NAME
   Apache::ProxyConf - Generate Proxy Configuration for browsers.

SYNOPSIS
     # In httpd.conf:

     <Location />
       SetHandler perl-script
       PerlHandler Apache::ProxyConf
       PerlSetVar ProxyConfConfig "/some/location/proxyconf.ini"
     </Location>

DESCRIPTION
   The Apache::ProxyConf is used to configure the proxy settings in
   browsers automatically. The modules returns a script that conforms to
   the Navigator Proxy Auto-Config File Format. The module is suitable for
   large scale installations that have multiple (cascading) proxies. It can
   be used to return 'the closest proxy' based on the network topology.
   Failover and load distribution is also provided.

 Browser configuration

   The (virtual) webserver must be entered in the 'Autoconfigure URL' of
   the browser to make use of the ProxyConf script.

   http://proxyconf.some.domain/

   In IE the URL must be specified in the 'Address' field, just below the
   'Use automatic configuration script' tickbox.

THE CONFIGURATION FILE
   The ProxyConf module first reads a .ini-style configuration file to
   determine the proxy settings of the network. The configuration file
   contains three sections: proxy, noproxy and https.

 The proxy section

   The sections proxy and https have an identical format. They contain
   lines of the form "subnet=proxyip:port".

   Single proxy
        [proxy]
        172.16.32.0/20=172.16.32.10:3128

       The subnet 172.16.32.0/20 has a single proxy defined. The proxy
       server is 172.16.32.10 and it listens on port 3128.

   Multiple proxies
        [proxy]
        172.16.0.0/20=172.16.0.10:3128,172.16.0.20:3128

       Multiple proxy servers are defined in a comma separated list. In
       this example clients in the 172.16.0.0/20 subnet use 172.16.0.10 as
       their primary proxy server. When this server becomes unavailable,
       the clients will move over to 172.16.0.20 for their proxy requests.

   Multiple proxies with load distribution
        [proxy]
        172.16.0.0/20=(172.16.0.10:3128,172.16.0.20:3128)

       When proxy servers are placed between brackets, the load is
       distribution amongst the proxies. Some clients will have the first
       proxy as primary and some clients will have the second proxy as
       primary. The other proxy is used as a backup. The order in which the
       proxies are tried depends on the IP address of the client. The
       script is deterministic, so for a given IP address the priority list
       is always the same.

   To determine the proxy list for a given IP address multiple rules may be
   applied. Subnets are tried from the highest to the lowest mask. The
   module puts all proxies that are found in a list.

 The noproxy section

   The noproxy section contains hosts that should be contacted by the
   clients directly. Noticeably, web servers that use NTLM authentication
   will not work when clients connect to them via a proxy server. The
   syntax for specifying noproxy hosts is "subnet=fqhn1,fqhn2,..".
   Alternatively, the multiline syntax can be used, as shown in this
   example.

    [noproxy]
    0.0.0.0/0=<<EOT
    webserver1.some.domain
    webserver2.some.domain
    EOT

   This section defines webservers that are non-proxyable for all networks.

 The https section

   The https section works like the proxy section. It is used to define
   other proxies for secure HTTP traffic than for the normal HTTP traffic.
   If this section is missing, or for a specific IP address there are no
   https rules, then the normal proxy rules apply.

EXAMPLE
   Consider the network in figure 1.

             Network A: 172.16.0.0/20

                _.-"""""""""""""""""-._
              .'                       `.
             /                           \
           |    Proxy A1: 172.16.0.10    |
           |                             |
           |    Proxy A2: 172.16.0.20    |
            \                           /
             `._                     _.'\
                `-.................-'    \
                                          \
                                           \  Network B: 172.16.16.0/20
                                            \
                                             \ _.-"""""""""""""""""-._
                                             .'                       `.
                                            /                           \
                                           |                             |
                                           |    Proxy B: 172.16.16.10    |
                                           |                             |
                                            \                           /
                                             `._                     _.'
                                             /  `-.................-'
                                            /
                                           /
             Network C: 172.16.32.0/20    /
                                         /
               _.-"""""""""""""""""-._  /
             .'                       `.
            /                           \
           |                             |
           |    Proxy C: 172.16.32.10    |
           |                             |
            \                           /
             `._                     _.'
                `-.................-'

                                       Figure 1.

   The proxies have the following connectivity:

    Proxy A1       Internet connectivity
    Proxy A2       Internet connectivity
    Proxy B        parents with proxy A1 and A2
    Proxy C        parents with proxy B and A1

   Clients in the three networks need to get the following proxy
   configuration:

    172.16.0.0/20  Half of the clients connect to proxy A1 and use proxy A2
                   as fallback, the other half use proxy A2 with A1 as
                   fallback.
    172.16.16.0/20 Clients use proxy B with proxy A2 as fallback.
    172.16.32.0/20 Clients use proxy C with proxy B as fallback.

   For secure HTTP traffic special rules apply. Because this traffic is not
   cached all clients connect to proxy A1 and A2 directly spreading the
   load equally.

   This is how the proxyconf.ini looks:

    [proxy]
    172.16.0.0/20=(172.16.0.10:3128,172.16.0.20:3128)
    172.16.16.0/20=172.16.16.10:3128,172.16.0.20:3128
    172.16.32.0/20=172.16.32.10:3128,172.16.16.10:3128

    [https]
    172.16.0.0/16=(172.16.0.10:3128,172.16.0.20:3128)

EXTRA OPTIONS
   It is possible to add additional noproxy hosts in the 'Autoconfigure
   URL' in the browser. This way a local webserver can be tested without
   losing the benefits of the proxy config. The following string must be
   entered in the 'Autoconfigure URL'.

   http://proxyconf.some.domain/?noproxy=hostname.some.domain

   Multiple hostnames are specified using a comma as separator.

   http://proxyconf.some.domain/?noproxy=fqhn1,fqhn2

DEBUGGING
   The proxy config service can be called with a debug option. Type the
   following URL in a browser:

   http://proxyconf.some.domain/?debug=1&ipaddr=172.16.0.100

   The script will generate a html page which contains the settings of all
   variables and displays the script it sends to the browser for the
   specified IP address.

AUTHOR
   Patrick Schoo <[email protected]>

   Originally written by Bert Driehuis <[email protected]>

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