[Click] How click generate feedback packets?

[Xm Zhu]

HI
I want to rewrite wireless MAC feedback mechanism under click. But it seems that there is no such kind of element under it. There is a FilterTX() used for filtering feedback packets but where the feedbacks come from? 
For example, in the following script
// Receive packets from the wireless interface.
// Strip the extra wifi header of the packet
// using ExtraDecap.
// Filter the transmission feedback packets out
// and decapsulate the 802.11 header
FromSimDevice(eth0, 4096)
        -> ExtraDecap()
        -> tx_filter :: FilterTX()
        -> PrintWifi("in ")
        -> WifiDecap()
        -> classifier0::Classifier(12/0806 20/0001, 12/0806 20/0002, 12/0800, -);
//IP Packets from ns
FromSimDevice(tap0, 4096)
        -> MarkIPHeader()
        -> GetIPAddress(16)
        -> dst_classifier::IPClassifier(dst eth0, -);
// Send the feedback packets to the rate selection for statistics 
//  processing
tx_filter[1]
        -> [1]rateselection::MadwifiRate(RT rinfo,ACTIVE true,ALT_RATE true,OFFSET 4)

This script is copied from "The madwifi wireless extension for nsclick" (section 4.1).However, no script for generate feedback.Also, I search from the element page of click. There seems no wifi feedback generator. Then, how FilterTX get feedbacks?

Thank you

       
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