[Click] can someone please explain how click deals with IP headers?

[Daniel McBrearty]

Thanks Roman. I was starting to suspect this. I guess the same applies
to other modules that expect IP packets.

Next question : when you are done processing the raw IP, how do you
put an ethernet header back on, prior to the Queue() -> ToDevice()
combination?

cheers

On 10/25/07, Roman Chertov <rchertov at purdue.edu> wrote:
> Daniel McBrearty wrote:
> > Hi
> >
> > Have been playing around with this great piece of software for a few
> > days. Had some success with it, but one thing seems to cause some
> > trouble.
> >
> > I seem not to be understanding something basic about how many elements
> > handle IP headers.
> >
> > For instance, if I have a config like this :
> >
> > ipc IPClassifier( ip proto udp, - );
> > FromDevice( etho, PROMISC true ) -> ipc;
> > ipc[0] -> Queue() -> ToDevice( eth1 );
> > ipc[1] -> Discard();
> >
> > Now, I run this in user mode, and send it a few hundred RTP packets.
> > It core dumps. The core dump goes if I remove ipc.
>
> It core dumps because it is trying to read IP headers from where
> Ethernet headers are.  You need to use a classifier first and then strip
> 14 bytes before you can send packets to the IPClassifier.
>
> Roman
>
> >
> > Other problems I have had have been trying to use SetIPAddress(
> > 1.2.3.4, dst ) in such a config, but the ip appears unchanged in
> > wireshark.
> >
> > Do these IP based elements expect the ethernet header to be stripped
> > off, or explicitly told the position relative to the start of an
> > ethernet header? I seem to remember seeing something like this when I
> > started reading the docs ... but I can't find that now.
> >
> > thanks
> >
> > Daniel
> > _______________________________________________
> > click mailing list
> > click at amsterdam.lcs.mit.edu
> > https://amsterdam.lcs.mit.edu/mailman/listinfo/click
> >
>


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