writeCommit problem

[korwin7474]

Im managing a variable that can assume '0' or '1' value.
if generic mib browser try to set '3' an exception make the agent crash.
of course i can try-except that, but im not able to send to client (mib browser) the error.
Thats the code on my pythonized mib:

def writeTest(self, varBind, **context):
    cbFun = context['cbFun']
    name, value = varBind
    if value in [0,1]:
        cbFun(varBind, **context)
    else:
        pass


def writeCommit(self, varBind, **context):
    # Put your code here
    print("arrivato al write commit")
    cbFun = context['cbFun']
    name, value = varBind
    cbFun((name, value), **context)
    my_agent.setcConnection(value)

can anyone help me?
Thanks

[etingof]

One thing is that you should always call cbFun. Otherwise internal state machine stalls.

To indicate an error you should add error key to **context. That should stop and rollback the whole request, then report SNMP error back to the browser.

[korwin7474]

Thank you, Ilya, I've updated my writeTest method as reported.

def writeTest(self, varBind, **context):
    print("status n.1",context['status'])
    cbFun = context['cbFun']
    name, value = varBind
    my_test = not( value in [0,1] )
    try:
        self.getOK(my_test,name,**context)
    except (pysnmp.smi.error.WrongValueError) as exc:
        context = dict(dict(context, error=exc))
        cbFun(varBind, **context) 
        print("status n.2",context['status'])
    else:
        print("test OK")
        cbFun(varBind, **context)
    print("status n.3",context['status'])

If i try (using mib browser) to set an out of range value (i.e. "3") the varialble is correctly not updated, but mib browser get timed out in response.
Context status :
status n.1 ok
status n.2 ok
status n.3 ok
but, i expected to read "status n.2 err"

Thank you for helping me.

[etingof]

Looking at the code, I am guessing that may be something is missing to respond an error back... I wonder if you could run snmpresponder with debugging enabled to see where the request ends up. That would be helpful.

[korwin7474]

that's what i can't understand:
.....
2019-06-20 17:05:26,366 flipFlopFsm: state writeCleanup status err -> transitioned into state stop
2019-06-20 17:05:26,370 sendVarBinds: stateReference 15457236, errorStatus 0, errorIndex 0, varBinds
.....

The status looks to pass from error to OK.