SNMP for custom values

Installing and Using OpenWrt
1

Hello, I have a particular need to publish custom SNMP values. For example, I have a LTE Cellular module connected and I would need to publish its IMEI to be found by a SNMP tool, for example, Paessler SNMP Tester. By the way, I already have an enterprise number from IANA if it's necessary.

I've had some progress by editing the /etc/config/snmpd file adding a section like this:

config exec
        option name drq-signalinfo
        option prog "/sbin/uqmi -d /dev/cdc-wdm0 --get-signal-info | awk '{print substr($0, 2, length($0) - 2)}'"
        option miboid .1.3.6.1.4.49085.3

When running a snmpwalk I get a response like this:

*2/28/2023 1:10:24 PM (14 ms) : 1.3.6.1.4.49085.1.1.1 = "1" [ASN_INTEGER]*
*2/28/2023 1:10:24 PM (20 ms) : 1.3.6.1.4.49085.1.2.1 = "drq-imei" [ASN_OCTET_STR]*
*2/28/2023 1:10:24 PM (25 ms) : 1.3.6.1.4.49085.1.3.1 = "/sbin/uqmi -d /dev/cdc-wdm0 --get-imei | awk '{print substr($0, 2, length($0) - 2)}'" [ASN_OCTET_STR]*
*2/28/2023 1:10:24 PM (139 ms) : 1.3.6.1.4.49085.1.100.1 = "0" [ASN_INTEGER]*
*2/28/2023 1:10:24 PM (235 ms) : 1.3.6.1.4.49085.1.101.1 = ""864744040333609"" [ASN_OCTET_STR]*
*2/28/2023 1:10:24 PM (332 ms) : 1.3.6.1.4.49085.1.102.1 = "0" [ASN_INTEGER]*
*2/28/2023 1:10:24 PM (336 ms) : 1.3.6.1.4.49085.1.103.1 = "" [ASN_OCTET_STR*

Which is not ideal, because it's bringing a lot of unnecessary values, and that number should be typed as integer, not string, so, I have the idea that I need to write a .mib file, but what I would know beyond the how to write it, I want to know what do I have to tell the /etc/config/snmpd file to read my definitions and return the expected data type and get rid of all those outputs that don't bring value to the snmp scan.

Thank you!!

2

maybe something like this ... ?

cat s_vlansm

#!/bin/sh
place="1.3.6.1.2.1.17.7.1.4.2.1.4.0"

source /tmp/snmp/s_vlanifmembers

while read CMD
do
  case "$CMD" in
    PING)
      echo PONG
      continue
      ;;
    getnext)
      read REQ
      oid=$(echo $REQ | tr -d .)
      eval ret=\$getnext_${oid}
      if test "x$ret" = "xNONE"
      then
        echo NONE
        continue
      fi
      ;;
    get)
      read REQ
      if test "x$REQ" = "x$place"
      then
        echo NONE
        continue
      else
        ret=$REQ
      fi
      ;;
    *)
      read REQ
      if test "x$REQ" = "x$place"
      then
        echo NONE
        continue
      else
        ret=$REQ
      fi
      ;;
  esac

  oid=$(echo $ret | tr -d .)
  if eval test "x\$type_${oid}" != "x"
  then
    echo $ret
    eval echo "\$type_${oid}"
    eval echo "\$value_${oid}"
  else
    echo NONE
  fi
done

cat /tmp/snmp/s_vlanifmembers

getnext_13612117714214=1.3.6.1.2.1.17.7.1.4.2.1.4.0.1
value_1361211771421401='58 00 00 00 00 00 00 00'
type_1361211771421401='octetstring'
getnext_1361211771421401=1.3.6.1.2.1.17.7.1.4.2.1.4.0.2
value_1361211771421402='41 88 00 00 00 00 00 00'
type_1361211771421402='octetstring'
getnext_1361211771421402=1.3.6.1.2.1.17.7.1.4.2.1.4.0.100
value_136121177142140100='46 04 00 00 00 00 00 00'
type_136121177142140100='octetstring'
getnext_136121177142140100=1.3.6.1.2.1.17.7.1.4.2.1.4.0.200
value_136121177142140200='40 70 00 00 00 00 00 00'
type_136121177142140200='octetstring'
getnext_136121177142140200='NONE'

and lastly ...
cat /etc/snmp/snmpd.conf

pass_persist .1.3.6.1.2.1.17.1.4.1.2 /bin/s_ifindex
pass_persist .1.3.6.1.2.1.17.7.1.1.1 /bin/s_vlansv
pass_persist .1.3.6.1.2.1.17.7.1.2.2.1.2 /bin/s_fdb
pass_persist .1.3.6.1.2.1.17.7.1.4.2.1.4 /bin/s_vlansm
pass_persist .1.3.6.1.2.1.17.7.1.4.2.1.5 /bin/s_vlansu
pass_persist .1.3.6.1.2.1.17.7.1.4.3.1.1 /bin/s_vlansn