package/base-files/default/etc/init.d/S45firewall

   1 #!/bin/sh
   2
   3 ## Please make changes in /etc/firewall.user
   4 ${FAILSAFE:+exit}
   5
   6 . /etc/functions.sh
   7 . /etc/network.overrides
   8 [ "$FAILSAFE" != "true" -a -e /etc/config/network ] && . /etc/config/network
   9
  10 WAN=$(nvram get wan_ifname)
  11 LAN=$(nvram get lan_ifname)
  12
  13 ## CLEAR TABLES
  14 for T in filter nat; do
  15   iptables -t $T -F
  16   iptables -t $T -X
  17 done
  18
  19 iptables -N input_rule
  20 iptables -N output_rule
  21 iptables -N forwarding_rule
  22
  23 iptables -t nat -N prerouting_rule
  24 iptables -t nat -N postrouting_rule
  25
  26 ### INPUT
  27 ###  (connections with the router as destination)
  28
  29   # base case
  30   iptables -P INPUT DROP
  31   iptables -A INPUT -m state --state INVALID -j DROP
  32   iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
  33   iptables -A INPUT -p tcp --tcp-flags SYN SYN --tcp-option \! 2 -j  DROP
  34
  35   #
  36   # insert accept rule or to jump to new accept-check table here
  37   #
  38   iptables -A INPUT -j input_rule
  39
  40   # allow
  41   iptables -A INPUT ${WAN:+-i \! $WAN}  -j ACCEPT       # allow from lan/wifi interfaces
  42   iptables -A INPUT -p icmp     -j ACCEPT       # allow ICMP
  43   iptables -A INPUT -p gre      -j ACCEPT       # allow GRE
  44
  45   # reject (what to do with anything not allowed earlier)
  46   iptables -A INPUT -p tcp -j REJECT --reject-with tcp-reset
  47   iptables -A INPUT -j REJECT --reject-with icmp-port-unreachable
  48
  49 ### OUTPUT
  50 ### (connections with the router as source)
  51
  52   # base case
  53   iptables -P OUTPUT DROP
  54   iptables -A OUTPUT -m state --state INVALID -j DROP
  55   iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
  56
  57   #
  58   # insert accept rule or to jump to new accept-check table here
  59   #
  60   iptables -A OUTPUT -j output_rule
  61
  62   # allow
  63   iptables -A OUTPUT -j ACCEPT          #allow everything out
  64
  65   # reject (what to do with anything not allowed earlier)
  66   iptables -A OUTPUT -p tcp -j REJECT --reject-with tcp-reset
  67   iptables -A OUTPUT -j REJECT --reject-with icmp-port-unreachable
  68
  69 ### FORWARDING
  70 ### (connections routed through the router)
  71
  72   # base case
  73   iptables -P FORWARD DROP
  74   iptables -A FORWARD -m state --state INVALID -j DROP
  75   iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
  76   iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
  77
  78   #
  79   # insert accept rule or to jump to new accept-check table here
  80   #
  81   iptables -A FORWARD -j forwarding_rule
  82
  83   # allow
  84   # if there is bridge splitting this workaround works too
  85   for iface in $LAN; do
  86         iptables -A FORWARD -i $iface -o $iface -j ACCEPT
  87         [ -z "$WAN" ] || iptables -A FORWARD -i $iface -o $WAN -j ACCEPT
  88   done
  89   # reject (what to do with anything not allowed earlier)
  90   # uses the default -P DROP
  91
  92 ### MASQ
  93   iptables -t nat -A PREROUTING -j prerouting_rule
  94   iptables -t nat -A POSTROUTING -j postrouting_rule
  95   [ -z "$WAN" ] || iptables -t nat -A POSTROUTING -o $WAN -j MASQUERADE
  96
  97 ## USER RULES
  98 [ -f /etc/firewall.user ] && . /etc/firewall.user