add iptables rules example

ip6tables.rules.example

@@ -0,0 +1,26 @@
+*filter
+:INPUT DROP [0:0]
+:FORWARD DROP [0:0]
+:OUTPUT ACCEPT [0:0]
+:TCP - [0:0]
+:UDP - [0:0]
+-A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
+-A INPUT -i lo -j ACCEPT
+-A INPUT -m conntrack --ctstate INVALID -j DROP
+
+# for ICMPv6 Neighbor Discovery Protocol
+# (note: need a corresponding line for each directly attached subnet)
+-A INPUT -p ipv6-icmp --icmpv6-type 128 -m conntrack --ctstate NEW -j ACCEPT
+-A INPUT -s fe80::/10 -p ipv6-icmp -j ACCEPT
+
+-A INPUT -p udp -m conntrack --ctstate NEW -j UDP
+-A INPUT -p tcp -m tcp --tcp-flags FIN,SYN,RST,ACK SYN -m conntrack --ctstate NEW -j TCP
+-A INPUT -p udp -j REJECT --reject-with icmp6-port-unreachable
+-A INPUT -p tcp -j REJECT --reject-with tcp-reset
+-A INPUT -j REJECT
+
+#  accept incoming connections on UDP port 546, to enable DHCPv6
+-A UDP -p udp --sport 547 --dport 546 -j ACCEPT
+
+
+COMMIT