On Mon, 28 Feb 2005 17:16:57 +0100
"Weber Matthias" [off-list ref] wrote:

Hi,

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.

I would be thankfull for any hint, link or code example.

Bye
Matthias

If you need this as a "one off" type project, then another possibility is
to hook onto netif_rx with jprobe (part of the kprobe) to redirect traffic
to a local function first.  
It wouldn't useable for a real production type protocol.