+## Special IPv4 source addresses. Forbid broadcast and multicast sources.
+## Mark the special zero address and link-local addresses as such. (This
+## also matches class-E addresses, which are probably permanently invalid.)
+for i in 0.0.0.0 169.254.0.0/16; do
+ run iptables -t mangle -A in-classify -g mark-from-link -s $i
+done
+run iptables -t mangle -A in-classify -g bad-source-address \
+ -s 224.0.0.0/3
+run iptables -t mangle -A in-classify -g bad-source-address \
+ -m addrtype --src-type BROADCAST \
+
+## Special IPv6 addresses. Format multicast sources, and mark zero and
+## link local addresses.
+for i in :: fe80::/10; do
+ run ip6tables -t mangle -A in-classify -g mark-from-link -s $i
+done
+run ip6tables -t mangle -A in-classify -g bad-source-address \
+ -s ff00::/8
+
+## Special IPv4 destination addresses. The zero address is invalid; mark
+## link-local and recognized broadcast addresses as link-local. We leave
+## multicast for later.
+for i in 0.0.0.0 240.0.0.0/4; do
+ run iptables -t mangle -A out-classify -g bad-destination-address -d $i
+done
+run iptables -t mangle -A out-classify -g mark-to-link -d 169.254.0.0/16
+run iptables -t mangle -A out-classify -g mark-to-link \
+ -m addrtype --dst-type BROADCAST
+
+## Special IPv6 destination addressses. The zero address is again invalid;
+## mark link local addresses. We do multicast later.
+run ip6tables -t mangle -A out-classify -g bad-destination-address \
+ -d ::
+run ip6tables -t mangle -A out-classify -g mark-to-link -d fe80::/10
+
+## Now deal with multicast. Link-local multicast is detected as being
+## link-local, so that we can prevent it being forwarded correctly.
+clearchain mangle:out-classify-mcast
+run iptables -t mangle -A out-classify-mcast -g mark-to-link \
+ -d 224.0.0.0/24
+for i in 0 1 2 3 4 5 6 7 8 9 a b c d e f; do
+ run ip6tables -t mangle -A out-classify-mcast -g mark-to-link \
+ -d ff${i}2::/16
+done
+run ip46tables -t mangle -A out-classify-mcast -g mark-to-mcast
+run iptables -t mangle -A out-classify -g out-classify-mcast \
+ -d 224.0.0.0/4
+run ip6tables -t mangle -A out-classify -g out-classify-mcast \
+ -d ff00::/8
+
+## Build the input classification chains. There's one chain `in-IFACE' for
+## each local interface. This chain does a further dispatch on the source
+## address to the appropriate `mark-from-CLASS' chain for the source network
+## class.
+seen=:
+for iface in $host_ifaces_<::>FWHOST; do
+ ifname=${iface%=*}
+ case $seen in *:$ifname:*) continue ;; esac
+ seen=$seen$ifname:
+ clearchain mangle:in-$ifname
+ run ip46tables -t mangle -A in-classify -i $ifname -g in-$ifname
+done
+
+## Now populate the `in-IFACE' and `out-classify' chains. We iterate over
+## the available networks and add addresses to the appropriate chains. Also,
+## build up a map of which interfaces receive from which address ranged so
+## that we can finish the chains off properly later. This contains entries
+## of the form IFACE=:ADDR:ADDR:...:
+ifnets=""