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Subject cvs commit: httpd-2.0/docs/manual/mod mod_proxy.xml
Date Thu, 24 Jul 2003 14:50:37 GMT
slive       2003/07/24 07:50:37

  Modified:    docs/manual/mod Tag: APACHE_2_0_BRANCH mod_proxy.xml
  Sync 2.0 with 2.1.
  Revision  Changes    Path
  No                   revision
  No                   revision  +135 -91   httpd-2.0/docs/manual/mod/mod_proxy.xml
  Index: mod_proxy.xml
  RCS file: /home/cvs/httpd-2.0/docs/manual/mod/mod_proxy.xml,v
  retrieving revision
  retrieving revision
  diff -u -d -b -u -r1.12.2.8 -r1.12.2.9
  --- mod_proxy.xml	6 Jul 2003 02:15:01 -0000
  +++ mod_proxy.xml	24 Jul 2003 14:50:36 -0000
  @@ -23,95 +23,120 @@
       The module can be configured to connect to other proxy modules for these
       and other protocols.</p>
  -    <p>This module was experimental in Apache 1.1.x. Improvements and bugfixes
  -    were made in Apache v1.2.x and Apache v1.3.x, then the module underwent a
  -    major overhaul for Apache v2.0. The protocol support was upgraded to
  -    <code>HTTP/1.1</code>, and filter support was enabled.</p>
  -    <p>During the overhaul process, <module>mod_proxy</module> features
  -    have been split into several module files: <module>mod_proxy_http</module>,
  -    <module>mod_proxy_ftp</module> and <module>mod_proxy_connect</module>.
  -    Thus, if you want to use one or more of the particular proxy functions,
  -    load <module>mod_proxy</module> <em>and</em> the appropriate
  -    module(s) into the server (either statically or dynamically via the
  -    <directive module="mod_so">LoadModule</directive> directive).</p>
  -    <p>Please note that the <strong>caching</strong> function present
in <module
  -    >mod_proxy</module> up to Apache v1.3.x has been <strong>removed</strong>
  -    from <module>mod_proxy</module> and incorporated into a new module,
  -    <module>mod_cache</module>. In other words, the Apache 2.0.x proxy doesn't

  -    cache - all caching functionality has been moved into
  -    <module>mod_cache</module>, which is capable of caching any content, not
  -    just content from the proxy.</p>
  +    <p>Apache's proxy features are divided into several modules in
  +    addition to <module>mod_proxy</module>:
  +    <module>mod_proxy_http</module>, <module>mod_proxy_ftp</module>
  +    and <module>mod_proxy_connect</module>.  Thus, if you want to use
  +    one or more of the particular proxy functions, load
  +    <module>mod_proxy</module> <em>and</em> the appropriate module(s)
  +    into the server (either statically at compile-time or dynamically
  +    via the <directive module="mod_so">LoadModule</directive>
  +    directive).</p>
  -    <p>If you need to use SSL when contacting remote servers, have a look at the
  -    <code>SSLProxy*</code> directives in <module>mod_ssl</module>.</p>
  +    <p>In addition, extended features are provided by other modules.
  +    Caching is provided by <module>mod_cache</module> and related
  +    modules.  The ability to contact remote servers using the SSL/TLS
  +    protocol is provided by the <code>SSLProxy*</code> directives of
  +    <module>mod_ssl</module>.  These additional modules will need
  +    to be loaded and configured to take advantage of these features.</p>
  -<section id="configs"><title>Common configuration topics</title>
  -    <ul>
  -    <li><a href="#forwardreverse">Forward and Reverse Proxies</a></li>
  -    <li><a href="#access">Controlling access to your proxy</a></li>
  -    <li><a href="#mimetypes">Why doesn't file type <var>xxx</var>
download via
  -    FTP?</a></li>
  -    <li><a href="#type">How can I force an FTP ASCII download of File
  -    <var>xxx</var>?</a></li>
  -    <li><a href="#percent2fhack">How can I access FTP files outside of my home
  -    directory?</a></li>
  -    <li><a href="#ftppass">How can I hide the FTP cleartext password in my
  -    browser's URL line?</a></li>
  -    <li><a href="#startup">Why does Apache start more slowly when using the
  -    proxy module?</a></li>
  -    <li><a href="#intranet">What other functions are useful for an intranet
  -    proxy server?</a></li>
  -    <li><a href="#envsettings">How can I make the proxy talk HTTP/1.0 and
  -    disable keepalives?</a></li>
  -    </ul>
       <section id="forwardreverse"><title>Forward and Reverse Proxies</title>
         <p>Apache can be configured in both a <dfn>forward</dfn> and
  -      <dfn>reverse</dfn> proxy configuration.</p>
  +      <dfn>reverse</dfn> proxy mode.</p>
  -      <p>A <dfn>forward proxy</dfn> is an intermediate system that enables
  -      browser to connect to a remote network to which it normally does not have
  -      access. A forward proxy can also be used to cache data, reducing load on
  -      the networks between the forward proxy and the remote webserver.</p>
  +      <p>An ordinary <dfn>forward proxy</dfn> is an intermediate
  +      server that sits between the client and the <em>origin
  +      server</em>.  In order to get content from the origin server,
  +      the client sends a request to the proxy naming the origin server
  +      as the target and the proxy then requests the content from the
  +      origin server and returns it to the client.  The client must be
  +      specially configured to use the forward proxy to access other
  +      sites.</p>
  -      <p>Apache's <module>mod_proxy</module> can be figured to behave
like a
  -      forward proxy using the <directive module="mod_proxy"
  -      >ProxyRemote</directive> directive. In addition, caching of data can be
  -      achieved by configuring <module>mod_cache</module>. Other dedicated
  -      forward proxy packages include <a href=""
  -      >Squid</a>.</p>
  +      <p>A typical usage of a forward proxy is to provide Internet
  +      access to internal clients that are otherwise restricted by a
  +      firewall.  The forward proxy can also use caching (as provided
  +      by <module>mod_cache</module>) to reduce network usage.</p>
  -      <p>A <dfn>reverse proxy</dfn> is a webserver system that is capable
  -      serving webpages sourced from other webservers - in addition to webpages
  -      on disk or generated dynamically by CGI - making these pages look like
  -      they originated at the reverse proxy.</p>
  +      <p>The forward proxy is activated using the <directive
  +      module="mod_proxy">ProxyRequests</directive> directive.  Because
  +      forward proxys allow clients to access arbitrary sites through
  +      your server and to hide their true origin, it is essential that
  +      you <a href="#access">secure your server</a> so that only
  +      authorized clients can access the proxy before activating a
  +      forward proxy.</p>
  -      <p>When configured with the mod_cache module the reverse proxy can act as
  -      a cache for slower backend webservers. The reverse proxy can also enable
  -      advanced URL strategies and management techniques, allowing webpages
  -      served using different webserver systems or architectures to coexist
  -      inside the same URL space. Reverse proxy systems are also ideal for
  -      implementing centralised logging websites with many or diverse website
  -      backends. Complex multi-tier webserver systems can be constructed using an
  -      <module>mod_proxy</module> frontend and any number of backend
  -      webservers.</p>
  +      <p>A <dfn>reverse proxy</dfn>, by contrast, appears to the
  +      client just like an ordinary web server.  No special
  +      configuration on the client is necessary.  The client makes
  +      ordinary requests for content in the name-space of the reverse
  +      proxy.  The reverse proxy then decides where to send those
  +      requests, and returns the content as if it was itself the
  +      origin.</p>
  -      <p>The reverse proxy is configured using the <directive
  -      module="mod_proxy">ProxyPass</directive> and <directive
  -      module="mod_proxy">ProxyPassReverse</directive> directives. Caching can
  -      enabled using mod_cache as with the forward proxy.</p>
  +      <p>A typical usage of a reverse proxy is to provide Internet
  +      users access to a server that is behind a firewall.  Reverse
  +      proxies can also be used to balance load among several back-end
  +      servers, or to provide caching for a slower back-end server.
  +      In addition, reverse proxies can be used simply to bring
  +      several servers into the same URL space.</p>
  +      <p>A reverse proxy is activated using the <directive
  +      module="mod_proxy">ProxyPass</directive> directive or the
  +      <code>[P]</code> flag to the <directive
  +      module="mod_rewrite">RewriteRule</directive> directive.  It is
  +      <strong>not</strong> necessary to turn <directive
  +      module="mod_proxy">ProxyRequests</directive> on in order to
  +      configure a reverse proxy.</p>
       </section> <!-- /forwardreverse -->
  +    <section id="examples"><title>Basic Examples</title>
  +    <p>The examples below are only a very basic idea to help you
  +    get started.  Please read the documentation on the individual
  +    directives.</p>
  +    <p>In addition, if you wish to have caching enabled, consult
  +    the documentation from <module>mod_cache</module>.</p>
  +    <example><title>Forward Proxy</title>
  +    ProxyRequests On<br />
  +    ProxyVia On<br />
  +    <br />
  +    &lt;Proxy *&gt;<br />
  +    <indent>
  +      Order deny,allow<br />
  +      Deny from all<br />
  +      Allow from<br />
  +    </indent>
  +    &lt;/Proxy&gr;
  +    </example>
  +    <example><title>Reverse Proxy</title>
  +    ProxyRequests Off<br />
  +    <br />
  +    &lt;Proxy *&gt;<br />
  +    <indent>
  +      Order deny,allow<br />
  +      Allow from all<br />
  +    </indent>
  +    &lt;/Proxy&gt;<br />
  +    <br />
  +    ProxyPass /foo/<br />
  +    ProxyPassReverse /foo/
  +    </example>
  +    </section> <!-- /examples -->
       <section id="access"><title>Controlling access to your proxy</title>
         <p>You can control who can access your proxy via the <directive
  -      module="mod_proxy" type="section">Proxy</directive> control block using
  +      module="mod_proxy" type="section">Proxy</directive> control block as in
         the following example:</p>
  @@ -124,11 +149,26 @@
  -      <p>When configuring a reverse proxy, access control takes on the
  -      attributes of the normal server <directive module="core" type="section"
  -      >Directory</directive> configuration.</p>
  +      <p>For more information on access control directives, see
  +      <module>mod_access</module>.</p>
  +      <p>Strictly limiting access is essential if you are using a
  +      forward proxy (using the <directive
  +      module="mod_proxy">ProxyRequests</directive> directive).
  +      Otherwise, your server can be used by any client to access
  +      arbitrary hosts while hiding his or her true identity.  This is
  +      dangerous both for your network and for the Internet at large.
  +      When using a reverse proxy (using the <directive
  +      module="mod_proxy">ProxyPass</directive> directive with
  +      <code>ProxyRequests Off</code>), access control is less
  +      critical because clients can only contact the hosts that you
  +      have specifically configured.</p>
       </section> <!-- /access -->
  +   <section id="ftp-proxy"><title>FTP Proxy</title>
       <section id="mimetypes"><title>Why doesn't file type <var>xxx</var>
       download via FTP?</title>
         <p>You probably don't have that particular file type defined as
  @@ -173,7 +213,7 @@
       in my browser's URL line?</title>
         <p>To log in to an FTP server by username and password, Apache uses
         different strategies. In absense of a user name and password in the URL
  -      altogether, Apache sends an anomymous login to the FTP server,
  +      altogether, Apache sends an anonymous login to the FTP server,
  @@ -215,9 +255,8 @@
           might intercept your password on its way.</p>
       </section> <!-- /ftppass -->
  -    <section id="startup"><title>Why does Apache start more slowly when using
  -    the proxy module?</title>
  +   </section> <!-- /ftpproxy -->
  +    <section id="startup"><title>Slow Startup</title>
         <p>If you're using the <directive module="mod_proxy"
         >ProxyBlock</directive> directive, hostnames' IP addresses are looked up
         and cached during startup for later match test. This may take a few
  @@ -225,10 +264,12 @@
       </section> <!-- /startup -->
  -    <section id="intranet"><title>What other functions are useful for an
  -    intranet proxy server?</title>
  +    <section id="intranet"><title>Intranet Proxy</title>
         <p>An Apache proxy server situated in an intranet needs to forward
  -      external requests through the company's firewall. However, when it has to
  +      external requests through the company's firewall (for this, configure
  +      the <directive module="mod_proxy">ProxyRemote</directive> directive
  +      to forward the respective <var>scheme</var> to the firewall proxy).
  +      However, when it has to
         access resources within the intranet, it can bypass the firewall when
         accessing hosts. The <directive module="mod_proxy">NoProxy</directive>
         directive is useful for specifying which hosts belong to the intranet and
  @@ -246,8 +287,7 @@
         files will then contain fully qualified hosts.</p>
       </section> <!-- /intranet -->
  -    <section id="envsettings"><title>How can I make the proxy talk HTTP/1.0
  -    disable keepalives?</title>
  +    <section id="envsettings"><title>Protocol Adjustments</title>
         <p>For circumstances where you have a application server which doesn't
         implement keepalives or HTTP/1.1 properly, there are 2 environment
         variables which when set send a HTTP/1.0 with no keepalive. These are set
  @@ -266,7 +306,6 @@
       </section> <!-- /envsettings -->
   <directivesynopsis type="section">
  @@ -506,10 +545,15 @@
       <p>When used inside a <directive type="section" module="core"
  -    >Location</directive> section, the first argument is ommitted and the local
  +    >Location</directive> section, the first argument is omitted and the local
       directory is obtained from the <directive type="section" module="core"
  +    <note type="warning">The <directive
  +    module="mod_proxy">ProxyRequests</directive> directive should
  +    usually be set <strong>off</strong> when using
  +    <directive>ProxyPass</directive>.</note>
       <p>If you require a more flexible reverse-proxy configuration, see the
       <directive module="mod_rewrite">RewriteRule</directive> directive with
       <code>[P]</code> flag.</p>
  @@ -563,7 +607,7 @@
       >ProxyPass</directive> directive.</p>
       <p>When used inside a <directive type="section" module="core"
  -    >Location</directive> section, the first argument is ommitted and the local
  +    >Location</directive> section, the first argument is omitted and the local
       directory is obtained from the <directive type="section" module="core"

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