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<h2>
Navigator Proxy Auto-Config File Format</h2></center>
<center><i>March 1996</i>
<p><i>(There are several examples and tips in the end of this document)</i>
</p><hr size="4"></center>
<br>
<p><br>
<br>
<br>
<br>
<br>
</p><p>The proxy autoconfig file is written in JavaScript. The file must define
the function:
</p><pre> function FindProxyForURL(url, host)
{
...
}</pre>
which will be called by the Navigator in the following way for every URL
that is retrieved by it:
<pre> ret = FindProxyForURL(url, host);</pre>
where:
<dl compact="compact">
<dt>
<tt>url</tt></dt>
<dd>
the full URL being accessed.</dd>
<dt>
<tt>host</tt></dt>
<dd>
the hostname extracted from the URL. This is only for convenience, it is
the exact same string as between <tt>://</tt> and the first <tt>:</tt>
or <tt>/</tt> after that. The port number is not included in this parameter.
It can be extracted from the URL when necessary.</dd>
<dt>
<tt>ret</tt></dt>
<dd>
(the return value) a string describing the configuration. The format of
this string is defined below.</dd>
</dl>
<hr size="4">
<h2>
Saving the Auto-Config File<br>
Setting the MIME Type</h2>
<ol>
<li>
You should save the JavaScript function to file with a
<tt>.pac</tt> filename
extension; for example:</li>
<pre> proxy.pac</pre>
<b>Note 1:</b> You should save the JavaScript function <b>by itself</b>,
not embed it in HTML.
<p><b>Note 2:</b> The examples in the end of this document are
<b>complete</b>,
there is no additional syntax needed to save it into a file and use it
(of course, the JavaScripts have to be edited to reflect your site's domain
name and/or subnets).
</p><li>
Next, you should configure your server to map the
<tt>.pac</tt> filename
extension to the MIME type:</li>
<pre> application/x-ns-proxy-autoconfig</pre>
If using a Netscape server, edit the <tt>mime.types</tt> file in the <tt>config</tt>
directory. If using Apache, CERN or NCSA servers, use the <tt>AddType</tt>
directive.
<br> </ol>
<hr size="4">
<h2>
Return Value Format</h2>
The JavaScript function returns a single string.
<p>If the string is null, no proxies should be used.
</p><p>The string can contain any number of the following building blocks,
separated by a semicolon:
</p><dl>
<dt>
<tt>DIRECT</tt></dt>
<dd>
Connections should be made directly, without any proxies.</dd>
<dt>
<tt>PROXY <i>host:port</i></tt></dt>
<dd>
The specified proxy should be used.</dd>
<dt>
<tt>SOCKS <i>host:port</i></tt></dt>
<dd>
The specified SOCKS server should be used.</dd>
<br>
<p>
<br>
<br> </p></dl>
If there are multiple semicolon-separated settings, the left-most setting
will be used, until the Navigator fails to establish the connection to
the proxy. In that case the next value will be used, etc.
<p>The Navigator will automatically retry a previously unresponsive proxy
after 30 minutes, then after 1 hour from the previous try (always adding
an extra 30 minutes).
</p><p>If all proxies are down, and there was no <tt>DIRECT</tt> option specified,
the Navigator will ask if proxies should be temporarily ignored, and direct
connections attempted. The Navigator will ask if proxies should be retried
after 20 minutes has passed (then the next time 40 minutes from the previous
question, always adding 20 minutes).
</p><h4>
Examples:</h4>
<dl>
<dt>
<tt>PROXY w3proxy.netscape.com:8080; PROXY mozilla.netscape.com:8081</tt></dt>
<dd>
Primary proxy is <tt>w3proxy:8080</tt>; if that goes down start using <tt>mozilla:8081</tt>
until the primary proxy comes up again.</dd>
<dt>
<tt>PROXY w3proxy.netscape.com:8080; PROXY mozilla.netscape.com:8081; DIRECT</tt></dt>
<dd>
Same as above, but if both proxies go down, automatically start making
direct connections. (In the first example above, Netscape will ask user
confirmation about making direct connections; in this third case, there
is no user intervention.)</dd>
<dt>
<tt>PROXY w3proxy.netscape.com:8080; SOCKS socks:1080</tt></dt>
<dd>
Use SOCKS if the primary proxy goes down.</dd>
<br>
<p>
<br>
<br> </p></dl>
<hr size="4">
<h2>
Predefined Functions and Environment for the JavaScript Function</h2>
<ul>
<li>
Hostname based conditions:</li>
<ul>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#isPlainHostName">isPlainHostName()</a></tt></li>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#dnsDomainIs">dnsDomainIs()</a></tt></li>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#localHostOrDomainIs">localHostOrDomainIs()</a></tt></li>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#isResolvable">isResolvable()</a></tt></li>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#isInNet">isInNet()</a></tt></li>
</ul>
<li>
Related utility functions:</li>
<ul>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#dnsResolve">dnsResolve()</a></tt></li>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#myIpAddress">myIpAddress()</a></tt></li>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#dnsDomainLevels">dnsDomainLevels()</a></tt></li>
</ul>
<li>
URL/hostname based conditions:</li>
<ul>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#shExpMatch">shExpMatch()</a></tt></li>
</ul>
<li>
Time based conditions:</li>
<ul>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#weekdayRange">weekdayRange()</a></tt></li>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#dateRange">dateRange()</a></tt></li>
<li>
<tt><a href="http://web.archive.org/web/20060424005037/http://wp.netscape.com/eng/mozilla/2.0/relnotes/demo/proxy-live.html#timeRange">timeRange()</a></tt></li>
</ul>
<li>
There is one associative array already defined (because a JavaScript currently
cannot define them on its own):</li>
<ul>
<li>
<tt>ProxyConfig.bindings</tt></li>
</ul>
</ul>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="isPlainHostName"></a><tt>isPlainHostName(host)</tt></h3>
<dl compact="compact">
<dt>
<tt>host</tt></dt>
<dd>
the hostname from the URL (excluding port number).</dd>
</dl>
True iff there is no domain name in the hostname (no dots).
<h4>
Examples:</h4>
<dl>
<dt>
<tt>isPlainHostName("www")</tt></dt>
<dd>
is true.</dd>
<dt>
<tt>isPlainHostName("www.netscape.com")</tt></dt>
<dd>
is false.</dd>
<br>
<p>
<br>
<br> </p></dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="dnsDomainIs"></a><tt>dnsDomainIs(host, domain)</tt></h3>
<dl compact="compact">
<dt>
<tt>host</tt></dt>
<dd>
is the hostname from the URL.</dd>
<dt>
<tt>domain</tt></dt>
<dd>
is the domain name to test the hostname against.</dd>
</dl>
Returns true iff the domain of hostname matches.
<h4>
Examples:</h4>
<dl>
<dt>
<tt>dnsDomainIs("www.netscape.com", ".netscape.com")</tt></dt>
<dd>
is true.</dd>
<dt>
<tt>dnsDomainIs("www", ".netscape.com")</tt></dt>
<dd>
is false.</dd>
<dt>
<tt>dnsDomainIs("www.mcom.com", ".netscape.com")</tt></dt>
<dd>
is false.</dd>
<br>
<p>
<br>
<br> </p></dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="localHostOrDomainIs"></a><tt>localHostOrDomainIs(host, hostdom)</tt></h3>
<dl compact="compact">
<dt>
<tt>host</tt></dt>
<dd>
the hostname from the URL.</dd>
<dt>
<tt>hostdom</tt></dt>
<dd>
fully qualified hostname to match against.</dd>
</dl>
Is true if the hostname matches exactly the specified hostname, or if there
is no domain name part in the hostname, but the unqualified hostname matches.
<h4>
Examples:</h4>
<dl>
<dt>
<tt>localHostOrDomainIs("www.netscape.com", "www.netscape.com")</tt></dt>
<dd>
is true (exact match).</dd>
<dt>
<tt>localHostOrDomainIs("www", "www.netscape.com")</tt></dt>
<dd>
is true (hostname match, domain not specified).</dd>
<dt>
<tt>localHostOrDomainIs("www.mcom.com", "www.netscape.com")</tt></dt>
<dd>
is false (domain name mismatch).</dd>
<dt>
<tt>localHostOrDomainIs("home.netscape.com", "www.netscape.com")</tt></dt>
<dd>
is false (hostname mismatch).</dd>
<br>
<p>
<br>
<br> </p></dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="isResolvable"></a><tt>isResolvable(host)</tt></h3>
<dl compact="compact">
<dt>
<tt>host</tt></dt>
<dd>
is the hostname from the URL.</dd>
</dl>
Tries to resolve the hostname. Returns true if succeeds.
<h4>
Examples:</h4>
<dl>
<dt>
<tt>isResolvable("www.netscape.com")</tt></dt>
<dd>
is true (unless DNS fails to resolve it due to a firewall or some other
reason).</dd>
<dt>
<tt>isResolvable("bogus.domain.foobar")</tt></dt>
<dd>
is false.</dd>
<br>
<p>
<br>
<br> </p></dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="isInNet"></a><tt>isInNet(host, pattern, mask)</tt></h3>
<dl compact="compact">
<dt>
<tt>host</tt></dt>
<dd>
a DNS hostname, or IP address. If a hostname is passed, it will be resoved
into an IP address by this function.</dd>
<dt>
<tt>pattern</tt></dt>
<dd>
an IP address pattern in the dot-separated format</dd>
<dt>
<tt>mask</tt></dt>
<dd>
mask for the IP address pattern informing which parts of the IP address
should be matched against. 0 means ignore, 255 means match.</dd>
</dl>
True iff the IP address of the host matches the specified IP address pattern.
<p>Pattern and mask specification is done the same way as for SOCKS configuration.
</p><h4>
Examples:</h4>
<dl>
<dt>
<tt>isInNet(host, "198.95.249.79", "255.255.255.255")</tt></dt>
<dd>
is true iff the IP address of host matches exactly 198.95.249.79.</dd>
<dt>
<tt>isInNet(host, "198.95.0.0", "255.255.0.0")</tt></dt>
<dd>
is true iff the IP address of the host matches 198.95.*.*.</dd>
<br>
<p>
<br>
<br> </p></dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="dnsResolve"></a><tt>dnsResolve(host)</tt></h3>
<dl compact="compact">
<dt>
<tt>host</tt></dt>
<dd>
hostname to resolve</dd>
</dl>
Resolves the given DNS hostname into an IP address, and returns it in the
dot separated format as a string.
<h4>
Example:</h4>
<dl>
<dt>
<tt>dnsResolve("home.netscape.com")</tt></dt>
<dd>
returns the string <tt>"198.95.249.79"</tt>.</dd>
</dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="myIpAddress"></a><tt>myIpAddress()</tt></h3>
Returns the IP address of the host that the Navigator is running on, as
a string in the dot-separated integer format.
<h4>
Example:</h4>
<dl>
<dt>
<tt>myIpAddress()</tt></dt>
<dd>
would return the string <tt>"198.95.249.79"</tt> if you were running the
Navigator on that host.</dd>
</dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="dnsDomainLevels"></a><tt>dnsDomainLevels(host)</tt></h3>
<dl compact="compact">
<dt>
<tt>host</tt></dt>
<dd>
is the hostname from the URL.</dd>
</dl>
Returns the number (integer) of DNS domain levels (number of dots) in the
hostname.
<h4>
Examples:</h4>
<dl>
<dt>
<tt>dnsDomainLevels("www")</tt></dt>
<dd>
returns 0.</dd>
<dt>
<tt>dnsDomainLevels("www.netscape.com")</tt></dt>
<dd>
returns 2.</dd>
<br>
<p>
<br>
<br> </p></dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="shExpMatch"></a><tt>shExpMatch(str, shexp)</tt></h3>
<dl compact="compact">
<dt>
<tt>str</tt></dt>
<dd>
is any string to compare (e.g. the URL, or the hostname).</dd>
<dt>
<tt>shexp</tt></dt>
<dd>
is a shell expression to compare against.</dd>
</dl>
Returns true if the string matches the specified shell expression.
<p><b>Actually, currently the patterns are <i>shell expressions</i>, not
regular expressions.</b>
</p><h4>
Examples:</h4>
<dl>
<dt>
<tt>shExpMatch("http://home.netscape.com/people/ari/index.html", "*/ari/*")</tt></dt>
<dd>
is true.</dd>
<dt>
<tt>shExpMatch("http://home.netscape.com/people/montulli/index.html", "*/ari/*")</tt></dt>
<dd>
is false.</dd>
<br>
<p>
<br>
<br> </p></dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="weekdayRange"></a><tt>weekdayRange(wd1, wd2, gmt)</tt></h3>
<dl compact="compact">
<dt>
<tt>wd1</tt></dt>
<dd>
and</dd>
<dt>
<tt>wd2</tt></dt>
<dd>
are one of the weekday strings:</dd>
<pre> SUN MON TUE WED THU FRI SAT</pre>
<dt>
<tt>gmt</tt></dt>
<dd>
is either the string: <tt>GMT</tt> or is left out.</dd>
<br>
<p>
<br>
<br> </p></dl>
Only the first parameter is mandatory. Either the second, the third, or
both may be left out.
<p>If only one parameter is present, the function yeilds a true value on
the weekday that the parameter represents. If the string
<tt>"GMT"</tt>
is specified as a second parameter, times are taken to be in GMT, otherwise
in local timezone.
</p><p>If both <tt>wd1</tt> and <tt>wd1</tt> are defined, the condition is
true if the current weekday is in between those two weekdays. Bounds are
inclusive. If the <tt>"GMT"</tt> parameter is specified, times are taken
to be in GMT, otherwise the local timezone is used.
</p><h4>
Examples:</h4>
<dl>
<dt>
<tt>weekdayRange("MON", "FRI")</tt></dt>
<dd>
true Monday trhough Friday (local timezone).</dd>
<dt>
<tt>weekdayRange("MON", "FRI", "GMT")</tt></dt>
<dd>
same as above, but GMT timezone.</dd>
<dt>
<tt>weekdayRange("SAT")</tt></dt>
<dd>
true on Saturdays local time.</dd>
<dt>
<tt>weekdayRange("SAT", "GMT")</tt></dt>
<dd>
true on Saturdays GMT time.</dd>
<dt>
<tt>weekdayRange("FRI", "MON")</tt></dt>
<dd>
true Friday through Monday (note, order does matter!).</dd>
<br>
<p>
<br>
<br> </p></dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="dateRange"></a><tt>dateRange(day)<br>
dateRange(day1, day2)<br>
dateRange(mon)<br>
dateRange(month1, month2)<br>
dateRange(year)<br>
dateRange(year1, year2)<br>
dateRange(day1, month1, day2, month2)<br>
dateRange(month1, year1, month2, year2)<br>
dateRange(day1, month1, year1, day2, month2, year2)<br>
dateRange(day1, month1, year1, day2, month2, year2, gmt)</tt></h3>
<dl compact="compact">
<dt>
<tt>day</tt></dt>
<dd>
is the day of month between 1 and 31 (as an integer).</dd>
<dt>
<tt>month</tt></dt>
<dd>
is one of the month strings:</dd>
<pre> JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC</pre>
<dt>
<tt>year</tt></dt>
<dd>
is the full year number, for example 1995 (but <b>not</b> 95). Integer.</dd>
<dt>
<tt>gmt</tt></dt>
<dd>
is either the string <tt>"GMT"</tt>, which makes time comparison occur
in GMT timezone; if left unspecified, times are taken to be in the local
timezone.</dd>
<br>
<p>
</p><p>Even though the above examples don't show, the <tt>"GMT"</tt> parameter
can be specified in any of the 9 different call profiles, always as the
last parameter.
<br>
<br> </p></dl>
If only a single value is specified (from each category: day, month, year),
the function returns a true value only on days that match that specification.
If both values are specified, the result is true between those times, including
bounds.
<h4>
Examples:</h4>
<dl>
<dt>
<tt>dateRange(1)</tt></dt>
<dd>
true on the first day of each month, local timezone.</dd>
<dt>
<tt>dateRange(1, "GMT")</tt></dt>
<dd>
true on the first day of each month, GMT timezone.</dd>
<dt>
<tt>dateRange(1, 15)</tt></dt>
<dd>
true on the first half of each month.</dd>
<dt>
<tt>dateRange(24, "DEC")</tt></dt>
<dd>
true on 24th of December each year.</dd>
<dt>
<tt>dateRange(24, "DEC", 1995)</tt></dt>
<dd>
true on 24th of December, 1995.</dd>
<dt>
<tt>dateRange("JAN", "MAR")</tt></dt>
<dd>
true on the first quarter of the year.</dd>
<dt>
<tt>dateRange(1, "JUN", 15, "AUG")</tt></dt>
<dd>
true from June 1st until August 15th, each year (including June 1st and
August 15th).</dd>
<dt>
<tt>dateRange(1, "JUN", 15, 1995, "AUG", 1995)</tt></dt>
<dd>
true from June 1st, 1995, until August 15th, same year.</dd>
<dt>
<tt>dateRange("OCT", 1995, "MAR", 1996)</tt></dt>
<dd>
true from October 1995 until March 1996 (including the entire month of
October 1995 and March 1996).</dd>
<dt>
<tt>dateRange(1995)</tt></dt>
<dd>
true during the entire year 1995.</dd>
<dt>
<tt>dateRange(1995, 1997)</tt></dt>
<dd>
true from beginning of year 1995 until the end of year 1997.</dd>
<br>
<p>
<br>
<br> </p></dl>
<!-- ---------------------------------------------------------- -->
<hr size="4">
<h3>
<a name="timeRange"></a><tt>timeRange(hour)<br>
timeRange(hour1, hour2)<br>
timeRange(hour1, min1, hour2, min2)<br>
timeRange(hour1, min1, sec1, hour2, min2, sec2)<br>
timeRange(hour1, min1, sec1, hour2, min2, sec2, gmt)</tt></h3>
<dl compact="compact">
<dt>
<tt>hour</tt></dt>
<dd>
is the hour from 0 to 23. (0 is midnight, 23 is 11 pm.)</dd>
<dt>
<tt>min</tt></dt>
<dd>
minutes from 0 to 59.</dd>
<dt>
<tt>sec</tt></dt>
<dd>
seconds from 0 to 59.</dd>
<dt>
<tt>gmt</tt></dt>
<dd>
either the string <tt>"GMT"</tt> for GMT timezone, or not specified, for
local timezone. Again, even though the above list doesn't show it, this
parameter may be present in each of the different parameter profiles, always
as the last parameter.</dd>
<br>
<p>
<br>
<br> </p></dl>
True during (or between) the specified time(s).
<h4>
Examples:</h4>
<dl>
<dt>
<tt>timerange(12)</tt></dt>
<dd>
true from noon to 1pm.</dd>
<dt>
<tt>timerange(12, 13)</tt></dt>
<dd>
same as above.</dd>
<dt>
<tt>timerange(12, "GMT")</tt></dt>
<dd>
true from noon to 1pm, in GMT timezone.</dd>
<dt>
<tt>timerange(9, 17)</tt></dt>
<dd>
true from 9am to 5pm.</dd>
<dt>
<tt>timerange(8, 30, 17, 00)</tt></dt>
<dd>
true from 8:30am to 5:00pm.</dd>
<dt>
<tt>timerange(0, 0, 0, 0, 0, 30)</tt></dt>
<dd>
true between midnight and 30 seconds past midnight.</dd>
<br>
<p>
<br>
<br> </p></dl>
<hr size="4">
<h2>
Example #1:
<font size="+0">Use proxy for everything except local hosts</font></h2>
This would work in Netscape's environment. All hosts which aren't fully
qualified, or the ones that are in local domain, will be connected to directly.
Everything else will go through
<tt>w3proxy:8080</tt>. If the proxy goes
down, connections become automatically direct.
<pre> function FindProxyForURL(url, host)
{
if (isPlainHostName(host) ||
dnsDomainIs(host, ".netscape.com"))
return "DIRECT";
else
return "PROXY w3proxy.netscape.com:8080; DIRECT";
}</pre>
<b>Note:</b> This is the simplest and most efficient autoconfig file for
cases where there's only one proxy.
<p>
</p><hr size="4">
<h2>
Example #1b:
<font size="+0">As above, but use proxy for local servers which
are outside the firewall</font></h2>
If there are hosts (such as the main Web server) that belong to the local
domain but are outside the firewall, and are only reachable through the
proxy server, those exceptions can be handled using the
<tt>localHostOrDomainIs()</tt>
function:
<pre> function FindProxyForURL(url, host)
{
if ((isPlainHostName(host) ||
dnsDomainIs(host, ".netscape.com")) &&
!localHostOrDomainIs(host, "www.netscape.com") &&
!localHostOrDoaminIs(host, "merchant.netscape.com"))
return "DIRECT";
else
return "PROXY w3proxy.netscape.com:8080; DIRECT";
}</pre>
The above will use the proxy for everything else except local hosts in
the <tt>netscape.com</tt> domain, with the further exception that hosts
<tt>www.netscape.com</tt>
and
<tt>merchant.netscape.com</tt> will go through the proxy.
<p><b>Note</b> the order of the above exceptions for efficiency: localHostOrDomainIs()
functions only get executed for URLs that are in local domain, not for
every URL. Be careful to note the parentheses around the <i>or</i> expression
before the <i>and</i> expression to achieve the abovementioned efficient
behaviour.
</p><p>
</p><hr size="4">
<h2>
Example #2:
<font size="+0">Use proxy only if cannot resolve host</font></h2>
This example would work in an environment where internal DNS is set up
so that it can only resolve internal host names, and the goal is to use
a proxy only for hosts which aren't resolvable:
<pre> function FindProxyForURL(url, host)
{
if (isResolvable(host))
return "DIRECT";
else
return "PROXY proxy.mydomain.com:8080";
}</pre>
The above requires consulting the DNS every time; it can be grouped smartly
with other rules so that DNS is consulted only if other rules do not yield
a result:
<pre> function FindProxyForURL(url, host)
{
if (isPlainHostName(host) ||
dnsDomainIs(host, ".mydomain.com") ||
isResolvable(host))
return "DIRECT";
else
return "PROXY proxy.mydomain.com:8080";
}</pre>
<hr size="4">
<h2>
Example #3:
<font size="+0">Subnet based decisions</font></h2>
In this example all the hosts in a given subnet are connected to directly,
others through the proxy.
<pre> function FindProxyForURL(url, host)
{
if (isInNet(host, "198.95.0.0", "255.255.0.0"))
return "DIRECT";
else
return "PROXY proxy.mydomain.com:8080";
}</pre>
Again, use of DNS in the above can be minimized by adding redundant rules
in the beginning:
<pre> function FindProxyForURL(url, host)
{
if (isPlainHostName(host) ||
dnsDomainIs(host, ".mydomain.com") ||
isInNet(host, "198.95.0.0", "255.255.0.0"))
return "DIRECT";
else
return "PROXY proxy.mydomain.com:8080";
}</pre>
<hr size="4">
<h2>
Example #4:
<font size="+0">Load balancing/routing based on URL patterns</font></h2>
This example is more sophisticated. There are four (4) proxy servers; one
of them is a hot stand-by for all of the other ones, so if any of the remaining
three goes down, the fourth one will take over.
<p>Furthermore, the three remaining proxy servers share the load based
on URL patterns, which makes their caching more effective (there is only
one copy of any document on the three servers -- as opposed to one copy
on each of them). The load is distributed like this:
<table border="2" cellpadding="8">
<tbody><tr>
<th>Proxy</th>
<th>Purpose</th>
</tr>
<tr>
<td align="center">#1</td>
<td align="center"><tt>.com</tt> domain</td>
</tr>
<tr>
<td align="center">#2</td>
<td align="center"><tt>.edu</tt> domain</td>
</tr>
<tr>
<td align="center">#3</td>
<td align="center">all other domains</td>
</tr>
<tr>
<td align="center">#4</td>
<td align="center">hot stand-by</td>
</tr>
</tbody></table>
</p><p>All local accesses are desired to be direct. All proxy servers run on
the port 8080 (they wouldn't need to). Note how strings can be concatenated
by the <tt>+</tt> operator in JavaScript.
</p><pre> function FindProxyForURL(url, host)
{
if (isPlainHostName(host) || dnsDomainIs(host, ".mydomain.com"))
return "DIRECT";
else if (shExpMatch(host, "*.com"))
return "PROXY proxy1.mydomain.com:8080; " +
"PROXY proxy4.mydomain.com:8080";
else if (shExpMatch(host, "*.edu"))
return "PROXY proxy2.mydomain.com:8080; " +
"PROXY proxy4.mydomain.com:8080";
else
return "PROXY proxy3.mydomain.com:8080; " +
"PROXY proxy4.mydomain.com:8080";
}</pre>
<hr size="4">
<h2>
Example #5:
<font size="+0">Setting a proxy for a specific protocol</font></h2>
Most of the standard JavaScript functionality is available for use in the
<tt>FindProxyForURL()</tt>
function. As an example, to set different proxies based on the protocol,
the <tt>substring()</tt> function can be used:
<pre> function FindProxyForURL(url, host)
{
if (url.substring(0, 5) == "http:") {
return "PROXY http-proxy.mydomain.com:8080";
}
else if (url.substring(0, 4) == "ftp:") {
return "PROXY ftp-proxy.mydomain.com:8080";
}
else if (url.substring(0, 7) == "gopher:") {
return "PROXY gopher-proxy.mydomain.com:8080";
}
else if (url.substring(0, 6) == "https:" ||
url.substring(0, 6) == "snews:") {
return "PROXY security-proxy.mydomain.com:8080";
}
else {
return "DIRECT";
}
}</pre>
<b>Note:</b> The same can be accomplished using the
<tt>shExpMatch()</tt>
function described earlier; for example:
<pre> ...
if (shExpMatch(url, "http:*")) {
return "PROXY http-proxy.mydomain.com:8080;
}
...</pre>
<hr size="4">
<h2>
Tips</h2>
<ul>
<li>
The autoconfig file can be output by a CGI script. This is useful e.g.
when making the autoconfig file act differently based on the client IP
address (the <tt>REMOTE_ADDR</tt> environment variable in CGI).</li>
<li>
Use of <tt>isInNet()</tt>, <tt>isResolvable()</tt> and
<tt>dnsResolve()</tt>
functions should be carefully considered, as they require DNS server to
be consulted (whereas all other autoconfig related functions are mere string
matching functions). If a proxy is used, the proxy will perform its own
DNS lookup which would double the impact on the DNS server. Most of the
time these functions are not necessary to achieve the desired result.</li>
<br>
<p>
<br>
<br> </p></ul>
<hr size="4"><i>March 1996</i>
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