clearchain mangle:in-classify mangle:in-default mangle:out-classify
clearchain mangle:local-source
+## An unpleasant hack. We can't reject packets from the mangle table, so
+## we mark packets with a bad destination and then detect this in the
+## filter table.
+clearchain mangle:bad-destination-address
+BAD_DEST=0xf6f377d2
+ip46tables -t mangle -A bad-destination-address -j MARK --set-mark $BAD_DEST
+ip46tables -t mangle -A bad-destination-address -j ACCEPT
+for i in $inchains; do
+ ip46tables -A $i -m mark --mark $BAD_DEST -g bad-destination-address
+done
+
## Packets over the loopback interface are automatically trusted. All manner
## of weird stuff happens on lo, and it's best not to second-guess it.
run ip46tables -t mangle -A in-classify -i lo -j ACCEPT
-s $addr
done
-## It's not valid to have a multicast address as a packet source: multicast
-## routing is done away from the source, so a multicast address would make
-## this impossible to do. So discard these packets. Also discard class-E
-## IPv4 addresses, since they aren't assigned.
-run iptables -t mangle -A in-classify -g bad-source-address \
- -s 224.0.0.0/3
-run ip6tables -t mangle -A in-classify -g bad-source-address \
- -s ff00::/8
-
m4_divert(41)m4_dnl
## Define the important networks.
for pass in 1 2; do
done
m4_divert(46)m4_dnl
+## 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
## Fill in the black holes in the network.
for addr in \
10.0.0.0/8 172.16.0.0/12 192.168.0.0/16 \
- 127.0.0.0/8 192.0.2.0/24
+ 127.0.0.0/8 \
+ 192.0.2.0/24 198.51.100.0/24 203.0.113.0/24
do
run iptables -t mangle -A in-default -s $addr -g bad-source-address
done
for addr in \
fc00::/7 \
- 2001:0db8::/32
+ 2001:db8::/32
do
run ip6tables -t mangle -A in-default -s $addr -g bad-source-address
done
run ip46tables -t mangle -A PREROUTING -j in-classify
run ip46tables -t mangle -A PREROUTING -j out-classify
+## Incoming stuff to or from a link-local address is OK.
+run ip46tables -t mangle -A INPUT \
+ -m mark --mark $to_link/$MASK_TO \
+ -j MARK --or-mark $fwd_link
+run ip46tables -t mangle -A INPUT \
+ -m mark --mark $from_link/$MASK_FROM \
+ -j MARK --or-mark $fwd_link
+
## Now it's safe to let stuff through.
for i in PREROUTING INPUT FORWARD OUTPUT POSTROUTING; do
run ip46tables -t mangle -P $i ACCEPT