+++ /dev/null
-NOTE: The Tcl support described in this file is disabled. The code is
-all still there, but you have to define DO_TCL manually while compiling to
-enable it. Compiling in Tcl filtering was causing random innd segfaults
-even if no Tcl filters were defined, so it's been turned off to prevent
-confusion.
-
-The Tcl code will be removed in the next major release of INN since no one
-appears to be using it and the code is unmaintained and has no champion.
-If you want to resurrect it, it may be better to start from scratch, since
-a lot has changed about INN since the filters were originally written and
-the Perl and Python filters have far more capabilities.
-
-
-Note, you need tcl 7.4. Rumour has it that 7.5 won't work.
----------------------------------------------------------------------------
-Subject: TCL-based Filtering for INN 1.5
-Date: Mon, 07 Feb 94 12:36:47 -0800
-From: Bob Heiney <heiney@pa.dec.com>
-
-
-Several times in the past few months, a site or two has started posting
-the same article over and over again, but with a different message id.
-Usually this is caused by broken software (e.g. mail <-> news gateways,
-which many have written, but few have written correctly).
-Occasionally, however, the reposting is intentional. A recent example
-would be the "Global Alert: Jesus Is Coming" message which was posted
-to over 2200 newsgroups (each copy with its own message id).
-
-I expect this to happen more often as the Internet continues its explosive
-growth. Although my site (decwrl) usually has enough excess capacity to
-weather these problems, many other sites cannot. One problem on
-comp.sys.sgi.misc several months ago spewed 40MB of duplicate articles
-before the offending sites were fixed, and this overflowed the spool at
-many sites. Even for sites with lots of resources, there's still no need
-to propagate erroneous or malicious duplicates.
-
-I wanted a way to protect my site that was highly specific, flexible, and
-quick.
-
-Examination of duplicated articles showed that although the message ids
-were different, it was usually easy for a news admin to come up with a
-few rules based on the headers of the article that could be used to
-differentiate the duplicates from other articles. (E.g. from
-John.Doe@foo.com to comp.sys.sgi.misc with 'foobar' in the subject".)
-I concluded that modifying innd to let me say "kill things that look
-like _this_" would solve my problem.
-
-I also wanted to allow enough flexibilty in the design that I could
-later work on automatic detection and elimination of excessive
-duplicates (using a body checksum instead of headers).
-
-Since I needed a fairly powerful language to do all this, and since the
-world doesn't need yet another special language, my solution was to add TCL
-support to INN. I then modified "ARTpost" to call a TCL procedure which
-could then accept or reject the article. The TCL code has access to an
-associative array called "Headers", which contains all of the articles
-headers. The TCL code may also call a 32-bit article-body checksum
-procedure (this is to aid in future automatic detection of duplicates).
-
-Here's what a sample TCL filter procedure looks like:
-
-proc filter_news {} {
- global o Headers
- set sum [checksum_article]
- puts $o "$Headers(Message-ID) $sum"
- set newsgroups [split $Headers(Newsgroups) ,]
- foreach i $newsgroups {
- if {$i=="alt.test" && [string match "*heiney@pa.dec.com*" $Headers(From)]} {
- return "dont like alt.test from heiney"
- }
- }
- return "accept"
-}
-
-The above TCL code does a few things. First it computes a 32-bit
-checksum and writes it and the message ID to a file. It then rejects
-articles from me to alt.test.
-
-The work I've done is totally integrated into the INN build and runtime
-environments. For example, to turn filtering off, you'd just type
-
- ctlinnd filter n
-
-To reload the TCL code that does the filtering, you just say
-
- ctlinnd reload filter.tcl 'your comment here'
-
-(You may specify TCL callbacks to be executed right before and/or right
-after reloading, in case your filter is doing fancy stuff.) See the
-ctlinnd man page for more info.
-
-Filtering capability that's this powerful can be used for many
-purposes, some benign and useful (excessive duplicate detections,
-on-the-fly statistics), others abusive. I would ask that news admins
-think carefully about any filtering they do.
-
-/Bob
-
-
~ian / innduct.git / blobdiff