Date: Thu, 7 Nov 2002 12:18:57 -0500 From: Steve Tremblett <sjt@cisco.com> To: freebsd-net@freebsd.org, freebsd-hackers@freebsd.org Subject: input source for network application Message-ID: <20021107121857.F264@sjt-u10.cisco.com>
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I've been toying with the idea of tackling a Netgraph TCP/IP
implementation and want to hack out some skeleton netgraph nodes just
to feel things out and play around with parsing. I'm somewhat confused
on how to start. I'd like to be able to tinker as I go and I'd rather
not have to write 5000 lines of code and complete a mini-stack before
trying it out :)
I'm in a bit of a bind. I want a sequence of ethernet frames to send
up through this framework. Hooking to ng_ether will give me this but I
am restricted to taking ALL frames (thus taking the machine offline) or
orphaned frames (where I will have to write some sort of traffic
generator to make frames of an invalid type). The third option here is
to hack ng_ether to deliver frames out the lower hook as well as up
into the kernel IP stack, thus giving me a complete stream without
taking the box offline. I've gotten libnet which seems to fit the bill
to generate any orphans I want, but making a stream of frames by hand
is a pain.
I've read about ng_tee but haven't had an opportunity to play with it.
Could I hack together something like this for an input source? Would
this allow for uninterrupted operation of the workstation while also
giving a stream of test data?
kernel
ip_input()
\
\-|
|- upper hook-\
ng_ether ng_tee---->
|- lower hook-/
|
wire
In case that diagram doesn't display in your mailer, I'm thinking of
connecting ng_tee to recieve input from ng_ether's lower hook and pass
it out through ng_ether's upper hook as well as into the input hook of
my own netgraph node.
Does anyone have any suggestions or ideas on tools or methods to assist
me in starting this venture? Am I thinking about this problem from the
right angle or is my head up my ass? :)
Thanks all :)
--
Steve Tremblett
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