Re: [pysnmp-users] pysnmp / pyasn1 decode problem with multi-line traps
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Re: [pysnmp-users] pysnmp / pyasn1 decode problem with multi-line traps
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From: Ilya E. <il...@gl...> - 2015-03-16 10:33:21
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Hi Tom,
You can check it like this:
from pyasn1.type.univ import OctetString
if isinstance(val, OctetString):
val = str(val)
...
The str() part is important because you are getting pyasn1 objects in
response while "re" expects strings.
-ilya
On 03/16/2015 01:15 PM, Tom Kr. wrote:
> Some good news to the beginning of the new week.
> After I changed the method from .getVarBindsList() to .getVarBinds(), I can read the data with the stupid line feed.
>
> Now I tried to search and replace the line feed with this lines
> for oid, val in varBinds:
> print("DEBUG_oid: %s" % oid)
> print("DEUBG_val: %s" % val)
> new_val = "".join(val)
> val = re.sub(r"[\r|\s]", "", new_val)
> print("DEBUG_oid_2: %s" % oid)
> print("DEBUG_val_2: %s" % val)
>
> Each time there is a trap with this characters I get this error message.
> return _compile(pattern, flags).sub(repl, string, count)
> ;TypeError: expected string or buffer
>
> How can I find out which type the val variable have?
> And how can I change this to string?
>
> Tom
>
>
>
>> Am 12.03.2015 um 16:18 schrieb Ilya Etingof <il...@gl...>:
>>
>>
>> Right, in 'val' you are getting the whole SNMP PDU value structure, not just a leaf scalar. That's the reason it does not match OctetString class instance check.
>>
>> Use .getVarBinds() method instead of .getVarBindsList(). The former returns a list of tuples of terminal values, while the latter returns original var-bindings list from SNMP PDU which always holds a record-like structure for value.
>>
>> -ilya
>>
>>> On 03/12/2015 05:29 PM, Tom Kr. wrote:
>>> Hmm, I'm confused.
>>> With this changes I also get hex values back and I still enter the else part for each value.
>>> import sys,os
>>> sys.path.append('/usr/share/pyshared/')
>>> from pysnmp.carrier.asynsock.dispatch import AsynsockDispatcher
>>> from pysnmp.carrier.asynsock.dgram import udp, udp6
>>> from pyasn1.codec.ber import decoder
>>> from pysnmp.proto import api
>>> #from pysnmp.proto.rfc1902 import OctetString
>>> from pyasn1.type.univ import OctetString
>>> def pySnmpCheck(oval):
>>> if isinstance(oval, OctetString):
>>> print("DEBUG: OctetString")
>>> val = oval.asOctets()
>>> else:
>>> print("DEBUG: else")
>>> val = oval
>>> return val
>>> If this information are useful, this is the header I've got.
>>> # python snmp-transports.py
>>> Notification message from (1, 3, 6, 1, 6, 1, 1):('xxx.xxx.xxx.xxx', 52032):
>>> Enterprise: 1.3.6.1.4.1.18494.2
>>> Agent Address: xxx.xxx.xxx.xxx
>>> Generic Trap: 'enterpriseSpecific'
>>> Specific Trap: 1
>>> Uptime: 1
>>> Var-binds:
>>> DEBUG: else
>>> 1.3.6.1.4.1.18494.2.1.9 = ObjectSyntax:
>>> simple=SimpleSyntax:
>>> string=0x4f70657261746f722058585858585858585858203a20585858585858585858582c2058585858585858202c204c6f63616c6c792061757468656e74696361746564202d207375636365737366756c6c79207369676e6564206f6e20746f20746865207465726d696e616c20275858582e5858582e582e584058272061742031343a3238207573696e672027585858585858585820585858205858585858585858272e0a4f70657261746f722050726f66696c65733a2058585858585858585858585858
>>> Tom
>>>
>>>
>>>
>>>> Am 12.03.2015 um 14:39 schrieb Ilya Etingof <il...@gl...>:
>>>>
>>>>
>>>> Oh, if you are using SNMPv1 you should check against the base class:
>>>>
>>>> from pyasn1.type.univ import OctetString
>>>>
>>>> if isinstance(oval, OctetString):
>>>> ...
>>>>
>>>> Perhaps this should be improved in pysnmp.
>>>>
>>>> -ilya
>>>>
>>>>> On 03/12/2015 04:29 PM, Tom Kr. wrote:
>>>>> I made the following changes to the script.
>>>>> ...
>>>>> from pysnmp.proto.rfc1902 import OctetString
>>>>> def pySnmpCheck(oval):
>>>>> if isinstance(oval, OctetString):
>>>>> print("DEBUG: OctetString")
>>>>> val = oval.asOctets()
>>>>> else:
>>>>> print("DEBUG: else")
>>>>> val = oval
>>>>> return val
>>>>> ...
>>>>> for oid, val in varBinds:
>>>>> val = pySnmpCheck(val)
>>>>> print('%s = %s' % (oid.prettyPrint(), val.prettyPrint()))
>>>>> ...
>>>>> Then I start grabbing the snmp messages again.
>>>>> Unfortunately every value of the message go through the else part.
>>>>> But how could this happen?
>>>>> Is there a possibility to check which type of string the values have?
>>>>> Tom
>>>>>
>>>>>
>>>>>
>>>>>> Am 11.03.2015 um 14:17 schrieb Ilya Etingof <il...@gl...>:
>>>>>>
>>>>>>
>>>>>> That's right, .asOctets() is only defined for OctetString type and its
>>>>>> subclasses. Therefore, to deal with octets of OctetString() you should
>>>>>> do additional check:
>>>>>>
>>>>>> from pysnmp.proto.rfc1902 import OctetString
>>>>>>
>>>>>> ...
>>>>>>
>>>>>> if isinstance(val, OctetString):
>>>>>> val = val.asOctets()
>>>>>>
>>>>>> Keep in mind that octet string is not always the same as printable
>>>>>> string. The former is not immune to your terminal potentially eating
>>>>>> non-printable characters or garbling output in a funny way. Also, text
>>>>>> encoding is not defined by OctetString. To be on a safe side default
>>>>>> OctetString printout is done in hex whenever a non-printable is seen in
>>>>>> its contents.
>>>>>>
>>>>>> -ilya
>>>>>>
>>>>>>>> On 03/11/2015 03:18 PM, Craig Small wrote:
>>>>>>>> On Wed, Mar 11, 2015 at 07:02:44AM +0100, Tom wrote:
>>>>>>>> ;AttributeError: ObjectSyntax instance has no attribute 'asOctets'
>>>>>>> Are you sure each row is returning something asOctets makes sense for?
>>>>>>> An Integer doesn't make sense.
>>>>>>>
>>>>>>>> Does it only works if a hex value is send by snmp?
>>>>>>> I believe it works for certain types of values, such as an OctetString
>>>>>>>
>>>>>>>> How can I check if the value is hex or not?
>>>>>>> Not sure, but the types are found in pyasn1.type.univ so you could
>>>>>>> compare it to, say, univ.OctetString
>>>>>>>
>>>>>>> ObjectSyntax seems to be the superset of all types, from what I can tell
>>>>>>> it means pysnmp wasn't sure what the type should be.
>>>>>>>
>>>>>>> It's been an interesting and educational discussion anyhow.
>>>>>>>
>>>>>>> - Craig
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