[Click] Click-align questions

[Eddie Kohler]

Kevin,

Thanks for this longago problem report.

There were several bugs you found, including
- click-align didn't know what Unstrip did;
- click-align's support for CheckIPHeader config arguments had rotted;
- if click-align created an intermediate config with two connected Aligns, and 
neither was needed, it would only remove one of them.

All of these bugs should now be fixed.  Sorry for the delay.

Eddie


springbo at cs.wisc.edu wrote:
> Hello,
> 
> I've run into some issues with click-align. Anything to get me going along
> the correct path would be greatly appreciated.
> 
> Click-align adds the align elements needed, but does not seem to add the
> elements needed to transform the packets back to the alignment needed to
> pass the packet to the host [ToHost()]. So if I pass a packet to the host
> downstream of a CheckIPHeader in an click-aligned configuration
> ('click-align test1.click'), then a dump from the host results in
> unaligned data. But if I manually change back to the correct alignment the
> traffic is correctly captured ('click-align test2.click').
> 
>>From there I decided to manually enter the correct alignments before
> passing data to the host, but the manual aligns seem to cause issues with
> click-align. Running click-align on test3.click generated an invalid
> configuration. The last line of the configuration has an align element
> with no input. Are manual aligns with click-align not a good idea?
> 
> Is there way to automatically reset alignment before passing ToHost, or
> better yet is there a way to get click-align to transform the alignment
> back? Or am I missing something?
> 
> These results were seen on both a 686 FC6 2.6.19.2 virtual machine and a
> x86_64 CentOs5 2.6.19.2 box. I downloaded and built the most recent dev
> tree this morning (click-align --version => click-align (Click) 1.6.0).
> 
> Also, it does not seem that click-align catches mis-alignments do to
> arguments passed to CheckIPHeader. Such that CheckIPHeader(14) still
> results in "warning: IP header unaligned, cannot use fast IP checksum"
> even after being passed through click-align. From the documentation of
> click-align I cannot tell if this is intended or not.
> 
> Thanks for any help,
> Kevin Springborn
> 
> 
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