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May 6th, 2004, 03:24 PM
#1
Netfilter Related states support
Basic Netfilter configurations question:
Iwould like to route thru a Linux box and use Netfilter to filter connections. At 1st step i wanna to allow only ftp from "inside" to "outside", so i have writthen the following script:
- im not using NAT at this time
- eth0 is inside and eth1 is outside
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echo 1 > /proc/sys/net/ipv4/ip_forward
IPTABLES –F INPUT
IPTABLES –F OUTPUT
IPTABLES –F FORWARD
IPTABLES –P INPUT DROP
IPTABLES –P OUTPUT DROP
IPTABLES -P FORWARD DROP
# allow ftp clients to go outside for ftp sessions
IPTABLES –A FORWARD -i eth0 –o eth1 –p tcp - -dport ftp –m state - -state NEW –j ACCEPT
IPTABLES –A FORWARD –m state - -state ESTABLISHED, RELATED –j ACCEPT
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my question is: (assuming that other things are correct):
Will this configuration allow ICMP response messages be forward BACK (outside-->inside) thru firewall? like "destination unreachable" or equivalents?
I think that it will, since ICMP messages like that will be identified by Netfilter as "RELATED" and will be pass back to client. But i would like you guys, Also sugestions are all ALLWAYS wellcome.
P.S. (if you know that there is another thread that had explained to death this subject please let me know - i tried "netfilter icmp related" and other combinations and didnt receive anything that matches to this issue)
Meu sítio
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