lib/snmp/pdu.rb
#
# Copyright (c) 2004 David R. Halliday
# All rights reserved.
#
# This SNMP library is free software. Redistribution is permitted under the
# same terms and conditions as the standard Ruby distribution. See the
# COPYING file in the Ruby distribution for details.
#
require 'snmp/ber'
require 'snmp/varbind'
include SNMP::BER
module SNMP
# Exceptions thrown during message/pdu decoding
class UnsupportedVersion < RuntimeError; end
class UnsupportedPduTag < RuntimeError; end
class InvalidPduTag < RuntimeError; end
class ParseError < RuntimeError; end
class InvalidErrorStatus < RuntimeError; end
class InvalidTrapVarbind < RuntimeError; end
class InvalidGenericTrap < RuntimeError; end
SYS_UP_TIME_OID = ObjectId.new("1.3.6.1.2.1.1.3.0")
SNMP_TRAP_OID_OID = ObjectId.new("1.3.6.1.6.3.1.1.4.1.0")
class Message
attr_reader :version
attr_reader :community
attr_reader :pdu
class << self
def decode(data)
message_data, remainder = decode_sequence(data)
assert_no_remainder(remainder)
version, remainder = decode_version(message_data)
community, remainder = decode_octet_string(remainder)
pdu, remainder = decode_pdu(version, remainder)
assert_no_remainder(remainder)
Message.new(version, community, pdu)
end
def decode_version(data)
version_data, remainder = decode_integer(data)
if version_data == SNMP_V1
version = :SNMPv1
elsif version_data == SNMP_V2C
version = :SNMPv2c
else
raise UnsupportedVersion, version_data.to_s
end
return version, remainder
end
def decode_pdu(version, data)
pdu_tag, pdu_data, remainder = decode_tlv(data)
case pdu_tag
when GetRequest_PDU_TAG
pdu = PDU.decode(GetRequest, pdu_data)
when GetNextRequest_PDU_TAG
pdu = PDU.decode(GetNextRequest, pdu_data)
when Response_PDU_TAG
pdu = PDU.decode(Response, pdu_data)
when SetRequest_PDU_TAG
pdu = PDU.decode(SetRequest, pdu_data)
when SNMPv1_Trap_PDU_TAG
raise InvalidPduTag, "SNMPv1-trap not valid for #{version.to_s}" if version != :SNMPv1
pdu = SNMPv1_Trap.decode(pdu_data)
when GetBulkRequest_PDU_TAG
raise InvalidPduTag, "get-bulk not valid for #{version.to_s}" if version != :SNMPv2c
pdu = PDU.decode(GetBulkRequest, pdu_data)
when InformRequest_PDU_TAG
raise InvalidPduTag, "inform not valid for #{version.to_s}" if version != :SNMPv2c
pdu = PDU.decode(InformRequest, pdu_data)
when SNMPv2_Trap_PDU_TAG
raise InvalidPduTag, "SNMPv2c-trap not valid for #{version.to_s}" if version != :SNMPv2c
pdu = PDU.decode(SNMPv2_Trap, pdu_data)
else
raise UnsupportedPduTag, pdu_tag.to_s
end
return pdu, remainder
end
end
def initialize(version, community, pdu)
@version = version
@community = community
@pdu = pdu
end
def response
Message.new(@version, @community, Response.from_pdu(@pdu))
end
def encode_version(version)
if version == :SNMPv1
encode_integer(SNMP_V1)
elsif version == :SNMPv2c
encode_integer(SNMP_V2C)
else
raise UnsupportedVersion, version.to_s
end
end
def encode
data = encode_version(@version)
data << encode_octet_string(@community)
data << @pdu.encode
encode_sequence(data)
end
end
class PDU
attr_accessor :request_id
attr_accessor :error_index
attr_accessor :varbind_list
alias vb_list varbind_list
def self.decode(pdu_class, pdu_data)
request_id, remainder = decode_integer(pdu_data)
error_status, remainder = decode_integer(remainder)
error_index, remainder = decode_integer(remainder)
varbind_list, remainder = VarBindList.decode(remainder)
assert_no_remainder(remainder)
pdu_class.new(request_id, varbind_list, error_status, error_index)
end
ERROR_STATUS_NAME = {
0 => :noError,
1 => :tooBig,
2 => :noSuchName,
3 => :badValue,
4 => :readOnly,
5 => :genErr,
6 => :noAccess,
7 => :wrongType,
8 => :wrongLength,
9 => :wrongEncoding,
10 => :wrongValue,
11 => :noCreation,
12 => :inconsistentValue,
13 => :resourceUnavailable,
14 => :commitFailed,
15 => :undoFailed,
16 => :authorizationError,
17 => :notWritable,
18 => :inconsistentName
}
ERROR_STATUS_CODE = ERROR_STATUS_NAME.invert
def initialize(request_id, varbind_list, error_status=0, error_index=0)
@request_id = request_id
self.error_status = error_status
@error_index = error_index.to_int
@varbind_list = varbind_list
end
def error_status=(status)
@error_status = ERROR_STATUS_CODE[status]
unless @error_status
if status.respond_to?(:to_int) && ERROR_STATUS_NAME[status.to_int]
@error_status = status
else
raise InvalidErrorStatus, status.to_s
end
end
end
def error_status
ERROR_STATUS_NAME[@error_status]
end
def encode_pdu(pdu_tag)
pdu_data = encode_integer(@request_id)
pdu_data << encode_integer(@error_status)
pdu_data << encode_integer(@error_index)
pdu_data << @varbind_list.encode
encode_tlv(pdu_tag, pdu_data)
end
def each_varbind(&block)
@varbind_list.each(&block)
end
end
class GetRequest < PDU
def encode
encode_pdu(GetRequest_PDU_TAG)
end
end
class GetNextRequest < PDU
def encode
encode_pdu(GetNextRequest_PDU_TAG)
end
end
class SetRequest < PDU
def encode
encode_pdu(SetRequest_PDU_TAG)
end
end
class GetBulkRequest < PDU
alias max_repetitions error_index
alias max_repetitions= error_index=
def encode
encode_pdu(GetBulkRequest_PDU_TAG)
end
def non_repeaters=(number)
@error_status = number
end
def non_repeaters
@error_status
end
end
class Response < PDU
class << self
def from_pdu(request)
Response.new(request.request_id, request.varbind_list,
:noError, 0)
end
end
def encode
encode_pdu(Response_PDU_TAG)
end
end
##
# The PDU class for traps in SNMPv2c. Methods are provided for retrieving
# the values of the mandatory varbinds: the system uptime and the OID of the
# trap. The complete varbind list is available through the usual varbind_list
# method. The first two varbinds in this list will always be the uptime
# and trap OID varbinds.
#
class SNMPv2_Trap < PDU
def encode
encode_pdu(SNMPv2_Trap_PDU_TAG)
end
##
# Returns the source IP address for the trap, usually derived from the
# source IP address of the packet that delivered the trap.
#
attr_accessor :source_ip
##
# Returns the value of the mandatory sysUpTime varbind for this trap.
#
# Throws InvalidTrapVarbind if the sysUpTime varbind is not present.
#
def sys_up_time
varbind = @varbind_list[0]
if varbind && (varbind.name == SYS_UP_TIME_OID)
return varbind.value
else
raise InvalidTrapVarbind, "Expected sysUpTime.0, found " + varbind.to_s
end
end
##
# Returns the value of the mandatory snmpTrapOID varbind for this trap.
#
# Throws InvalidTrapVarbind if the snmpTrapOID varbind is not present.
#
def trap_oid
varbind = @varbind_list[1]
if varbind && (varbind.name == SNMP_TRAP_OID_OID)
return varbind.value
else
raise InvalidTrapVarbind, "Expected snmpTrapOID.0, found " + varbind.to_s
end
end
end
##
# The PDU class for SNMPv2 Inform notifications. This class is identical
# to SNMPv2_Trap.
#
class InformRequest < SNMPv2_Trap
def encode
encode_pdu(InformRequest_PDU_TAG)
end
end
##
# The PDU class for traps in SNMPv1.
#
class SNMPv1_Trap
##
# Returns the source IP address for the trap, usually derived from the
# source IP address of the packet that delivered the trap.
#
attr_accessor :source_ip
attr_accessor :enterprise
attr_accessor :agent_addr
attr_accessor :specific_trap
attr_accessor :timestamp
attr_accessor :varbind_list
alias :vb_list :varbind_list
def self.decode(pdu_data)
oid_data, remainder = decode_object_id(pdu_data)
enterprise = ObjectId.new(oid_data)
ip_data, remainder = decode_ip_address(remainder)
agent_addr = IpAddress.new(ip_data)
generic_trap, remainder = decode_integer(remainder)
specific_trap, remainder = decode_integer(remainder)
time_data, remainder = decode_timeticks(remainder)
timestamp = TimeTicks.new(time_data)
varbind_list, remainder = VarBindList.decode(remainder)
assert_no_remainder(remainder)
SNMPv1_Trap.new(enterprise, agent_addr, generic_trap, specific_trap,
timestamp, varbind_list)
end
def initialize(enterprise, agent_addr, generic_trap, specific_trap, timestamp, varbind_list)
@enterprise = enterprise
@agent_addr = agent_addr
self.generic_trap = generic_trap
@specific_trap = specific_trap
@timestamp = timestamp
@varbind_list = varbind_list
end
# Name map for all of the generic traps defined in RFC 1157.
GENERIC_TRAP_NAME = {
0 => :coldStart,
1 => :warmStart,
2 => :linkDown,
3 => :linkUp,
4 => :authenticationFailure,
5 => :egpNeighborLoss,
6 => :enterpriseSpecific
}
# Code map for all of the generic traps defined in RFC 1157.
GENERIC_TRAP_CODE = GENERIC_TRAP_NAME.invert
def generic_trap=(trap)
@generic_trap = GENERIC_TRAP_CODE[trap]
unless @generic_trap
if trap.respond_to?(:to_i) && GENERIC_TRAP_NAME[trap.to_i]
@generic_trap = trap
else
raise InvalidGenericTrap, trap.to_s
end
end
end
def generic_trap
GENERIC_TRAP_NAME[@generic_trap]
end
def encode
pdu_data = @enterprise.encode <<
@agent_addr.encode <<
encode_integer(@generic_trap) <<
encode_integer(@specific_trap) <<
@timestamp.encode <<
@varbind_list.encode
encode_tlv(SNMPv1_Trap_PDU_TAG, pdu_data)
end
def each_varbind(&block)
@varbind_list.each(&block)
end
end
end