http://downloads.netgear.com/files/GPL/DM111P(B)_v3.29u_src.tar.gz

[bcm963xx.git] / targets / fs.src / etc / l7-protocols / file_types / README

diff --git a/targets/fs.src/etc/l7-protocols/file_types/README b/targets/fs.src/etc/l7-protocols/file_types/README
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-Patterns in this directory are not for network protocols, but rather for
-file types.  They are for cases in which you would like to
-promote/restrict transfer of one file type regardless of what protocol
-it is being transfered over.
-
-Writing patterns for this directory is pretty easy.  Often
-/usr/share/magic has everything you need to know. If you'd like
-something that isn't here, please ask for it.
-
-Notes:
-
-0) Support for doing this is pretty sketchy.  Proceed at your own risk.
-
-1) These patterns cannot use the ^ and $ anchors, because although you
-may be matching the beginning of a file, it's not the beginning of a
-connection.
-
-2) A connection may very well contain more than one file transfer and/or
-things other than file transfers. These will match the first file sent
-(or nothing if the first stuff isn't a file) and continue to apply that
-classification to all subsequent files of that connection, regardless of
-their content.  For instance:
-
-- HTTP can send several files over the same connection.  l7-filter can
-match the first one, but subsequent ones just get the original match
-applied to them. 
-
-- SMB sends all sorts of chatter over the same TCP connection as files
-are sent over, so we can't match its file transfers at all.
-
-3) Since the file starts later than the application layer protocol
-information, you may need to increase the number of packets and bytes
-examined.  Use /proc/net/layer7_numpackets to increase the number of
-packets examined. i.e. "echo 12 > /proc/net/layer7_numpackets".
-To increase the number of bytes examined, you'll need to recompile
-your kernel.  See the documentation at http://l7-filter.sf.net
-
-4) If you want a filter for both a file type and the application layer
-protocol that this file type is transported over (i.e. HTML and HTTP),
-you've got a difficult situation.  Each connection can only be 
-classified as one thing at a time.  The obvious thing is to set up
-a tree like this:
-
-(root)
- \_ HTTP
- |   \_ HTML
- |   \_ PDF
- \_ FTP
-     \_ TAR
-     \_ PS
-     \_ PDF
-
-But if you do this, you'll find that the file types never match, because
-the connections have already been classifed by their protocol.
-
-So what's the solution?  Well, you can do this instead:
-
-(root)
- \_ port 80
- |   \_ HTML
- |   \_ PDF
- \_ port 21
-     \_ TAR
-     \_ PS
-     \_ PDF
-
-(Except, of course, that FTP data doesn't actually go over port 21, so 
-some extra magic is needed there.)
-
-Or perhaps you could use IMQ to create several unrelated regions of
-classification.  i.e. On ingress, classify and shape on protocol
-and on egress, classify and shape on file type.  I haven't tried this.