openwrt/target/default/target_skeleton/etc/init.d/S45firewall

   1 #!/bin/sh
   2 . /etc/functions.sh
   3 WAN=$(nvram get wan_ifname)
   4 LAN=$(nvram get lan_ifname)
   5
   6 ## CLEAR TABLES
   7 for T in filter nat mangle; do
   8   iptables -t $T -F
   9   iptables -t $T -X
  10 done
  11
  12 iptables -N input_rule
  13 iptables -N output_rule
  14 iptables -N forwarding_rule
  15
  16 iptables -t nat -N prerouting_rule
  17 iptables -t nat -N postrouting_rule
  18
  19 ### INPUT
  20 ###  (connections with the router as destination)
  21
  22   # base case
  23   iptables -P INPUT DROP
  24   iptables -A INPUT -m state --state INVALID -j DROP
  25   iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
  26   iptables -A INPUT -p tcp --syn --tcp-option \! 2 -j  DROP
  27
  28   # allow
  29   iptables -A INPUT -i \! $WAN  -j ACCEPT       # allow from lan/wifi interfaces
  30   iptables -A INPUT -p icmp     -j ACCEPT       # allow ICMP
  31   iptables -A INPUT -p gre      -j ACCEPT       # allow GRE
  32   #
  33   # insert accept rule or to jump to new accept-check table here
  34   #
  35   iptables -A INPUT -j input_rule
  36
  37   # reject (what to do with anything not allowed earlier)
  38   iptables -A INPUT -p tcp -j REJECT --reject-with tcp-reset
  39   iptables -A INPUT -j REJECT --reject-with icmp-port-unreachable
  40
  41 ### OUTPUT
  42 ### (connections with the router as source)
  43
  44   # base case
  45   iptables -P OUTPUT DROP
  46   iptables -A OUTPUT -m state --state INVALID -j DROP
  47   iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
  48
  49   # allow
  50   iptables -A OUTPUT -j ACCEPT          #allow everything out
  51   #
  52   # insert accept rule or to jump to new accept-check table here
  53   #
  54   iptables -A OUTPUT -j output_rule
  55
  56   # reject (what to do with anything not allowed earlier)
  57   iptables -A OUTPUT -p tcp -j REJECT --reject-with tcp-reset
  58   iptables -A OUTPUT -j REJECT --reject-with icmp-port-unreachable
  59
  60 ### FORWARDING
  61 ### (connections routed through the router)
  62
  63   # base case
  64   iptables -P FORWARD DROP
  65   iptables -A FORWARD -m state --state INVALID -j DROP
  66   iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
  67   iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
  68
  69   # allow
  70   iptables -A FORWARD -i br0 -o br0 -j ACCEPT
  71   iptables -A FORWARD -i $LAN -o $WAN -j ACCEPT
  72   #
  73   # insert accept rule or to jump to new accept-check table here
  74   #
  75   iptables -A FORWARD -j forwarding_rule
  76
  77   # reject (what to do with anything not allowed earlier)
  78   # uses the default -P DROP
  79
  80 ### MASQ
  81   iptables -t nat -A PREROUTING -j prerouting_rule
  82   iptables -t nat -A POSTROUTING -j postrouting_rule
  83   iptables -t nat -A POSTROUTING -o $WAN -j MASQUERADE
  84
  85 ## USER RULES
  86 . /etc/firewall.user