mdw@git.distorted.org.uk Git - firewall/blob - icmp.m4

   1 ### -*-sh-*-
   2 ###
   3 ### ICMP filtering for firewall scripts
   4 ###
   5 ### (c) 2008 Mark Wooding
   6 ###
   7
   8 ###----- Licensing notice ---------------------------------------------------
   9 ###
  10 ### This program is free software; you can redistribute it and/or modify
  11 ### it under the terms of the GNU General Public License as published by
  12 ### the Free Software Foundation; either version 2 of the License, or
  13 ### (at your option) any later version.
  14 ###
  15 ### This program is distributed in the hope that it will be useful,
  16 ### but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ### GNU General Public License for more details.
  19 ###
  20 ### You should have received a copy of the GNU General Public License
  21 ### along with this program; if not, write to the Free Software Foundation,
  22 ### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  23
  24 m4_divert(50)m4_dnl
  25 ###--------------------------------------------------------------------------
  26 ### ICMP filtering.
  27
  28 clearchain check-icmp
  29
  30 ## Ping needs inspecting on a host-by-host basis.
  31 for type in echo-request echo-reply; do
  32   run iptables -A check-icmp -p icmp --icmp-type $type -j RETURN
  33 done
  34
  35 ## Certainly don't allow ping to broadcast addresses.
  36 run iptables -A check-icmp -g forbidden \
  37         -p icmp --icmp-type echo-request \
  38         -m addrtype --dst-type BROADCAST
  39
  40 m4_divert(58)m4_dnl
  41 ## Other ICMP is basically benign, we claim.
  42 run iptables -A check-icmp -j ACCEPT
  43
  44 ## Done.
  45 for i in INPUT FORWARD; do
  46   run iptables -A $i -p icmp -j check-icmp
  47 done
  48
  49 m4_divert(-1)
  50 ###----- That's all, folks --------------------------------------------------