i would content that while you believe your source IP is 1.2.3.4 in this scenario--it; in fact, is not.
I know. 1.2.3.4 is just for the example :)
try:
iptables -A INPUT -j LOG --log-prefix "FW DROP INPUT: "
and see what the logs have to say about it.
This will log all incoming packets?
Thanks, Jacob
