Is it possible to have iptables
rules to drop packets by IP protocol type as described in [http://www.tutorialspoint.com/ipv4/ipv4_packet_structure.htm]? (ICMP is 1, TCP is 6 and UDP is 17, but what if I want to block an arbitrary type, say 47 for GRE)
Is there anything better than -m string
then specify an explicit offset to do this?