[Click] Alignment problem on ARM

[Roberto Riggio]

Actually wifidecal pulls 8 bytes (wifi header + llc) and pushes 14 bytes 
(ethernet header), shouldn't this require
the 2 bytes offset Align(4 2)?

R.

On 01/21/2010 07:24 PM, Cliff Frey wrote:
> 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 <mailto: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.
>
>
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