SNMP v1/v2c trap support

[admin]

New package with trap support: https://dl.openrb.com/lm-19-imx6/pkg/lua...4_imx6.ipk

Resident script (0 second sleep time). It binds to UDP port 162 and listens to incoming messages then parses them. snmp.parsetrap returns community name (string) and variable list (table) on success, nil plus error message otherwise.

Code:

if not sock then
  snmp = require('snmp')
  socket = require('socket')

  -- create UDP socket, listen on port 162
  sock = socket.udp()
  sock:setsockname('*', 162)
  sock:settimeout(1)
end

data, ip, port = sock:receivefrom()

-- incoming message
if data then
  -- parse message
  commres, vberr = snmp.parsetrap(data)

  -- valid message
  if commres then
    log(ip, commres, vberr)
  -- parse failed, see logs for more info
  else
    log('error', vberr)
  end
end