Hi everybody!!!
I have a problem with a simple netfilter application that I have
programmed. I have my application expecting packet on port 554, when they
arrives they are sent to my application and later they are reinjected.
However when I try to modify one of this packet, to add more information, I
cannot reinject the packet later. I make a copy of the packet received and
add the new data, later I recalculate the TCP checksum and IP checksum and
try to reinject with ipq_set_verdict, however the result is that the
application that expects that packetk never receives it, and instead my
application starts to receive that packet, but without the modification that
it was made. I think that the problem is in the checksum calculatio, maybe
is wrong and then the application do not reinject the packet, but what is
the reason to start to receive that packet again?.
If anybody has an idea, please tell me.
Thanks in advance.
Antonio.
