Sharing network problem - again

Question

Hi, i hoped to avoid posting this problem, but i just can't get internet sharing working!
My setup is this: I have a PC connected directly to a adsl-modem via a netcard, and via a second netcard (and a crossed cable) i have a second PC connected to the first, both are running Archlinux, the first is up to date, but the second is 0.6 (since i can't update...).
The 2 PC's have no problems communicating, ping and ssh is working perfectly both ways.
To share the connection, i have this in the rc.conf:
The one connected to the modem:
lo="lo 127.0.0.1"
eth0="dhcp"
eth1="eth1 192.168.1.1 netmask 255.255.255.0 broadcast 192.168.1.255"
INTERFACES="lo eth0 eth1"
# Routes to start at boot-up (in this order)
# Declare each route then list in ROUTES
# (prefix a route in ROUTES with a ! to disable it)
gateway="default gw 192.168.0.1"
ROUTES=(!gateway)
The one needing the connection:
lo="lo 127.0.0.1"
eth0="eth0 192.168.1.2 netmask 255.255.255.0 broadcast 192.168.1.255"
#eth0="dhcp"
INTERFACES=(lo eth0)
# Routes to start at boot-up (in this order)
# Declare each route then list in ROUTES
# (prefix a route in ROUTES with a ! to disable it)
gateway="default gw 192.168.1.1"
ROUTES=(gateway)
And i have this "firewall" installed on the one connected to the internet:
#!/bin/sh
# rc.firewall-2.4
FWVER=0.75
# Initial SIMPLE IP Masquerade test for 2.4.x kernels
# using IPTABLES.
# Once IP Masquerading has been tested, with this simple
# ruleset, it is highly recommended to use a stronger
# IPTABLES ruleset either given later in this HOWTO or
# from another reputable resource.
# Log:
# 0.75 - Added more kernel modules to the comments section
# 0.74 - the ruleset now uses modprobe vs. insmod
# 0.73 - REJECT is not a legal policy yet; back to DROP
# 0.72 - Changed the default block behavior to REJECT not DROP
# 0.71 - Added clarification that PPPoE users need to use
# "ppp0" instead of "eth0" for their external interface
# 0.70 - Added commented option for IRC nat module
# - Added additional use of environment variables
# - Added additional formatting
# 0.63 - Added support for the IRC IPTABLES module
# 0.62 - Fixed a typo on the MASQ enable line that used eth0
# instead of $EXTIF
# 0.61 - Changed the firewall to use variables for the internal
# and external interfaces.
# 0.60 - 0.50 had a mistake where the ruleset had a rule to DROP
# all forwarded packets but it didn't have a rule to ACCEPT
# any packets to be forwarded either
# - Load the ip_nat_ftp and ip_conntrack_ftp modules by default
# 0.50 - Initial draft
echo -e "nnLoading simple rc.firewall version $FWVER..n"
# The location of the iptables and kernel module programs
# If your Linux distribution came with a copy of iptables,
# most likely all the programs will be located in /sbin. If
# you manually compiled iptables, the default location will
# be in /usr/local/sbin
# ** Please use the "whereis iptables" command to figure out
# ** where your copy is and change the path below to reflect
# ** your setup
#IPTABLES=/sbin/iptables
IPTABLES=/usr/sbin/iptables
DEPMOD=/sbin/depmod
MODPROBE=/sbin/modprobe
#Setting the EXTERNAL and INTERNAL interfaces for the network
# Each IP Masquerade network needs to have at least one
# external and one internal network. The external network
# is where the natting will occur and the internal network
# should preferably be addressed with a RFC1918 private address
# scheme.
# For this example, "eth0" is external and "eth1" is internal"
# NOTE: If this doesnt EXACTLY fit your configuration, you must
# change the EXTIF or INTIF variables above. For example:
# If you are a PPPoE or analog modem user:
# EXTIF="ppp0"
EXTIF="eth0"
INTIF="eth1"
echo " External Interface: $EXTIF"
echo " Internal Interface: $INTIF"
#======================================================================
#== No editing beyond this line is required for initial MASQ testing ==
echo -en " loading modules: "
# Need to verify that all modules have all required dependencies
echo " - Verifying that all kernel modules are ok"
$DEPMOD -a
# With the new IPTABLES code, the core MASQ functionality is now either
# modular or compiled into the kernel. This HOWTO shows ALL IPTABLES
# options as MODULES. If your kernel is compiled correctly, there is
# NO need to load the kernel modules manually.
# NOTE: The following items are listed ONLY for informational reasons.
# There is no reason to manual load these modules unless your
# kernel is either mis-configured or you intentionally disabled
# the kernel module autoloader.
# Upon the commands of starting up IP Masq on the server, the
# following kernel modules will be automatically loaded:
# NOTE: Only load the IP MASQ modules you need. All current IP MASQ
# modules are shown below but are commented out from loading.
# ===============================================================
echo "----------------------------------------------------------------------"
#Load the main body of the IPTABLES module - "iptable"
# - Loaded automatically when the "iptables" command is invoked
# - Loaded manually to clean up kernel auto-loading timing issues
echo -en "ip_tables, "
$MODPROBE ip_tables
#Load the IPTABLES filtering module - "iptable_filter"
# - Loaded automatically when filter policies are activated
#Load the stateful connection tracking framework - "ip_conntrack"
# The conntrack module in itself does nothing without other specific
# conntrack modules being loaded afterwards such as the "ip_conntrack_ftp"
# module
# - This module is loaded automatically when MASQ functionality is
# enabled
# - Loaded manually to clean up kernel auto-loading timing issues
echo -en "ip_conntrack, "
$MODPROBE ip_conntrack
#Load the FTP tracking mechanism for full FTP tracking
# Enabled by default -- insert a "#" on the next line to deactivate
echo -en "ip_conntrack_ftp, "
$MODPROBE ip_conntrack_ftp
#Load the IRC tracking mechanism for full IRC tracking
# Enabled by default -- insert a "#" on the next line to deactivate
echo -en "ip_conntrack_irc, "
$MODPROBE ip_conntrack_irc
#Load the general IPTABLES NAT code - "iptable_nat"
# - Loaded automatically when MASQ functionality is turned on
# - Loaded manually to clean up kernel auto-loading timing issues
echo -en "iptable_nat, "
$MODPROBE iptable_nat
#Loads the FTP NAT functionality into the core IPTABLES code
# Required to support non-PASV FTP.
# Enabled by default -- insert a "#" on the next line to deactivate
echo -en "ip_nat_ftp, "
$MODPROBE ip_nat_ftp
#Loads the IRC NAT functionality into the core IPTABLES code
# Required to support NAT of IRC DCC requests
# Disabled by default -- remove the "#" on the next line to activate
#echo -e "ip_nat_irc"
#$MODPROBE ip_nat_irc
echo "----------------------------------------------------------------------"
# Just to be complete, here is a partial list of some of the other
# IPTABLES kernel modules and their function. Please note that most
# of these modules (the ipt ones) are automatically loaded by the
# master kernel module for proper operation and don't need to be
# manually loaded.
# ip_nat_snmp_basic - this module allows for proper NATing of some
# SNMP traffic
# iptable_mangle - this target allows for packets to be
# manipulated for things like the TCPMSS
# option, etc.
# ipt_mark - this target marks a given packet for future action.
# This automatically loads the ipt_MARK module
# ipt_tcpmss - this target allows to manipulate the TCP MSS
# option for braindead remote firewalls.
# This automatically loads the ipt_TCPMSS module
# ipt_limit - this target allows for packets to be limited to
# to many hits per sec/min/hr
# ipt_multiport - this match allows for targets within a range
# of port numbers vs. listing each port individually
# ipt_state - this match allows to catch packets with various
# IP and TCP flags set/unset
# ipt_unclean - this match allows to catch packets that have invalid
# IP/TCP flags set
# iptable_filter - this module allows for packets to be DROPped,
# REJECTed, or LOGged. This module automatically
# loads the following modules:
# ipt_LOG - this target allows for packets to be
# logged
# ipt_REJECT - this target DROPs the packet and returns
# a configurable ICMP packet back to the
# sender.
echo -e " Done loading modules.n"
#CRITICAL: Enable IP forwarding since it is disabled by default since
# Redhat Users: you may try changing the options in
# /etc/sysconfig/network from:
# FORWARD_IPV4=false
# to
# FORWARD_IPV4=true
echo " Enabling forwarding.."
echo "1" > /proc/sys/net/ipv4/ip_forward
# Dynamic IP users:
# If you get your IP address dynamically from SLIP, PPP, or DHCP,
# enable this following option. This enables dynamic-address hacking
# which makes the life with Diald and similar programs much easier.
echo " Enabling DynamicAddr.."
echo "1" > /proc/sys/net/ipv4/ip_dynaddr
# Enable simple IP forwarding and Masquerading
# NOTE: In IPTABLES speak, IP Masquerading is a form of SourceNAT or SNAT.
# NOTE #2: The following is an example for an internal LAN address in the
# 192.168.0.x network with a 255.255.255.0 or a "24" bit subnet mask
# connecting to the Internet on external interface "eth0". This
# example will MASQ internal traffic out to the Internet but not
# allow non-initiated traffic into your internal network.
# ** Please change the above network numbers, subnet mask, and your
# *** Internet connection interface name to match your setup
#Clearing any previous configuration
# Unless specified, the defaults for INPUT and OUTPUT is ACCEPT
# The default for FORWARD is DROP (REJECT is not a valid policy)
echo " Clearing any existing rules and setting default policy.."
$IPTABLES -P INPUT ACCEPT
$IPTABLES -F INPUT
$IPTABLES -P OUTPUT ACCEPT
$IPTABLES -F OUTPUT
$IPTABLES -P FORWARD DROP
$IPTABLES -F FORWARD
$IPTABLES -t nat -F
echo " FWD: Allow all connections OUT and only existing and related ones IN"
$IPTABLES -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT
$IPTABLES -A FORWARD -j LOG
echo " Enabling SNAT (MASQUERADE) functionality on $EXTIF"
$IPTABLES -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE
echo -e "nrc.firewall-2.4 v$FWVER done.n"
And to start it:
#!/bin/sh
# chkconfig: 2345 11 89
# description: Loads the rc.firewall-2.4 ruleset.
# processname: firewall-2.4
# pidfile: /var/run/firewall.pid
# config: /etc/rc.d/rc.firewall-2.4
# probe: true
# v05/24/03
# Part of the copyrighted and trademarked TrinityOS document.
# http://www.ecst.csuchico.edu/~dranch
# Written and Maintained by David A. Ranch
# [email protected]
# Updates
# 05/24/03 - removed a old networking up check that had some
# improper SGML ampersand conversions.
# Source function library.
. /etc/rc.d/functions
# Check that networking is up.
[ "XXXX${NETWORKING}" = "XXXXno" ] && exit 0
[ -x /sbin/ifconfig ] || exit 0
# The location of various iptables and other shell programs
# If your Linux distribution came with a copy of iptables, most
# likely it is located in /sbin. If you manually compiled
# iptables, the default location is in /usr/local/sbin
# ** Please use the "whereis iptables" command to figure out
# ** where your copy is and change the path below to reflect
# ** your setup
IPTABLES=/usr/sbin/iptables
# See how we were called.
case "$1" in
start)
/etc/rc.firewall-2.4
stop)
echo -e "nFlushing firewall and setting default policies to DROPn"
$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
# Delete all User-specified chains
$IPTABLES -X
# Reset all IPTABLES counters
$IPTABLES -Z
restart)
$0 stop
$0 start
status)
$IPTABLES -L
mlist)
cat /proc/net/ip_conntrack
echo "Usage: firewall-2.4 {start|stop|status|mlist}"
exit 1
esac
exit 0
But it just won't work! If you can spot any problems please let me know!
UPDATE:
Just talked to my ISP, and they tell me that my IP-adress is locked to one PC. Could this be the problem? or does the forwarding handles this as well?

Answer 1

Hey tgc, thank you for posting your problem so generously explained!
I had no idea of how to do it, and I only had to change a small obvious typo to make it work. At least I suppose the typo is the reason for your sharing not to work....
Lets see...did you change the
eth0="eth0 192.168.1.2 netmask 255.255.255.0 broadcast 192.168.0.255"
to
eth0="eth0 192.168.1.2 netmask 255.255.255.0 broadcast 192.168.1.255"
just now? I'm sure I had to change that, but I have a strange memory
So, the way the configuraton looks now, works perfectly for sharing my isdn connection with my laptop over wlan.
Desktop: isdn, eth0 -> wireless router / hub
Laptop: wlan0
So, what I'm saying anyway, is that your configuration works for me Thanks!