Forwarding the IP packet from tun0 to/from eth0

johnniealan · #1 (**permalink**) 05-19-2009

Hi all,

I am working on TUN/TAP for tunnelling IP packets from the application to the network.

I am able to open the tun device and assign the IP address to tun0. The steps I followed are given,

1. Opened the tun device /dev/net/tun
2. Assigned a IP address to the tun0 using ifconfig tun0 10.66.67.247
3. Added to the routing table using the following command route add -host 10.66.67.247 dev tun0
4. I have loaded the tun device using modprobe tun and I was able to see the device when I gave the command lsmod | sort

Code:

         tsdev                   7520  0 
         tun                    10336  1

5. the output of the command route is

Code:

10.66.67.247    *   255.255.255.255     UH    0      0        0 tun0
10.66.67.192    *   255.255.255.192     U     0      0        0 eth0
default 10.66.67.193    0.0.0.0         UG    0      0        0 eth0

6. I have installed uml-utilities & bridge utilities.
7. finally I wrote a IP frame to tun0 device . The IP packet was for opening a ftp session on other machine (10.66.67.220.

I could seee the packet received in tun0 device using ifconfig and wireshark.

Code:

tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
          inet addr:10.66.67.247  P-t-P:10.66.67.247  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:1 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500 
          RX bytes:60 (60.0 b)  TX bytes:0 (0.0 b)

The IP Packet which I sent is received in the tun0 device, but furhter its not been routed to the eth0 device.

My question is, how do I route the IP packets recevied in tun0 device to the network via eth0 and vice versa.

Is there any package or driver i need to install inorder to configure the tun device for routing it to the eth0

Thanks for your inputs in Advance
Johnnie Alan J

Lazydog · #2 (**permalink**) 06-04-2009

Turn on FORWARDing.

johnniealan · #3 (**permalink**) 06-05-2009

hi,

Thanks for your inputs.

But may i know which forwarding your are talking about. do you mean /proc/sys/net/ipv4/ip_forward? .

I have enabled in the file mentioned above

regards
johnnie alan j

stdout · #4 (**permalink**) 06-10-2009

hi johnie,

i'm a bit unclear here,
can you draw us a small picture what are you trying to accomplish?

johnniealan · #5 (**permalink**) 06-11-2009

hi all,

I am sending an IP packet to another machine on the same LAN using tun0 device. The Packet is traversed through PREROUTING and doesnt go the FORWARD chain.

tun0 (10.66.67.247) <-------> eth0 (10.66.67.208)<----> machine2 ( 10.66.67.220)

I am send an IP packet to 220 machine.

Tun0 is up and running.

Thanks in advance
Alan J

Lazydog · #6 (**permalink**) 07-10-2009

[quote=johnniealan;302324481
tun0 (10.66.67.247) <-------> eth0 (10.66.67.208)<----> machine2 ( 10.66.67.220)[/quote]

Are both of these ip address on the same machine? I don't see any eth# on the side for machine 2.

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