Packet injection

Packet injection

[Scott MacKay]

I was wondering, is there any sample code of injecting
new packets while userspace processing?  I was looking
for something that could add a new packet in the QUEUE
target userspace program or to inject a packet back at
the start of the whole processing.  I was looking to
inject with the hope of writing the entire packet
header structure, not just the IP contents.  Any
samples or URLS?

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Packet Injection

[Oliver Korpilla]

Hello!

I'm new to the list, and what I've found in the list archives regarding
packet injection is somewhat lacking in detail.

What I want to do:

I want to write a tool that sends and receives packets within the kernel
context. It's generates traffic on one interface and receives the result
of some blackbox modification to it on another interface.

So I need both packet filtering / netfilter like capabilities and packet
injection capabilities.

While the way to go for the receiving end of the application is pretty
straightforward, my question is: How to inject packets inside the kernel?

One idea was to create the packets externally, store them in kernel RAM,
and use netfilter hooks to inject them. The injection would be done by a
linux kernel module or rather by a periodic tasklet registered by that
module.

Can you comment whether this is a feasible approach?

Or could you come up with a better one, that fulfills the requirement of
being in-kernel?

Thanks and with kind regards,
Oliver Korpilla