Replacing tcp_v4_rcv from a module

[Gong Su <gongsu@cs.columbia.edu>]

I need some customized function inside tcp_v4_rcv so I wrote a module to
replace tcp_protocol->handler with my own function pointer; and currently
my own tcp_v4_rcv is just a copy of the original tcp_v4_rcv. But as soon
as traffic came in, my machine locks up hard. I can't think of a reason
why it would do so since I've changed other functions the same way, e.g.,
replacing ip_packet_type->func with my own ip_rcv function pointer without
problem. Am I missing something obvious? Thanks for any enlightenment.

-- 
/Gong