Re: netsnmp_create_handler_registration

Many thanks,

For pointing me in the right direction.

It took me some time with the debugger to find out where I can get this 
mysterious (x) - well I did know that it was the reqinfo->mode pointer you 
explained, but I didn't know how to get it -.

Converting my .so to executable, so that I can use the debugger, I 
discovered amidst a few function pointers, that custom handlers are actually 
called with 4 arguments. This I discovered no more or less by comparing 
function addresses to my own handler address:

__inline__ static int handler(netsnmp_mib_handler *handler, 
netsnmp_handler_registration *reginfo, netsnmp_agent_request_info *areqinfo, 
netsnmp_request_info *reqinfo)

Uptill now I thought that it was just an empty variable list (Remember an 
older mail of mine asking about calling conventions for handlers?). So the 
required variable is areqinfo->mode.

I think it deserves both a FAQ and a wiki spot. I have to leave on a 
business trip, but when I come back (end of January) I intend to document my 
experiences with custom handlers. Maybe you can tell me then how best to go 
about it.

BR,
Nikos
----- Original Message ----- 
From: "Wes Hardaker" <[email protected]>
To: "Nikos Balkanas" <[email protected]>
Cc: <[email protected]>
Sent: Monday, January 05, 2009 6:19 PM
Subject: Re: netsnmp_create_handler_registration


>>>>>> On Sat, 3 Jan 2009 15:33:51 +0200, "Nikos Balkanas" 
>>>>>> <[email protected]> said:
>
> NB> During a SET operation the custom handler will be called 4 times, 2
> NB> with old values and 2 with new ones (Reserve1, Reserve2, Action,
> NB> Commit).
>
> The values in the varbinds are always the new ones (IE, the ones from
> the SET packet).
>
> NB> If the same handler is used also for GET operations
> NB> (HANDLER_CAN_RWRITE) will be called once only (let's call it
> NB> Reserve1).
>
> It's called GET actually :-)
>
> NB> How can one distinguish between GET and SET calls?
>
> The reqinfo->mode variable will be set to one of (snmp_agent.h):
>
> #define MODE_GET              SNMP_MSG_GET
> #define MODE_GETNEXT          SNMP_MSG_GETNEXT
> #define MODE_GETBULK          SNMP_MSG_GETBULK
> #define MODE_GET_STASH        SNMP_MSG_INTERNAL_GET_STASH
>
> #define MODE_SET_BEGIN        SNMP_MSG_INTERNAL_SET_BEGIN
> #define MODE_SET_RESERVE1     SNMP_MSG_INTERNAL_SET_RESERVE1
> #define MODE_SET_RESERVE2     SNMP_MSG_INTERNAL_SET_RESERVE2
> #define MODE_SET_ACTION       SNMP_MSG_INTERNAL_SET_ACTION
> #define MODE_SET_COMMIT       SNMP_MSG_INTERNAL_SET_COMMIT
> #define MODE_SET_FREE         SNMP_MSG_INTERNAL_SET_FREE
> #define MODE_SET_UNDO         SNMP_MSG_INTERNAL_SET_UNDO
>
> There is even a MODE_IS_GET(x) macro that tells you if the incoming mode
> is a GET type vs a SET type operation.
>
>
> -- 
> Wes Hardaker
> Sparta, Inc. 


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