Add BCP38 implementation package (from CeroWrt).

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>

net/bcp38/files/run.sh

@@ -0,0 +1,104 @@
+#!/bin/sh
+# BCP38 filtering implementation for CeroWrt.
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 3 of the License, or (at your option) any later
+# version.
+#
+# Author: Toke Høiland-Jørgensen <toke@toke.dk>
+
+STOP=$1
+IPSET_NAME=bcp38-ipv4
+IPTABLES_CHAIN=BCP38
+
+. /lib/functions.sh
+
+config_load bcp38
+
+add_bcp38_rule()
+{
+	local subnet="$1"
+	local action="$2"
+
+	if [ "$action" == "nomatch" ]; then
+		ipset add "$IPSET_NAME" "$subnet" nomatch
+	else
+		ipset add "$IPSET_NAME" "$subnet"
+	fi
+}
+
+detect_upstream()
+{
+	local interface="$1"
+
+	subnets=$(ip route show dev "$interface"  | grep 'scope link' | awk '{print $1}')
+	for subnet in $subnets; do
+		# ipset test doesn't work for subnets, so strip out the subnet part
+		# and test for that; add as exception if there's a match
+		addr=$(echo $subnet | sed 's|/[0-9]\+$||')
+		ipset test "$IPSET_NAME" $addr 2>/dev/null && add_bcp38_rule $subnet nomatch
+	done
+}
+
+run() {
+    	local section="$1"
+    	local enabled
+	local interface
+	local detect_upstream
+	config_get_bool enabled "$section" enabled 0
+	config_get interface "$section" interface
+	config_get detect_upstream "$section" detect_upstream
+
+	if [ "$enabled" -eq "1" -a -n "$interface" -a -z "$STOP" ] ; then
+		setup_ipset
+		setup_iptables "$interface"
+		config_list_foreach "$section" match add_bcp38_rule match
+		config_list_foreach "$section" nomatch add_bcp38_rule nomatch
+		[ "$detect_upstream" -eq "1" ] && detect_upstream "$interface"
+	fi
+	exit 0
+}
+
+setup_ipset()
+{
+	ipset create "$IPSET_NAME" hash:net family ipv4
+	ipset flush "$IPSET_NAME"
+}
+
+setup_iptables()
+{
+	local interface="$1"
+	iptables -N "$IPTABLES_CHAIN" 2>/dev/null
+	iptables -F "$IPTABLES_CHAIN" 2>/dev/null
+
+	iptables -I output_rule -j "$IPTABLES_CHAIN"
+	iptables -I input_rule -j "$IPTABLES_CHAIN"
+	iptables -I forwarding_rule -j "$IPTABLES_CHAIN"
+
+	# always accept DHCP traffic
+	iptables -A "$IPTABLES_CHAIN" -p udp --dport 67:68 --sport 67:68 -j RETURN
+	iptables -A "$IPTABLES_CHAIN" -o "$interface" -m set --match-set "$IPSET_NAME" dst -j REJECT --reject-with icmp-net-unreachable
+	iptables -A "$IPTABLES_CHAIN" -i "$interface" -m set --match-set "$IPSET_NAME" src -j DROP
+}
+
+destroy_ipset()
+{
+	ipset flush "$IPSET_NAME" 2>/dev/null
+	ipset destroy "$IPSET_NAME" 2>/dev/null
+}
+
+destroy_iptables()
+{
+	iptables -D output_rule -j "$IPTABLES_CHAIN" 2>/dev/null
+	iptables -D input_rule -j "$IPTABLES_CHAIN" 2>/dev/null
+	iptables -D forwarding_rule -j "$IPTABLES_CHAIN" 2>/dev/null
+	iptables -F "$IPTABLES_CHAIN" 2>/dev/null
+	iptables -X "$IPTABLES_CHAIN" 2>/dev/null
+}
+
+destroy_iptables
+destroy_ipset
+config_foreach run bcp38
+
+exit 0