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

   1 #!/bin/sh
   2 . /etc/functions.sh
   3 export WAN=$(nvram get wan_ifname)
   4 export LAN=$(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 ### Port forwarding
  20 # iptables -t nat -A prerouting_rule -p tcp --dport 22 -j DNAT --to 192.168.1.2
  21 # iptables        -A forwarding_rule -p tcp --dport 22 -d 192.168.1.2 -j ACCEPT
  22
  23 ### INPUT
  24 ###  (connections with the router as destination)
  25
  26   # base case
  27   iptables -P INPUT DROP
  28   iptables -A INPUT -m state --state INVALID -j DROP
  29   iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
  30
  31   # allow
  32   iptables -A INPUT -i \! $WAN -j ACCEPT        # allow from lan/wifi interfaces
  33   iptables -A INPUT -p icmp -j ACCEPT           # allow ICMP
  34   iptables -A INPUT -p 47 -j ACCEPT             # allow GRE
  35   #
  36   # insert accept rule or to jump to new accept-check table here
  37   #
  38   iptables -A INPUT -j input_rule
  39
  40   # reject (what to do with anything not allowed earlier)
  41   iptables -A INPUT -p tcp --syn --tcp-option \! 2 -j  DROP
  42   iptables -A INPUT -p tcp -j REJECT --reject-with tcp-reset
  43   iptables -A INPUT -j REJECT --reject-with icmp-port-unreachable
  44
  45 ### OUTPUT
  46 ### (connections with the router as source)
  47
  48   # base case
  49   iptables -P OUTPUT DROP
  50   iptables -A OUTPUT -m state --state INVALID -j DROP
  51   iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
  52
  53   # allow
  54   iptables -A OUTPUT -j ACCEPT          #allow everything out
  55   #
  56   # insert accept rule or to jump to new accept-check table here
  57   #
  58   iptables -A OUTPUT -j output_rule
  59
  60   # reject (what to do with anything not allowed earlier)
  61   iptables -A OUTPUT -p tcp -j REJECT --reject-with tcp-reset
  62   iptables -A OUTPUT -j REJECT --reject-with icmp-port-unreachable
  63
  64 ### FORWARDING
  65 ### (connections routed through the router)
  66
  67   # base case
  68   iptables -P FORWARD DROP
  69   iptables -A FORWARD -m state --state INVALID -j DROP
  70   iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
  71   iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
  72
  73   # allow
  74   iptables -A FORWARD -i br0 -o br0 -j ACCEPT
  75   iptables -A FORWARD -i $LAN -o $WAN -j ACCEPT
  76   #
  77   # insert accept rule or to jump to new accept-check table here
  78   #
  79   iptables -A FORWARD -j forwarding_rule
  80
  81   # reject (what to do with anything not allowed earlier)
  82   # uses the default -P DROP
  83
  84 ### MASQ
  85   iptables -t nat -A PREROUTING -j prerouting_rule
  86   iptables -t nat -A POSTROUTING -j postrouting_rule
  87   iptables -t nat -A POSTROUTING -o $WAN -j MASQUERADE