Fwd: help:userlevel ToHost returen Packets kernel drop silently

---------- Forwarded message ----------
From: Huiqing Fu <huiqingfu2012 <at> gmail.com>
Date: 2012/7/18
Subject: help:userlevel ToHost returen Packets kernel drop silently
To: click-request <at> amsterdam.lcs.mit.edu

hi,
I met a problem when using userlevel ToHost. I can get packets via
FromDevice, and ToHost does return packets to TUN, because tcpdump did
catch packets in TUN. So I think the application can not receive packets is
because the kernel drop returned packets silently. I want to know how can I
make the kernel accept and give the returned packets to application.
In fact, I modify the fromhost-tunnel.click, but I did not change the
MY_GATEWAY
192.150.187.1), I am not sure weather it is a problem.
The following is the key codes in my click file:
fd :: FromDevice(eth0,SNIFFER false)
......

fd_cl[1] -> CheckIPHeader(14)

        // check for responses from the test network

        -> ipc :: IPClassifier(udp port 5500, -)     //set port 5500 udp
filter fhq

        // replace the real destination address with the fake address

        ->StoreEtherAddress(TEST_MAC,0)