通过传递从snmp-get值丢失

Question

I want to read a GPIO-pin of a RaspberryPi via snmp. I wrote a script in python to read the pin. For testing purposes I delivered the value 17 and 99.

/usr/local/bin/snmp-gpio17.py :

#!/usr/bin/python3 -u
import RPi.GPIO as GPIO
from time import sleep
GPIO.setmode(GPIO.BCM)
GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_UP)
if not GPIO.input(17):
   var=17
else:
   var=99
print ( var )

This script is called by /usr/local/bin/snmp-gpio17.sh :

#!/bin/bash
if [ "$1" = "-g" ]
then
echo .1.3.6.1.4.1.18565.1.12.101.1.17
echo gauge
python /usr/local/bin/snmp-gpio17.py
fi
exit 0

In /etc/snmp/snmpd.conf , I added the line

pass .1.3.6.1.4.1.18565.1.12.101.1.17 /bin/sh  /usr/local/bin/snmp-gpio17.sh

When I run the script on the RasPi it works:

root@raspberrypi:~# /usr/local/bin/snmp-gpio17.sh -g
.1.3.6.1.4.1.18565.1.12.101.1.17
gauge
17

but when I try to read the OID (locally or over the network) I get:

karls@mintbox ~ $ snmpget -v1 -c public 192.168.129.4 .1.3.6.1.4.1.18565.1.12.101.1.17
iso.3.6.1.4.1.18565.1.12.101.1.17 = Gauge32: 0

I also set up measurement of the cpu-temperature via snmp with another pass-line and it works fine. I use nearly the same script:

#!/bin/bash
if [ "$1" = "-g" ]
then
echo .1.3.6.1.4.1.18565.1.12.101.1.101
echo gauge
cat /sys/class/thermal/thermal_zone0/temp
fi
exit 0

So the snmp-communication seems to be OK (I compared answers with wireshark), but snmpd on the RasPi gets wrong information from the bash-script.

Anyone have an idea?

Regards, Karl

Answer 1

[solved] It works now, even if I remove user snmp from group gpio. My problem in testing was, that I did not wait between two tests. I found out, that snmpd on the RasPi caches the result of a get for 30 seconds. Only if you wait that long, you get the new result! Thanks to all