Just before this happens, suppose some third party C spoofs a packet
from A to B with sequence number N+1.
loop:
Now A sends its FIN with sequence number N.
B responds by acking N+1 (well really N+2, but that's being
pedantic)
That wasn't the corresponding FIN that A was expecting, so...
goto loop
At this point I had to unplug my machine from the Ethernet.
For what its worth, I've only witnessed this between a Digital Unix
sender (spinoza) and a Linux receiver (sirpa-a)
- Stefan