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Old 05-15-2012, 12:45 PM   #13
knc1
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Posts: 16,339
Karma: 17324624
Join Date: Feb 2012
Location: Central Texas
Device: No K1, PW2, KV, KOA
This one is tested and known to work - I'm writing to you through it at this moment.
This post shows a bit more of the details.

Quote:
Originally Posted by geekmaster View Post
Okay, so we just need a simple set of instructions on how to set up the host PC as an internet gateway to use with the kindle.

In that case, *I* would like to know the answer to this question too (I do not have time to "RTFM" right now)...
On the Kindle - set the default route to use /dev/usb0
(It may be set by the usbnet start, but if not, set it)

On the PC -
With "WORLD" set to the output device (sometimes: eth0);
With "IPT" set to /sbin/iptables (or its location on your machine):
Code:
# Default policy
DEF_POLICY='ACCEPT'

# NIC that connects to the outside world (via modem, cable, aDSL, whatever)
# Or if using dial-up and ppp - set WORLD to the name of the ppp interface (ppp0).
# Whereas, on the Kindle, you would prohibit using the ppp interface (that's the 3G card).
WORLD='eth0'

# Set default policy
$IPT -P INPUT   $DEF_POLICY   # Packets arriving
$IPT -P OUTPUT  $DEF_POLICY   # Packets locally generated
$IPT -P FORWARD $DEF_POLICY   # Packets in transit

# Anything output to world must masquerade
$IPT -t nat -A POSTROUTING -o $WORLD -j MASQUERADE

# Anything on input chain established or related is acceptable
$IPT -t filter -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Anything on input chain that's new is acceptable EXCEPT from world
$IPT -t filter -A INPUT -m state --state NEW -i '!'$WORLD -j ACCEPT

# Now handle any packets that where not handled by the above rules
$IPT -t filter -A INPUT -p tcp -i $WORLD -j REJECT --reject-with tcp-reset
$IPT -t filter -A INPUT        -i $WORLD -j DROP
Which turns the firewall into a one-way, network address translation, firewall. No __NEW__ connections allowed in-bound, only replies to out-bound traffic.

Then poke the box into "router mode":
Code:
# Enable IPv4 forwarding 0 == Disable, 1 == Enable
echo 1 > /proc/sys/net/ipv4/ip_forward
Note 1: If the PC already has iptable rules - then intellegently merge the above functions into them.

Note 2: Do not do the above on the Kindle. The above is too simple to keep you out of trouble.

Edit:
When did this forum turn into a Linux Newbie site?
Hello Web Masters - Better just put up a "Linux Newbie" forum - these questions will never go away.

Last edited by knc1; 05-15-2012 at 01:17 PM.
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