Is it possible to write an Apache protocol handler in PHP?

Question

Hello,

I wonder if and how it is possible to write a custom "protocol handler" (listening at a custom port) for Apache 2 in PHP?

In C and mod_perl you can write so-called "protocol handlers", which intercept the early Apache stage (after a client socket connection has been accept()ed, but before any content has been written to it) and can for example handle FTP or SMTP protocols. Is it possible in PHP as well?

For example, I have the following simple mod_perl handler, which I'd like to port to PHP (to compare the memory usage - since my mod_perl-handler needs 20m per child). My handler listens at the port 843 and writes the string POLICY to the client socket:

package SocketPolicy;

# Run: semanage port -a -t http_port_t -p tcp 843
# And add following lines to the httpd.conf
# Listen 843
# <VirtualHost _default_:843>
#       PerlModule                   SocketPolicy
#       PerlProcessConnectionHandler SocketPolicy
# </VirtualHost>

use strict;
use warnings FATAL => 'all';
use APR::Const(-compile => 'SO_NONBLOCK');
use APR::Socket();
use Apache2::ServerRec();
use Apache2::Connection();
use Apache2::Const(-compile => qw(OK DECLINED));

use constant POLICY =>
qq{<?xml version="1.0"?>
<!DOCTYPE cross-domain-policy SYSTEM
"http://www.adobe.com/xml/dtds/cross-domain-policy.dtd"&gt;
<cross-domain-policy>
<allow-access-from domain="*" to-ports="8080"/>
</cross-domain-policy>
\0};

sub handler {
        my $conn   = shift;
        my $socket = $conn->client_socket();
        my $offset = 0;

        # set the socket to the blocking mode
        $socket->opt_set(APR::Const::SO_NONBLOCK => 0);

        do {
                my $nbytes = $socket->send(substr(POLICY, $offset),
                             length(POLICY) - $offset);
                # client connection closed or interrupted
                return Apache2::Const::DECLINED unless $nbytes;
                $offset += $nbytes;
        } while ($offset < length(POLICY));

        my $slog = $conn->base_server()->log();
        $slog->warn('served socket policy to: ', $conn->remote_ip());
        return Apache2::Const::OK;
}

1;

Thanks, Alex

Answer 1

Technically yes you can with the socket extension given that you also allow you script to run long enough. By default a PHP script will be terminated after 60 sec or so.

So the main issue is to keep your PHP script running like a daemon.

Answer 2

It's perfectly possible.... there's even a full web server written in PHP

Answer 3

No, mod_php doesn't implement the Apache handler phases that mod_perl does.

See http://svn.php.net/viewvc/php/php-src/branches/PHP_5_3/sapi/apache2handler/php_functions.c?revision=296107&view=markup#l516

Answer 4

Yes and no.... PHP has an Apache interface which uses the Apache handler API, as well as other interfaces, such as CLI, CGI etc. The PHP Apache API integration chooses not to expose the lower-level handling details like mod_perl does, so if you need access to these callbacks you'll have to write your own PHP Apache handler API implementation.