Re: [pysnmp-users] pysnmp / pyasn1 decode problem with multi-line traps

[Tom Kr. <to...@we...>]

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
>>> 
>