Tuntap

From OSR

What is Tuntap*?

TUN/TAP provides packet reception and transmission for user space programs. It can be viewed as a simple Point-to-Point or Ethernet device, which instead of receiving packets from a physical media, receives them from user space program and instead of sending packets via physical media writes them to the user space program.

When a program opens /dev/net/tun, driver creates and registers corresponding net device tunX or tapX. After a program closed above devices, driver will automatically delete tunXX or tapXX device and all routes corresponding to it.

Setup the Linux kernel (host OS)

Make sure that the tuntap module and kernel module auto-loader is included in your kernel.

Add the following line to /etc/modprobe.conf

   alias char-major-10-200 tun

To automatically load the driver when the application accesses /dev/net/tun, run the following command:

   /sbin/depmod –a

Configure Bochs to use the tuntap interface

Make sure Bochs has ne2000 support. Check Bochs for more information.

Download a guest OS disk image from the Bochs diskimage website. I used DLX Linux as my guest OS.

Edit your .bochsrc configuration file and add the following line:

   ne2k: ioaddr=0x300, irq=9, mac=fe:fd:00:00:00:01, ethmod=tuntap, ethdev=/dev/net/tun,
   script=/path/to/tunconfig

You will find instructions on howto create the tunconfig script in the next section.

Setup the private network between the host and the guest

I've setup a private network between the host and the guest with the following parameters. If your parameters are different, adapt the rest of the section to suit your needs.

   Host IP : 192.168.3.100
   Guest IP : 192.168.3.101

Create the /path/to/tunconfig script and make it executable:

   #!/bin/bash
   /sbin/ifconfig ${1##/*/} 192.168.3.100

The script gets the interface name as the first parameter. Linux will forward incoming packets between interfaces.

Run Bochs as root and install your guest OS.

Create and run the following script in your guest OS to start the network services:

#!/bin/sh

# net-up.sh: set up network access

DEVICE=eth0
IPADDR=192.168.3.101
NETMASK=255.255.255.0
NETWORK=192.168.3.0
GATEWAY=192.168.3.100

ifconfig $DEVICE $IPADDR netmask $NETMASK up
route add -net $NETWORK netmask $NETMASK $DEVICE
route add default gw $GATEWAY

You may have to disable your firewall and add the following line to /etc/hosts.allow in the host OS:

   ALL: 192.168.3.101

At this point, you should be able to ping/telnet/ftp/ssh the guest from the host and vice-versa.

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