196 free connections: +<a href="#QS_SrvMaxConnPerIP">QS_SrvMaxConnPerIP</a> 50 700 +</pre> +</td></tr> +</table> +</p> + +<a name="Many_Requests_to_a_Single_URL"></a> +<h3>Many Requests to a Single URL</h3> +<p> +If you have to limit the number of requests to an URL, mod_qos can help +with that, too. You may limit the number of requests per second to +an URL. mod_qos will then calculate the necessary delay time to be added +to each requests accessing this resource in order to achieve the defined +limitation. +<br><br>Example:<br> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +# does not allow more than 150 requests/sec: +<a href="#QS_LocRequestPerSecLimit">QS_LocRequestPerSecLimit</a> /download/mod_qos.so.gz 150 + +# but do not allow more than 600 concurrent requests: +<a href="#QS_LocRequestLimit">QS_LocRequestLimit</a> /download/mod_qos.so.gz 600 +</pre> +</td></tr> +</table> +</p> +<a name="Many_Requests_to_a_Single_URL_SLOW"></a> +<p> +Alternatively, if you need to reduce the number of processed requests +per time to a very low value, you might add a (predefined or +dynamically calculated) delay to each request and process only +one of them at the same time. However, this will delay every +request to the defined URI, even the server is idle. +<br><br>Example:<br> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +# does not allow more than 4 requests/sec by adding a wait time of 250ms +# to each request and process only one request at once: +SetEnvIf Request_URI ^/download/mod_qos.so.gz <a href="#QS_SrvSerialize">QS_SrvSerialize</a>=1 +SetEnvIf Request_URI ^/download/mod_qos.so.gz <a href="#QS_Delay">QS_Delay</a>=250 +<a href="#QS_SrvSerialize">QS_SrvSerialize</a> on + +# but do not allow more than 600 concurrent requests: +<a href="#QS_EventRequestLimit">QS_EventRequestLimit</a> <a href="#QS_SrvSerialize">QS_SrvSerialize</a> 600 +</pre> +</td></tr> +</table> +</p> + +<a name="Limit_per_IP"></a> +<p> +mod_qos can also restrict the access to an URL by limiting the number +of requests from a single IP address (<code>LimitDownloadCounter</code> is +the <a href="glossary.html#repeat">counter</a> to use while the +<code>LimitDownloadNow</code> pattern is used to limit access to this +specific resource only still allowing the IP address to access +other resources). +<br><br>Example:<br> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +# does not allow more than 4 downloads of mod_qos.so.gz per minute from a single IP address: +SetEnvIf Request_URI ^/download/mod_qos.so.gz LimitDownloadCounter +SetEnvIf Request_URI ^/download/mod_qos.so.gz <a href="#QS_Cond">QS_Cond</a>=LimitDownloadNow +<a href="#QS_CondClientEventLimitCount">QS_CondClientEventLimitCount</a> 4 60 LimitDownloadCounter LimitDownloadNow +</pre> +</td></tr> +</table> +</p> + +<a name="bandwidth_restriction"></a> +<h3>Bandwidth Restriction</h3> +<p> +It's sometimes necessary to restrict the bandwidth consumed by +clients downloading certain type of data in order to avoid +that the entire bandwidth of your Internet connection is +exploited by less important data traffic, e.g. if your web server +hosts large files to be downloaded.<br/> +mod_qos allows you to defined the bandwidth which may be +used when accessing a defined URL or when the server returns a +certain content-type. +<br><br>Example:<br> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +# limits the download bandwidth when accessing ISO images to 1 megabyte/sec +# and does not allow more then 300 clients to download such file type in +# parallel: +<a href="#QS_LocKBytesPerSecLimitMatch">QS_LocKBytesPerSecLimitMatch</a> \.iso 1024 +<a href="#QS_LocRequestLimitMatch">QS_LocRequestLimitMatch</a> \.iso 300 +</pre> +</td></tr> +</table> +</p> + +<a name="brute_force"></a> +<h3>Brute Force</h3> +<p> +Sometimes, you want to limit how often a resource may be accessed +within a certain amount of time, e.g., to defend against brute-force +respectively dictionary attacks or an account lockout DoS (someone +systematically locks user accounts by too many invalid sign-in +attempts). mod_qos allows you to limit this either server wide +(any request accessing the resource) by using the +<code><a href="#QS_EventLimitCount">QS_EventLimitCount</a></code> directive, +or on a per client IP basis using the +<code><a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a></code> +directive. +<br><br>Example:<br> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +# allows a single IP address to access the URI /wp-login.php not more +# than 10 times within an hour: +SetEnvIf Request_URI ^/wp-login.php LimitLogin +<a href="#QS_ClientEventLimitCount">QS_ClientEventLimitCount</a> 10 3600 LimitLogin +</pre> +</td></tr> +</table> +<small> +<i>Note: Multiple users may share an IP addresses which might cause false +positives. You might avoid this by decrementing the counter on successful +user authentication / login, e.g. by setting the variable +<code><a href="#_Decrement">LimitLogin_Decrement=1</a></code>. +</i></small> +</p> +<p> +A brute force attack might also be performed by many distributed +clients (thousands of clients, but every client performs a few +requests only). To add protection to your server, you might configure an +overall limitation for critical resources allowing only known clients +(<a href="#privilegedusers">VIPs</a>) +to access your server without any restrictions. The +<code><a href="#QS_CondEventLimitCount">QS_CondEventLimitCount</a></code> +directive might be used to achieve this. +</p> +<a name="ddos"></a> +<a name="Too_Many_Client_Connections"></a> +<h3>Too Many Client Connections</h3> +<p> +mod_qos may <a href="#QS_ClientPrefer">prefer</a> "known" client IP +addresses in the case that too many clients access the server. +"Known" clients are those which have once been identified by the +application by setting the corresponding +<a href="#QS_VipIPHeaderName ">HTTP response header</a>. +Such identification may happen at successful user login. +Connections from clients which are not known to mod_qos +(never marked by the corresponding response header) are denied +if the server runs on low TCP connection resources (20% or +fewer free connections in this example). mod_qos may +also prefer those clients which communicate with the server +instantaneously and fast, and denies access to slow clients +sending data irregularly, in case the server has not enough +resources.</p> +<p> +You may also set limitations defining how many resources +may be requested by a single IP address source, e.g., using +the <code><a href="#QS_SrvMaxConnPerIP">QS_SrvMaxConnPerIP</a></code> +directive and you can <a href="#HTTP_Keep-Alive">disable HTTP keep-alive</a> +dynamically.</p> +<p> +For more information about how mod_qos can help you in such situations, see the article +<a href="http://mod-qos.sourceforge.net/dos.html">"Denial of Service Defense"</a>. +<br><br>Example:<br> +<table border="0" cellspacing="5" cellpadding="10" width="100%"> +<tr><td bgcolor="#E2EDE2"> +<pre> +# maximum number of active TCP connections is limited to 896 (limited +# by the available memory, adjust the settings according to the used +# hardware): +MaxClients 896 + +# idle timeout: +Timeout 5 + +# keep alive (for up to 85% of all connections): +KeepAlive on +MaxKeepAliveRequests 40 +KeepAliveTimeout 2 +<a href="#QS_SrvMaxConnClose">QS_SrvMaxConnClose</a> 85% + +# name of the HTTP response header which marks preferred clients (this +# may be used to let the application decide which clients are "good" and +# have higher privileges, e.g. authenticated users. +# you may also use the <a href="#QS_VipIPUser">QS_VipIPUser</a> directive when using an Apache +# authentication module such as mod_auth_basic or <a href="http://auth-openid.sourceforge.net/">mod_auth_oid <img src="images/link.png"/></a>): +<a href="#QS_VipIPHeaderName">QS_VipIPHeaderName</a> mod-qos-login + +# enables the known client prefer mode (server allows new TCP connections +# from known/good clients only if there are more than 716 open TCP connections): +<a href="#QS_ClientPrefer">QS_ClientPrefer</a> 80% + +# don't allow more than 30 TCP connections per client source address being +# processed if the server has 500 or more open connections: +<a href="#QS_SrvMaxConnPerIP">QS_SrvMaxConnPerIP</a> 30 500 +</pre> +</td></tr> +</table> +</p> + + +</td></tr> +</tbody> +</table> +<br> +<hr> +<small><small>© 2007-2023, Pascal Buchbinder - mod_qos version 11.74</small></small> +</body> +</html> |