Class: LogStash::Codecs::Netflow

Inherits:
Base
  • Object
show all
Defined in:
lib/logstash/codecs/netflow.rb

Overview

The “netflow” codec is for decoding Netflow v5/v9 flows.

Instance Method Summary collapse

Constructor Details

#initialize(params = {}) ⇒ Netflow

Returns a new instance of Netflow.



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# File 'lib/logstash/codecs/netflow.rb', line 38

def initialize(params={})
  super(params)
  @threadsafe = false
end

Instance Method Details

#decode(payload, &block) ⇒ Object 



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# File 'lib/logstash/codecs/netflow.rb', line 69

def decode(payload, &block)
  header = Header.read(payload)

  unless @versions.include?(header.version)
    @logger.warn("Ignoring Netflow version v#{header.version}")
    return
  end

  if header.version == 5
    flowset = Netflow5PDU.read(payload)
  elsif header.version == 9
    flowset = Netflow9PDU.read(payload)
  else
    @logger.warn("Unsupported Netflow version v#{header.version}")
    return
  end

  flowset.records.each do |record|
    if flowset.version == 5
      event = LogStash::Event.new

      # FIXME Probably not doing this right WRT JRuby?
      #
      # The flowset header gives us the UTC epoch seconds along with
      # residual nanoseconds so we can set @timestamp to that easily
      event.timestamp = LogStash::Timestamp.at(flowset.unix_sec, flowset.unix_nsec / 1000)
      event[@target] = {}

      # Copy some of the pertinent fields in the header to the event
      ['version', 'flow_seq_num', 'engine_type', 'engine_id', 'sampling_algorithm', 'sampling_interval', 'flow_records'].each do |f|
        event[@target][f] = flowset[f]
      end

      # Create fields in the event from each field in the flow record
      record.each_pair do |k,v|
        case k.to_s
        when /_switched$/
          # The flow record sets the first and last times to the device
          # uptime in milliseconds. Given the actual uptime is provided
          # in the flowset header along with the epoch seconds we can
          # convert these into absolute times
          millis = flowset.uptime - v
          seconds = flowset.unix_sec - (millis / 1000)
          micros = (flowset.unix_nsec / 1000) - (millis % 1000)
          if micros < 0
            seconds--
            micros += 1000000
          end
          # FIXME Again, probably doing this wrong WRT JRuby?
          event[@target][k.to_s] = Time.at(seconds, micros).utc.strftime("%Y-%m-%dT%H:%M:%S.%3NZ")
        else
          event[@target][k.to_s] = v
        end
      end

      yield event
    elsif flowset.version == 9
      case record.flowset_id
      when 0
        # Template flowset
        record.flowset_data.templates.each do |template|
          catch (:field) do
            fields = []
            template.fields.each do |field|
              entry = netflow_field_for(field.field_type, field.field_length)
              if ! entry
                throw :field
              end
              fields += entry
            end
            # We get this far, we have a list of fields
            #key = "#{flowset.source_id}|#{event["source"]}|#{template.template_id}"
            key = "#{flowset.source_id}|#{template.template_id}"
            @templates[key, @cache_ttl] = BinData::Struct.new(:endian => :big, :fields => fields)
            # Purge any expired templates
            @templates.cleanup!
          end
        end
      when 1
        # Options template flowset
        record.flowset_data.templates.each do |template|
          catch (:field) do
            fields = []
            template.option_fields.each do |field|
              entry = netflow_field_for(field.field_type, field.field_length)
              if ! entry
                throw :field
              end
              fields += entry
            end
            # We get this far, we have a list of fields
            #key = "#{flowset.source_id}|#{event["source"]}|#{template.template_id}"
            key = "#{flowset.source_id}|#{template.template_id}"
            @templates[key, @cache_ttl] = BinData::Struct.new(:endian => :big, :fields => fields)
            # Purge any expired templates
            @templates.cleanup!
          end
        end
      when 256..65535
        # Data flowset
        #key = "#{flowset.source_id}|#{event["source"]}|#{record.flowset_id}"
        key = "#{flowset.source_id}|#{record.flowset_id}"
        template = @templates[key]

        if ! template
          #@logger.warn("No matching template for flow id #{record.flowset_id} from #{event["source"]}")
          @logger.warn("No matching template for flow id #{record.flowset_id}")
          next
        end

        length = record.flowset_length - 4

        # Template shouldn't be longer than the record and there should
        # be at most 3 padding bytes
        if template.num_bytes > length or ! (length % template.num_bytes).between?(0, 3)
          @logger.warn("Template length doesn't fit cleanly into flowset", :template_id => record.flowset_id, :template_length => template.num_bytes, :record_length => length)
          next
        end

        array = BinData::Array.new(:type => template, :initial_length => length / template.num_bytes)

        records = array.read(record.flowset_data)

        records.each do |r|
          event = LogStash::Event.new(
            LogStash::Event::TIMESTAMP => LogStash::Timestamp.at(flowset.unix_sec),
            @target => {}
          )

          # Fewer fields in the v9 header
          ['version', 'flow_seq_num'].each do |f|
            event[@target][f] = flowset[f]
          end

          event[@target]['flowset_id'] = record.flowset_id

          r.each_pair do |k,v|
            case k.to_s
            when /_switched$/
              millis = flowset.uptime - v
              seconds = flowset.unix_sec - (millis / 1000)
              # v9 did away with the nanosecs field
              micros = 1000000 - (millis % 1000)
              event[@target][k.to_s] = Time.at(seconds, micros).utc.strftime("%Y-%m-%dT%H:%M:%S.%3NZ")
            else
              event[@target][k.to_s] = v
            end
          end

          yield event
        end
      else
        @logger.warn("Unsupported flowset id #{record.flowset_id}")
      end
    end
  end
end

#register ⇒ Object 



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# File 'lib/logstash/codecs/netflow.rb', line 44

def register
  require "logstash/codecs/netflow/util"
  @templates = Vash.new()

  # Path to default Netflow v9 field definitions
  filename = ::File.expand_path('netflow/netflow.yaml', ::File.dirname(__FILE__))

  begin
    @fields = YAML.load_file(filename)
  rescue Exception => e
    raise "#{self.class.name}: Bad syntax in definitions file #{filename}"
  end

  # Allow the user to augment/override/rename the supported Netflow fields
  if @definitions
    raise "#{self.class.name}: definitions file #{@definitions} does not exists" unless File.exists?(@definitions)
    begin
      @fields.merge!(YAML.load_file(@definitions))
    rescue Exception => e
      raise "#{self.class.name}: Bad syntax in definitions file #{@definitions}"
    end
  end
end