+## commonrules CHAIN
+##
+## Add standard IP filtering rules to the CHAIN.
+commonrules () {
+ set -e
+ chain=$1
+
+ ## Pass fragments through, assuming that the eventual destination will sort
+ ## things out properly. Except for TCP, that is, which should never be
+ ## fragmented.
+ run iptables -A $chain -p tcp -f -g tcp-fragment
+ run iptables -A $chain -f -j ACCEPT
+}
+