Re: [lwip-users] [Fwd: TAP/TUN device]

[Kieran Mansley]

On Thu, 2007-03-15 at 11:37 +0000, Kelvin Lawson wrote:
> Dinesh,
> 
> Please direct any help requests to the LWIP users mailing list.
> 
> 
> -------- Original Message --------
> Subject:      TAP/TUN device
> Date:         Thu, 15 Mar 2007 16:52:50 +0530
> From:         Dinesh Chachan <address@hidden>
> To:   Kelvin Lawson <address@hidden>, address@hidden,
> address@hidden
> 
> 
> 
> Hi Sir
> 
> I required your help regarding tun device. please help me out. I created
> two tun devices using two different Client server programs running over
> LWIP in the same system with the following command
> 
> for tun0 -> ifconfig tun0 inet 192.168.1.2 <http://192.168.1.2>
> pointopoint 192.168.1.3 <http://192.168.1.3>
> for tun1 -> ifconfig tun0 inet 192.168.1.1 <http://192.168.1.1>
> pointopoint 192.168.1.2 <http://192.168.1.2>
> 
> both the devices are created propely. I can see the configuration by the
> help of ifconfig command.
> 
> Now one process of mine writes some IP packets to the tun1 device. The
> IP packet has the destination address as 192.168.1.2
> <http://192.168.1.2>. but tun0 receives no packets.
> 
> According to me the kernel should fetch the IP packet from tun1 read the
> destination address of the IP Packet and accordingly foward it to the
> tun0 device. Am i right? If no please correct me.

Have you enabled IP forwarding between interfaces in your linux kernel?
I think a lot of people have this turned off by default for security
reasons these days.

e.g. 
echo "1" > /proc/sys/net/ipv4/ip_forward

Kieran