Get amount of fast retransmissions from TCP info

[Lars Erik StorbukÃs]

I'm trying to get amount of congestion events in TCP caused by
DUPACK's (fast retransmissions), and can't seem to find any variable
in the TCP info struct which hold that value. There are three
variables in the TCP info struct that seem to hold similar congestion
values: __u8 tcpi_retransmits;__u32 tcpi_retrans; __u32
tcpi_total_retrans;

Does anyone have any pointers on how to find this value in the TCP code?

Please CC me personally if answering this question. Any help is
greatly appreciated.