Sunt

SNMP Agent for Linux written in Rust.

Intro

SNMP is still the common ground for getting data into various kinds of monitoring systems. Sunt aims to be a modern SNMP agent that is aware of how things are run nowadays, stripped to the essentials but adding features where they make sense.

Supported tables:

hrStorageTable
dskTable
diskIOTable
ifTable
nsExtendOutput1Table (SNMP extend)

Example queries

snmpwalk     -v2c -c test 127.0.0.1 .1
snmptable    -v2c -c sunt 127.0.0.1 hrStorageTable
snmptable    -v2c -c sunt 127.0.0.1 dskTable
snmptable    -v2c -c sunt 127.0.0.1 diskIOTable
snmptable    -v2c -c sunt 127.0.0.1 ifTable
snmpbulkwalk -v2c -c test 127.0.0.1 dskTable
snmpbulkwalk -v2c -c derp 127.0.0.1 .1.3.6.1.2.1.31.1.1.1

# snmptable  -v2c -c sunt 192.168.0.1 dskTable | cut -c -140
SNMP table: UCD-SNMP-MIB::dskTable

 dskIndex                 dskPath               dskDevice dskMinimum dskMinPercent  dskTotal  dskAvail   dskUsed dskPercent dskPercentNode
        1                       /        /dev/vghive/root          0            -1  20511356  11301592   8144804         39             16
        2                   /data                /dev/md0          0            -1 961300936 333643156 627657780         65              0
        3            /var/lib/lxc     /dev/vghive/var-lxc          0            -1  20961280  16288304   4672976         22              0
        4                /var/log     /dev/vghive/var-log          0            -1  10483712   9686808    719080          6              0
        5       /media/prometheus  /dev/vghive/prometheus          0            -1  10475520   3404028   7071492         67              0
        6 /var/lib/libvirt/images /dev/vghive/var-libvirt          0            -1  26204160   6710120  19494040         74              0
        7              /media/bkp                /dev/bkp          0            -1  15348720  13136192   1409816          9              4

Notable differences to net-snmpd

No write access whatsoever
No access control, community string is completely ignored
hrStorageTable:
- Only actual mountpoints are included (no RAM etc).
- Duplicate mountpoints (bind mounts) are filtered out (useful for Docker/LXC hosts).
diskIOTable:
- dm-* devices are reported as the actual device, e.g. vghive/data or crypted_home.
ifTable
- Only Physical interfaces, Bridges and VLAN interfaces are exported (VM interfaces and VPN tunnels are filtered).

Considerably faster response

Tested using

  time snmptable -v2c -c community host diskIOTable
  time snmptable -v2c -c community host hrStorageTable
  time snmptable -v2c -c community host ifTable
  time snmpbulkwalk -v2c -c community host .1 > /dev/null

Over a local gigabit connection:

      Table        |   Sunt                 |  net-snmpd
  ---------------- | ---------------------- | --------------------
    diskIOTable    |   real    0m0,028s     |  real    0m0,038s
    (26 entries)   |   user    0m0,019s     |  user    0m0,020s
                   |   sys     0m0,005s     |  sys     0m0,006s
                   |                        |
    hrStorageTable |   real    0m0,028s     |  real    0m0,031s
    (17 entries)   |   user    0m0,020s     |  user    0m0,017s
                   |   sys     0m0,006s     |  sys     0m0,008s
                   |                        |
    ifTable        |   real    0m0,041s     |  real    0m0,088s
    (26 entries)   |   user    0m0,019s     |  user    0m0,027s
                   |   sys     0m0,012s     |  sys     0m0,011s
                   |                        |
    full bulkwalk  |   real    0m0,041s     |  real    0m3,183s
    (start at .1)  |   user    0m0,021s     |  user    0m0,360s
                   |   sys     0m0,008s     |  sys     0m0,105s
                   |                        |

Over a remote connection with about 20ms latency:

      Table        |   Sunt                 |  net-snmpd
  ---------------- | ---------------------- | --------------------
    diskIOTable    |   real    0m0,103s     |  real    0m0,624s
    (26 entries)   |   user    0m0,026s     |  user    0m0,020s
                   |   sys     0m0,012s     |  sys     0m0,011s
                   |                        |
    hrStorageTable |   real    0m0,057s     |  real    0m0,317s
    (17 entries)   |   user    0m0,025s     |  user    0m0,027s
                   |   sys     0m0,008s     |  sys     0m0,012s
                   |                        |
    ifTable        |   real    0m0,130s     |  real    0m3,474s
    (26 entries)   |   user    0m0,022s     |  user    0m0,044s
                   |   sys     0m0,019s     |  sys     0m0,030s
                   |                        |
    full bulkwalk  |   real    0m0,265s     |  real    0m55,677s
    (start at .1)  |   user    0m0,021s     |  user    0m0,620s
                   |   sys     0m0,007s     |  sys     0m0,253s

Note that this test is somewhat unfair because sunt returns way fewer data.

SNMP Extend support

Sunt has support for SNMP extend. To use it, create a YAML file with a set of commands like this:

extend:
  # SNMP extend command for NTP monitoring
  ntpq_delay:  { cmd: '/usr/local/bin/ntpwatch', args: ['delay' ] }
  ntpq_jitter: { cmd: '/usr/local/bin/ntpwatch', args: ['jitter'] }
  ntpq_offset: { cmd: '/usr/local/bin/ntpwatch', args: ['offset'] }
  "true":      { cmd: '/bin/true' }
  echo:        { cmd: '/bin/echo', args: ["testing"] }

Then start sunt with the -e option, pointing to that yaml file. You can then query the table:

# snmptable  -v2c -c wayne 127.0.0.1 nsExtendOutput1Table
SNMP table: NET-SNMP-EXTEND-MIB::nsExtendOutput1Table

 nsExtendOutput1Line nsExtendOutputFull nsExtendOutNumLines nsExtendResult
             testing            testing                   1              0
                                                          0              0
               21217              21217                   1              0
                 650                650                   1              0
                1580               1580                   1              0

Or walk the values: