Why when the time changed backwards, there were many TIME_WAIT sockets

From: Steven Ding (dwj_at_asia.com)
Date: 11/21/04 

Date: Sun, 21 Nov 2004 12:02:29 +0800

Several days ago I encountered a very very strange thing.
I set one of my servers' time backward to sometime in year 2003 with
rdate. The server has a lot of TCP connections at that time.

However, several hours later, I found that there were many many sockets
with the state TIME_WAIT and no local ports available.

I know of the TIME_WAIT is used for retransmit the FIN2 ack to the peer
party and it should only be kept in a timer, which in many systems is
about twice the timer for retranssion.

But after I checked I found that TCP timers should be counted by a
"tick" rather than the system time. But the "tick" should not be
affected by the system time. So I wonder why so many TIME_WAIT sockets
cannot be cleaned in this case.

Thanks in advance!

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