LinuxQuestions.org - internet connection sharing

- Linux - Software (https://www.linuxquestions.org/questions/linux-software-2/)

- - internet connection sharing (https://www.linuxquestions.org/questions/linux-software-2/internet-connection-sharing-316234/)

you're very welcome!! let me know if any issues come-up... good luck!!

hmm.. kinda an issue, not that big of one I guess....

but pre this, I had apache set up, as well as proftpd and they worked fine...

now they aren't working.. is it related, or did I change something without realizing it ?

ssh also isn't working...... which is more of an issue than anything... I planned on using that mostly when I needed to do anything with the machine.

you mean, like, to access those services on your box from the internet??

well, yeah, or the local network.. from the windows machine..

and when I try to connect with ssh, it just times out.

same with http

Quote:

Originally posted by meinzorn
hmm.. kinda an issue, not that big of one I guess....

but pre this, I had apache set up, as well as proftpd and they worked fine...

now they aren't working.. is it related, or did I change something without realizing it ?

ssh also isn't working...... which is more of an issue than anything... I planned on using that mostly when I needed to do anything with the machine.

Quote:

well, yeah, or the local network..

and when I try to connect with ssh, it just times out.

same with http

no problem, we just need to add a few rules to the script allowing http, ftp, and ssh (the original script i wrote was designed for complete stealth on the external interface, as i didn't know you were running services on it)...

here you go (the relevant rules are in bold):

here you go:

Code:

#!/bin/sh



IPT="/usr/sbin/iptables"



LAN_IFACE="eth0"

INET_IFACE="ppp0"



echo "0" > /proc/sys/net/ipv4/ip_forward

echo "1" > /proc/sys/net/ipv4/tcp_syncookies

echo "0" > /proc/sys/net/ipv4/tcp_timestamps

echo "1" > /proc/sys/net/ipv4/conf/all/rp_filter

echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

echo "0" > /proc/sys/net/ipv4/conf/all/accept_source_route

echo "1" > /proc/sys/net/ipv4/conf/all/secure_redirects

echo "1" > /proc/sys/net/ipv4/conf/all/log_martians



$IPT -F

$IPT -F -t nat

$IPT -F -t mangle



$IPT -X

$IPT -X -t nat

$IPT -X -t mangle



$IPT -P INPUT DROP

$IPT -P FORWARD DROP

$IPT -P OUTPUT ACCEPT



$IPT -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

$IPT -A INPUT -i lo -m state --state NEW -j ACCEPT

$IPT -A INPUT -p ICMP --icmp-type 8 -m state --state NEW -j ACCEPT

$IPT -A INPUT -p TCP --dport 21 -m state --state NEW -j ACCEPT

$IPT -A INPUT -p TCP --dport 22 -m state --state NEW -j ACCEPT

$IPT -A INPUT -p TCP --dport 80 -m state --state NEW -j ACCEPT

$IPT -A INPUT -j LOG --log-prefix "INPUT DROP: "



$IPT -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

$IPT -A FORWARD -i $LAN_IFACE -o $INET_IFACE \

-m state --state NEW -j ACCEPT

$IPT -A FORWARD -j LOG --log-prefix "FORWARD DROP: "



$IPT -t nat -A POSTROUTING -o $INET_IFACE -j MASQUERADE



/sbin/modprobe ip_conntrack_ftp

/sbin/modprobe ip_nat_ftp



/sbin/modprobe ip_conntrack_irc

/sbin/modprobe ip_nat_irc



echo "1" > /proc/sys/net/ipv4/ip_forward



echo "So let it be written. So let it be done."

ok, so if I need a port opened for whatever reason, it's just like those added lines, only change the port number?

yeah, basically... but it wouldn't be a bad idea to do some reading about iptables/netfilter so you can have a better understanding of what the script is doing:

http://www.linuxguruz.com/iptables/howto/

http://www.linuxguruz.com/iptables/

http://www.justlinux.com/nhf/Securit...es_Basics.html

http://iptables-tutorial.frozentux.n...-tutorial.html

for more iptables info: http://www.google.com/linux?hl=en&lr...es&btnG=Search

;-)

BTW, that script is logging every packet that gets blocked by the firewall... you can see what packets are getting blocked in "real-time" by doing a:

Code:

tail -f /var/log/syslog

(you need to have sysklogd installed for this to work)

this is good for troubleshooting and stuff... like, for example when you weren't able to SSH to the box - by monitoring the log file you would have noticed the port 22 packets getting blocked... so you would have known it was a firewall issue right away...

it's also good for seeing all the weird spiders that crawl all over the internet... hehe...