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IETF RFC 8956
Last modified on Thursday, December 31st, 2020
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Internet Engineering Task Force (IETF) C. Loibl, Ed.
Request for Comments: 8956 next layer Telekom GmbH
Updates: 8955 R. Raszuk, Ed.
Category: Standards Track NTT Network Innovations
ISSN: 2070-1721 S. Hares, Ed.
Huawei
December 2020
Dissemination of Flow Specification Rules for IPv6
 Abstract
"Dissemination of Flow Specification Rules" (RFC 8955) provides a
Border Gateway Protocol (BGP) extension for the propagation of
traffic flow information for the purpose of rate limiting or
filtering IPv4 protocol data packets.
This document extends RFC 8955 with IPv6 functionality. It also
updates RFC 8955 by changing the IANA Flow Spec Component Types
registry.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/RFC 8956.
Copyright Notice
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.
Table of Contents
1. Introduction
1.1. Definitions of Terms Used in This Memo
2. IPv6 Flow Specification Encoding in BGP
3. IPv6 Flow Specification Components
3.1. Type 1 - Destination IPv6 Prefix
3.2. Type 2 - Source IPv6 Prefix
3.3. Type 3 - Upper-Layer Protocol
3.4. Type 7 - ICMPv6 Type
3.5. Type 8 - ICMPv6 Code
3.6. Type 12 - Fragment
3.7. Type 13 - Flow Label (new)
3.8. Encoding Examples
4. Ordering of Flow Specifications
5. Validation Procedure
6. IPv6 Traffic Filtering Action Changes
6.1. Redirect IPv6 (rt-redirect-ipv6) Type 0x000d
7. Security Considerations
8. IANA Considerations
8.1. Flow Spec IPv6 Component Types
8.2. IPv6-Address-Specific Extended Community Flow Spec IPv6
Actions
9. Normative References
Appendix A. Example Python Code: flow_rule_cmp_v6
Acknowledgments
Contributors
Authors' Addresses
1. Introduction
The growing amount of IPv6 traffic in private and public networks
requires the extension of tools used in IPv4-only networks to also
support IPv6 data packets.
This document analyzes the differences between describing IPv6
[RFC 8200] flows and those of IPv4 packets. It specifies new Border
Gateway Protocol [RFC 4271] encoding formats to enable "Dissemination
of Flow Specification Rules" [RFC 8955] for IPv6.
This specification is an extension of the base established in
[RFC 8955]. 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.
1.1. Definitions of Terms Used in This Memo
AFI: Address Family Identifier
AS: Autonomous System
NLRI: Network Layer Reachability Information
SAFI: Subsequent Address Family Identifier
VRF: Virtual Routing and Forwarding
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 [RFC 2119] [RFC 8174] when, and only when, they appear in all
capitals, as shown here.
2. IPv6 Flow Specification Encoding in BGP
[RFC 8955] defines SAFIs 133 (Dissemination of Flow Specification
rules) and 134 (L3VPN Dissemination of Flow Specification rules) in
order to carry the corresponding 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 [RFC 4760]. The
(AFI, SAFI) pair carried in the Multiprotocol Extension Capability
MUST be (AFI=2, SAFI=133) for IPv6 Flow Specification rules and
(AFI=2, SAFI=134) for L3VPN Dissemination of Flow Specification
rules.
3. IPv6 Flow Specification Components
The encoding of each of the components begins with a Type field (1
octet) followed by a variable length parameter. The following
sections define component types and parameter encodings for IPv6.
Types 4 (Port), 5 (Destination Port), 6 (Source Port), 9 (TCP Flags),
10 (Packet Length), and 11 (DSCP), as defined in [RFC 8955], also
apply to IPv6. Note that IANA has updated the "Flow Spec Component
Types" registry in order to contain both IPv4 and IPv6 Flow
Specification component type numbers in a single registry
(Section 8).
3.1. Type 1 - Destination IPv6 Prefix
Encoding: <type (1 octet), length (1 octet), offset (1 octet),
pattern (variable), padding (variable) >
This defines the destination prefix to match. The offset has been
defined to allow for flexible matching to portions of an IPv6 address
where one is required to skip over the first N bits of the address.
(These bits skipped are often indicated as "don't care" bits.) 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 pattern contains enough octets
for the bits used in matching (length minus offset bits).
length: This indicates the N-th most significant bit in the
address where bitwise pattern matching stops.
offset: This indicates the number of most significant address bits
to skip before bitwise pattern matching starts.
pattern: This contains the matching pattern. The length of the
pattern is defined by the number of bits needed for
pattern matching (length minus offset).
padding: This contains the minimum number of bits required to pad
the component to an octet boundary. Padding bits MUST be
0 on encoding and MUST be ignored on decoding.
If length = 0 and offset = 0, this component matches every address;
otherwise, length MUST be in the range offset < length < 129 or the
component is malformed.
Note: This Flow Specification component can be represented by the
notation ipv6address/length if offset is 0 or ipv6address/offset-
length. The ipv6address in this notation is the textual IPv6
representation of the pattern shifted to the right by the number of
offset bits. See also Section 3.8.
3.2. Type 2 - Source IPv6 Prefix
Encoding: <type (1 octet), length (1 octet), offset (1 octet),
pattern (variable), padding (variable) >
This defines the source prefix to match. The length, offset,
pattern, and padding are the same as in Section 3.1.
3.3. Type 3 - Upper-Layer Protocol
Encoding: <type (1 octet), [numeric_op, value]+>
This contains a list of {numeric_op, value} pairs that are used to
match the first Next Header value octet in IPv6 packets that is not
an extension header and thus indicates that the next item in the
packet is the corresponding upper-layer header (see Section 4 of
[RFC 8200]).
This component uses the Numeric Operator (numeric_op) described in
Section 4.2.1.1 of [RFC 8955]. Type 3 component values SHOULD be
encoded as a single octet (numeric_op len=00).
Note: While IPv6 allows for more than one Next Header field in the
packet, the main goal of the Type 3 Flow Specification component is
to match on the first upper-layer IP protocol value. Therefore, the
definition is limited to match only on this specific Next Header
field in the packet.
3.4. Type 7 - ICMPv6 Type
Encoding: <type (1 octet), [numeric_op, value]+>
This defines a list of {numeric_op, value} pairs used to match the
Type field of an ICMPv6 packet (see also Section 2.1 of [RFC 4443]).
This component uses the Numeric Operator (numeric_op) described in
Section 4.2.1.1 of [RFC 8955]. Type 7 component values SHOULD be
encoded as a single octet (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 upper-layer IP
protocol 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.
3.5. Type 8 - ICMPv6 Code
Encoding: <type (1 octet), [numeric_op, value]+>
This defines a list of {numeric_op, value} pairs used to match the
code field of an ICMPv6 packet (see also Section 2.1 of [RFC 4443]).
This component uses the Numeric Operator (numeric_op) described in
Section 4.2.1.1 of [RFC 8955]. Type 8 component values SHOULD be
encoded as a single octet (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 upper-layer IP
protocol 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.
3.6. Type 12 - Fragment
Encoding: <type (1 octet), [bitmask_op, bitmask]+>
This defines a list of {bitmask_op, bitmask} pairs used to match
specific IP fragments.
This component uses the Bitmask Operator (bitmask_op) described in
Section 4.2.1.2 of [RFC 8955]. The Type 12 component bitmask MUST be
encoded as a single octet 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:
IsF: Is a fragment other than the first -- match if IPv6 Fragment
Header (Section 4.5 of [RFC 8200]) Fragment Offset is not 0
FF: First fragment -- match if IPv6 Fragment Header (Section 4.5 of
[RFC 8200]) Fragment Offset is 0 AND M flag is 1
LF: Last fragment -- match if IPv6 Fragment Header (Section 4.5 of
[RFC 8200]) Fragment Offset is not 0 AND M flag is 0
0: MUST be set to 0 on NLRI encoding and MUST be ignored during
decoding
3.7. Type 13 - Flow Label (new)
Encoding: <type (1 octet), [numeric_op, value]+>
This contains a list of {numeric_op, value} pairs that are used to
match the 20-bit Flow Label IPv6 header field (Section 3 of
[RFC 8200]).
This component uses the Numeric Operator (numeric_op) described in
Section 4.2.1.1 of [RFC 8955]. Type 13 component values SHOULD be
encoded as 4-octet quantities (numeric_op len=10).
3.8. Encoding Examples
3.8.1. Example 1
The following example demonstrates the prefix encoding for packets
from ::1234:5678:9a00:0/64-104 to 2001:db8::/32 and upper-layer
protocol tcp.
+======+======================+=========================+==========+
| len | destination | source | ul-proto |
+======+======================+=========================+==========+
| 0x12 | 01 20 00 20 01 0d bb | 02 68 40 12 34 56 78 9a | 03 81 06 |
+------+----------------------+-------------------------+----------+
Table 1
Decoded:
+=======+============+=================================+
| Value | | |
+=======+============+=================================+
| 0x12 | length | 18 octets (if len<240, 1 octet) |
+-------+------------+---------------------------------+
| 0x01 | type | Type 1 - Dest. IPv6 Prefix |
+-------+------------+---------------------------------+
| 0x20 | length | 32 bits |
+-------+------------+---------------------------------+
| 0x00 | offset | 0 bits |
+-------+------------+---------------------------------+
| 0x20 | pattern | |
+-------+------------+---------------------------------+
| 0x01 | pattern | |
+-------+------------+---------------------------------+
| 0x0d | pattern | |
+-------+------------+---------------------------------+
| 0xb8 | pattern | (no padding needed) |
+-------+------------+---------------------------------+
| 0x02 | type | Type 2 - Source IPv6 Prefix |
+-------+------------+---------------------------------+
| 0x68 | length | 104 bits |
+-------+------------+---------------------------------+
| 0x40 | offset | 64 bits |
+-------+------------+---------------------------------+
| 0x12 | pattern | |
+-------+------------+---------------------------------+
| 0x34 | pattern | |
+-------+------------+---------------------------------+
| 0x56 | pattern | |
+-------+------------+---------------------------------+
| 0x78 | pattern | |
+-------+------------+---------------------------------+
| 0x9a | pattern | (no padding needed) |
+-------+------------+---------------------------------+
| 0x03 | type | Type 3 - Upper-Layer Protocol |
+-------+------------+---------------------------------+
| 0x81 | numeric_op | end-of-list, value size=1, == |
+-------+------------+---------------------------------+
| 0x06 | value | 06 |
+-------+------------+---------------------------------+
Table 2
This constitutes an NLRI with an NLRI length of 18 octets.
Padding is not needed either for the destination prefix pattern
(length - offset = 32 bits) or for the source prefix pattern (length
- offset = 40 bits), as both patterns end on an octet boundary.
3.8.2. Example 2
The following example demonstrates the prefix encoding for all
packets from ::1234:5678:9a00:0/65-104 to 2001:db8::/32.
+========+======================+=========================+
| length | destination | source |
+========+======================+=========================+
| 0x0f | 01 20 00 20 01 0d b8 | 02 68 41 24 68 ac f1 34 |
+--------+----------------------+-------------------------+
Table 3
Decoded:
+=======+=============+=================================+
| Value | | |
+=======+=============+=================================+
| 0x0f | length | 15 octets (if len<240, 1 octet) |
+-------+-------------+---------------------------------+
| 0x01 | type | Type 1 - Dest. IPv6 Prefix |
+-------+-------------+---------------------------------+
| 0x20 | length | 32 bits |
+-------+-------------+---------------------------------+
| 0x00 | offset | 0 bits |
+-------+-------------+---------------------------------+
| 0x20 | pattern | |
+-------+-------------+---------------------------------+
| 0x01 | pattern | |
+-------+-------------+---------------------------------+
| 0x0d | pattern | |
+-------+-------------+---------------------------------+
| 0xb8 | pattern | (no padding needed) |
+-------+-------------+---------------------------------+
| 0x02 | type | Type 2 - Source IPv6 Prefix |
+-------+-------------+---------------------------------+
| 0x68 | length | 104 bits |
+-------+-------------+---------------------------------+
| 0x41 | offset | 65 bits |
+-------+-------------+---------------------------------+
| 0x24 | pattern | |
+-------+-------------+---------------------------------+
| 0x68 | pattern | |
+-------+-------------+---------------------------------+
| 0xac | pattern | |
+-------+-------------+---------------------------------+
| 0xf1 | pattern | |
+-------+-------------+---------------------------------+
| 0x34 | pattern/pad | (contains 1 bit of padding) |
+-------+-------------+---------------------------------+
Table 4
This constitutes an NLRI with an NLRI length of 15 octets.
The source prefix pattern is 104 - 65 = 39 bits in length. After the
pattern, one bit of padding needs to be added so that the component
ends on an octet boundary. However, only the first 39 bits are
actually used for bitwise pattern matching, starting with a 65-bit
offset from the topmost bit of the address.
4. Ordering of Flow Specifications
The definition for the order of traffic filtering rules from
Section 5.1 of [RFC 8955] is 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
Specification 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>.
5. Validation Procedure
The validation procedure is the same as specified in Section 6 of
[RFC 8955] with the exception that item a) of the validation procedure
should now read as follows:
| a) A destination prefix component with offset=0 is embedded in
| the Flow Specification
6. IPv6 Traffic Filtering Action Changes
Traffic Filtering Actions from Section 7 of [RFC 8955] 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.
6.1. Redirect IPv6 (rt-redirect-ipv6) Type 0x000d
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 IPv6-Address-Specific Extended Community uses the same encoding
as the IPv6-Address-Specific Route-Target Extended Community
(Section 2 of [RFC 5701]) with the Type value always 0x000d.
The Local Administrator subfield contains a number from a numbering
space that is administered by the organization to which the IP
address carried in the Global Administrator subfield has been
assigned by an appropriate authority.
Interferes with: All BGP Flow Specification redirect Traffic
Filtering Actions (with itself and those specified in Section 7.4 of
[RFC 8955]).
7. Security Considerations
This document extends the functionality in [RFC 8955] to be applicable
to IPv6 data packets. The same security considerations from
[RFC 8955] now also apply to IPv6 networks.
[RFC 7112] describes the impact of oversized IPv6 header chains when
trying to match on the transport header; Section 4.5 of [RFC 8200]
also requires that the first fragment must include the upper-layer
header, but there could be wrongly formatted packets not respecting
[RFC 8200]. IPv6 Flow Specification component Type 3 (Section 3.3)
will not be enforced for those illegal packets. Moreover, there are
hardware limitations in several routers (Section 1 of [RFC 8883]) that
may make it impossible to enforce a policy signaled by a Type 3 Flow
Specification component or Flow Specification components that match
on upper-layer properties of the packet.
8. IANA Considerations
This section complies with [RFC 7153].
8.1. Flow Spec IPv6 Component Types
IANA has created and maintains a registry entitled "Flow Spec
Component Types". IANA has added this document as a reference for
that registry. Furthermore, the registry has been updated to also
contain the IPv6 Flow Specification Component Types as described
below. The registration procedure remains unchanged.
8.1.1. Registry Template
Type Value: contains the assigned Flow Specification component type
value
IPv4 Name: contains the associated IPv4 Flow Specification
component name as specified in [RFC 8955]
IPv6 Name: contains the associated IPv6 Flow Specification
component name as specified in this document
Reference: contains references to the specifications
8.1.2. Registry Contents
Type Value: 0
IPv4 Name: Reserved
IPv6 Name: Reserved
Reference: [RFC 8955], RFC 8956
Type Value: 1
IPv4 Name: Destination Prefix
IPv6 Name: Destination IPv6 Prefix
Reference: [RFC 8955], RFC 8956
Type Value: 2
IPv4 Name: Source Prefix
IPv6 Name: Source IPv6 Prefix
Reference: [RFC 8955], RFC 8956
Type Value: 3
IPv4 Name: IP Protocol
IPv6 Name: Upper-Layer Protocol
Reference: [RFC 8955], RFC 8956
Type Value: 4
IPv4 Name: Port
IPv6 Name: Port
Reference: [RFC 8955], RFC 8956
Type Value: 5
IPv4 Name: Destination Port
IPv6 Name: Destination Port
Reference: [RFC 8955], RFC 8956
Type Value: 6
IPv4 Name: Source Port
IPv6 Name: Source Port
Reference: [RFC 8955], RFC 8956
Type Value: 7
IPv4 Name: ICMP Type
IPv6 Name: ICMPv6 Type
Reference: [RFC 8955], RFC 8956
Type Value: 8
IPv4 Name: ICMP Code
IPv6 Name: ICMPv6 Code
Reference: [RFC 8955], RFC 8956
Type Value: 9
IPv4 Name: TCP Flags
IPv6 Name: TCP Flags
Reference: [RFC 8955], RFC 8956
Type Value: 10
IPv4 Name: Packet Length
IPv6 Name: Packet Length
Reference: [RFC 8955], RFC 8956
Type Value: 11
IPv4 Name: DSCP
IPv6 Name: DSCP
Reference: [RFC 8955], RFC 8956
Type Value: 12
IPv4 Name: Fragment
IPv6 Name: Fragment
Reference: [RFC 8955], RFC 8956
Type Value: 13
IPv4 Name: Unassigned
IPv6 Name: Flow Label
Reference: RFC 8956
Type Value: 14-254
IPv4 Name: Unassigned
IPv6 Name: Unassigned
Type Value: 255
IPv4 Name: Reserved
IPv6 Name: Reserved
Reference: [RFC 8955], RFC 8956
8.2. IPv6-Address-Specific Extended Community Flow Spec IPv6 Actions
IANA maintains a registry entitled "Transitive IPv6-Address-Specific
Extended Community Types". For the purpose of this work, IANA has
assigned a new value:
+============+===================================+===========+
| Type Value | Name | Reference |
+============+===================================+===========+
| 0x000d | Flow spec rt-redirect-ipv6 format | RFC 8956 |
+------------+-----------------------------------+-----------+
Table 5: Transitive IPv6-Address-Specific Extended
Community Types Registry
9. Normative References
[RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC 2119, March 1997,
<https://www.rfc-editor.org/info/RFC 2119>.
[RFC 4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC 4271, January 2006,
<https://www.rfc-editor.org/info/RFC 4271>.
[RFC 4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC 4443, March 2006,
<https://www.rfc-editor.org/info/RFC 4443>.
[RFC 4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760,
DOI 10.17487/RFC 4760, January 2007,
<https://www.rfc-editor.org/info/RFC 4760>.
[RFC 5701] Rekhter, Y., "IPv6 Address Specific BGP Extended Community
Attribute", RFC 5701, DOI 10.17487/RFC 5701, November 2009,
<https://www.rfc-editor.org/info/RFC 5701>.
[RFC 7112] Gont, F., Manral, V., and R. Bonica, "Implications of
Oversized IPv6 Header Chains", RFC 7112,
DOI 10.17487/RFC 7112, January 2014,
<https://www.rfc-editor.org/info/RFC 7112>.
[RFC 7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP
Extended Communities", RFC 7153, DOI 10.17487/RFC 7153,
March 2014, <https://www.rfc-editor.org/info/RFC 7153>.
[RFC 8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC 8174,
May 2017, <https://www.rfc-editor.org/info/RFC 8174>.
[RFC 8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC 8200, July 2017,
<https://www.rfc-editor.org/info/RFC 8200>.
[RFC 8883] Herbert, T., "ICMPv6 Errors for Discarding Packets Due to
Processing Limits", RFC 8883, DOI 10.17487/RFC 8883,
September 2020, <https://www.rfc-editor.org/info/RFC 8883>.
[RFC 8955] Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
Bacher, "Dissemination of Flow Specification Rules",
RFC 8955, DOI 10.17487/RFC 8955, December 2020,
<https://www.rfc-editor.org/info/RFC 8955>.
Appendix A. Example Python Code: flow_rule_cmp_v6
<CODE BEGINS>
"""
Copyright (c) 2020 IETF Trust and the persons identified as authors
of the code. 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
(https://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 none 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 an 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 according 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
RFC 8956.
"""
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>
Acknowledgments
The authors would like to thank Pedro Marques, Hannes Gredler, Bruno
Rijsman, Brian Carpenter, and Thomas Mangin for their valuable input.
Contributors
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
United States of America
Email: akarch@cisco.com
Authors' Addresses
Christoph Loibl (editor)
next layer Telekom GmbH
Mariahilfer Guertel 37/7
1150 Vienna
Austria
Phone: +43 664 1176414
Email: cl@tix.at
Robert Raszuk (editor)
NTT Network Innovations
940 Stewart Dr
Sunnyvale, CA 94085
United States of America
Email: robert@raszuk.net
Susan Hares (editor)
Huawei
7453 Hickory Hill
Saline, MI 48176
United States of America
Email: shares@ndzh.com
RFC TOTAL SIZE: 34485 bytes
PUBLICATION DATE: Thursday, December 31st, 2020
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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