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#1 2004-07-27 14:48:48

tgc
Member
From: DK
Registered: 2004-03-09
Posts: 96

sharing network problem - again

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
# dranch@trinnet.net
#
# 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?

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#2 2004-07-28 20:44:30

filoktetes
Member
From: Skien, Norway
Registered: 2003-12-29
Posts: 286

Re: sharing network problem - again

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 smile

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 smile Thanks!

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