[Click] Alignment problem on ARM

[Cliff Frey]

So the problem is that the aligninfo is incorrect for either FromDevice,
AthdescDecap, or WifiDecap.

looking at tools/click-align/click-align.cc, you can see that FromDevice is
assumed to push out packets with alignment 2 4, and neither AthdescDecap or
WifiDecap are mentioned, which should mean that they are assumed to not
affect the alignment (they only pull multiples of 4 bytes).

If AthdescDecap or WifiDecap actually do something different, you can fix
the issue in click-align.cc by adding the offending class.  If FromDevice is
actually pushing out packets of alignment 4 0, then that is a very weird
driver that you are using, and I'm not sure what the best next step would
be... perhaps adding a configuration parameter to FromDevice that
click-align could look at... or fixing your ethernet driver to be
standard...  I'm not sure.

You can more easily test which element is misbehaving by adding Align()
elements to your config, enabling CLICK_ALIGN_COUNT in
elements/standard/align.hh, and looking to see which Align elements are
doing anything.

Cliff

On Thu, Jan 21, 2010 at 3:46 AM, Roberto Riggio <
roberto.riggio at create-net.org> wrote:

> Hi,
>
> I have a problem with click on an Intel ixp4xx platform (arm).
>
> This is the script I'm using:
>
>
> FromDevice(moni0)->AthdescDecap()->WifiDecap()->Classifier(12/06??)->Print()->Discard();
>
> If I run click-align on that script i get the following output:
>
> # 1 "<stdin>"
> FromDevice at 1 :: FromDevice(moni0);
> # 1 "<stdin>"
> AthdescDecap at 2 :: AthdescDecap;
> # 1 "<stdin>"
> WifiDecap at 3 :: WifiDecap;
> # 1 "<stdin>"
> Classifier at 4 :: Classifier(12/06??);
> # 1 "<stdin>"
> Print at 5 :: Print;
> # 1 "<stdin>"
> Discard at 6 :: Discard;
> # 0 "<click-align>"
> AlignmentInfo at click_align@7 :: AlignmentInfo(Classifier at 4  4 2);
> # 16 ""
> FromDevice at 1 -> AthdescDecap at 2
>     -> WifiDecap at 3
>     -> Classifier at 4
>     -> Print at 5
>     -> Discard at 6;
>
> However the alignment info is wrong, it should be
> AlignmentInfo(Classifier at 4  4 0). In fact
> if I edit the click-align output manually the router works fine.
>
> R.
>
>
> _______________________________________________
> click mailing list
> click at amsterdam.lcs.mit.edu
> https://amsterdam.lcs.mit.edu/mailman/listinfo/click
>