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packet lib: implement basic part of BGP-4

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Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
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YAMAMOTO Takashi 2013-09-24 10:19:53 +09:00 committed by FUJITA Tomonori
parent ba7bde95fd
commit ba92a9e634
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# Copyright (C) 2013 Nippon Telegraph and Telephone Corporation.
# Copyright (C) 2013 YAMAMOTO Takashi <yamamoto at valinux co jp>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
RFC 4271 BGP-4
"""
# todo
# - streaming parser
# - notify data
# - notify subcode constants
# - RFC 1997 BGP Communities Attribute
# - RFC 2918 Route Refresh Capability for BGP-4
# - RFC 3107 Carrying Label Information in BGP-4
# - RFC 4360 BGP Extended Communities Attribute
# - RFC 4364 BGP/MPLS IP Virtual Private Networks (VPNs)
# - RFC 4486 Subcodes for BGP Cease Notification Message
# - RFC 4760 Multiprotocol Extensions for BGP-4
import struct
from ryu.ofproto.ofproto_parser import msg_pack_into
from ryu.lib.stringify import StringifyMixin
from ryu.lib.packet import packet_base
from ryu.lib import addrconv
BGP_MSG_OPEN = 1
BGP_MSG_UPDATE = 2
BGP_MSG_NOTIFICATION = 3
BGP_MSG_KEEPALIVE = 4
BGP_MSG_ROUTE_REFRESH = 5 # RFC 2918
# RFC 4271 4.5.
BGP_ERROR_MESSAGE_HEADER_ERROR = 1
BGP_ERROR_OPEN_MESSAGE_ERROR = 2
BGP_ERROR_UPDATE_MESSAGE_ERROR = 3
BGP_ERROR_HOLD_TIMER_EXPIRED = 4
BGP_ERROR_FSM_ERROR = 5
BGP_ERROR_CEASE = 6
_VERSION = 4
_MARKER = 16 * '\xff'
BGP_OPT_CAPABILITY = 2 # RFC 3392
BGP_ATTR_FLAG_OPTIONAL = 1 << 7
BGP_ATTR_FLAG_TRANSITIVE = 1 << 6
BGP_ATTR_FLAG_PARTIAL = 1 << 5
BGP_ATTR_FLAG_EXTENDED_LENGTH = 1 << 4
BGP_ATTR_TYPE_ORIGIN = 1
BGP_ATTR_TYPE_AS_PATH = 2
BGP_ATTR_TYPE_NEXT_HOP = 3
BGP_ATTR_TYPE_MULTI_EXIT_DISC = 4
BGP_ATTR_TYPE_LOCAL_PREF = 5
BGP_ATTR_TYPE_ATOMIC_AGGREGATE = 6
BGP_ATTR_TYPE_AGGREGATOR = 7
BGP_ATTR_TYPE_MP_REACH_NLRI = 14 # RFC 4760
BGP_ATTR_TYPE_MP_UNREACH_NLRI = 15 # RFC 4760
def pad(bin, len_):
assert len(bin) <= len_
return bin + (len_ - len(bin)) * '\0'
class _IPAddrPrefix(StringifyMixin):
_PACK_STR = '!B' # length
def __init__(self, length, ip_addr):
self.length = length
self.ip_addr = ip_addr
@classmethod
def parser(cls, buf):
(length, ) = struct.unpack_from(cls._PACK_STR, buffer(buf))
rest = buf[struct.calcsize(cls._PACK_STR):]
byte_length = (length + 7) / 8
ip_addr = addrconv.ipv4.bin_to_text(pad(rest[:byte_length], 4))
rest = rest[byte_length:]
return cls(length=length, ip_addr=ip_addr), rest
def serialize(self):
# fixup
byte_length = (self.length + 7) / 8
bin_ip_addr = addrconv.ipv4.text_to_bin(self.ip_addr)
if (self.length % 8) == 0:
bin_ip_addr = bin_ip_addr[:byte_length]
else:
# clear trailing bits in the last octet.
# rfc doesn't require this.
mask = 0xff00 >> (self.length % 8)
last_byte = chr(ord(bin_ip_addr[byte_length - 1]) & mask)
bin_ip_addr = bin_ip_addr[:byte_length - 1] + last_byte
self.ip_addr = addrconv.ipv4.bin_to_text(pad(bin_ip_addr, 4))
buf = bytearray()
msg_pack_into(self._PACK_STR, buf, 0, self.length)
return buf + bytes(bin_ip_addr)
class BGPOptParam(StringifyMixin):
_PACK_STR = '!BB' # type, length
def __init__(self, type_, value, length=None):
self.type = type_
self.length = length
self.value = value
@classmethod
def parser(cls, buf):
(type_, length) = struct.unpack_from(cls._PACK_STR, buffer(buf))
rest = buf[struct.calcsize(cls._PACK_STR):]
value = bytes(rest[:length])
rest = rest[length:]
return cls(type_=type_, length=length, value=value), rest
def serialize(self):
# fixup
self.length = len(self.value)
buf = bytearray()
msg_pack_into(self._PACK_STR, buf, 0, self.type, self.length)
return buf + bytes(self.value)
class BGPWithdrawnRoute(_IPAddrPrefix):
pass
class BGPPathAttribute(StringifyMixin):
_PACK_STR = '!BB' # flags, type
_PACK_STR_LEN = '!B' # length
_PACK_STR_EXT_LEN = '!H' # length w/ BGP_ATTR_FLAG_EXTENDED_LENGTH
def __init__(self, flags, type_, value, length=None):
self.flags = flags
self.type = type_
self.length = length
self.value = value
@classmethod
def parser(cls, buf):
(flags, type_) = struct.unpack_from(cls._PACK_STR, buffer(buf))
rest = buf[struct.calcsize(cls._PACK_STR):]
if (flags & BGP_ATTR_FLAG_EXTENDED_LENGTH) != 0:
len_pack_str = cls._PACK_STR_EXT_LEN
else:
len_pack_str = cls._PACK_STR_LEN
(length,) = struct.unpack_from(len_pack_str, buffer(rest))
rest = rest[struct.calcsize(len_pack_str):]
value = bytes(rest[:length])
rest = rest[length:]
return cls(flags=flags, type_=type_, length=length, value=value), rest
def serialize(self):
# fixup
self.length = len(self.value)
if self.length > 255:
self.flags |= BGP_ATTR_FLAG_EXTENDED_LENGTH
len_pack_str = self._PACK_STR_EXT_LEN
else:
self.flags &= ~BGP_ATTR_FLAG_EXTENDED_LENGTH
len_pack_str = self._PACK_STR_LEN
buf = bytearray()
msg_pack_into(self._PACK_STR, buf, 0, self.flags, self.type)
msg_pack_into(len_pack_str, buf, len(buf), self.length)
return buf + bytes(self.value)
class BGPNLRI(_IPAddrPrefix):
pass
class BGPMessage(packet_base.PacketBase):
"""Base class for BGP-4 messages.
An instance has the following attributes at least.
Most of them are same to the on-wire counterparts but in host byte
order.
__init__ takes the correspondig args in this order.
========================== ===============================================
Attribute Description
========================== ===============================================
marker Marker field. Ignored when encoding.
len Length field. Ignored when encoding.
type Type field. one of BGP\_MSG\_ constants.
========================== ===============================================
"""
_HDR_PACK_STR = '!16sHB' # marker, len, type
_HDR_LEN = struct.calcsize(_HDR_PACK_STR)
_TYPES = {}
@classmethod
def register_type(cls, type_):
def _register_type(subcls):
cls._TYPES[type_] = subcls
return subcls
return _register_type
def __init__(self, type_, len_=None, marker=None):
if marker is None:
self.marker = _MARKER
else:
self.marker = marker
self.len = len_
self.type = type_
@classmethod
def parser(cls, buf):
(marker, len_, type_) = struct.unpack_from(cls._HDR_PACK_STR,
buffer(buf))
subcls = cls._TYPES[type_]
kwargs = subcls.parser(buf[cls._HDR_LEN:])
return subcls(marker=marker, len_=len_, type_=type_, **kwargs)
def serialize(self):
# fixup
self.marker = _MARKER
tail = self.serialize_tail()
self.len = self._HDR_LEN + len(tail)
hdr = bytearray(struct.pack(self._HDR_PACK_STR, self.marker,
self.len, self.type))
return hdr + tail
def __len__(self):
# XXX destructive
buf = self.serialize()
return len(buf)
@BGPMessage.register_type(BGP_MSG_OPEN)
class BGPOpen(BGPMessage):
"""BGP-4 OPEN Message encoder/decoder class.
An instance has the following attributes at least.
Most of them are same to the on-wire counterparts but in host byte
order.
__init__ takes the correspondig args in this order.
========================== ===============================================
Attribute Description
========================== ===============================================
marker Marker field. Ignored when encoding.
len Length field. Ignored when encoding.
type Type field. The default is BGP_MSG_OPEN.
version Version field. The default is 4.
my_as My Autonomous System field. 2 octet unsigned
integer.
hold_time Hold Time field. 2 octet unsigned integer.
The default is 0.
bgp_identifier BGP Identifier field. An IPv4 address.
For example, '192.0.2.1'
opt_param_len Optional Parameters Length field.
Ignored when encoding.
opt_param Optional Parameters field. A list of
BGPOptParam instances. The default is [].
========================== ===============================================
"""
_PACK_STR = '!BHH4sB'
_MIN_LEN = BGPMessage._HDR_LEN + struct.calcsize(_PACK_STR)
def __init__(self, my_as, bgp_identifier, type_=BGP_MSG_OPEN,
opt_param_len=0, opt_param=[],
version=_VERSION, hold_time=0, len_=None, marker=None):
super(BGPOpen, self).__init__(marker=marker, len_=len_, type_=type_)
self.version = version
self.my_as = my_as
self.bgp_identifier = bgp_identifier
self.hold_time = hold_time
self.opt_param_len = opt_param_len
self.opt_param = opt_param
@classmethod
def parser(cls, buf):
(version, my_as, hold_time,
bgp_identifier, opt_param_len) = struct.unpack_from(cls._PACK_STR,
buffer(buf))
rest = buf[struct.calcsize(cls._PACK_STR):]
binopts = rest[:opt_param_len]
opt_param = []
while binopts:
opt, binopts = BGPOptParam.parser(binopts)
opt_param.append(opt)
return {
"version": version,
"my_as": my_as,
"hold_time": hold_time,
"bgp_identifier": addrconv.ipv4.bin_to_text(bgp_identifier),
"opt_param_len": opt_param_len,
"opt_param": opt_param,
}
def serialize_tail(self):
# fixup
self.version = _VERSION
binopts = bytearray()
for opt in self.opt_param:
binopts += opt.serialize()
self.opt_param_len = len(binopts)
msg = bytearray(struct.pack(self._PACK_STR,
self.version,
self.my_as,
self.hold_time,
addrconv.ipv4.text_to_bin(
self.bgp_identifier),
self.opt_param_len))
msg += binopts
return msg
@BGPMessage.register_type(BGP_MSG_UPDATE)
class BGPUpdate(BGPMessage):
"""BGP-4 UPDATE Message encoder/decoder class.
An instance has the following attributes at least.
Most of them are same to the on-wire counterparts but in host byte
order.
__init__ takes the correspondig args in this order.
========================== ===============================================
Attribute Description
========================== ===============================================
marker Marker field. Ignored when encoding.
len Length field. Ignored when encoding.
type Type field. The default is BGP_MSG_UPDATE.
withdrawn_routes_len Withdrawn Routes Length field.
Ignored when encoding.
withdrawn_routes Withdrawn Routes field. A list of
BGPWithdrawnRoute instances.
The default is [].
total_path_attribute_len Total Path Attribute Length field.
Ignored when encoding.
path_attributes Path Attributes field. A list of
BGPPathAttribute instances.
The default is [].
nlri Network Layer Reachability Information field.
A list of BGPNLRI instances.
The default is [].
========================== ===============================================
"""
def __init__(self, type_=BGP_MSG_UPDATE,
withdrawn_routes_len=None,
withdrawn_routes=[],
total_path_attribute_len=None,
path_attributes=[],
nlri=[],
len_=None, marker=None):
super(BGPUpdate, self).__init__(marker=marker, len_=len_, type_=type_)
self.withdrawn_routes_len = withdrawn_routes_len
self.withdrawn_routes = withdrawn_routes
self.total_path_attribute_len = total_path_attribute_len
self.path_attributes = path_attributes
self.nlri = nlri
@classmethod
def parser(cls, buf):
offset = 0
(withdrawn_routes_len,) = struct.unpack_from('!H', buffer(buf), offset)
binroutes = buffer(buf[offset + 2:
offset + 2 + withdrawn_routes_len])
offset += 2 + withdrawn_routes_len
(total_path_attribute_len,) = struct.unpack_from('!H', buffer(buf),
offset)
binpathattrs = buffer(buf[offset + 2:
offset + 2 + total_path_attribute_len])
binnlri = buffer(buf[offset + 2 + total_path_attribute_len:])
withdrawn_routes = []
while binroutes:
r, binroutes = BGPWithdrawnRoute.parser(binroutes)
withdrawn_routes.append(r)
path_attributes = []
while binpathattrs:
pa, binpathattrs = BGPPathAttribute.parser(binpathattrs)
path_attributes.append(pa)
offset += 2 + total_path_attribute_len
nlri = []
while binnlri:
n, binnlri = BGPNLRI.parser(binnlri)
nlri.append(n)
return {
"withdrawn_routes_len": withdrawn_routes_len,
"withdrawn_routes": withdrawn_routes,
"total_path_attribute_len": total_path_attribute_len,
"path_attributes": path_attributes,
"nlri": nlri,
}
def serialize_tail(self):
# fixup
binroutes = bytearray()
for r in self.withdrawn_routes:
binroutes += r.serialize()
self.withdrawn_routes_len = len(binroutes)
binpathattrs = bytearray()
for pa in self.path_attributes:
binpathattrs += pa.serialize()
self.total_path_attribute_len = len(binpathattrs)
binnlri = bytearray()
for n in self.nlri:
binnlri += n.serialize()
msg = bytearray()
offset = 0
msg_pack_into('!H', msg, offset, self.withdrawn_routes_len)
msg += binroutes
offset += 2 + self.withdrawn_routes_len
msg_pack_into('!H', msg, offset, self.total_path_attribute_len)
msg += binpathattrs
offset += 2 + self.total_path_attribute_len
msg += binnlri
return msg
@BGPMessage.register_type(BGP_MSG_KEEPALIVE)
class BGPKeepAlive(BGPMessage):
"""BGP-4 KEEPALIVE Message encoder/decoder class.
An instance has the following attributes at least.
Most of them are same to the on-wire counterparts but in host byte
order.
__init__ takes the correspondig args in this order.
========================== ===============================================
Attribute Description
========================== ===============================================
marker Marker field. Ignored when encoding.
len Length field. Ignored when encoding.
type Type field. The default is BGP_MSG_KEEPALIVE.
========================== ===============================================
"""
_MIN_LEN = BGPMessage._HDR_LEN
def __init__(self, type_=BGP_MSG_KEEPALIVE, len_=None, marker=None):
super(BGPKeepAlive, self).__init__(marker=marker, len_=len_,
type_=type_)
@classmethod
def parser(cls, buf):
return {}
def serialize_tail(self):
return bytearray()
@BGPMessage.register_type(BGP_MSG_NOTIFICATION)
class BGPNotification(BGPMessage):
"""BGP-4 NOTIFICATION Message encoder/decoder class.
An instance has the following attributes at least.
Most of them are same to the on-wire counterparts but in host byte
order.
__init__ takes the correspondig args in this order.
========================== ===============================================
Attribute Description
========================== ===============================================
marker Marker field. Ignored when encoding.
len Length field. Ignored when encoding.
type Type field. The default is
BGP_MSG_NOTIFICATION.
error_code Error code field.
error_subcode Error subcode field.
data Data field. The default is ''.
========================== ===============================================
"""
_PACK_STR = '!BB'
_MIN_LEN = BGPMessage._HDR_LEN + struct.calcsize(_PACK_STR)
def __init__(self,
error_code,
error_subcode,
data='',
type_=BGP_MSG_NOTIFICATION, len_=None, marker=None):
super(BGPNotification, self).__init__(marker=marker, len_=len_,
type_=type_)
self.error_code = error_code
self.error_subcode = error_subcode
self.data = data
@classmethod
def parser(cls, buf):
(error_code, error_subcode,) = struct.unpack_from(cls._PACK_STR,
buffer(buf))
data = bytes(buf[2:])
return {
"error_code": error_code,
"error_subcode": error_subcode,
"data": data,
}
def serialize_tail(self):
msg = bytearray(struct.pack(self._PACK_STR, self.error_code,
self.error_subcode))
msg += self.data
return msg