Can't get IP Forwarding to work with Host-only adapter

[grattemedi]

Hello,

I'm developing a software to demonstrate how Man in the middle works using arp cache poisoning. I can't get ip forwarding to work with Host-only adapter!

I was previously using a bridged network on tun/tap devices that I was creating myself. My network was designed like this :

[*]1 bridge br0

[*]2 tun/tap interfaces tap0 and tap1

Then I add the tap0 and tap1 to the bridge and configure my 2 VMs to use bridged network on tap0 and tap1. With this configuration, ip-forwading works perfectly fine! My bridge br0 can play the role of the attacker and forward ip between my first and second VM.

Now I'm trying to use host-only adapter, so that i could use later in my program the VBoxManage hostonly ipconfig command line. In the configuration I want to be, my 1st VM wants to talk to my 2nd VM but its arp cache has been corrupted so that packets are sent to the host (host-only interface). My problem is packets aren't forwarded by the host, and they normally should be.

I'm enabling ip forwarding on the host-only adapter (vboxnet0), as I was doing before with my bridge br0 :

echo 1 > /proc/sys/net/ipv4/conf/*/forwarding 
echo 0 > /proc/sys/net/ipv4/conf/*/send_redirects

Unfortunately, even though each machine in this configuration can communicate with one another, the vboxnet0 interface doesn't forward ip packets. Shouldn't host only interface behave like a normal networking interface?

Thank you,

Laurent Sebag