Class: NETSNMP::Varbind

Inherits:
Object
  • Object
show all
Defined in:
lib/netsnmp/varbind.rb

Overview

Abstracts the PDU variable structure into a ruby object

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(oid, value: nil, type: nil) ⇒ Varbind

Returns a new instance of Varbind.



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# File 'lib/netsnmp/varbind.rb', line 11

def initialize(oid, value: nil, type: nil)
  @oid = OID.build(oid)
  @type = type
  @value = convert_val(value) if value
end

Instance Attribute Details

#oid ⇒ Object (readonly)

Returns the value of attribute oid.



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# File 'lib/netsnmp/varbind.rb', line 9

def oid
  @oid
end

#value ⇒ Object (readonly)

Returns the value of attribute value.



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# File 'lib/netsnmp/varbind.rb', line 9

def value
  @value
end

Instance Method Details

#convert_application_asn(asn) ⇒ Object 



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# File 'lib/netsnmp/varbind.rb', line 110

def convert_application_asn(asn)
  case asn.tag
  when 0 # IP Address
    IPAddr.new_ntoh(asn.value)
  when 1, # ASN counter 32
       2 # gauge
    unpack_32bit_integer(asn.value)
  when 3 # timeticks
    Timetick.new(unpack_32bit_integer(asn.value))
    # when 4 # opaque
    # when 5 # NSAP
  when 6 # ASN Counter 64
    unpack_64bit_integer(asn.value)
    # when 7 # ASN UInteger
  end
end

#convert_to_asn(typ, value) ⇒ Object 



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# File 'lib/netsnmp/varbind.rb', line 75

def convert_to_asn(typ, value)
  asn_type = typ
  asn_val = value
  if typ.is_a?(Symbol)
    asn_type = case typ
               when :ipaddress then 0
               when :counter32
                 asn_val = [value].pack("N*")
                 asn_val = asn_val[1..-1] while asn_val[0] == "\x00".b && asn_val[1].unpack1("B") != "1"
                 1
               when :gauge
                 asn_val = [value].pack("N*")
                 asn_val = asn_val[1..-1] while asn_val[0] == "\x00".b && asn_val[1].unpack1("B") != "1"
                 2
               when :timetick
                 return Timetick.new(value).to_asn
               when :opaque then 4
               when :nsap then 5
               when :counter64
                 asn_val = [
                   (value >> 96) & 0xFFFFFFFF,
                   (value >> 64) & 0xFFFFFFFF,
                   (value >> 32) & 0xFFFFFFFF,
                   value & 0xFFFFFFFF
                 ].pack("NNNN")
                 asn_val = asn_val[1..-1] while asn_val.start_with?("\x00")
                 6
               when :uinteger then 7
               else
                 raise Error, "#{typ}: unsupported application type"
               end
  end
  OpenSSL::ASN1::ASN1Data.new(asn_val, asn_type, :APPLICATION)
end

#convert_val(asn_value) ⇒ Object 



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# File 'lib/netsnmp/varbind.rb', line 50

def convert_val(asn_value)
  case asn_value
  when OpenSSL::ASN1::OctetString
    val = asn_value.value

    # it's kind of common in snmp, some stuff can't be converted,
    # like Hexa Strings. Parse them into a readable format a la netsnmp
    # https://github.com/net-snmp/net-snmp/blob/ed90aaaaea0d9cc6c5c5533f1863bae598d3b820/snmplib/mib.c#L650
    is_hex_string = val.each_char.any? { |c| !c.match?(/[[:print:]]/) && !c.match?(/[[:space:]]/) }

    val = HexString.new(val) if is_hex_string
    val
  when OpenSSL::ASN1::Primitive
    val = asn_value.value
    val = val.to_i if val.is_a?(OpenSSL::BN)
    val
  when OpenSSL::ASN1::ASN1Data
    # application data
    convert_application_asn(asn_value)
  # when OpenSSL::BN
  else
    asn_value # assume it's already primitive
  end
end

#to_asn ⇒ Object 



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# File 'lib/netsnmp/varbind.rb', line 25

def to_asn
  asn_oid = OID.to_asn(@oid)
  asn_val = if @type
              convert_to_asn(@type, @value)
            else
              case @value
              when String
                OpenSSL::ASN1::OctetString.new(@value)
              when Integer
                OpenSSL::ASN1::Integer.new(@value)
              when true, false
                OpenSSL::ASN1::Boolean.new(@value)
              when nil
                OpenSSL::ASN1::Null.new(nil)
              when IPAddr
                OpenSSL::ASN1::ASN1Data.new(@value.hton, 0, :APPLICATION)
              when Timetick
                @value.to_asn
              else
                raise Error, "#{@value}: unsupported varbind type"
              end
            end
  OpenSSL::ASN1::Sequence.new([asn_oid, asn_val])
end

#to_der ⇒ Object 



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# File 'lib/netsnmp/varbind.rb', line 21

def to_der
  to_asn.to_der
end

#to_s ⇒ Object 



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# File 'lib/netsnmp/varbind.rb', line 17

def to_s
  "#<#{self.class}:0x#{object_id.to_s(16)} @oid=#{@oid} @value=#{@value}>"
end