Packet Injection

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

Re: source-mac filtering

[Ramin Dousti]

On Sun, Jan 11, 2004 at 05:50:52PM +0000, Antony Stone wrote:

> On Sunday 11 January 2004 5:39 pm, Håkan Engblom wrote:
> 
> > Yes, I've come to realize that.
> >
> > Is it technically necessary for the dhcp-server to do so, or could it be
> > that some other dhcpd behaves different ?
> 
> It is technically necessary, because DHCP clients do not have IP addressing 
> information when they begin the communication; everything is done using 
> ethernet broadcasts.   Such packets cannot be acquired using a standard 
> socket bind, so the server application needs to listen at a lower level than 
> the TCP/IP stack allows.

I guess he's asking why dhcp-server uses NETLINK. Your answer is for the
clients, right?

Ramin

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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