[Click] LLRPC Examples

[Eddie Kohler]

Cliff Frey wrote:
> please always include the click mailing list in your replies (but I messed
> this up too, so sorry about that).
> 
> The documentation is confusing.  Because you *can* sent arguments to a read
> handler (and a read handler can modify state).

I agree that the docs here are a little confusing, but it's not clear 
immediately how to improve them.  Should ReadHandler be called something else 
-- like SimpleReadHandler?  It would perhaps be cleanest to remove it 
entirely, but too incompatible.

Eddie

> 
> I would grep for READ_PARAM in the elements/ directory.  I would look at
> IPRouteTable's 'lookup' handler for an example.
> 
> Cliff
> 
> 
> On Fri, May 14, 2010 at 10:25 AM, Sanhueza, Patricio <
> patricio.sanhueza at gdcanada.com> wrote:
> 
>>  Hi Cliff
>>
>>
>>
>> Sorry, it stemmed from misreading/misinterpreting the following line on the
>> click website
>>
>>
>>
>> There is currently no way to *pass data to a read handler *or *return data
>> from a write handler*. Use LLRPCs if you need a more RPC-like read-write
>> interface
>>
>>
>>
>> http://read.cs.ucla.edu/click/element
>>
>>
>>
>> I am kind of confused as how to pass data into a read handler? Or get data
>> back from a write handler? How do the optional parameters work in
>>
>> *READ **handler** [**params…**]*
>>
>> Call a read *handler*, passing the *params*, if any, as arguments, and
>> return the results. On success, responds with a "success" message (response
>> code 2xy) followed by a line like "DATA *n*". Here, *n* is a decimal
>> integer indicating the length of the read handler data. The *n* bytes
>> immediately following (the CRLF that terminates) the DATA line are the
>> handler's results.
>>
>>
>>
>> The callback signature for a read handler is
>>
>>
>>
>> String (*ReadHandler) (Element *element, void *thunk) //how to I get access
>> to the parameters?
>>
>>
>>
>>
>>
>> Essentially I need an interface into an element that I can pass data into
>> it, and it return data back, so that is why I was looking into the LLRPC
>> mechanism instead.
>>
>>
>>
>> I looked at the ControlSocket documentation but I am looking for a concrete
>> example.
>>
>>
>>
>> Example::  LLRPC counter#0xC004C001 4 ????
>>
>>
>>
>> Thanks,
>>
>>
>>
>> Patricio
>>
>>
>>
>> *From:* Cliff Frey [mailto:cliff at meraki.com]
>> *Sent:* Friday, May 14, 2010 11:01 AM
>> *To:* Sanhueza, Patricio
>> *Subject:* Re: [Click] LLRPC Examples
>>
>>
>>
>> look at the documentation for ControlSocket
>> http://read.cs.ucla.edu/click/elements/controlsocket
>>
>>
>>
>> Although I'm curious why you are interested in the LLRPC mechanism.  It is
>> generally much easier to use read, write, or read+param handlers to
>> implement this sort of functionality (these can also be accessed over
>> controlsocket).
>>
>>
>>
>> Cliff
>>
>> On Fri, May 14, 2010 at 6:44 AM, Sanhueza, Patricio <
>> patricio.sanhueza at gdcanada.com> wrote:
>>
>> Hello
>>
>> I am wondering if I can get an example of using LLRPC with say the
>> Counter element? More specifically, what would be the server command
>> message sent to the ControlSocket to get the count? I am trying to test
>> this on the standard elements before implementing a custom one. Also, is
>> there any documentation on LLRPC within click that I can get my hands
>> on? There is paper on the Internet called "Programming the Click Modular
>> Router", but the LLRPC section is empty.
>>
>> Patricio
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
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