RFC 8956

Dissemination of Flow Specification Rules for IPv6

📅 published December 2020, from ietf

Dissemination of Flow Specification Rules for IPv6 🎀 (Part 1 of 3)

  • RFC: 8956
  • Authors: C. Loibl, Ed. (next layer Telekom GmbH), R. Raszuk, Ed. (NTT Network Innovations), S. Hares, Ed. (Huawei)
  • Category: Standards Track
  • Date: December 2020
  • ISSN: 2070-1721
  • Updates: RFC 8955
  • Stream: IETF, which is the Internet Engineering Task Force

Abstract ✨

okay so bestie, "Dissemination of Flow Specification Rules" (RFC 8955) gives BGP an extension for spreading traffic flow info around, so networks can rate limit or filter IPv4 packets 🦋

this doc extends RFC 8955 with IPv6 support 💅 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 give feedback on it can be found at https://www.rfc-editor.org/info/rfc8956 🔍

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, because 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 they 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 🌈

more and more IPv6 traffic is zooming through private and public networks, so the tools we use on IPv4-only networks need to level up and handle IPv6 packets too 💖

this doc looks at how describing IPv6 flows [RFC8200] is different from describing IPv4 packets. It defines new Border Gateway Protocol [RFC4271] encoding formats so that "Dissemination of Flow Specification Rules" [RFC8955] works for IPv6 🦋

this spec is an extension of the base set up in [RFC8955]. It only defines the delta changes needed to support IPv6. All the other definitions and operation mechanisms of "Dissemination of Flow Specification Rules" stay in the main spec and aren't repeated here, so no copy-paste drama 💅

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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 🎯

2. IPv6 Flow Specification Encoding in BGP 🛣️

[RFC8955] defines SAFIs 133 (Dissemination of Flow Specification rules) and 134 (L3VPN Dissemination of Flow Specification rules) to carry the matching Flow Specification ✨

Implementations that want 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]. 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 🧩

every component's encoding starts with a Type field (1 octet), followed by a variable length parameter. The next sections define the 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 [RFC8955], also apply to IPv6. Heads up: IANA has updated the "Flow Spec Component Types" registry so it holds both IPv4 and IPv6 Flow Specification component type numbers in one 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 lets you do flexible matching on parts of an IPv6 address, where you need to skip over the first N bits of the address. (The bits that get skipped are often called "don't care" bits.) This is especially handy when part of the IPv6 address is an embedded IPv4 address and matching only needs to happen on that embedded IPv4 address 🪄 The encoded pattern contains enough octets for the bits used in matching (length minus offset bits).

length: This is the N-th most significant bit in the address where bitwise pattern matching stops.

offset: This is the number of most significant address bits to skip before bitwise pattern matching starts.

pattern: This holds the matching pattern. The length of the pattern is set by the number of bits needed for pattern matching (length minus offset).

padding: This holds the minimum number of bits needed to pad the component out 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 written in the notation ipv6address/length if offset is 0, or ipv6address/offset-length if it isn't. 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 work exactly the same as in Section 3.1 🦋

3.3. Type 3 - Upper-Layer Protocol 🍰

Encoding:

<type (1 octet), [numeric_op, value]+>

This holds a list of {numeric_op, value} pairs used to match the first Next Header value octet in IPv6 packets that is not an extension header. That tells you the next item in the packet is the matching upper-layer header (see Section 4 of [RFC8200]) 🔍

This component uses the Numeric Operator (numeric_op) described in Section 4.2.1.1 of [RFC8955]. Type 3 component values SHOULD be encoded as a single octet (numeric_op len=00).

Note: IPv6 allows more than one Next Header field in the packet, but the main goal of the Type 3 Flow Specification component is to match the first upper-layer IP protocol value. So the definition is limited to matching 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 [RFC4443]) ✨

This component uses the Numeric Operator (numeric_op) described in Section 4.2.1.1 of [RFC8955]. Type 7 component values SHOULD be encoded as a single octet (numeric_op len=00).

If the ICMPv6 type component is present, 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), when the packet is fragmented and this is not the first fragment, or when 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 [RFC4443]) 🫧

This component uses the Numeric Operator (numeric_op) described in Section 4.2.1.1 of [RFC8955]. Type 8 component values SHOULD be encoded as a single octet (numeric_op len=00).

If the ICMPv6 code component is present, 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), when the packet is fragmented and this is not the first fragment, or when 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 [RFC8955]. 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 the IPv6 Fragment Header (Section 4.5 of [RFC8200]) Fragment Offset is not 0 🍒
  • FF: First fragment. Match if the IPv6 Fragment Header (Section 4.5 of [RFC8200]) Fragment Offset is 0 AND the M flag is 1 🌟
  • LF: Last fragment. Match if the IPv6 Fragment Header (Section 4.5 of [RFC8200]) Fragment Offset is not 0 AND the M flag is 0 🏁
  • 0: MUST be set to 0 on NLRI encoding and MUST be ignored during decoding 🙈

okay bestie that's the first chunk 💖 Part 2 is next, where we cover the Type 13 Flow Label, encoding examples, and the rest of the spec, so stay tuned 🧚✨

3.7. Type 13 - Flow Label (new) ✨

Okay so this is the Flow Label component, and it's giving main character energy 🦋

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 [RFC8200]). 💖

This component uses the Numeric Operator (numeric_op) described in Section 4.2.1.1 of [RFC8955]. Type 13 component values SHOULD be encoded as 4-octet quantities (numeric_op len=10). 🎀

3.8. Encoding Examples 🌸

3.8.1. Example 1

Bestie, this example shows the prefix encoding for packets from ::1234:5678:9a00:0/64-104 to 2001:db8::/32 with upper-layer protocol tcp. Let's gooo 💅

+======+======================+=========================+==========+
| 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

This one is the prefix encoding for all packets from ::1234:5678:9a00:0/65-104 to 2001:db8::/32. Iconic 🧚

+========+======================+=========================+
| 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. Very precise, very important, bestie 🙈

4. Ordering of Flow Specifications 👑

The definition for the order of traffic filtering rules from Section 5.1 of [RFC8955] 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 [RFC8955] 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 [RFC8955] 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 [RFC5701]) 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 [RFC8955]). 😭

7. Security Considerations 💀

Okay bestie, this part is SERIOUS, so read it carefully 🙈

This document extends the functionality in [RFC8955] to be applicable to IPv6 data packets. The same security considerations from [RFC8955] now also apply to IPv6 networks.

[RFC7112] describes the impact of oversized IPv6 header chains when trying to match on the transport header; Section 4.5 of [RFC8200] also requires that the first fragment must include the upper-layer header, but there could be wrongly formatted packets not respecting [RFC8200]. 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 [RFC8883]) 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 [RFC7153]. 🧚

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 [RFC8955]

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 ✨

okay so here's the actual registry, bestie 📋 every type value lines up with its IPv4 and IPv6 names, plus the doc that defines it 💅

Type Value:  0
IPv4 Name:   Reserved
IPv6 Name:   Reserved
Reference:   [RFC8955], RFC 8956

Type Value:  1
IPv4 Name:   Destination Prefix
IPv6 Name:   Destination IPv6 Prefix
Reference:   [RFC8955], RFC 8956

Type Value:  2
IPv4 Name:   Source Prefix
IPv6 Name:   Source IPv6 Prefix
Reference:   [RFC8955], RFC 8956

Type Value:  3
IPv4 Name:   IP Protocol
IPv6 Name:   Upper-Layer Protocol
Reference:   [RFC8955], RFC 8956

Type Value:  4
IPv4 Name:   Port
IPv6 Name:   Port
Reference:   [RFC8955], RFC 8956

Type Value:  5
IPv4 Name:   Destination Port
IPv6 Name:   Destination Port
Reference:   [RFC8955], RFC 8956

Type Value:  6
IPv4 Name:   Source Port
IPv6 Name:   Source Port
Reference:   [RFC8955], RFC 8956

Type Value:  7
IPv4 Name:   ICMP Type
IPv6 Name:   ICMPv6 Type
Reference:   [RFC8955], RFC 8956

Type Value:  8
IPv4 Name:   ICMP Code
IPv6 Name:   ICMPv6 Code
Reference:   [RFC8955], RFC 8956

Type Value:  9
IPv4 Name:   TCP Flags
IPv6 Name:   TCP Flags
Reference:   [RFC8955], RFC 8956

Type Value:  10
IPv4 Name:   Packet Length
IPv6 Name:   Packet Length
Reference:   [RFC8955], RFC 8956

Type Value:  11
IPv4 Name:   DSCP
IPv6 Name:   DSCP
Reference:   [RFC8955], RFC 8956

Type Value:  12
IPv4 Name:   Fragment
IPv6 Name:   Fragment
Reference:   [RFC8955], 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:   [RFC8955], RFC 8956

8.2. IPv6-Address-Specific Extended Community Flow Spec IPv6 Actions

IANA keeps a registry called "Transitive IPv6-Address-Specific Extended Community Types" 📚 For this work, IANA assigned a brand-new value, and it's giving main character energy 🦋

+============+===================================+===========+
| 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

These are the docs this one leans on, and yes, I'm listing every single one 💖

Appendix A. Example Python Code: flow_rule_cmp_v6

Here's the sorting code, ready to run, no cap 🐍✨

<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

Huge thank-yous to Pedro Marques, Hannes Gredler, Bruno Rijsman, Brian Carpenter, and Thomas Mangin for all their super valuable input 🫶💜

Contributors

Big shoutout to these legends for helping shape this doc 🌸

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

And here are the editors, so you know exactly who to thank (or blame) 🧚

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
📦 where this page comes from