Here's my iptables script:
#!/bin/sh service iptables stop iptables -F iptables -P INPUT DROP iptables -P OUTPUT ACCEPT iptables -P FORWARD DROP iptables -A INPUT -i lo -j ACCEPT iptables -A INPUT -p tcp -m multiport --dports 22,80,443 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -p udp --sport 53 --dport 1024:65535 -j ACCEPT service iptables save service iptables restart
It works fine on Centos 6.3, but on Centos 6.0 I can't establish outbound HTTP connections. (I probably can't establish any outbound TCP/IP connections.) DNS lookup, however, works just fine, as does apparently anything else based on UDP.
I'm guessing this has something to do with TCP's three-way handshake, of which I know almost nothing. That being the case, there must be a difference in the versions of one of the modules where the earlier version requires explicit specification of
INPUT rules to allow the handshake. So, what rule(s) would I need to create to allow the TCP handshake and therefore receive data?