Hamachi on an IP Gateway

Riddick · 01-27-2007, 05:02 PM

Dear All,
I have a computer with 2 Ethernet ports which IP forwards (routes) my home metwork traffic and does other server-like tasks (DHCP etc...)

Because the external IP address given by my ISP (and therefore to this box) is not a public one, I cannot really get into contact with this computer from the public internet.

I would like to use hamachi to manage my box, but the iptables rules seem to confuse it - the clients that connect through this computer have no problem using hamachi, so it is not a question of the connection.

I attach the iptables script kindly taken from: http://www.aboutdebian.com/firewall.htm

Quote:

#!/bin/sh

# IPTABLES FIREWALL script for the Linux 2.4 kernel.
# This script is a derivitive of the script presented in
# the IP Masquerade HOWTO page at:
# http://www.tldp.org/HOWTO/IP-Masquer...-examples.html
# It was simplified to coincide with the configuration of
# the sample system presented in the Guides section of
# www.aboutdebian.com
#
# This script is presented as an example for testing ONLY
# and should not be used on a production firewall server.
#
# PLEASE SET THE USER VARIABLES
# IN SECTIONS A AND B OR C

echo -e "\n\nSETTING UP IPTABLES FIREWALL..."

# === SECTION A
# ----------- FOR EVERYONE

# SET THE INTERFACE DESIGNATION AND ADDRESS AND NETWORK ADDRESS
# FOR THE NIC CONNECTED TO YOUR _INTERNAL_ NETWORK
# The default value below is for "eth0". This value
# could also be "eth1" if you have TWO NICs in your system.
# You can use the ifconfig command to list the interfaces
# on your system. The internal interface will likely have
# have an address that is in one of the private IP address
# ranges.
# Note that this is an interface DESIGNATION - not
# the IP address of the interface.

# Enter the designation for the Internal Interface's
INTIF="eth1"

# Enter the NETWORK address the Internal Interface is on
INTNET="192.168.0.0/24"

# Enter the IP address of the Internal Interface
INTIP="192.168.0.1/24"

# SET THE INTERFACE DESIGNATION FOR YOUR "EXTERNAL" (INTERNET) CONNECTION
# The default value below is "ppp0" which is appropriate
# for a MODEM connection.
# If you have two NICs in your system change this value
# to "eth0" or "eth1" (whichever is opposite of the value
# set for INTIF above). This would be the NIC connected
# to your cable or DSL modem (WITHOUT a cable/DSL router).
# Note that this is an interface DESIGNATION - not
# the IP address of the interface.
# Enter the external interface's designation for the
# EXTIF variable:

EXTIF="eth0"

# ! ! ! ! ! Use ONLY Section B *OR* Section C depending on
# ! ! ! ! the type of Internet connection you have.
# ! ! ! ! ! Uncomment ONLY ONE of the EXTIP statements.

# === SECTION B
# ----------- FOR THOSE WITH STATIC PUBLIC IP ADDRESSES

# SET YOUR EXTERNAL IP ADDRESS
# If you specified a NIC (i.e. "eth0" or "eth1" for
# the external interface (EXTIF) variable above,
# AND if that external NIC is configured with a
# static, public IP address (assigned by your ISP),
# UNCOMMENT the following EXTIP line and enter the
# IP address for the EXTIP variable:

#EXTIP="your.static.IP.address"

# === SECTION C
# ---------- DIAL-UP MODEM, AND RESIDENTIAL CABLE-MODEM/DSL (Dynamic IP) USERS

# SET YOUR EXTERNAL INTERFACE FOR DYNAMIC IP ADDRESSING
# If you get your IP address dynamically from SLIP, PPP,
# BOOTP, or DHCP, UNCOMMENT the command below.
# (No values have to be entered.)
# Note that if you are uncommenting these lines then
# the EXTIP line in Section B must be commented out.

EXTIP="`/sbin/ifconfig eth0 | grep 'inet addr' | awk '{print $2}' | sed -e 's/.*://'`"

# -------- No more variable setting beyond this point --------

echo "Loading required stateful/NAT kernel modules..."

/sbin/depmod -a
/sbin/modprobe ip_tables
/sbin/modprobe ip_conntrack
/sbin/modprobe ip_conntrack_ftp
/sbin/modprobe ip_conntrack_irc
/sbin/modprobe iptable_nat
/sbin/modprobe ip_nat_ftp
/sbin/modprobe ip_nat_irc

echo " Enabling IP forwarding..."
echo "1" > /proc/sys/net/ipv4/ip_forward
echo "1" > /proc/sys/net/ipv4/ip_dynaddr

echo " External interface: $EXTIF"
echo " External interface IP address is: $EXTIP"
echo " Loading firewall server rules..."

UNIVERSE="0.0.0.0/0"

# Clear any existing rules and setting default policy to DROP
iptables -P INPUT DROP
iptables -F INPUT
iptables -P OUTPUT DROP
iptables -F OUTPUT
iptables -P FORWARD DROP
iptables -F FORWARD
iptables -F -t nat

# Flush the user chain.. if it exists
if [ "`iptables -L | grep drop-and-log-it`" ]; then
iptables -F drop-and-log-it
fi

# Delete all User-specified chains
iptables -X

# Reset all IPTABLES counters
iptables -Z

# Creating a DROP chain
iptables -N drop-and-log-it
iptables -A drop-and-log-it -j LOG --log-level info
iptables -A drop-and-log-it -j REJECT

echo -e " - Loading INPUT rulesets"

#######################################################################
# INPUT: Incoming traffic from various interfaces. All rulesets are
# already flushed and set to a default policy of DROP.
#

# loopback interfaces are valid.
iptables -A INPUT -i lo -s $UNIVERSE -d $UNIVERSE -j ACCEPT

# local interface, local machines, going anywhere is valid
iptables -A INPUT -i $INTIF -s $INTNET -d $UNIVERSE -j ACCEPT

# allow dhcp traffic
iptables -A INPUT -i $INTIF -p udp --dport 67 --sport 68 -j ACCEPT
#iptables -A INPUT -i $INTIF -p udp --dport 68 --sport 67 -j ACCEPT

# remote interface, claiming to be local machines, IP spoofing, get lost
iptables -A INPUT -i $EXTIF -s $INTNET -d $UNIVERSE -j drop-and-log-it

# remote interface, any source, going to permanent PPP address is valid
iptables -A INPUT -i $EXTIF -s $UNIVERSE -d $EXTIP -j ACCEPT

# Allow any related traffic coming back to the MASQ server in
iptables -A INPUT -i $EXTIF -s $UNIVERSE -d $EXTIP -m state --state ESTABLISHED,RELATED -j ACCEPT

#Matteo's BitTorrent Rule
#iptables -A INPUT -i $EXTIF -s $UNIVERSE -d 192.168.0.10 -p tcp -sport 6881 -j accept

# OPTIONAL: Uncomment the following two commands if plan on running
# an Apache Web site on the firewall server itself
#
#echo -e " - Allowing EXTERNAL access to the WWW server"
#iptables -A INPUT -i $EXTIF -m state --state NEW,ESTABLISHED,RELATED -p tcp -s $UNIVERSE -d $EXTIP --dport 80 -j ACCEPT

# Catch all rule, all other incoming is denied and logged.
iptables -A INPUT -s $UNIVERSE -d $UNIVERSE -j drop-and-log-it

echo -e " - Loading OUTPUT rulesets"

#######################################################################
# OUTPUT: Outgoing traffic from various interfaces. All rulesets are
# already flushed and set to a default policy of DROP.
#

# loopback interface is valid.
iptables -A OUTPUT -o lo -s $UNIVERSE -d $UNIVERSE -j ACCEPT

# local interfaces, any source going to local net is valid
iptables -A OUTPUT -o $INTIF -s $EXTIP -d $INTNET -j ACCEPT

# local interface, any source going to local net is valid
iptables -A OUTPUT -o $INTIF -s $INTIP -d $INTNET -j ACCEPT

# allow dhcp traffic
iptables -A OUTPUT -o $INTIF -p udp --dport 68 --sport 67 -j ACCEPT
#iptables -A OUTPUT -o $INTIF -p udp --dport 67 --sport 68 -j ACCEPT

#Matteo to internet
#iptables -A OUTPUT -o $INTIF -p udp

# outgoing to local net on remote interface, stuffed routing, deny
iptables -A OUTPUT -o $EXTIF -s $UNIVERSE -d $INTNET -j drop-and-log-it

# anything else outgoing on remote interface is valid
iptables -A OUTPUT -o $EXTIF -s $EXTIP -d $UNIVERSE -j ACCEPT

# Catch all rule, all other outgoing is denied and logged.
iptables -A OUTPUT -s $UNIVERSE -d $UNIVERSE -j drop-and-log-it

echo -e " - Loading FORWARD rulesets"

#######################################################################
# FORWARD: Enable Forwarding and thus IPMASQ
# Allow all connections OUT and only existing/related IN

iptables -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT

# Catch all rule, all other forwarding is denied and logged.
iptables -A FORWARD -j drop-and-log-it

# Enable SNAT (MASQUERADE) functionality on $EXTIF
iptables -t nat -A POSTROUTING -o $EXTIF -j SNAT --to $EXTIP

echo -e " Firewall server rule loading complete\n\n"

Thanks for any help!

Riddick