RE: struct dlil_if_flt_str
RE: struct dlil_if_flt_str
- Subject: RE: struct dlil_if_flt_str
- From: "Carl Smith" <email@hidden>
- Date: Tue, 15 Mar 2005 17:16:47 -0500
- Thread-topic: struct dlil_if_flt_str
" Do you really want to futz with the frame header on the input path?"
Actually Yes. It can be the header retained in the mbuf, but what I am
doing is looking for a particular frame type, our registered type,
extracting confidential information encrypted in the packet, setting the
new/replaced frame type, i.e. 0x800 and so on, then passing it up the
stack. Now if someone or something is doing some kind of header
filtering or type checking and throwing away unknown packets types, I'm
screwed.
If the later is the case then I need to be lower then a dlil interface
filter.
If there is a problem with where I have my packet capture/filtering
setup I would really appreciate any comments to eliminate some 'throw'
away work.
Thanks
Carl
-----Original Message-----
From: darwin-kernel-bounces+csmith=email@hidden
[mailto:darwin-kernel-bounces+csmith=email@hidden]
On Behalf Of Justin Walker
Sent: Tuesday, March 15, 2005 5:01 PM
To: darwin-kernel Dev
Subject: Re: struct dlil_if_flt_str
On Mar 15, 2005, at 13:17, Carl Smith wrote:
> Not sure if I asked the question clearly enough in my last post, but
to
> rephrase the question -
>
> Can I manipulate the Ethernet header, and packet data using the data
> passed into my dlil_if_flt_str function, filter_if_input?
Do you really want to futz with the frame header on the input path? As
implied by Josh's earlier reply, anything above the DLIL layer will not
see the frame header (it is provided to the filters at the DLIL layer
"for information purposes". The only code that might look at it after
your filter would be other filters, and you have no idea what they
might be up to.
The only information retained as the packet is passed to the network
layer is the identity of the interface that received the packet (and
that is kept in the mbuf header).
> I am just anxious because I do not want to spend a lot of development
> time 'barking up the wrong tree'.
We learn by barking at trees and other things that move in the forest
:-}
Cheers,
Justin
--
Justin C. Walker, Curmudgeon-At-Large *
Institute for General Semantics | If you're not confused,
| You're not paying attention
*--------------------------------------*-------------------------------*
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