Asim,
I wasnt able to compile your packet_type_test.c :( I even tried your
scripts (i.e. make-native.sh and make-uml.sh), which seem to me that
proceeded to compile the example against the kernel source (which I
have installed and in place), but all I got was a huge list of errors
and warnings, and no .o compiled in the end.

./make-native.sh modules
./make-uml.sh modules

I used ubuntu 4.10 with kernel 2.6.8.1-3 and kernel source 2.6.8.1.

Any clues?
Thanks. 
-Pedro Fortuna

On Mon, 28 Feb 2005 14:09:56 -0600, Asim Shankar [off-list ref] wrote:

quoted

i need a possibility to catch IP4 packets (from ethernet devices) before OS' netmodules (IP, UDP, TCP, ICMP, ARP, ROUTE, NETFILTER ...) takes care about them and
* to delete them from input buffer such that OS' netmodules can't receive them
* to modify packet headers and move packets to interface related output buffers
* to keep them in input buffers such that OS' netmodules can take care about them.

You can process packets even before ip_rcv() gets them by registering
your own packet handler (struct packet_type) using dev_add_pack().  I
have a small sample at:
http://limnos.csrd.uiuc.edu/notes/code-samples/samples/kernel/packet_type/packet_type_test.c
This may not be the cleanest way, but it isn't that dirty either.

Also see:
http://www.phrack.org/show.php?p=55&a=12

-- Asim