What you need to to is to simply allow a certain types of ICMP types to pass through your netfilter.

ICMP has several types of packages. The ones that need be allowed to pass are:
each type can be specified by name (echo-request ttl-zero-during-transit ttl-zero-during-reassembly) or by number (8 and 11) For more informatoin see iptables --protocol icmp --help

The code in your netfilter/iptables script would then looks somewhat like this

specifying the icmp types

icmp_types_to_accept="\
echo-request \
ttl-zero-during-transit \
ttl-zero-during-reassembly"  # numerical values for those ICMP types are 8 and 11; see iptables --protocol icmp --help

loading the rules into the kernel

for icmp_type in $icmp_types_to_accept; do
  $exe_iptables -A chain_accept_icmp_packets -p icmp -s $net_all --icmp-type $icmp_type -j ACCEPT
done

For more info go here http://github.com/sunoano/bash/blob/mas … ket_filter