[Click] Elements handlers

[Marko Zec]

On Friday 11 March 2005 14:24, Rafael Paoliello Guimaraes wrote:
> Ok... But this will just print the result. And I want to return the
> result, not to print it. Just like what it is done by read
> handlers... But the only difference with respect to read handlers is
> that I want to pass some arguments to this handler.


Hi Rafael,

can you try the attached patch, it introduces the "readparam" handler 
access method for the userspace click.  It should allow you to do things 
like this:

tpx30% telnet localhost 4444
...
Click::ControlSocket/1.1
readparam rt.lookup 1.2.3.5
200 Read handler 'rt.lookup' OK
DATA 10
3 5.6.7.8

Take a look at lookup_handler() in elements/ip/iproutetable.cc as an 
example on how to implement read handlers that accept arguments.  OTOH, 
I'm not sure if/how we could support such a "parameterized" read model 
in the kernel-space click using the filesystem interface...

Hope this helps,

Marko



>
> Cheers,
>
> ===========================================
>   Rafael Paoliello Guimaraes
>   PhD Student - Computer Networking Group
>   Department of Computer Architecture (DAC)
>   Polytechnic University of Catalonia (UPC)
>   Phone: +34-934017187   Fax: +34-934017055
>   URL: http://people.ac.upc.es/rpaoliel
> ===========================================
>
> Beyers Cronje wrote:
> > PS When I say "return the results" I meant via click_chatter().
> >
> > -----Original Message-----
> > From: Beyers Cronje
> > Sent: Friday, March 11, 2005 3:09 PM
> > To: 'Rafael Paoliello Guimaraes'
> > Cc: click at amsterdam.lcs.mit.edu
> > Subject: RE: [Click] Elements handlers
> >
> >
> > Hi Rafael,
> >
> > A standard Write handler should do the trick. Just pass the
> > argument the your "routes" handler and do the neccesary lookups
> > inside your handler routine and return the results.
> >
> > Beyers
> >
> > -----Original Message-----
> > From: click-bounces at amsterdam.lcs.mit.edu
> > [mailto:click-bounces at amsterdam.lcs.mit.edu]On Behalf Of Rafael
> > Paoliello Guimaraes
> > Sent: Friday, March 11, 2005 2:31 PM
> > To: Marko Zec
> > Cc: click at amsterdam.lcs.mit.edu
> > Subject: Re: [Click] Elements handlers
> >
> >
> > Ok, I know this. I have done this with read handlers and write
> > handlers... I have even read that if I want a read/write handler, I
> > should register two handlers with the same name, one for write and
> > one for read. But my case is different. I want to register a
> > handler that is read and write at the same time. For example, in
> > the LinearIPLookup table there is a read handler called "table"
> > that simply returns the routing table. Well, suppose I wanted to
> > provide an additional handler (routes) that given a destination
> > address, would return the entries on the routing table that could
> > be use to route data to this address... How thid could be done?
> >
> > Example:
> >
> > if the routing table is:
> >
> > DST           OUT
> > 10.0.2.0/24   1
> > 20.7.4.0/24   2
> > 10.0.0.0/16   1
> >
> > if I called this new handler like this: routes(10.0.2.1)
> > it would return me the following string:
> >
> > 10.0.2.0/24   1
> > 10.0.0.0/16   1
> >
> > Is it possible to be implemented (or is there any alternative way
> > to do this), or would I have to modify the Element class?
> >
> > Cheers,
> >
> > ===========================================
> >   Rafael Paoliello Guimaraes
> >   PhD Student - Computer Networking Group
> >   Department of Computer Architecture (DAC)
> >   Polytechnic University of Catalonia (UPC)
> >   Phone: +34-934017187   Fax: +34-934017055
> >   URL: http://people.ac.upc.es/rpaoliel
> > ===========================================
> >
> > Marko Zec wrote:
> >>On Thursday 10 March 2005 21:22, Rafael Paoliello Guimaraes wrote:
> >>>Hi,
> >>>
> >>>I am writing some new Click elements and I have a doubt concerning
> >>>the handlers of an element. I have seen read handler and write
> >>>handlers implemented, but I have not seen any read/write handler.
> >>> Is there this possibility? I want the handler to return me a
> >>> string based on some arguments I introduce.
> >>>
> >>>I have implemented the following handler:
> >>>
> >>>String
> >>>MyElement::thehandler_handler(const String &conf_in, Element *e,
> >>> void *thunk, ErrorHandler *errh)
> >>>
> >>>
> >>>But I don't know how to add it to the element? Is this right? How
> >>>should I do it?
> >>
> >>The Element class provides the add_handlers() virtual function
> >> which you may override to explicitely export custom handler hooks.
> >>  Just grep through existing elements for add_handlers...
> >>
> >>Marko
> >
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