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<H1 ALIGN="CENTER">Apache module mod_proxy</h1>
This module is contained in the <code>mod_proxy.c</code> file for Apache 1.1.x,
or the <code>modules/proxy</code> subdirectory for Apache 1.2, and
is not compiled in by default. It provides for an <b>HTTP 1.0</b> caching proxy
server. It is only available in Apache 1.1 and later. Common configuration
questions are addressed <a href="#configs">here</a>.
<h3>Note:</h3>
<p>This module was experimental in Apache 1.1.x. As of Apache 1.2, mod_proxy
stability is <i>greatly</i> improved.<p>
<h2>Summary</h2>
This module implements a proxy/cache for Apache. It implements
proxying capability for
<code>FTP</code>,
<code>CONNECT</code> (for SSL),
<code>HTTP/0.9</code>, and
<code>HTTP/1.0</code>.
The module can be configured to connect to other proxy modules for these
and other protocols.
<h2>Directives</h2>
<ul>
<li><a href="#proxyrequests">ProxyRequests</a>
<li><a href="#proxyremote">ProxyRemote</a>
<li><a href="#proxypass">ProxyPass</a>
<li><a href="#proxyblock">ProxyBlock</a>
<li><a href="#noproxy">NoProxy</a>
<li><a href="#proxydomain">ProxyDomain</a>
<li><a href="#cacheroot">CacheRoot</a>
<li><a href="#cachesize">CacheSize</a>
<li><a href="#cachemaxexpire">CacheMaxExpire</a>
<li><a href="#cachedefaultexpire">CacheDefaultExpire</a>
<li><a href="#cachelastmodifiedfactor">CacheLastModifiedFactor</a>
<li><a href="#cachegcinterval">CacheGcInterval</a>
<li><a href="#cachedirlevels">CacheDirLevels</a>
<li><a href="#cachedirlength">CacheDirLength</a>
<li><a href="#nocache">NoCache</a>
</ul>
<hr>
<A name="proxyrequests"><h2>ProxyRequests</h2></A>
<strong>Syntax:</strong> ProxyRequests <em>on/off</em><br>
<strong>Default:</strong> <code>ProxyRequests Off</code><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> ProxyRequest is only available in
Apache 1.1 and later.<p>
This allows or prevents Apache from functioning as a proxy
server. Setting ProxyRequests to 'off' does not disable use of the <a
href="#proxypass">ProxyPass</a> directive.
<A name="proxyremote"><h2>ProxyRemote</h2></A>
<strong>Syntax:</strong> ProxyRemote <em>&lt;match&gt; &lt;remote-server&gt;</em><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> ProxyRemote is only available in
Apache 1.1 and later.<p>
This defines remote proxies to this proxy. &lt;match&gt; is either the
name of a URL-scheme that the remote server supports, or a partial URL
for which the remote server should be used, or '*' to indicate the
server should be contacted for all requests. &lt;remote-server&gt; is a
partial URL for the remote server. Syntax:
<pre>
&lt;remote-server&gt; = &lt;protocol&gt;://&lt;hostname&gt;[:port]
</pre>
&lt;protocol&gt; is the protocol that should be used to communicate
with the remote server; only "http" is supported by this module.
Example:
<pre>
ProxyRemote http://goodguys.com/ http://mirrorguys.com:8000
ProxyRemote * http://cleversite.com
ProxyRemote ftp http://ftpproxy.mydomain.com:8080
</pre>
In the last example, the proxy will forward FTP requests, encapsulated
as yet another HTTP proxy request, to another proxy which can handle
them.
<A name="proxypass"><h2>ProxyPass</h2></A>
<strong>Syntax:</strong> ProxyPass <em>&lt;path&gt; &lt;url&gt;</em><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> ProxyPass is only available in
Apache 1.1 and later.<p>
This directive allows remote servers to be mapped into the space of the local
server; the local server does not act as a proxy in the conventional sense,
but appears to be a mirror of the remote server. &lt;path&gt; is the name of
a local virtual path; &lt;url&gt; is a partial URL for the remote server.
Suppose the local server has address http://wibble.org; then
<pre>
ProxyPass /mirror/foo http://foo.com
</pre>
Will cause a local request for the http://wibble.org/mirror/foo/bar to be
internally converted into a proxy request to http://foo.com/bar
<A name="proxyblock"><h2>ProxyBlock</h2></A>
<strong>Syntax:</strong> ProxyBlock <em>&lt;word/host/domain list&gt;</em><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> ProxyBlock is only available in
Apache 1.2 and later.<p>
The ProxyBlock directive specifies a list of words, hosts and/or domains,
separated by spaces. HTTP, HTTPS, and FTP document requests to matched words,
hosts or domains are <em>blocked</em> by the proxy server. The proxy module
will also attempt to determine IP addresses of list items which may be
hostnames during startup, and cache them for match test as well. Example:
<pre>
ProxyBlock joes_garage.com some_host.co.uk rocky.wotsamattau.edu
</pre>
'rocky.wotsamattau.edu' would also be matched if referenced by IP address.<p>
Note that 'wotsamattau' would also be sufficient to match 'wotsamattau.edu'.<p>
Note also that
<pre>
ProxyBlock *
</pre>
blocks connections to all sites.
<A name="noproxy"><h2>NoProxy</h2></A>
<strong>Syntax:</strong> NoProxy { <A HREF="#domain"><em>&lt;Domain&gt;</em></A>
| <A HREF="#subnet"><em>&lt;SubNet&gt;</em></A>
| <A HREF="#ipaddr"><em>&lt;IpAddr&gt;</em></A>
| <A HREF="#hostname"><em>&lt;Hostname&gt;</em></A>
} <br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> NoProxy is only available in
Apache 1.3 and later.<p>
This directive is only useful for apache proxy servers within intranets.
The NoProxy directive specifies a list of subnets, IP addresses, hosts
and/or domains, separated by spaces. A request to a host which matches
one or more of these is always served directly, without forwarding to
the configured ProxyRemote proxy server(s).<br>Example:
<pre>
ProxyRemote * http://firewall.mycompany.com:81
NoProxy .mycompany.com 192.168.112.0/21
</pre>
The arguments to the NoProxy directive are one of the following type list:
<DL>
<!-- ===================== Domain ======================= -->
<A NAME="domain">
<DT><EM>Domain</EM>
<DD>A <EM>Domain</EM> is a partially qualified DNS domain name, preceded
by a period.
It represents a list of hosts which logically belong to the same DNS
domain or zone (i.e. the suffixes of the hostnames are all ending in
<EM>Domain</EM>).<BR>
Examples: <SAMP>.com</SAMP> <SAMP>.apache.org.</SAMP><BR>
To distinguish <EM>Domain</EM>s from <A HREF="#hostname"><EM>Hostname</EM></A>s (both
syntactically and semantically; a DNS domain can have a DNS A record,
too!), <EM>Domain</EM>s are always written
with a leading period.<BR>
Note: Domain name comparisons are done without regard to the case,
and <EM>Domain</EM>s are always assumed to be anchored in the root
of the DNS tree, therefore two domains <SAMP>.MyDomain.com</SAMP> and
<SAMP>.mydomain.com.</SAMP> (note the trailing period) are
considered equal. Since a domain comparison does not involve a DNS
lookup, it is much more efficient than subnet comparison.
<!-- ===================== SubNet ======================= -->
<A NAME="subnet">
<DT><EM>SubNet</EM>
<DD>A <EM>SubNet</EM> is a partially qualified internet address in
numeric (dotted quad) form, optionally followed by a slash and the
netmask, specified as the number of significant bits in the
<EM>SubNet</EM>. It is used to represent a subnet of hosts which can
be reached over a common network interface. In the absence of the
explicit net mask it is assumed that omitted (or zero valued)
trailing digits specify the mask. (In this case, the netmask can
only be multiples of 8 bits wide.)<BR>
Examples:
<DL>
<DT><SAMP>192.168</SAMP> or <SAMP>192.168.0.0</SAMP>
<DD>the subnet 192.168.0.0 with an implied netmask of 16 valid bits
(sometimes used in the netmask form <SAMP>255.255.0.0</SAMP>)
<DT><SAMP>192.168.112.0/21</SAMP>
<DD>the subnet <SAMP>192.168.112.0/21</SAMP> with a netmask of 21
valid bits (also used in the form 255.255.248.0)
</DL>
As a degenerate case, a <EM>SubNet</EM> with 32 valid bits is the
equivalent to an <EM>IPAddr</EM>, while a <EM>SubNet</EM> with zero
valid bits (e.g., 0.0.0.0/0) is the same as the constant
<EM>_Default_</EM>, matching any IP address.
<!-- ===================== IPAddr ======================= -->
<A NAME="ipaddr">
<DT><EM>IPAddr</EM>
<DD>A <EM>IPAddr</EM> represents a fully qualified internet address in
numeric (dotted quad) form. Usually, this address represents a
host, but there need not necessarily be a DNS domain name
connected with the address.<BR>
Example: 192.168.123.7<BR>
Note: An <EM>IPAddr</EM> does not need to be resolved by the DNS system, so
it can result in more effective apache performance.<BR>
<p><strong>See Also:</strong>
<a href="../dns-caveats.html">DNS Issues</a></p>
<!-- ===================== Hostname ======================= -->
<A NAME="hostname">
<DT><EM>Hostname</EM>
<DD>A <EM>Hostname</EM> is a fully qualified DNS domain name which can
be resolved to one or more <A HREF="#ipaddr"><EM>IPAddrs</EM></A> via the DNS domain name service.
It represents a logical host (in contrast to <A HREF="#domain"><EM>Domain</EM></A>s, see
above) and must be resolvable to at least one <A HREF="#ipaddr"><EM>IPAddr</EM></A> (or
often to a list of hosts with different <A HREF="#ipaddr"><EM>IPAddr</EM></A>'s).<BR>
Examples: <SAMP>prep.ai.mit.edu</SAMP>
<SAMP>www.apache.org.</SAMP><BR>
Note: In many situations, it is more effective to specify an
<A HREF="#ipaddr"><EM>IPAddr</EM></A> in place of a <EM>Hostname</EM> since a DNS lookup
can be avoided. Name resolution in Apache can take a remarkable deal
of time when the connection to the name server uses a slow PPP
link.<BR>
Note: <EM>Hostname</EM> comparisons are done without regard to the case,
and <EM>Hostname</EM>s are always assumed to be anchored in the root
of the DNS tree, therefore two hosts <SAMP>WWW.MyDomain.com</SAMP>
and <SAMP>www.mydomain.com.</SAMP> (note the trailing period) are
considered equal.<BR>
<p><strong>See Also:</strong>
<a href="../dns-caveats.html">DNS Issues</a></p>
</DL>
<A name="proxydomain"><h2>ProxyDomain</h2></A>
<strong>Syntax:</strong> ProxyDomain <em>&lt;Domain&gt;</em><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> ProxyDomain is only available in
Apache 1.3 and later.<p>
This directive is only useful for apache proxy servers within intranets.
The ProxyDomain directive specifies the default domain which the apache
proxy server will belong to. If a request to a host without a domain name
is encountered, a redirection response to the same host
with the configured <em>Domain</em> appended will be generated.
<br>Example:
<pre>
ProxyRemote * http://firewall.mycompany.com:81
NoProxy .mycompany.com 192.168.112.0/21
ProxyDomain .mycompany.com
</pre>
<A name="cacheroot"><h2>CacheRoot</h2></A>
<strong>Syntax:</strong> CacheRoot <em>&lt;directory&gt;</em><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> CacheRoot is only available in
Apache 1.1 and later.<p>
Sets the name of the directory to contain cache files; this must be
writable
by the httpd server.
<A name="cachesize"><h2>CacheSize</h2></A>
<strong>Syntax:</strong> CacheSize <em>&lt;size&gt;</em><br>
<strong>Default:</strong> <code>CacheSize 5</code><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> CacheSize is only available in
Apache 1.1 and later.<p>
Sets the desired space usage of the cache, in Kb (1024 byte units). Although
usage may grow above this setting, the garbage collection will delete files
until the usage is at or below this setting.
<A name="cachegcinterval"><h2>CacheGcInterval</h2></A>
<strong>Syntax:</strong> CacheGcInterval <em>&lt;time&gt;</em><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> CacheGcinterval is only available in
Apache 1.1 and later.<p>
Check the cache every &lt;time&gt; hours, and delete files if the space
usage is greater than that set by CacheSize.
<A name="cachemaxexpire"><h2>CacheMaxExpire</h2></A>
<strong>Syntax:</strong> CacheMaxExpire <em>&lt;time&gt;</em><br>
<strong>Default:</strong> <code>CacheMaxExpire 24</code><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> CacheMaxExpire is only available in
Apache 1.1 and later.<p>
Cachable HTTP documents will be retained for at most &lt;time&gt; hours without
checking the origin server. Thus documents can be at most &lt;time&gt;
hours out of date. This restriction is enforced even if an expiry date
was supplied with the document.
<A name="cachelastmodifiedfactor"><h2>CacheLastModifiedFactor</h2></A>
<strong>Syntax:</strong> CacheLastModifiedFactor <em>&lt;factor&gt;</em><br>
<strong>Default:</strong> <code>CacheLastModifiedFactor 0.1</code><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> CacheLastModifiedFactor is only available in
Apache 1.1 and later.<p>
If the origin HTTP server did not supply an expiry date for the
document, then estimate one using the formula
<pre>
expiry-period = time-since-last-modification * &lt;factor&gt;
</pre>
For example, if the document was last modified 10 hours ago, and
&lt;factor&gt; is 0.1, then the expiry period will be set to 10*0.1 = 1 hour.
<p>If the expiry-period would be longer than that set by CacheMaxExpire,
then the latter takes precedence.
<A name="cachedirlevels"><h2>CacheDirLevels</h2></A>
<strong>Syntax:</strong> CacheDirLevels <em>&lt;levels&gt;</em><br>
<strong>Default:</strong> <code>CacheDirLevels 3</code><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> CacheDirLevels is only available in
Apache 1.1 and later.<p>
CacheDirLevels sets the number of levels of subdirectories in the cache.
Cached data will be saved this many directory levels below CacheRoot.
<A name="cachedirlength"><h2>CacheDirLength</h2></A>
<strong>Syntax:</strong> CacheDirLength <em>&lt;length&gt;</em><br>
<strong>Default:</strong> <code>CacheDirLength 1</code><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> CacheDirLength is only available in
Apache 1.1 and later.<p>
CacheDirLength sets the number of characters in proxy cache subdirectory names.
<A name="cachedefaultexpire"><h2>CacheDefaultExpire</h2></A>
<strong>Syntax:</strong> CacheDefaultExpire <em>&lt;time&gt;</em><br>
<strong>Default:</strong> <code>CacheDefaultExpire 1</code><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> CacheDefaultExpire is only available in
Apache 1.1 and later.<p>
If the document is fetched via a protocol that does not support expiry times,
then use &lt;time&gt; hours as the expiry time.
<a href="#cachemaxexpire">CacheMaxExpire</a> does <strong>not</strong>
override.
<A name="nocache"><h2>NoCache</h2></A>
<strong>Syntax:</strong> NoCache <em>&lt;word/host/domain list&gt;</em><br>
<strong>Context:</strong> server config, virtual host<br>
<strong>Status:</strong> Base<br>
<strong>Module:</strong> mod_proxy<br>
<strong>Compatibility:</strong> NoCache is only available in
Apache 1.1 and later.<p>
The NoCache directive specifies a list of words, hosts and/or domains, separated
by spaces. HTTP and non-passworded FTP documents from matched words, hosts or
domains are <em>not</em> cached by the proxy server. The proxy module will
also attempt to determine IP addresses of list items which may be hostnames
during startup, and cache them for match test as well. Example:
<pre>
NoCache joes_garage.com some_host.co.uk bullwinkle.wotsamattau.edu
</pre>
'bullwinkle.wotsamattau.edu' would also be matched if referenced by IP
address.<p>
Note that 'wotsamattau' would also be sufficient to match 'wotsamattau.edu'.<p>
Note also that
<pre>
NoCache *
</pre>
disables caching completely.<p>
<hr>
<a name="configs"><h2>Common configuration topics</h2></a>
<ul>
<li><a href="#access">Controlling access to your proxy</a>
<li><a href="#shortname">Using Netscape hostname shortcuts</a>
<li><a href="#mimetypes">Why doesn't file type <i>xxx</i> download via FTP?</a>
<li><a href="#startup">Why does Apache start more slowly when using the
proxy module?</a>
<li><a href="#socks">Can I use the Apache proxy module with my SOCKS proxy?</a>
<li><a href="#intranet">What other functions are useful for an intranet proxy server?</a>
</ul>
<h2><a name="access">Controlling access to your proxy</a></h2>
You can control who can access your proxy via the normal &lt;Directory&gt;
control block using the following example:<p>
<pre>
&lt;Directory proxy:*&gt;
&lt;Limit GET PUT POST DELETE CONNECT OPTIONS&gt;
order deny,allow
deny from [machines you'd like *not* to allow by IP address or name]
allow from [machines you'd like to allow by IP address or name]
&lt;/Limit&gt;
&lt;/Directory&gt;
</pre><p>
A &lt;Files&gt; block will also work, and is the only method known to work
for all possible URLs in Apache versions earlier than 1.2b10.<p>
<h2><a name="shortname">Using Netscape hostname shortcuts</a></h2>
There is an optional patch to the proxy module to allow Netscape-like
hostname shortcuts to be used. It's available
<a href="http://www.apache.org/dist/contrib/patches/1.2/netscapehost.patch">
here</a>.<p>
<h2><a name="mimetypes">Why doesn't file type <i>xxx</i> download via FTP?</a></h2>
You probably don't have that particular file type defined as
<i>application/octet-stream</i> in your proxy's mime.types configuration
file. A useful line can be<p>
<pre>
application/octet-stream bin dms lha lzh exe class tgz taz
</pre>
<h2><a name="startup">Why does Apache start more slowly when using the
proxy module?</a></h2>
If you're using the <code>ProxyBlock</code> or <code>NoCache</code>
directives, hostnames' IP addresses are looked up and cached during
startup for later match test. This may take a few seconds (or more)
depending on the speed with which the hostname lookups occur.<p>
<h2><a name="socks">Can I use the Apache proxy module with my SOCKS proxy?</a></h2>
Yes. Just build Apache with the rule <code>SOCKS4=yes</code> in your
<i>Configuration</i> file, and follow the instructions there. SOCKS5
capability can be added in a similar way (there's no <code>SOCKS5</code>
rule yet), so use the <code>EXTRA_LDFLAGS</code> definition, or build Apache
normally and run it with the <i>runsocks</i> wrapper provided with SOCKS5,
if your OS supports dynamically linked libraries.<p>
Some users have reported problems when using SOCKS version 4.2 on Solaris.
The problem was solved by upgrading to SOCKS 4.3.<p>
Remember that you'll also have to grant access to your Apache proxy machine by
permitting connections on the appropriate ports in your SOCKS daemon's
configuration.<p>
<h2><a name="intranet">What other functions are useful for an intranet proxy server?</a></h2>
<p>An Apache proxy server situated in an intranet needs to forward external
requests through the company's firewall. However, when it has to access
resources within the intranet, it can bypass the firewall when accessing
hosts. The <A HREF="#noproxy">NoProxy</A> directive is useful for specifying
which hosts belong to the intranet and should be accessed directly.</p>
<p>Users within an intranet tend to omit the local domain name from their
WWW requests, thus requesting "http://somehost/" instead of
"http://somehost.my.dom.ain/". Some commercial proxy servers let them get
away with this and simply serve the request, implying a configured
local domain. When the <A HREF="#proxydomain">ProxyDomain</A> directive
is used and the server is <A HREF="#proxyrequests">configured for
proxy service</A>, Apache can return a redirect response and send the client
to the correct, fully qualified, server address. This is the preferred method
since the user's bookmark files will then contain fully qualified hosts.</p>
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