Does it make sense to have an iptable rule as below?
-A INPUT -p esp -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT
I could not find any documentation that would explain the meaning of "states" on an ESP flow. TCP/UDP/ICMP are explained in this link (http://www.iptables.info/en/connection-state.html).
Since ESP does not have the concept of port or connection, is it meaningful to have a rule as above? How will conntrack determine the state of a flow here? If it actually means something, could someone kindly explain and point out the documentation?