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

[Beyers Cronje]

You dont have to use Stip/Unstrip. You can also specify the IP header offset
by specifying it in MarkIPHeader or CheckIPHeader.

I.e.
ipc::IPClassifier( ip proto udp, - );
ip::Classifier(12/0800); // Filter on IP Packets
FromDevice(eth0) ->  ip -> MarkIPHeader(14) -> ipc;
ipc[0] -> Queue -> ToDevice( eth1 );
ipc[1] -> Discard;

Regards

Beyers

On 10/25/07, Seth Hall <hall.692 at osu.edu> wrote:
>
> I believe that unstrip should do what you want if you want the
> original ethernet header put back.
>     http://read.cs.ucla.edu/click/elements/unstrip
>
> You can build your own ethernet header with etherencap.
>
>   .Seth
>
> On Oct 25, 2007, at 2:12 PM, Daniel McBrearty wrote:
>
> > 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
> >>>
> >>
> >
> >
> > --
> > Daniel McBrearty
> > email : danielmcbrearty at gmail.com
> > http://www.engoi.com
> > http://danmcb.vox.com
> > http://danmcb.blogger.com
> > find me on linkedin and facebook
> > BTW : 0873928131
> > _______________________________________________
> > click mailing list
> > click at amsterdam.lcs.mit.edu
> > https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>
> ---
> Seth Hall
> Network Security - Office of the CIO
> The Ohio State University
> Phone: 614-292-9721
>
>
>
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