[pysnmp-dev] Can't get ConstraintsUnion to fail

[Graham H. <gr...@ze...>]

Hi

I'm playing with a MIB where I want to experiment with the range of values
allowed for a particular param.

This is with PySNMP 4.2.5, PyASN1 0.1.9 on Ubuntu 16.04.1 with Python 2.7.

The current syntax for the param is:

SYNTAX Integer32(2..10)

and, indeed, if the agent sends a value outside that range (say, 12), an
exception is thrown. Great.

The problem is that if I alter that syntax to:

SYNTAX Integer32(0|2..10)

and re-run the bulkCmd(), the operation now succeeds even though the agent
is still sending an illegal value (12).

When I examine the output from compiling the MIB file, I can see that the
old code:

someParam = MibTableColumn((1, 2, 3, 4),
Integer32().subtype(subtypeSpec=ValueRangeConstraint(2,
10))).setMaxAccess("readonly")

has become what seems sensible:

someParam = MibTableColumn((1, 2, 3, 4),
Integer32().subtype(subtypeSpec=ConstraintsUnion(ValueRangeConstraint(0,0),ValueRangeConstraint(2,10),))).setMaxAccess("readonly")

However, when I breakpoint through the code, I can see that it gets into:

pyasn1/type/constraint.py(192)_testValue():
-> v(value, idx)
(Pdb) print self
ConstraintsUnion(ConstraintsUnion(ValueRangeConstraint(0, 0),
ValueRangeConstraint(2, 10)),
ConstraintsIntersection(ConstraintsIntersection(),
ValueRangeConstraint(-2147483648, 2147483647)))

and this looks wrong to me. I can see that the "inner" ConstraintsUnion
will fail, but won't the ConstraintsIntersection succeed, meaning that the
"outer" ConstraintsUnion will also succeed ?

My apologies if this is too terse a description, I can provide more detail
if you require.

Regards,

Graham


-- 


*Graham Hudspith      Zeetta Networks Limited*Software Engineer    Engine
Shed, Station Approach,
gr...@ze...    Temple Meads,
                     Bristol,
                     BS1 6QH
                     United Kingdom
                     zeetta.com <http://www.zeetta.com/>