X-Git-Url: https://git.distorted.org.uk/~mdw/firewall/blobdiff_plain/0291d6d55d3dc38a12d61abc007dda5cc3aa5110..c1c877c2eeabab5614c10a3870494d7f4ec271e7:/classify.m4

diff --git a/classify.m4 b/classify.m4
index 27eb376..6ad069c 100644
--- a/classify.m4
+++ b/classify.m4
@@ -1,4 +1,4 @@
-### -*-m4-*-
+### -*-sh-*-
 ###
 ### Classify packets according to source and destination networks.
 ###
@@ -69,16 +69,21 @@ clearchain mangle:local-source
 ## 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
 
-## Local bootp packets have bizarre addresses.  Don't block them just because
-## of this.
+## Local broadcast and link-local multicast packets sometimes have bizarre
+## addresses.  Don't block them just because of this.
 run iptables -t mangle -A in-classify -j RETURN \
 	-s 0.0.0.0 -d 255.255.255.255 \
-	-p udp --source-port $port_bootpc --destination-port $port_bootps
+	-p udp
+run iptables -t mangle -A in-classify -j RETURN \
+	-s 0.0.0.0 -d 224.0.0.0/24 \
+	-p udp
 
 ## Since packets with source and destination addresses both local will go
 ## over the loopback interface, I shouldn't see a packet from me over any
 ## other interface.  Except that I will if I sent a broadcast or multicast.
-## Allow the broadcasts, and remember not to trust them.
+## Allow the broadcasts, and remember not to trust them.  There are no
+## broadcast addresses in IPv6 (only link-local multicast)m so we don't have
+## to worry about that.
 run iptables -t mangle -A local-source -j RETURN \
 	-m addrtype --dst-type BROADCAST
 run iptables -t mangle -A local-source -j RETURN \
@@ -93,6 +98,15 @@ for addr in $host_6addrs; do
 	  -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
@@ -105,22 +119,30 @@ m4_divert(46)m4_dnl
 ## default interface.
 trace "nets = $allnets $allnets6"
 for net in $allnets; do
-  case $net in
-    "$defaultiface":*)
-      ;;
-    *)
-      run iptables -t mangle -A in-$defaultiface \
+  defaultp=nil
+  for iface in $defaultifaces; do
+    case $net in $iface:*) defaultp=t ;; esac
+  done
+  case $defaultp in
+    nil)
+      for iface in $defaultifaces; do
+	run iptables -t mangle -A in-$iface \
 	      -s ${net#*:} -g bad-source-address
+      done
       ;;
   esac
 done
 for net in $allnets6; do
-  case $net in
-    "$defaultiface":*)
-      ;;
-    *)
-      run ip6tables -t mangle -A in-$defaultiface \
+  defaultp=nil
+  for iface in $defaultifaces; do
+    case $net in $iface:*) defaultp=t ;; esac
+  done
+  case $defaultp in
+    nil)
+      for iface in $defaultifaces; do
+	run ip6tables -t mangle -A in-$iface \
 	      -s ${net#*:} -g bad-source-address
+      done
       ;;
   esac
 done
@@ -142,7 +164,10 @@ done
 m4_divert(92)m4_dnl
 ## Put the final default decision on the in-default chain, and attach the
 ## classification chains to the PREROUTING hook.
-run ip46tables -t mangle -A in-$defaultiface -g mark-from-$defaultclass
+for iface in $defaultifaces; do
+  run ip46tables -t mangle -A in-$iface -g mark-from-$defaultclass
+done
+run ip46tables -t mangle -A out-classify -g mark-to-$defaultclass
 run ip46tables -t mangle -A PREROUTING -j in-classify
 run ip46tables -t mangle -A PREROUTING -j out-classify