consider
3 pcs

pc 1 sends packet to pc 2 through pc 3

(by listening to the eth0 at pc 2)
pc 2 gets the message send from pc 1 to pc 3 for checking some information, if okay forward to pc, if not okay drop it~~

I now have a problem:

I can get the message passing through pc 2 and display at pc 2,
but how I can stop forward to pc 3?????

I have tried
pass the packet to the usespace by using
iptables -j QUEUE.....and then run the same program in userspace
However, it turns out that I get nothing at pc 2,not to say at pc 3.

I have guessed why this problem happens,

1)is it the connection between pc 1 and pc 3 has not been made, so no data sending from pc 1 to pc3.

2)the program for listening the packet at pc 2 is run in userspace, so it starts listening eth0 after the packet has already been passed through it.
So at pc 2 receive nothing...............


so how I can solve ???Am I wrong.??


Thanks all~~~~~I need to solve ......it ....~~