Is it possible to modify a field of a packet which arrives in (INPUT) eth0?
 

Hi all,
this is my problem:

I use a Raspberry linux box with a service which does something magic..;) This service bridges a Wireless Sensor Network (WSN) with a LAN (ethernet). To do this trick it bridges eth0....

After i start this service (6LBR for the most inquiring ones of you) i can also see br0 and tap0.

Now, correct me if i am wrong, it is br0 which bridges eth0 with tap0, isn't it?

tap0 is connected to the service.

This service doesn't work if some particular packets comes from my campus (ethernet) LAN. For the most inquiring ones of you these packets are from VRRP protocol.

In order to make 6LBR service work i know how to modify a field of a packet (the source link-layer option of IPv6 packet), BUT...i don't know if there is a way to modify a single field of a packet in INPUT in eth0.
I thought about iptables and i'm trying to learn to use it...or..any other suggestion?

Thanks in advance!
Carlo

It is easy if you can program code in netfilter.