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| Version: 9.3.28.v20191105</span></td><td style="width: 50%"></td></tr></table><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Denial of Service Filter</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="qos-filter.html"><i class="fa fa-chevron-left" aria-hidden="true"></i> Previous</a> </td><th width="60%" align="center">Chapter 18. Provided Servlets, Filters, and Handlers<br><a accesskey="p" href="index.html"><i class="fa fa-home" aria-hidden="true"></i> Home</a></th><td width="20%" align="right"> <a accesskey="n" href="gzip-filter.html">Next <i class="fa fa-chevron-right" aria-hidden="true"></i></a></td></tr></table><hr></div><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="jetty-callout"><h5 class="callout"><a href="http://www.webtide.com/">Contact the core Jetty developers at |
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| </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="dos-filter"></a>Denial of Service Filter</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="section"><a href="dos-filter.html#dos-filter-metadata">Info</a></span></dt><dt><span class="section"><a href="dos-filter.html#dos-filter-usage">Usage</a></span></dt><dt><span class="section"><a href="dos-filter.html#dos-filter-using">Using the DoS Filter</a></span></dt></dl></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="dos-filter-metadata"></a>Info</h3></div></div></div><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">Classname: <code class="literal">org.eclipse.jetty.servlets.DoSFilter</code></li><li class="listitem">Maven Artifact: org.eclipse.jetty:jetty-servlets</li><li class="listitem">Javadoc: <a class="link" href="http://www.eclipse.org/jetty/javadoc/9.3.28.v20191105/org/eclipse/jetty/servlets/DoSFilter.html" target="_top">http://www.eclipse.org/jetty/javadoc/9.3.28.v20191105/org/eclipse/jetty/servlets/DoSFilter.html</a></li></ul></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="dos-filter-usage"></a>Usage</h3></div></div></div><p>The Denial of Service (DoS) filter limits exposure to request flooding, whether malicious, or as a result of a misconfigured client. |
| The DoS filter keeps track of the number of requests from a connection per second. |
| If the requests exceed the limit, Jetty rejects, delays, or throttles the request, and sends a warning message. |
| The filter works on the assumption that the attacker might be written in simple blocking style, so by suspending requests you are hopefully consuming the attacker’s resources. |
| The DoS filter is related to the QoS filter, using Continuations to prioritize requests and avoid thread starvation.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="dos-filter-using"></a>Using the DoS Filter</h3></div></div></div><p>Jetty places throttled requests in a priority queue, giving priority first to authenticated users and users with an HttpSession, then to connections identified by their IP addresses. |
| Connections with no way to identify them have lowest priority. |
| To uniquely identify authenticated users, you should implement the The extractUserId(ServletRequest request) function.</p><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="_required_jars_2"></a>Required JARs</h4></div></div></div><p>To use the DoS Filter, these JAR files must be available in WEB-INF/lib:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">$JETTY_HOME/lib/jetty-util.jar</li><li class="listitem">$JETTY_HOME/lib/jetty-servlets.jar</li></ul></div></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="_sample_configuration_2"></a>Sample Configuration</h4></div></div></div><p>Place the configuration in a webapp’s <code class="literal">web.xml</code> or <code class="literal">jetty-web.xml</code>. |
| The default configuration allows 25 requests per connection at a time, servicing more important requests first, and queuing up the rest. |
| This example allow 30 requests at a time:</p><pre xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times"><code><filter> |
| <filter-name>DoSFilter</filter-name> |
| <filter-class>org.eclipse.jetty.servlets.DoSFilter</filter-class> |
| <init-param> |
| <param-name>maxRequestsPerSec</param-name> |
| <param-value>30</param-value> |
| </init-param> |
| </filter></code></pre></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a name="dos-filter-init"></a>Configuring DoS Filter Parameters</h4></div></div></div><p>The following <code class="literal">init</code> parameters control the behavior of the filter:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">maxRequestsPerSec</span></dt><dd>Maximum number of requests from a connection per second. |
| Requests in excess of this are first delayed, then throttled. |
| Default is 25.</dd><dt><span class="term">delayMs</span></dt><dd><p class="simpara">Delay imposed on all requests over the rate limit, before they are considered at all:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">100 (ms) = Default</li><li class="listitem">-1 = Reject request</li><li class="listitem">0 = No delay</li><li class="listitem">any other value = Delay in ms</li></ul></div></dd><dt><span class="term">maxWaitMs</span></dt><dd>Length of time, in ms, to blocking wait for the throttle semaphore. |
| Default is 50 ms.</dd><dt><span class="term">throttledRequests</span></dt><dd>Number of requests over the rate limit able to be considered at once. |
| Default is 5.</dd><dt><span class="term">throttleMs</span></dt><dd>Length of time, in ms, to async wait for semaphore. Default is 30000L.</dd><dt><span class="term">maxRequestMs</span></dt><dd>Length of time, in ms, to allow the request to run. Default is 30000L.</dd><dt><span class="term">maxIdleTrackerMs</span></dt><dd>Length of time, in ms, to keep track of request rates for a connection, before deciding that the user has gone away, and discarding it. |
| Default is 30000L.</dd><dt><span class="term">insertHeaders</span></dt><dd>If true, insert the DoSFilter headers into the response. |
| Defaults to true.</dd><dt><span class="term">trackSessions</span></dt><dd>If true, usage rate is tracked by session if a session exists. |
| Defaults to true.</dd><dt><span class="term">remotePort</span></dt><dd>If true and session tracking is not used, then rate is tracked by IP and port (effectively connection). |
| Defaults to false.</dd><dt><span class="term">ipWhitelist</span></dt><dd>A comma-separated list of IP addresses that will not be rate limited.</dd><dt><span class="term">managedAttr</span></dt><dd>If set to true, then this servlet is set as a ServletContext attribute with the filter name as the attribute name. |
| This allows a context external mechanism (for example, JMX via <code class="literal">ContextHandler.MANAGED_ATTRIBUTES</code>) to manage the configuration of the filter.</dd></dl></div></div></div></div><script type="text/javascript"> |
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