SNMP plugin IF-MIB::ifTable physical interface problem

[mnctech]

Bug report

Utilizing the new (and old) SNMP plugin for IF-MIB::ifTable there is an issue where the physaddress is being returned via SNMP correctly but Telegraf is turning it into characters before outputting it.

Relevant telegraf.conf:

[[inputs.snmp]]
  agents = [ "172.16.1.13" ]
  version = 2
  community = "public"
  interval = "10s"
  timeout = "10s"

  name = "pts_stats"
  [[inputs.snmp.field]]
    name = "hostname"
    oid = ".1.3.6.1.2.1.1.5.0"
    is_tag = true

  [[inputs.snmp.field]]
    name = "ifTable"
    oid = "IF-MIB::ifPhysAddress.1"

System info:

ubuntu 16.04 desktop with Telegraf 1.0 and the new SNMP plugin

telegraf output

interface_stats,agent_host=172.16.1.13,host=Dell210,hostname=unnamed ifTable="�>" 1473690400000000000

tcpdump of SNMP response

10:33:00.000413 IP 172.16.3.13.50536 > 172.16.1.13.161: GetRequest(28) .1.3.6.1.2.1.1.5.0
10:33:00.043629 IP 172.16.1.13.161 > 172.16.3.13.50536: GetResponse(51) .1.3.6.1.2.1.1.5.0="development-server"
10:33:00.043877 IP 172.16.3.13.50536 > 172.16.1.13.161: GetRequest(30) .1.3.6.1.2.1.2.2.1.6.1
10:33:00.082439 IP 172.16.1.13.161 > 172.16.3.13.50536: GetResponse(36) .1.3.6.1.2.1.2.2.1.6.1=fa_16_3e_ee_85_8c

[sparrc]

can you run an SNMP get on the MIB and OID?

snmpget -c public -v2c 172.16.1.13 IF-MIB::ifPhysAddress.1
snmpget -c public -v2c 172.16.1.13 .1.3.6.1.2.1.2.2.1.6.1

[mnctech]

jdavies@Dell210:~$ snmpget -c public -v2c 172.16.1.13 IF-MIB::ifPhysAddress.1
IF-MIB::ifPhysAddress.1 = STRING: fa:16:3e:ee:85:8c

jdavies@Dell210:~$ snmpget -c public -v2c 172.16.1.13 .1.3.6.1.2.1.2.2.1.6.1
iso.3.6.1.2.1.2.2.1.6.1 = Hex-STRING: FA 16 3E EE 85 8C

[sparrc]

@phemmer looks like there might be a bug with Hex strings in the snmp plugin

[phemmer]

Hrm, this is going to be sticky. The value comes across the wire as an OCTET STRING, making it indistinguishable from normal text. It's the MIB which defines the field as a PhysAddress, which is then rendered as a hex-colon string.

The only way I can see to handle this is to add a conversion for string to mac addr. For the automatic table stuff, we'd have to pull the syntax type out of the MIB, and automatically map the conversion.

EDIT (9/12): I've got this coded up. Basically added support for MAC addresses and IP addresses encoded as octet strings. Need to update tests & docs. Probably won't be done til wednesday.
Also, I wouldn't consider this a bug. More a feature request.