Re: [pysnmp-users] pySNMP error handling - OSError: [Errno 64] Host is down - exception created ins

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Hi All,

Another observation is that it seems to work fine first time:

Returns:

No SNMP response received before timeout

But then errors out after. if I wait a decent time (60-120 seconds) then it works again the first time, but bombs out again.

Might have to do with networking / caching.

Regards,

Frank

On 14 Jul 2017, at 21:25, Frank <in...@ho...<mailto:in...@ho...>> wrote:

Hi,

Just FYI, The error is identical using Python 3.5: (Apologies - should have sent 3.5 in the first place!).

10.10.10.10
  SNMPv1 community string 'public' on port '161:
Traceback (most recent call last):
  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 142, in handle_write
    self.socket, outgoingMessage, transportAddress
  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 35, in <lambda>
    self._sendto = lambda s, b, a: s.sendto(b, a)
OSError: [Errno 65] No route to host

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/carrier/asyncore/dispatch.py", line 46, in runDispatcher
    use_poll=True, map=self.__sockMap, count=1)
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/asyncore.py", line 207, in loop
    poll_fun(timeout, map)
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/asyncore.py", line 188, in poll2
    readwrite(obj, flags)
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/asyncore.py", line 123, in readwrite
    obj.handle_error()
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/asyncore.py", line 110, in readwrite
    obj.handle_write_event()
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/asyncore.py", line 442, in handle_write_event
    self.handle_write()
  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 148, in handle_write
    raise error.CarrierError('sendto() failed for %s: %s' % (transportAddress, sys.exc_info()[1]))
pysnmp.carrier.error.CarrierError: sendto() failed for ('10.10.10.10', 161): [Errno 65] No route to host

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "./networking.py", line 71, in <module>
    main()
  File "./networking.py", line 66, in main
    snmp_query(['10.10.10.10', '10.10.10.20'], 'v1/public:161', ['1.3.6.1.2.1.1.2.0', '1.3.6.1.2.1.1.1.0'])
  File "./networking.py", line 28, in snmp_query
    result = snmp_get(target, snmp_str, snmp_port, oids, int(snmp_ver[1:]))
  File "./networking.py", line 41, in snmp_get
    *snmp_oids)
  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/entity/rfc3413/oneliner/cmdgen.py", line 183, in getCmd
    **kwargs):
  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/hlapi/asyncore/sync/cmdgen.py", line 113, in getCmd
    snmpEngine.transportDispatcher.runDispatcher()
  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/carrier/asyncore/dispatch.py", line 50, in runDispatcher
    raise PySnmpError('poll error: %s' % ';'.join(format_exception(*exc_info())))
pysnmp.error.PySnmpError: poll error: Traceback (most recent call last):
;  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 142, in handle_write
    self.socket, outgoingMessage, transportAddress
;  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 35, in <lambda>
    self._sendto = lambda s, b, a: s.sendto(b, a)
;OSError: [Errno 65] No route to host
;
During handling of the above exception, another exception occurred:

;Traceback (most recent call last):
;  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/carrier/asyncore/dispatch.py", line 46, in runDispatcher
    use_poll=True, map=self.__sockMap, count=1)
;  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/asyncore.py", line 207, in loop
    poll_fun(timeout, map)
;  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/asyncore.py", line 188, in poll2
    readwrite(obj, flags)
;  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/asyncore.py", line 123, in readwrite
    obj.handle_error()
;  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/asyncore.py", line 110, in readwrite
    obj.handle_write_event()
;  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/asyncore.py", line 442, in handle_write_event
    self.handle_write()
;  File "/Users/guardian/Sync/Projects/test/lib/python3.5/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 148, in handle_write
    raise error.CarrierError('sendto() failed for %s: %s' % (transportAddress, sys.exc_info()[1]))
;pysnmp.carrier.error.CarrierError: sendto() failed for ('10.10.10.10', 161): [Errno 65] No route to host

Pretty much identical as in 3.6.1 and no - I didn't just do a search and replace!!! :D

Frank

On 14 Jul 2017, at 20:45, Frank Tonjes <in...@ho...<mailto:in...@ho...>> wrote:

Hi All,

I've only been using Python since Dec last year, so please excuse my lack of Knowledge, but I'm trying to write a script which tests polling before adding the devices in our 3rd party tools. One of the tests are SNMP. Currently I'm looking at just the SNMP v1/v2c as most of our devices fall into this category (well most are v2c with some old stuff on v1).

I've found some examples online and looked at examples others have used and come up with this 'test' script. It's only to test, so I know it's not following good python practice!!!:

#!/usr/bin/env python

import re
from pysnmp.hlapi import *
from pysnmp.entity.rfc3413.oneliner import cmdgen

def snmp_query(targets, sequence, oids):

    # If we get single strings, make it a list with 1 item in it!
    if isinstance(targets, str):
        targets = list([targets])

    if isinstance(oids, str):
        oids = list([oids])

    for target in targets:
        print(target)

        for seq in str.split(sequence, sep=','):

            info = re.search(r'^(v[123])/(.*):(\d+)$', seq)
            if info:

                (snmp_ver, snmp_str, snmp_port) = (info.group(1), info.group(2), info.group(3))
                print("  SNMP{0} community string '{1}' on port '{2}:".format(snmp_ver, snmp_str, snmp_port))

                if snmp_ver == 'v1' or snmp_ver == 'v2':
                    result = snmp_get(target, snmp_str, snmp_port, oids, int(snmp_ver[1:]))
                    print(result)

    exit()

def snmp_get(host, snmp_community, snmp_port, snmp_oids, snmp_ver):

    cgen = cmdgen.CommandGenerator()

    if snmp_ver == 1:
        error_indication, error_status, error_index, varbinds = cgen.getCmd(
            cmdgen.CommunityData(snmp_community, mpModel=0), cmdgen.UdpTransportTarget((host, snmp_port)),
            *snmp_oids)
    elif snmp_ver == 2:
        error_indication, error_status, error_index, varbinds = cgen.getCmd(
            cmdgen.CommunityData(snmp_community), cmdgen.UdpTransportTarget((host, snmp_port)),
            *snmp_oids)
    else:
        print("\n  ERROR: Only snmp_ver of '1' or '2' is supported using snmp_get!")
        exit()

    if error_indication:
        return error_indication
    elif error_status:
        return '%s at %s' % (error_status.prettyPrint(), error_index and varbinds[int(error_index) - 1][0] or '?')
    else:
        result = {}
        for varbind in varbinds:

            oid, value = varbind
            result[str(oid)] = str(value)

        return result

def main():

    snmp_query(['10.10.10.10', '10.10.10.20'], 'v1/public:161', ['1.3.6.1.2.1.1.2.0', '1.3.6.1.2.1.1.1.0'])
    exit()

if __name__ == "__main__":
    main()

It seems to be failing with pysnmp somewhere and doesn't return any errors within the error handling I've copied from the example section in PySNMP documentation:

The output after running the script is:

10.10.10.10
  SNMPv1 community string ‘public' on port '161:
Traceback (most recent call last):
  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 142, in handle_write
    self.socket, outgoingMessage, transportAddress
  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 35, in <lambda>
    self._sendto = lambda s, b, a: s.sendto(b, a)
OSError: [Errno 64] Host is down

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/carrier/asyncore/dispatch.py", line 46, in runDispatcher
    use_poll=True, map=self.__sockMap, count=1)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncore.py", line 207, in loop
    poll_fun(timeout, map)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncore.py", line 188, in poll2
    readwrite(obj, flags)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncore.py", line 123, in readwrite
    obj.handle_error()
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncore.py", line 110, in readwrite
    obj.handle_write_event()
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncore.py", line 442, in handle_write_event
    self.handle_write()
  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 148, in handle_write
    raise error.CarrierError('sendto() failed for %s: %s' % (transportAddress, sys.exc_info()[1]))
pysnmp.carrier.error.CarrierError: sendto() failed for ('10.10.10.10', 161): [Errno 64] Host is down

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "./networking.py", line 71, in <module>
    main()
  File "./networking.py", line 66, in main
    snmp_query(['10.10.10.10', '10.10.10.20'], 'v1/public:161', ['1.3.6.1.2.1.1.2.0', '1.3.6.1.2.1.1.1.0'])
  File "./networking.py", line 28, in snmp_query
    result = snmp_get(target, snmp_str, snmp_port, oids, int(snmp_ver[1:]))
  File "./networking.py", line 41, in snmp_get
    *snmp_oids)
  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/entity/rfc3413/oneliner/cmdgen.py", line 183, in getCmd
    **kwargs):
  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/hlapi/asyncore/sync/cmdgen.py", line 113, in getCmd
    snmpEngine.transportDispatcher.runDispatcher()
  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/carrier/asyncore/dispatch.py", line 50, in runDispatcher
    raise PySnmpError('poll error: %s' % ';'.join(format_exception(*exc_info())))
pysnmp.error.PySnmpError: poll error: Traceback (most recent call last):
;  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 142, in handle_write
    self.socket, outgoingMessage, transportAddress
;  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 35, in <lambda>
    self._sendto = lambda s, b, a: s.sendto(b, a)
;OSError: [Errno 64] Host is down
;
During handling of the above exception, another exception occurred:

;Traceback (most recent call last):
;  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/carrier/asyncore/dispatch.py", line 46, in runDispatcher
    use_poll=True, map=self.__sockMap, count=1)
;  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncore.py", line 207, in loop
    poll_fun(timeout, map)
;  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncore.py", line 188, in poll2
    readwrite(obj, flags)
;  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncore.py", line 123, in readwrite
    obj.handle_error()
;  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncore.py", line 110, in readwrite
    obj.handle_write_event()
;  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncore.py", line 442, in handle_write_event
    self.handle_write()
;  File "/Users/guardian/Sync/Projects/serenity/lib/python3.6/site-packages/pysnmp/carrier/asyncore/dgram/base.py", line 148, in handle_write
    raise error.CarrierError('sendto() failed for %s: %s' % (transportAddress, sys.exc_info()[1]))
;pysnmp.carrier.error.CarrierError: sendto() failed for ('10.10.10.10', 161): [Errno 64] Host is down

I'm on Python 3.6.1 and saw you only support 3.5 so set up a virtualenv with 3.5 and get exactly the same error. It obviously sees the 'Errno 64', but seems this error is not making it back to the error handling (error_indication or error_status?).
I’m on macOS Sierra 10.12.5 and devices are all on my local LAN - nothing fancy either.

Any idea where to look - does this look like a bug - or is there something wrong with my implementation? Is there a better or more propper way to do what I'm trying to do?
Idea is to have a pollSequence and use the first one that works e.g. pollSequence of 'v2/public:161,v1/readonly:1961' lets me specific 2 different types of polling with version/community/port no.
It seems to work fine if the device is reachable via said polling info - but fails like this when the Host is down or doesn't talk SNMP!

Any help would be greatly appreciated. I'm planning to do a lot more complex things with SNMP so need to make sure I'm on the right path early on!

Regards,

Frank
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Re: [pysnmp-users] pySNMP error handling - OSError: [Errno 64] Host is down - exception created ins

Re: [pysnmp-users] pySNMP error handling - OSError: [Errno 64] Host is down - exception created instead of returned via error_indication or error_status.