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authorhongbotian <hongbo.tianhongbo@huawei.com>2015-11-30 02:41:33 -0500
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+<html><head><META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>The Apache Tomcat Connector - AJP Protocol Reference - AJPv13 extensions Proposal</title><meta name="author" value="Henri Gomez"><meta name="email" value="hgomez@apache.org"><link href="../style.css" type="text/css" rel="stylesheet"></head><body bgcolor="#ffffff" text="#000000" link="#525D76" alink="#525D76" vlink="#525D76"><table border="0" width="100%" cellspacing="4"><!--PAGE HEADER--><tr><td colspan="2"><!--TOMCAT LOGO--><a href="http://tomcat.apache.org/"><img src="../images/tomcat.gif" align="left" alt="Apache Tomcat" border="0"></a><!--APACHE LOGO--><a href="http://www.apache.org/"><img src="http://www.apache.org/images/asf-logo.gif" align="right" alt="Apache Logo" border="0"></a></td></tr><!--HEADER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><tr><!--LEFT SIDE NAVIGATION--><td width="20%" valign="top" nowrap="true"><p><strong>Links</strong></p><ul><li><a href="../index.html">Docs Home</a></li></ul><p><strong>Reference Guide</strong></p><ul><li><a href="../reference/workers.html">workers.properties</a></li><li><a href="../reference/uriworkermap.html">uriworkermap.properties</a></li><li><a href="../reference/status.html">Status Worker</a></li><li><a href="../reference/apache.html">Apache HTTP Server</a></li><li><a href="../reference/iis.html">IIS</a></li></ul><p><strong>Generic HowTo</strong></p><ul><li><a href="../generic_howto/quick.html">For the impatient</a></li><li><a href="../generic_howto/workers.html">All about workers</a></li><li><a href="../generic_howto/timeouts.html">Timeouts</a></li><li><a href="../generic_howto/loadbalancers.html">Load Balancing</a></li><li><a href="../generic_howto/proxy.html">Reverse Proxy</a></li></ul><p><strong>Webserver HowTo</strong></p><ul><li><a href="../webserver_howto/apache.html">Apache HTTP Server</a></li><li><a href="../webserver_howto/iis.html">IIS</a></li><li><a href="../webserver_howto/nes.html">Netscape/SunOne/Sun</a></li></ul><p><strong>AJP Protocol Reference</strong></p><ul><li><a href="../ajp/ajpv13a.html">AJPv13</a></li><li><a href="../ajp/ajpv13ext.html">AJPv13 Extension Proposal</a></li></ul><p><strong>Miscellaneous Documentation</strong></p><ul><li><a href="../miscellaneous/faq.html">Frequently asked questions</a></li><li><a href="../miscellaneous/changelog.html">Changelog</a></li><li><a href="http://issues.apache.org/bugzilla/buglist.cgi?query_format=advanced&amp;short_desc_type=allwordssubstr&amp;short_desc=&amp;product=Tomcat+Connectors&amp;long_desc_type=substring&amp;long_desc=&amp;bug_file_loc_type=allwordssubstr&amp;bug_file_loc=&amp;keywords_type=allwords&amp;keywords=&amp;bug_status=NEW&amp;bug_status=ASSIGNED&amp;bug_status=REOPENED&amp;emailassigned_to1=1&amp;emailtype1=substring&amp;email1=&amp;emailassigned_to2=1&amp;emailreporter2=1&amp;emailcc2=1&amp;emailtype2=substring&amp;email2=&amp;bugidtype=include&amp;bug_id=&amp;votes=&amp;chfieldfrom=&amp;chfieldto=Now&amp;chfieldvalue=&amp;cmdtype=doit&amp;order=Reuse+same+sort+as+last+time&amp;field0-0-0=noop&amp;type0-0-0=noop&amp;value0-0-0=">Current Tomcat Connectors bugs</a></li><li><a href="../miscellaneous/doccontrib.html">Contribute documentation</a></li><li><a href="../miscellaneous/jkstatustasks.html">JK Status Ant Tasks</a></li><li><a href="../miscellaneous/reporttools.html">Reporting Tools</a></li><li><a href="http://tomcat.apache.org/connectors-doc-archive/jk2/index.html">Old JK/JK2 documentation</a></li></ul><p><strong>News</strong></p><ul><li><a href="../news/20110701.html">2011</a></li><li><a href="../news/20100101.html">2010</a></li><li><a href="../news/20090301.html">2009</a></li><li><a href="../news/20081001.html">2008</a></li><li><a href="../news/20070301.html">2007</a></li><li><a href="../news/20060101.html">2006</a></li><li><a href="../news/20050101.html">2005</a></li><li><a href="../news/20041100.html">2004</a></li></ul></td><!--RIGHT SIDE MAIN BODY--><td width="80%" valign="top" align="left"><table border="0" width="100%" cellspacing="4"><tr><td align="left" valign="top"><h1>The Apache Tomcat Connector - AJP Protocol Reference</h1><h2>AJPv13 extensions Proposal</h2></td><td align="right" valign="top" nowrap="true"><small><a href="printer/ajpv13ext.html"><img src="../images/printer.gif" border="0" alt="Printer Friendly Version"><br>print-friendly<br>version
+ </a></small></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Introduction"><strong>Introduction</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+This document is a proposal of evolution of the current
+Apache JServ Protocol version 1.3, also known as ajp13.
+I'll not cover here the full protocol but only the add-on from ajp13.
+
+This nth pass include comments from the tomcat-dev list and
+misses discovered during developpment.
+</p>
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Missing features in AJP13"><strong>Missing features in AJP13</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+ajp13 is a good protocol to link a servlet engine like tomcat to a web server like Apache:
+
+<ul>
+<li>
+use persistants connections to avoid reconnect time at each request
+</li>
+<li>
+encode many http commands to reduce stream size
+</li>
+<li>
+send to servlet engine many info from web server (like SSL certs)
+</li>
+</ul>
+<p>
+But ajp13 lacks support for :
+</p>
+<ul>
+<li>
+ security between web server and servlet engine.
+ Anybody can connect to an ajp13 port (no login mecanism used)
+ You could connect, for example with telnet, and keep the remote thread
+ up by not sending any data (no timeout in connection)
+</li>
+<li>
+ context information passed from servlet engine to web server.
+ Part of the configuration of JK, the web server connector, is to
+ indicate to the web server which URI to handle.
+ The mod_jk JkMount directive, told to web server which URI must be
+ forwarded to servlet engine.
+ A servlet engine allready knows which URI it handle and TC 3.3 is
+ allready capable to generate a config file for JK from the list
+ of available contexts.
+</li>
+<li>
+ state update of contexts from servlet engine to web server.
+ Big site with farm of Tomcat, like ISP and virtuals hosters,
+ may need to stop a context for admin purposes. In that case the front
+ web server must know that the context is currently down, to eventually
+ relay the request to another Tomcat
+</li>
+<li>
+ verify state of connection before sending request.
+ Actually JK send the request to the servlet engine and next wait
+ for the answer. But one of the beauty of the socket API, is you that
+ you could write() to a closed connection without any error reporting,
+ but a read() to a closed connection return you the error code.
+</li>
+</ul>
+
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Proposed add-ons to AJP13"><strong>Proposed add-ons to AJP13</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+Let's descrive here the features and add-on that could be added to AJP13.
+Since this document is a proposal, a reasonable level of chaos must be expected at first.
+Be sure that discussion on tomcat list will help clarify points, add
+features but the current list seems to be a 'minimun vital'
+
+<ul>
+
+<li>
+Advanced login features at connect time
+</li>
+
+<li>
+Basic authorisation system, where a shared secret key is
+present in web server and servlet engine.
+</li>
+
+<li>
+Basic protocol negociation, just to be sure that if functionnalities are added
+to AJP13 in the future, current implementations will still works.
+</li>
+
+<li>
+Clean handling of 'Unknown packets'
+</li>
+
+<li>
+Extended env vars passed from web-server to servlet engine.
+</li>
+
+<li>
+Add extra SSL informations needed by Servlet 2.3 API (like SSL_KEY_SIZE)
+</li>
+
+</ul>
+
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Advanced login"><strong>Advanced login</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+
+<ol>
+<li>
+WEB-SERVER send LOGIN INIT CMD + NEGOCIATION DATA + WEB SERVER INFO
+</li>
+<li>
+ TOMCAT respond with LOGIN SEED CMD + RANDOM DATA
+</li>
+<li>
+ WEB-SERVER calculted the MD5 of RANDOM DATA+SECRET DATA
+</li>
+<li>
+ WEB-SERVER send LOGIN COMP CMD + MD5 (SECRET DATA + RANDOM DATA)
+</li>
+<li>
+ TOMCAT respond with LOGIN STATUS CMD + NEGOCIED DATA + SERVLET ENGINE INFO
+</li>
+</ol>
+
+To prevent DOS attack, the servlet engine will wait
+the LOGIN CMD only 15/30 seconds and reports the
+timeout exception for admins investigation.
+
+The login command will contains basic protocol
+negociation information like compressing ability,
+crypto, context info (at start up), context update at
+run-time (up/down), level of SSL env vars, AJP protocol
+level supported (level1/level2/level3...)
+
+The Web server info will contain web server info and
+connector name (ie Apache 1.3.26 + mod_ssl 2.8.8 + mod_jk 1.2.1 + mod_perl 1.25).
+
+The servlet engine will mask the negociation mask with it's own
+mask (what it can do) and return it when loggin is accepted.
+
+This will help having a basic AJP13 implementation (level 1)
+on a web-server working with a more advanced protocol handler on
+the servlet engine side or vice-versa.
+
+AJP13 was designed to be small and fast and so many
+SSL informations present in the web-server are not
+forwarded to the servlet engine.
+
+We add here four negociations flags to provide more
+informations on client SSL data (certs), server SSL datas,
+crypto used, and misc datas (timeout...).
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Messages Stream"><strong>Messages Stream</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+<div class="example"><pre>
++----------------+------------------+-----------------+
+| LOGIN INIT CMD | NEGOCIATION DATA | WEB SERVER INFO |
++----------------+------------------+-----------------+
+
++----------------+----------------+
+| LOGIN SEED CMD | MD5 of entropy |
++----------------+----------------+
+
++----------------+----------------------------+
+| LOGIN COMP CMD | MD5 of RANDOM + SECRET KEY |
++----------------+----------------------------+
+
++-----------+---------------+---------------------+
+| LOGOK CMD | NEGOCIED DATA | SERVLET ENGINE INFO |
++-----------+---------------+---------------------+
+
++------------+--------------+
+| LOGNOK CMD | FAILURE CODE |
++------------+--------------+
+</pre></div>
+
+<ul>
+<li>
+LOGIN INIT CMD, LOGIN SEED CMD, LOGIN COMP CMD, LOGOK CMD, LOGNOK CMD are 1 byte long.
+</li>
+<li>
+MD5, MD5 of RANDOM + SECRET KEY are 32 chars long.
+</li>
+<li>
+NEGOCIATION DATA, NEGOCIED DATA, FAILURE CODE are 32 bits long.
+</li>
+<li>
+WEB SERVER INFO, SERVLET ENGINE INFO are CString.
+</li>
+</ul>
+
+The secret key will be set by a new propertie in
+workers.properties : secretkey
+<div class="example"><pre>
+worker.ajp13.port=8009
+worker.ajp13.host=localhost
+worker.ajp13.type=ajp13
+worker.ajp13.secretkey=myverysecretkey
+</pre></div>
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Shutdown feature"><strong>Shutdown feature</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+AJP13 miss a functionnality of AJP12, which is shutdown command.
+A logout will tell servlet engine to shutdown itself.
+<div class="example"><pre>
++--------------+----------------------------+
+| SHUTDOWN CMD | MD5 of RANDOM + SECRET KEY |
++--------------+----------------------------+
+
++------------+
+| SHUTOK CMD |
++------------+
+
++-------------+--------------+
+| SHUTNOK CMD | FAILURE CODE |
++-------------+--------------+
+</pre></div>
+
+<ul>
+<li>
+SHUTDOWN CMD, SHUTOK CMD, SHUTNOK CMD are 1 byte long.
+</li>
+<li>
+MD5 of RANDOM + SECRET KEY are 32 chars long.
+</li>
+<li>
+FAILURE CODE is 32 bits long.
+</li>
+</ul>
+
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Extended Env Vars feature"><strong>Extended Env Vars feature</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+NOTA:
+
+While working on AJP13 in JK, I really discovered "JkEnvVar".
+The following "Extended Env Vars feature" description may not
+be implemented in extended AJP13 since allready available in original
+implementation.
+
+DESC:
+
+Many users will want to see some of their web-server env vars
+passed to their servlet engine.
+
+To reduce the network traffic, the web-servlet will send a
+table to describing the external vars in a shorter fashion.
+
+We'll use there a functionnality allready present in AJP13,
+attributes list :
+
+In the AJP13, we've got :
+
+<div class="example"><pre>
+AJP13_FORWARD_REQUEST :=
+ prefix_code 2
+ method (byte)
+ protocol (string)
+ req_uri (string)
+ remote_addr (string)
+ remote_host (string)
+ server_name (string)
+ server_port (integer)
+ is_ssl (boolean)
+ num_headers (integer)
+ request_headers *(req_header_name req_header_value)
+
+ ?context (byte string)
+ ?servlet_path (byte string)
+ ?remote_user (byte string)
+ ?auth_type (byte string)
+ ?query_string (byte string)
+ ?route (byte string)
+ ?ssl_cert (byte string)
+ ?ssl_cipher (byte string)
+ ?ssl_session (byte string)
+
+ ?attributes *(attribute_name attribute_value)
+ request_terminator (byte)
+</pre></div>
+
+Using short 'web server attribute name' will reduce the
+network traffic.
+
+<div class="example"><pre>
++-------------------+---------------------------+-------------------------------+----+
+| EXTENDED VARS CMD | WEB SERVER ATTRIBUTE NAME | SERVLET ENGINE ATTRIBUTE NAME | ES |
++-------------------+---------------------------+-------------------------------+----+
+</pre></div>
+
+ie :
+
+<div class="example"><pre>
+JkExtVars S1 SSL_CLIENT_V_START javax.servlet.request.ssl_start_cert_date
+JkExtVars S2 SSL_CLIENT_V_END javax.servlet.request.ssl_end_cert_date
+JkExtVars S3 SSL_SESSION_ID javax.servlet.request.ssl_session_id
+
+
++-------------------+----+-------------------------------------------+
+| EXTENDED VARS CMD | S1 | javax.servlet.request.ssl_start_cert_date |
++-------------------+----+-------------------------------------------+
++----+-----------------------------------------+
+| S2 | javax.servlet.request.ssl_end_cert_date |
++----+-----------------------------------------+
++----+-----------------------------------------+
+| S3 | javax.servlet.request.ssl_end_cert_date |
++----+-----------------------------------------+
+</pre></div>
+
+During transmission in extended AJP13 we'll see attributes name
+containing S1, S2, S3 and attributes values of
+2001/01/03, 2002/01/03, 0123AFE56.
+
+This example showed the use of extended SSL vars but
+any 'personnal' web-server vars like custom authentification
+vars could be reused in the servlet engine.
+The cost will be only some more bytes in the AJP traffic.
+
+<ul>
+<li>
+EXTENDED VARS CMD is 1 byte long.
+</li>
+<li>
+WEB SERVER ATTRIBUTE NAME, SERVLET ENGINE ATTRIBUTE NAME are CString.
+</li>
+<li>
+ES is an empty CString.
+</li>
+</ul>
+
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Context informations forwarding for Servlet engine to Web Server"><strong>Context informations forwarding for Servlet engine to Web Server</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+Just after the LOGON PHASE, the web server will ask for the list of contexts
+and URLs/URIs handled by the servlet engine.
+It will ease installation in many sites, reduce questions about configuration
+on tomcat-user list, and be ready for servlet API 2.3.
+
+This mode will be activated by a new directive JkAutoMount
+
+ie: JkAutoMount examples myworker1 /examples/
+
+If we want to get ALL the contexts handled by the servlet engine, willcard
+could be used :
+
+ie: JkAutoMount * myworker1 *
+
+A servlet engine could have many contexts, /examples, /admin, /test.
+We may want to use only some contexts for a given worker. It was
+done previously, in apache HTTP server for example, by setting by
+hand the JkMount accordingly in each [virtual] area of Apache.
+
+If you web-server support virtual hosting, we'll forward also that
+information to servlet engine which will only return contexts for
+that virtual host.
+In that case the servlet engine will only return the URL/URI matching
+these particular virtual server (defined in server.xml).
+This feature will help ISP and big sites which mutualize large farm
+of Tomcat in load-balancing configuration.
+
+<div class="example"><pre>
++-----------------+-------------------+----------+----------+----+
+| CONTEXT QRY CMD | VIRTUAL HOST NAME | CONTEXTA | CONTEXTB | ES |
++-----------------+-------------------+----------+----------+----+
+
++------------------+-------------------+----------+-------------------+----------+---------------+----+
+| CONTEXT INFO CMD | VIRTUAL HOST NAME | CONTEXTA | URL1 URL2 URL3 ES | CONTEXTB | URL1 URL2 ... | ES |
++------------------+-------------------+----------+-------------------+----------+---------------+----+
+</pre></div>
+
+We'll discover via context-query, the list of URL/MIMES handled by the remove servlet engine
+for a list of contextes.
+In wildcard mode, CONTEXTA will contains just '*'.
+
+<ul>
+<li>
+CONTEXT QRY CMD and CONTEXT INFO CMD are 1 byte long.
+</li>
+<li>
+VIRTUAL HOST NAME is a CString, ie an array of chars terminated by a null byte (/0).
+</li>
+<li>
+An empty string is just a null byte (/0).
+</li>
+<li>
+ES is an empty CString. Indicate end of URI/URLs or end of CONTEXTs.
+</li>
+</ul>
+
+NB:<br>
+When VirtualMode is not to be used, the VIRTUAL HOST NAME is '*'.
+In that case the servlet engine will send all contexts handled.
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Context informations updates from Servlet engine to Web Server"><strong>Context informations updates from Servlet engine to Web Server</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+Context update are messages caming from the servlet engine each time a context
+is desactivated/reactivated. The update will be in use when the directive JkUpdateMount.
+This directive will set the AJP13_CONTEXT_UPDATE_NEG flag.
+
+ie: JkUpdateMount myworker1
+
+<div class="example"><pre>
++--------------------+-------------------+----------+--------+----------+--------+----+
+| CONTEXT UPDATE CMD | VIRTUAL HOST NAME | CONTEXTA | STATUS | CONTEXTB | STATUS | ES |
++--------------------+-------------------+----------+--------+----------+--------+----+
+</pre></div>
+
+<ul>
+<li>
+CONTEXT UPDATE CMD, STATUS are 1 byte long.
+</li>
+<li>
+VIRTUAL HOST NAME, CONTEXTS are CString.
+</li>
+<li>
+ES is an empty CString. Indicate end of CONTEXTs.
+</li>
+</ul>
+
+NB:<br>
+When VirtualMode is not in use, the VIRTUAL HOST NAME is '*'.
+STATUS is one byte indicating if context is UP/DOWN/INVALID
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Context status query to Servlet engine"><strong>Context status query to Servlet engine</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+This query will be used by the web-server to determine if a given
+contexts are UP, DOWN or INVALID (and should be removed).
+
+<div class="example"><pre>
++-------------------+--------------------+----------+----------+----+
+| CONTEXT STATE CMD | VIRTUAL HOST NAME | CONTEXTA | CONTEXTB | ES |
++-------------------+--------------------+----------+----------+----+
+
++-------------------------+-------------------+----------+--------+----------+--------+----+
+| CONTEXT STATE REPLY CMD | VIRTUAL HOST NAME | CONTEXTA | STATUS | CONTEXTB | STATUS | ES |
++-------------------------+-------------------+----------+-------------------+--------+----+
+</pre></div>
+
+<ul>
+<li>
+CONTEXT STATE CMD, CONTEXT STATE REPLY CMD, STATUS are 1 byte long.
+</li>
+<li>
+VIRTUAL HOST NAME, CONTEXTs are CString
+</li>
+<li>
+ES is an empty CString
+</li>
+</ul>
+
+NB:<br>
+When VirtualMode is not in use, the VIRTUAL HOST NAME is an empty string.
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Handling of unknown packets"><strong>Handling of unknown packets</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+Sometimes even with a well negocied protocol, we may be in a situation
+where one end (web server or servlet engine), will receive a message it
+couldn't understand. In that case the receiver will send an
+'UNKNOW PACKET CMD' with attached the unhandled message.
+
+<div class="example"><pre>
++--------------------+------------------------+-------------------+
+| UNKNOWN PACKET CMD | UNHANDLED MESSAGE SIZE | UNHANDLED MESSAGE |
++--------------------+------------------------+-------------------+
+</pre></div>
+
+Depending on the message, the sender will report an error and if
+possible will try to forward the message to another endpoint.
+
+<ul>
+<li>
+UNKNOWN PACKET CMD is 1 byte long.
+</li>
+<li>
+UNHANDLED MESSAGE SIZE is 16bits long.
+</li>
+<li>
+UNHANDLED MESSAGE is an array of byte (length is contained in UNHANDLED MESSAGE SIZE)
+</li>
+</ul>
+
+NB:<br>
+added UNHANDLED MESSAGE SIZE (development)
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Verification of connection before sending request"><strong>Verification of connection before sending request</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+NOTA: This fonctionality may never be used, since it may slow up the normal process
+since requiring on the web-server side an extra IO (read) before forwarding
+the request.....
+
+One of the beauty of socket APIs, is that you could write on a half closed socket.
+When servlet engine close the socket, the web server will discover it only at the
+next read() to the socket.
+Basically, in the AJP13 protocol, the web server send the HTTP HEADER and HTTP BODY
+(POST by chunk of 8K) to the servlet engine and then try to receive the reply.
+If the connection was broken the web server will learn it only at receive time.
+
+We could use a buffering scheme but what happen when you use the servlet engine
+for upload operations with more than 8ko of datas ?
+
+The hack in the AJP13 protocol is to add some bytes to read after the end of the
+service :
+
+<div class="example"><pre>
+EXAMPLE OF DISCUSSION BETWEEN WEB SERVER AND SERVLET ENGINE
+
+AJP HTTP-HEADER (+ HTTP-POST) (WEB-&gt;SERVLET)
+
+AJP HTTP-REPLY (SERVLET-&gt;WEB)
+
+AJP END OF DISCUSSION (SERVLET-&gt;WEB)
+
+---&gt; AJP STATUS (SERVLET-&gt;WEB AJP13)
+</pre></div>
+
+The AJP STATUS will not be read by the servlet engine at the end of
+the request/response #N but at the begining of the next session.
+
+More at that time the web server could also use OS dependants functions
+(or better APR functions) to determine if there is also more data
+to read. And that datas could be CONTEXT Updates.
+
+This will avoid the web server sending a request to a
+desactivated context. In that case, if the load-balancing is used,
+it will search for another servlet engine to handle the request.
+
+And that feature will help ISP and big sites with farm of tomcat,
+to updates their servlet engine without any service interruption.
+
+<div class="example"><pre>
++------------+-------------+
+| STATUS CMD | STATUS DATA |
++------------+-------------+
+</pre></div>
+
+<ul>
+<li>
+STATUS CMD and STATUS DATA are one byte long.
+</li>
+</ul>
+</p>
+</blockquote></td></tr></table>
+
+</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Conclusion"><strong>Conclusion</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+The goal of the extended AJP13 protocol is to overcome some of the original AJP13 limitation.
+An easier configuration, a better support for large site and farm of Tomcat,
+a simple authentification system and provision for protocol updates.
+
+Using the stable ajp13 implementation in JK (native) and in servlet
+engine (java), it's a reasonable evolution of the well known ajp13.
+</p>
+</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Commands and IDs in extended AJP13 Index"><strong>Commands and IDs in extended AJP13 Index</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+Index of Commands and ID to be added in AJP13 Protocol
+</p>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Commands IDs"><strong>Commands IDs</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+<table>
+ <tr><th>Command Name</th><th>Command Number</th></tr>
+ <tr><td>AJP13_LOGINIT_CMD</td><td>0x10</td></tr>
+ <tr><td>AJP13_LOGSEED_CMD</td><td>0x11</td></tr>
+ <tr><td>AJP13_LOGCOMP_CMD</td><td>0x12</td></tr>
+ <tr><td>AJP13_LOGOK_CMD</td><td>0x13</td></tr>
+ <tr><td>AJP13_LOGNOK_CMD</td><td>0x14</td></tr>
+ <tr><td>AJP13_CONTEXT_QRY_CMD</td><td>0x15</td></tr>
+ <tr><td>AJP13_CONTEXT_INFO_CMD</td><td>0x16</td></tr>
+ <tr><td>AJP13_CONTEXT_UPDATE_CMD</td><td>0x17</td></tr>
+ <tr><td>AJP13_STATUS_CMD</td><td>0x18</td></tr>
+ <tr><td>AJP13_SHUTDOWN_CMD</td><td>0x19</td></tr>
+ <tr><td>AJP13_SHUTOK_CMD</td><td>0x1A</td></tr>
+ <tr><td>AJP13_SHUTNOK_CMD</td><td>0x1B</td></tr>
+ <tr><td>AJP13_CONTEXT_STATE_CMD</td><td>0x1C</td></tr>
+ <tr><td>AJP13_CONTEXT_STATE_REP_CMD</td><td>0x1D</td></tr>
+ <tr><td>AJP13_UNKNOW_PACKET_CMD</td><td>0x1E</td></tr>
+</table>
+
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Negociations Flags"><strong>Negociations Flags</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+<table>
+ <tr><th>Command Name</th><th>Number</th><th>Description</th></tr>
+ <tr><td>AJP13_CONTEXT_INFO_NEG</td><td>0x80000000</td><td>web-server want context info after login</td></tr>
+ <tr><td>AJP13_CONTEXT_UPDATE_NEG</td><td>0x40000000</td><td>web-server want context updates</td></tr>
+ <tr><td>AJP13_GZIP_STREAM_NEG</td><td>0x20000000</td><td>web-server want compressed stream</td></tr>
+ <tr><td>AJP13_DES56_STREAM_NEG</td><td>0x10000000</td><td>web-server want crypted DES56 stream with secret key</td></tr>
+ <tr><td>AJP13_SSL_VSERVER_NEG</td><td>0x08000000</td><td>Extended info on server SSL vars</td></tr>
+ <tr><td>AJP13_SSL_VCLIENT_NEG</td><td>0x04000000</td><td>Extended info on client SSL vars</td></tr>
+ <tr><td>AJP13_SSL_VCRYPTO_NEG</td><td>0x02000000</td><td>Extended info on crypto SSL vars</td></tr>
+ <tr><td>AJP13_SSL_VMISC_NEG</td><td>0x01000000</td><td>Extended info on misc SSL vars</td></tr>
+</table>
+
+<br>
+
+<table>
+ <tr><th>Negociation ID</th><th>Number</th><th>Description</th></tr>
+ <tr><td>AJP13_PROTO_SUPPORT_AJPXX_NEG</td><td>0x00FF0000</td><td>mask of protocol supported</td></tr>
+ <tr><td>AJP13_PROTO_SUPPORT_AJP13L1_NEG</td><td>0x00010000</td><td>communication could use AJP13 Level 1</td></tr>
+ <tr><td>AJP13_PROTO_SUPPORT_AJP13L2_NEG</td><td>0x00020000</td><td>communication could use AJP13 Level 2</td></tr>
+ <tr><td>AJP13_PROTO_SUPPORT_AJP13L3_NEG</td><td>0x00040000</td><td>communication could use AJP13 Level 3</td></tr>
+</table>
+
+<br>
+All others flags must be set to 0 since they are reserved for future use.
+
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Failure IDs"><strong>Failure IDs</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+<table>
+ <tr><th>Failure Id</th><th>Number</th></tr>
+ <tr><td>AJP13_BAD_KEY_ERR</td><td>0xFFFFFFFF</td></tr>
+ <tr><td>AJP13_ENGINE_DOWN_ERR</td><td>0xFFFFFFFE</td></tr>
+ <tr><td>AJP13_RETRY_LATER_ERR</td><td>0xFFFFFFFD</td></tr>
+ <tr><td>AJP13_SHUT_AUTHOR_FAILED_ERR</td><td>0xFFFFFFFC</td></tr>
+</table>
+</p>
+</blockquote></td></tr></table>
+
+<table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Status"><strong>Status</strong></a></font></td></tr><tr><td><blockquote>
+<p>
+<table>
+ <tr><th>Failure Id</th><th>Number</th></tr>
+ <tr><td>AJP13_CONTEXT_DOWN</td><td>0x01</td></tr>
+ <tr><td>AJP13_CONTEXT_UP</td><td>0x02</td></tr>
+ <tr><td>AJP13_CONTEXT_OK</td><td>0x03</td></tr>
+</table>
+</p>
+</blockquote></td></tr></table>
+
+</blockquote></td></tr></table></td></tr><!--FOOTER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><!--PAGE FOOTER--><tr><td colspan="2"><div align="center"><font color="#525D76" size="-1"><em>
+ Copyright &copy; 1999-2011, Apache Software Foundation
+ </em></font></div></td></tr></table></body></html> \ No newline at end of file