[Click] control packetflow

[Eddie Kohler]

Michael Neufeld wrote:
> If you aren't already using the "Paint" annotation for something, I'd be 
> tempted to use that. So instead of Element A controlling Element B 
> directly, it'd paint packets depending on its current state. Downstream, 
> Element B would examine the Paint annotation and do the approprate 
> splitting/duplication.
...

Hi all,

Mike's solution will totally work.

Another way to do it would be with a plain old Switch element (plus a Tee). 
Then you could change the flow control with a write handler, rather than the 
per-packet Paint annotation.

elementclass SwitchFlowControl {
    input -> sw :: Switch(0) -> [0] output;
    sw [1] -> [1] output;
    sw [2] -> t :: Tee -> [0] output;
              t [1] -> [1] output;
}
sfc :: SwitchFlowControl; ...

Then:   echo 0 > /click/sfc/sw/switch      # sends only to sfc's 1st output
         echo 1 > /click/sfc/sw/switch      # sends only to sfc's 2nd output
         echo 2 > /click/sfc/sw/switch      # sends to both sfc's outputs

Elements can call each others' handlers too, of course.

Eddie