| IDR Working Group | C. Loibl, Ed. |
| Internet-Draft | next layer Telekom GmbH |
| Intended status: Standards Track | R. Raszuk, Ed. |
| Expires: January 11, 2021 | Bloomberg LP |
| S. Hares, Ed. | |
| Huawei | |
| July 10, 2020 |
Dissemination of Flow Specification Rules for IPv6
draft-ietf-idr-flow-spec-v6-12
Dissemination of Flow Specification Rules I-D.ietf-idr-rfc5575bis provides a protocol extension for propagation of traffic flow information for the purpose of rate limiting or filtering. I-D.ietf-idr-rfc5575bis specifies those extensions for IPv4 protocol data packets only.
This specification extends I-D.ietf-idr-rfc5575bis and defines changes to the original document in order to make it also usable and applicable to IPv6 data packets.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 11, 2021.
Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
The growing amount of IPv6 traffic in private and public networks requires the extension of tools used in the IPv4 only networks to be also capable of supporting IPv6 data packets.
In this document authors analyze the differences of IPv6 [RFC8200] flows description from those of traditional IPv4 packets and propose subset of new encoding formats to enable Dissemination of Flow Specification Rules [I-D.ietf-idr-rfc5575bis] for IPv6.
This specification should be treated as an extension of base [I-D.ietf-idr-rfc5575bis] specification and not its replacement. It only defines the delta changes required to support IPv6 while all other definitions and operation mechanisms of Dissemination of Flow Specification Rules will remain in the main specification and will not be repeated here.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
The [I-D.ietf-idr-rfc5575bis] defines new SAFIs 133 (Dissemination of Flow Specification) and 134 (L3VPN Dissemination of Flow Specification) applications in order to carry corresponding to each such application Flow Specification.
Implementations wishing to exchange IPv6 Flow Specifications MUST use BGP's Capability Advertisement facility to exchange the Multiprotocol Extension Capability Code (Code 1) as defined in [RFC4760]. While [I-D.ietf-idr-rfc5575bis] specifies Flow Specification for IPv4 (AFI=1) only, the (AFI, SAFI) pair carried in the Multiprotocol Extension Capability MUST be: (AFI=2, SAFI=133) for IPv6 Flow Specification, and (AFI=2, SAFI=134) for VPNv6 Flow Specification.
For both SAFIs the indication to which address family they are referring to will be recognized by AFI value (AFI=1 for IPv4 or VPNv4, AFI=2 for IPv6 and VPNv6 respectively).
It needs to be observed that such choice of proposed encoding is compatible with filter validation against routing reachability information as described in Section 6 of [I-D.ietf-idr-rfc5575bis].
The following components are redefined or added for the purpose of accommodating the IPv6 header encoding. Unless otherwise specified all other components defined in [I-D.ietf-idr-rfc5575bis] Section 4.2.2 also apply to IPv6 Flow Specification.
Encoding: <type (1 octet), length (1 octet), offset (1 octet), prefix (variable)>
Defines the destination prefix to match. The offset has been defined to allow for flexible matching on part of the IPv6 address where it is required to skip (don't care) of N first bits of the address. This can be especially useful where part of the IPv6 address consists of an embedded IPv4 address and matching needs to happen only on the embedded IPv4 address. The encoded prefix contains enough octets for the bits used in matching (length minus offset bits).
Encoding: <type (1 octet), length (1 octet), offset (1 octet), prefix (variable)>
Defines the source prefix to match. The length, offset and prefix are the same as in Section 3.1
Encoding: <type (1 octet), [numeric_op, value]+>
Contains a list of {numeric_op, value} pairs that are used to match the last Next Header ([RFC8200] Section 3) value octet in IPv6 packets.
This component uses the Numeric Operator (numeric_op) described in [I-D.ietf-idr-rfc5575bis] Section 4.2.1.1. Type 3 component values SHOULD be encoded as single byte (numeric_op len=00).
Note: While IPv6 allows for more then one Next Header field in the packet the main goal of Type 3 flow specification component is to match on the subsequent IP protocol value. Therefore the definition is limited to match only on last Next Header field in the packet.
Encoding: <type (1 octet), [numeric_op, value]+>
Defines a list of {numeric_op, value} pairs used to match the type field of an ICMPv6 packet (see also [RFC4443] Section 2.1).
This component uses the Numeric Operator (numeric_op) described in [I-D.ietf-idr-rfc5575bis] Section 4.2.1.1. Type 7 component values SHOULD be encoded as single byte (numeric_op len=00).
In case of the presence of the ICMPv6 type component only ICMPv6 packets can match the entire Flow Specification. The ICMPv6 type component, if present, never matches when the packet's last Next Header field value is not 58 (ICMPv6), if the packet is fragmented and this is not the first fragment, or if the system is unable to locate the transport header. Different implementations may or may not be able to decode the transport header.
Encoding: <type (1 octet), [numeric_op, value]+>
Defines a list of {numeric_op, value} pairs used to match the code field of an ICMPv6 packet (see also [RFC4443] Section 2.1).
This component uses the Numeric Operator (numeric_op) described in [I-D.ietf-idr-rfc5575bis] Section 4.2.1.1. Type 8 component values SHOULD be encoded as single byte (numeric_op len=00).
In case of the presence of the ICMPv6 code component only ICMPv6 packets can match the entire Flow Specification. The ICMPv6 code component, if present, never matches when the packet's last Next Header field value is not 58 (ICMPv6), if the packet is fragmented and this is not the first fragment, or if the system is unable to locate the transport header. Different implementations may or may not be able to decode the transport header.
Encoding: <type (1 octet), [bitmask_op, bitmask]+>
Defines a list of {bitmask_op, bitmask} pairs used to match specific IP fragments.
This component uses the Bitmask Operator (bitmask_op) described in [I-D.ietf-idr-rfc5575bis] Section 4.2.1.2. The Type 12 component bitmask MUST be encoded as single byte bitmask (bitmask_op len=00).
0 1 2 3 4 5 6 7
+---+---+---+---+---+---+---+---+
| 0 | 0 | 0 | 0 |LF |FF |IsF| 0 |
+---+---+---+---+---+---+---+---+
Figure 1: Fragment Bitmask Operand
Bitmask values:
Encoding: <type (1 octet), [numeric_op, value]+>
Contains a list of {numeric_op, value} pairs that are used to match the 20-bit Flow Label IPv6 header field ([RFC8200] Section 3).
This component uses the Numeric Operator (numeric_op) described in [I-D.ietf-idr-rfc5575bis] Section 4.2.1.1. Type 13 component values SHOULD be encoded as 1-, 2-, or 4-byte quantities (numeric_op len=00, len=01 or len=10).
The following example demonstrates the prefix encoding for: "all packets to ::1234:5678:9A00:0/64-104 from 100::/8 and port 25".
+--------+-------------------------+-------------+----------+
| length | destination | source | port |
+--------+-------------------------+-------------+----------+
| 0x0f | 01 68 40 12 34 56 78 9A | 02 08 00 01 | 04 81 19 |
+--------+-------------------------+-------------+----------+
+-------+------------+------------------------------+
| Value | | |
+-------+------------+------------------------------+
| 0x0f | length | 16 octets (len<240 1-octet) |
| 0x01 | type | Type 1 - Dest. IPv6 Prefix |
| 0x68 | length | 104 bit |
| 0x40 | offset | 64 bit |
| 0x12 | prefix | |
| 0x34 | prefix | |
| 0x56 | prefix | |
| 0x78 | prefix | |
| 0x9A | prefix | |
| 0x02 | type | Type 2 - Source IPv6 Prefix |
| 0x08 | length | 8 bit |
| 0x00 | offset | 0 bit |
| 0x01 | prefix | |
| 0x04 | type | Type 4 - Port |
| 0x81 | numeric_op | end-of-list, value size=1, = |
| 0x19 | value | 25 |
+-------+------------+------------------------------+
Decoded:
The following example demonstrates the prefix encoding for: "all packets to ::1234:5678:9A00:0/65-104".
+--------+-------------------------+
| length | destination |
+--------+-------------------------+
| 0x08 | 01 68 41 24 68 ac f1 34 |
+--------+-------------------------+
+-------+------------+------------------------------+
| Value | | |
+-------+------------+------------------------------+
| 0x08 | length | 8 octets (len<240 1-octet) |
| 0x01 | type | Type 1 - Dest. IPv6 Prefix |
| 0x68 | length | 104 bit |
| 0x41 | offset | 65 bit |
| 0x24 | prefix | starting with the 66ths bit |
| 0x68 | prefix | |
| 0xac | prefix | |
| 0xf1 | prefix | |
| 0x34 | prefix | |
+-------+------------+------------------------------+
Decoded:
The definition for the order of traffic filtering rules from [I-D.ietf-idr-rfc5575bis] Section 5.1 can be reused with new consideration for the IPv6 prefix offset. As long as the offsets are equal, the comparison is the same, retaining longest-prefix-match semantics. If the offsets are not equal, the lowest offset has precedence, as this flow matches the most significant bit.
The code in Appendix A shows a Python3 implementation of the resulting comparison algorithm. The full code was tested with Python 3.7.2 and can be obtained at https://github.com/stoffi92/draft-ietf-idr-flow-spec-v6/tree/master/flowspec-cmp.
The validation procedure is the same as specified in [I-D.ietf-idr-rfc5575bis] Section 6 with the exception that item a) of the validation procedure should now read as follows:
Traffic Filtering Actions from [I-D.ietf-idr-rfc5575bis] Section 7 can also be applied to IPv6 Flow Specifications. To allow an IPv6 address specific route-target, a new Traffic Filtering Action IPv6 address specific extended community is specified in Section 6.1 below:
The redirect IPv6 address specific extended community allows the traffic to be redirected to a VRF routing instance that lists the specified IPv6 address specific route-target in its import policy. If several local instances match this criteria, the choice between them is a local matter (for example, the instance with the lowest Route Distinguisher value can be elected).
This extended community uses the same encoding as the IPv6 address specific Route Target extended community [RFC5701] Section 2 with the high-order octet of the Type always set to 0x80 and the Sub-Type always TBD.
Interferes with: All BGP Flow Specification redirect Traffic Filtering Actions (with itself and those specified in [I-D.ietf-idr-rfc5575bis] Section 7.4).
No new security issues are introduced to the BGP protocol by this specification over the security considerations in [I-D.ietf-idr-rfc5575bis]
This section complies with [RFC7153]
IANA is requested to create and maintain a new registry entitled: "Flow Spec IPv6 Component Types" containing the initial entries as specified in Table 1.
| Value | Name | Reference |
|---|---|---|
| 1 | Destination IPv6 Prefix | [this document] |
| 2 | Source IPv6 Prefix | [this document] |
| 3 | Next Header | [this document] |
| 4 | Port | [this document] |
| 5 | Destination port | [this document] |
| 6 | Source port | [this document] |
| 7 | ICMPv6 type | [this document] |
| 8 | ICMPv6 code | [this document] |
| 9 | TCP flags | [this document] |
| 10 | Packet length | [this document] |
| 11 | DSCP | [this document] |
| 12 | Fragment | [this document] |
| 13 | Flow Label | [this document] |
In order to manage the limited number space and accommodate several usages, the following policies defined by [RFC8126] are used:
| Type Values | Policy |
|---|---|
| 0 | Reserved |
| [1 .. 127] | Specification Required |
| [128 .. 254] | Expert Review |
| 255 | Reserved |
IANA maintains a registry entitled "Generic Transitive Experimental Use Extended Community Sub-Types". For the purpose of this work, IANA is requested to assign a new value:
| Sub-Type Value | Name | Reference |
|---|---|---|
| TBD | Flow spec rt-redirect-ipv6 format | [this document] |
Authors would like to thank Pedro Marques, Hannes Gredler and Bruno Rijsman, Brian Carpenter, and Thomas Mangin for their valuable input.
Danny McPherson Verisign, Inc. Email: dmcpherson@verisign.com
Burjiz Pithawala Individual Email: burjizp@gmail.com
Andy Karch Cisco Systems 170 West Tasman Drive San Jose, CA 95134 USA Email: akarch@cisco.com
<CODE BEGINS>
"""
Copyright (c) 2020 IETF Trust and the persons identified as authors
of draft-ietf-idr-flow-spec-v6. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, is permitted pursuant to, and subject to the license
terms contained in, the Simplified BSD License set forth in Section
4.c of the IETF Trust’s Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info).
"""
import itertools
import collections
import ipaddress
EQUAL = 0
A_HAS_PRECEDENCE = 1
B_HAS_PRECEDENCE = 2
IP_DESTINATION = 1
IP_SOURCE = 2
FS_component = collections.namedtuple('FS_component',
'component_type value')
class FS_IPv6_prefix_component:
def __init__(self, prefix, offset=0,
component_type=IP_DESTINATION):
self.offset = offset
self.component_type = component_type
# make sure if offset != 0 that non of the
# first offset bits are set in the prefix
self.value = prefix
if offset != 0:
i = ipaddress.IPv6Interface(
(self.value.network_address, offset))
if i.network.network_address != \
ipaddress.ip_address('0::0'):
raise ValueError('Bits set in the offset')
class FS_nlri(object):
"""
FS_nlri class implementation that allows sorting.
By calling .sort() on a array of FS_nlri objects these
will be sorted according to the flow_rule_cmp algorithm.
Example:
nlri = [ FS_nlri(components=[
FS_component(component_type=4,
value=bytearray([0,1,2,3,4,5,6])),
]),
FS_nlri(components=[
FS_component(component_type=5,
value=bytearray([0,1,2,3,4,5,6])),
FS_component(component_type=6,
value=bytearray([0,1,2,3,4,5,6])),
]),
]
nlri.sort() # sorts the array accorinding to the algorithm
"""
def __init__(self, components = None):
"""
components: list of type FS_component
"""
self.components = components
def __lt__(self, other):
# use the below algorithm for sorting
result = flow_rule_cmp_v6(self, other)
if result == B_HAS_PRECEDENCE:
return True
else:
return False
def flow_rule_cmp_v6(a, b):
"""
Implementation of the flowspec sorting algorithm in
draft-ietf-idr-flow-spec-v6.
"""
for comp_a, comp_b in itertools.zip_longest(a.components,
b.components):
# If a component type does not exist in one rule
# this rule has lower precedence
if not comp_a:
return B_HAS_PRECEDENCE
if not comp_b:
return A_HAS_PRECEDENCE
# Higher precedence for lower component type
if comp_a.component_type < comp_b.component_type:
return A_HAS_PRECEDENCE
if comp_a.component_type > comp_b.component_type:
return B_HAS_PRECEDENCE
# component types are equal -> type specific comparison
if comp_a.component_type in (IP_DESTINATION, IP_SOURCE):
if comp_a.offset < comp_b.offset:
return A_HAS_PRECEDENCE
if comp_a.offset < comp_b.offset:
return B_HAS_PRECEDENCE
# both components have the same offset
# assuming comp_a.value, comp_b.value of type
# ipaddress.IPv6Network
# and the offset bits are reset to 0 (since they are
# not represented in the NLRI)
if comp_a.value.overlaps(comp_b.value):
# longest prefixlen has precedence
if comp_a.value.prefixlen > \
comp_b.value.prefixlen:
return A_HAS_PRECEDENCE
if comp_a.value.prefixlen < \
comp_b.value.prefixlen:
return B_HAS_PRECEDENCE
# components equal -> continue with next
# component
elif comp_a.value > comp_b.value:
return B_HAS_PRECEDENCE
elif comp_a.value < comp_b.value:
return A_HAS_PRECEDENCE
else:
# assuming comp_a.value, comp_b.value of type
# bytearray
if len(comp_a.value) == len(comp_b.value):
if comp_a.value > comp_b.value:
return B_HAS_PRECEDENCE
if comp_a.value < comp_b.value:
return A_HAS_PRECEDENCE
# components equal -> continue with next
# component
else:
common = min(len(comp_a.value),
len(comp_b.value))
if comp_a.value[:common] > \
comp_b.value[:common]:
return B_HAS_PRECEDENCE
elif comp_a.value[:common] < \
comp_b.value[:common]:
return A_HAS_PRECEDENCE
# the first common bytes match
elif len(comp_a.value) > len(comp_b.value):
return A_HAS_PRECEDENCE
else:
return B_HAS_PRECEDENCE
return EQUAL
<CODE ENDS>