How do tt_timerq and tmerq manage tcp syncache?

[Nagaraju]

Hi,

In  FreeBSD 4.9,
tcp_syncache implements a hash table with buckets, where an entry is created
on SYN request.
Function syncache_timer takes care of SYN-ACK retransmissions and removing
old entries from syncache.
It uses two variables timerq (array of link lists) and tt_timerq (array of
callouts).
Size of both arrays is SYNCACHE_MAXREXMTS+1. (SYNCACHE_MAXREXMTS = 3)
Can someone explain, how these two variable do manage, required
functionality (removing old entries and retransmitting SYN-ACK etc)?

Thanks&Regards,
Nagaraju.