Apache Traffic Server Header Filter plugin
==========================================

This is a simple plugin for filtering out headers from requests (or
responses). Typical configuration is done either with a global
configuration, in .../etc/trafficserver/plugin.config:

    header_filter.so /usr/local/etc/hdr_filters.conf


Or, alternatively, in a per-remap rule configuration 

    map http://a.com/ http://b.com @plugin=header_filter.so @pparam=hdr_filters.conf


Even if you don't have a global configuration, if your remap rules
schedules actions in hooks other than during remap, you must also add the
header_filter.so to the plugin.config (see above), but without args:

    header_filter.so


The configuration files looks like

[READ_REQUEST_HDR]
	X-From-Someone
	Cookie

[READ_RESPONSE_HDR]
	X-From-Server
	Set-Cookie

[SEND_RESPONSE_HDR]
	X-Fie "Test"    # Match the entire string
	X-Foo /Test/    # Match the (Perl) regex
	X-Bar [Test*    # Match the prefix string
	X-Fum *Test]    # Match the postfix string


Comments are prefixed with #, and in most cases, the regular expression
matching is the best choice (very little overhead). The pattern matches
can also take an option '!' to reverse the test. The default action is
to delete all headers that do (not) match the pattern. E.g.

[SEND_REQUEST_HDR]
	X-Fie   /test/
	X-Foo ! /test/i


The final "i" qualifier (works on all pattern matches) forces the match or
comparison to be made case insensitive (just like in Perl).


It's also possible to replace or add headers, using the = and +
operators. For example

[SEND_REQUEST_HDR]
	Host =www.example.com=
	X-Foo +ATS+


This will force the Host: header to have exactly one value,
www.example.com, while X-Foo will have at least one header with the value
ATS, but there could be more instances of the header from the existing
header in the request.


Possible hooks are

	 READ_REQUEST_HDR
	 SEND_REQUEST_HDR
	 READ_RESPONSE_HDR
	 SEND_RESPONSE_HDR


If not specified, the default hook to add the rules (headers to filter) is
READ_REQUEST_HDR. It's completely acceptable (and useful) to configure a
remap rule to delete headers in a later hook (e.g. when reading a response
from the server). This is what actually makes the plugin even remotely
useful.



BUILDING
========

A simple

    % make
    % make install


should do it, assuming that you have the tsxs script in your search
path. This script is installed with your installation of Apache Traffic
Server.