Ipv6 routing header merge #442

anjan-keysight · 2025-09-12T06:57:39Z

IPv6 Segment Routing Header Support

Proposal is for IPv6 segment routing (Type 4) header, This is the first of the IPv6 routing extension header support in OTG model.

The model is made generic to accommodate other IPv6 extension header types, hop-by-hop or fragment. Currently we will support routing extensions only. In routing also we will currently support Type 4 which is segment routing.

Note: The IPv6 next_header if set to AUTO, will be updated to reflect the correct next header type, which is 43 for IPv6 route.

RFC for reference

...
f1Ipv6 := f1.Packet().Add().Ipv6()
f1Ipv6.NextHeader().Auto()

f1Rout := f1.Packet().Add().Ipv6ExtensionHeader().Add().Routing()
f1Rout.NextHeader().Auto()
f1Rout.HdrExtLen().Auto()
f1SR := f1Rout.SegmentRouting()

f1SR.SegmentsLeft().Auto()
f1SR.LastEntry().Auto()
f1SR.Flags().PFlag().SetValue(1)
f1SR.Flags().OFlag().SetValue(1)

f1SegList := f1SR.SegmentList()
f1SegList.Add().Segment().SetValue("0a:0b:0c:00:00:00")
f1SegList.Add().Segment().SetValue("01:02:03:00:00:00")
f1SegList.Add().Segment().SetValue("00:00:00:04:05:06")

f1SRTlv1 := f1SR.Tlvs().Add()
f1SRTlv1.Type().Auto()
f1SRTlv1.Length().Auto()
f1SRTlv1Egr := f1SRTlv1.Egress()

f1SRTlv1Egr.Flags().SetValue(2)
f1SRTlv1Egr.Value().SetValue("0a:0b:0c:00:00:00")
...

apratimmukherjee · 2025-09-12T10:45:29Z

flow/packet-headers/header.yaml

        macsec:
          $ref: './macsec.yaml#/components/schemas/Flow.Macsec'
          x-field-uid: 23
+        ipv6_routing_extension:


This looks incorrect way to approach this. We should be probably having an array of ipv6 extension headers as discussed with choice of routing as one option ( only one as of now )

yes, among of the following Ipv6 header extensions. model is to support the 4th.
Hop-by-Hop Options
Fragment
Destination Options
Routing
Authentication
Encapsulating Security Payload

Updated based on discussion.

apratimmukherjee · 2025-09-12T10:47:07Z

flow/packet-headers/ipv6_routing.yaml

+          x-field-pattern:
+            description: 8-bit selector that identifies the type of header immediately
+              following the SRH. It uses the same values as the IPv4 Protocol field.
+              The default value 59 indicates that there is no next header.


We should probably at least provide a reference to iana/ietf specification for list of values and mention udp and tcp values since that would probably be a likely use-case.

Description updated with tcp / udp values and iana reference.

apratimmukherjee · 2025-09-12T10:47:57Z

flow/packet-headers/ipv6_routing.yaml

+            format: integer
+            length: 8
+            default: 59
+            x-constants:


Mention at least tcp and udp from below in documentation. This is not otherwise visible to the user at all

Updated description

Should provide link to IANA provided in previous comment and also mention that 59 means no next header, indicating that after this extension header, the payload is directly appended.

apratimmukherjee · 2025-09-12T10:48:44Z

flow/packet-headers/ipv6_routing.yaml

+              sctp: 132
+            features: [auto, count]
+          x-field-uid: 1
+        hdr_ext_len:


This should be at a higher level extension header object not repeated in each extension header

I think in some cases absence of auto makes this very hard to use . Also , increment/decrement etc. might not have much meaning for this field.

Added auto and restructured model.

It is still not part of extension header as it should be.

Moved it one level up.

apratimmukherjee · 2025-09-12T10:50:48Z

flow/packet-headers/ipv6_routing.yaml

+              8-octet units, not including the first 8 octets of the SRH itself.
+            format: integer
+            length: 8
+            default: 2


I hope 2 is correct with default settings.

Default is now 0.

apratimmukherjee · 2025-09-12T10:56:04Z

flow/packet-headers/ipv6_routing.yaml

+          description: Variable-length padding bytes. Must be set to 0 on transmission.
+          type: string
+          format: hex
+          default: '00'


Does not align with default length above

Length is common across all TLV types with auto support. Length will be updated based on TLV data.

apratimmukherjee · 2025-09-12T10:56:55Z

flow/packet-headers/ipv6_routing.yaml

+              0 to 5.
+            format: integer
+            length: 8
+            default: 0


Ideal default should be byte padded length of pattern below automatically . Only specify and set for negative testing.

TLV type and length can be auto now.

apratimmukherjee · 2025-09-12T10:59:39Z

flow/packet-headers/ipv6_routing.yaml

+            description: The HMAC digest, truncated to 32 octets. Its length must
+              be a multiple of 8 octets.
+            format: mac
+            type: string


It is very unclear to me why format is mac if length is variable. How will user set this correctly. Even if not now, how would we generate correct hmac value automatically via model if some impl. supports that. It looks very difficult to set this correctly from a script . Also, need to think when packets vary and hmac might vary,

Removed hmac tlv as its not supported in IxN also.

apratimmukherjee · 2025-09-12T11:00:37Z

flow/packet-headers/ipv6_routing.yaml

+          description: The variable-length opaque data carried by the TLV.
+          format: hex
+          type: string
+          default: '00'


Default length and this dont match I think .

Length is common across all TLV types with auto support. Length will be updated based on TLV data.

apratimmukherjee · 2025-09-12T11:02:15Z

flow/packet-headers/ipv6_routing.yaml

+            $ref: '#/components/schemas/Flow.Ipv6SegmentRouting.Segment'
+          x-field-uid: 8
+        tlvs:
+          $ref: '#/components/schemas/Flow.Ipv6SegmentRouting.Tlvs'


Should this not be an array ? How to have just 1 TLV and not the rest . Can some of these TLVs come multiple times esp. path tracing tlv . This somehow seems to be on the wrong track to me,

this will be arrays Tlv objects

Made TLVs as array.

SuryyaKrJana · 2025-09-15T07:17:52Z

flow/packet-headers/ipv6_routing.yaml

+          default: segment_routing
+          x-field-uid: 1
+          x-enum:
+            segment_routing:


I think, we can give name as ipv6_routing (as per rfc: its routing) base choice value . it will be one of the values.
Hop-by-Hop Options
Fragment
Destination Options
Routing
Authentication
Encapsulating Security Payload.

As per rfc, if one or more headers the order is like this. that probably we can document this in future addition.
IPv6 header
Hop-by-Hop Options header
Destination Options header (note 1)
Routing header
Fragment header
Authentication header (note 2)
Encapsulating Security Payload header (note 2)
Destination Options header (note 3)
Upper-Layer header

SuryyaKrJana · 2025-09-15T08:32:22Z

flow/packet-headers/ipv6_routing.yaml

+            features:
+              - count
+          x-field-uid: 1
+        p_flag:


I think, go snappi code will good if change the properly.
Flags().SetProtected(true)
Flags().SetOAM(true)
Flags().SetAlert(true) etc...

Yes, I have updated the Flags section, removed unused flags and renamed remaining ones.

SuryyaKrJana · 2025-09-15T08:38:48Z

flow/packet-headers/ipv6_routing.yaml

+            $ref: '#/components/schemas/Flow.Ipv6SegmentRouting.Segment'
+          x-field-uid: 8
+        tlvs:
+          $ref: '#/components/schemas/Flow.Ipv6SegmentRouting.Tlvs'


this will be arrays Tlv objects

SuryyaKrJana · 2025-09-15T08:49:21Z

flow/packet-headers/ipv6_routing.yaml

+          format: hex
+          default: '00'
+          x-field-uid: 3
+    Flow.Ipv6SegmentRouting.TlvHmac:


If DUT tries to verify this feild should be generated by properly by means of what RFC says. So, how we are giving the input of pre-shared key, whether traffic will generate the HMAC accordingly?

key: The pre-shared key identified by HMAC Key ID
HMAC algorithm: Identified by the HMAC Key ID
Text: A concatenation of the following fields from the IPv6 header and the SRH, as it would be received at the node verifying the HMAC:

IPv6 header: Source address (16 octets)
SRH: Last Entry (1 octet)
SRH: Flags (1 octet)
SRH: HMAC 16 bits following Length
SRH: HMAC Key ID (4 octets)
SRH: All addresses in the Segment List (variable octets)

HMAC TLV is removed from model.

apratimmukherjee

Still have some structural changes TBD and some comments to improve documentation/align attribute names.

apratimmukherjee · 2025-09-18T05:18:13Z

flow/packet-headers/header.yaml

          x-field-uid: 23
+        ipv6_extension_headers:
+          description: Ipv6 extension packet headers. For routing extension headers
+            the IPv6 next header is 43.


I think we should mention that ipv6_extension_header should be preceded by ipv6_header or other ipv6_extension_header(s) and the next_header field in the preceding header should be set to the correct value depending on the choice of extension header configured. This should be done automatically by the implementation if the auto choice is selected for the next_header field in the preceding header.
For Routing Extension header , this value is 43. The available defined values are listed in https://www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xhtml#extension-header

Updated description.

apratimmukherjee · 2025-09-18T05:18:40Z

flow/packet-headers/ipv6_routing.yaml

+components:
+  schemas:
+    Flow.Ipv6ExtHeaders:
+      description: Ipv6 extension packet headers.


Ipv6 -> IPv6 throughout inside description.

apratimmukherjee · 2025-09-18T05:20:12Z

flow/packet-headers/ipv6_routing.yaml

+          x-enum:
+            segment_routing:
+              x-field-uid: 1
+        next_header:


This should be attribute of common extension header, not segment_routing sub-choice.

move it up in hierarchy.

apratimmukherjee · 2025-09-18T05:24:09Z

flow/packet-headers/ipv6_routing.yaml

+            format: integer
+            length: 8
+            default: 59
+            x-constants:


Should provide link to IANA provided in previous comment and also mention that 59 means no next header, indicating that after this extension header, the payload is directly appended.

apratimmukherjee · 2025-09-18T05:25:10Z

flow/packet-headers/ipv6_routing.yaml

+              sctp: 132
+            features: [auto, count]
+          x-field-uid: 1
+        hdr_ext_len:


It is still not part of extension header as it should be.

apratimmukherjee · 2025-09-18T05:30:03Z

flow/packet-headers/ipv6_routing.yaml

+              x-field-uid: 4
+            path_trace:
+              x-field-uid: 5
+        type:


We might remove this for now , basically any user defined arbitrary value makes it custom tlv and other attributes become meaningless.

Removed type field.

apratimmukherjee · 2025-09-18T05:31:06Z

flow/packet-headers/ipv6_routing.yaml

+          x-field-uid: 2
+        length:
+          x-field-pattern:
+            description: The length of the TLV value in bytes.


If auto is selected , the implementation should automatically set the length field to the correct length as per the selected TLV and attributes,

apratimmukherjee · 2025-09-18T05:32:36Z

flow/packet-headers/ipv6_routing.yaml

+            features:
+              - count
+          x-field-uid: 5
+        u2_flag:


Better maybe just u_flag or unused_flag

Renamed all flag fields.

apratimmukherjee · 2025-09-18T05:34:16Z

flow/packet-headers/ipv6_routing.yaml

+          default: '00'
+          x-field-uid: 1
+    Flow.Ipv6SegmentRouting.TlvIngressNode:
+      description: A TLV that may be used to carry the IPv6 address of the ingress


Reference to RFC esp. to Type value and calling it out specifically would be useful for all the TLVs in the model here,

apratimmukherjee · 2025-09-18T05:35:03Z

flow/packet-headers/ipv6_routing.yaml

+            features:
+              - count
+          x-field-uid: 2
+        value:


egress_ipv6_ip ?

alakendu · 2025-09-18T06:54:12Z

flow/packet-headers/header.yaml

+            the IPv6 next header is 43.
+          type: array
+          items:
+            $ref: './ipv6_routing.yaml#/components/schemas/Flow.Ipv6ExtHeaders'


Object name could be Flow.Ipv6ExtHeader as this is an array of object.

alakendu · 2025-09-20T14:33:51Z

flow/packet-headers/ipv6_routing.yaml

+        tlvs:
+          type: array
+          items:
+            $ref: '#/components/schemas/Flow.Ipv6SegmentRouting.Tlvs'


I feel class name could be Flow.Ipv6SegmentRouting.Tlv no s.
Note: tlvs is absolutely fine. So, no need to change the property name.

alakendu · 2025-09-21T14:46:10Z

flow/packet-headers/header.yaml

        lacp:
          $ref: './lacp.yaml#/components/schemas/Flow.Lacp'
          x-field-uid: 24
+        ipv6_extension_header:


I feel this would be ipv6_extension_headers as it contain array of Flow.Ipv6ExtHeader

Removed array and retained header as discussed.

alakendu · 2025-09-21T14:48:07Z

flow/packet-headers/ipv6_routing.yaml

+            default: 0
+            features: [auto, count]
+          x-field-uid: 2
+        ingress:


It will better to defined TLV Type within the description. This comment for all TLV types.

alakendu · 2025-09-21T14:49:37Z

flow/packet-headers/ipv6_routing.yaml

+          x-field-uid: 2
+        timestamp:
+          description: Timestamp indicating when the measurement was taken.
+          format: hex


This will not support other pattern. Better to use Hex which support pattern (values,, increment, ..)

Vibaswan and others added 10 commits August 29, 2025 21:05

add ipv6 routing packet header

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anjan-keysight requested review from PrasenjitAdhikary, alakendu and apratimmukherjee September 12, 2025 06:58

apratimmukherjee reviewed Sep 12, 2025

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apratimmukherjee requested a review from SuryyaKrJana September 12, 2025 11:02

anjan-keysight and others added 2 commits September 15, 2025 03:58

Make routing extensions array

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SuryyaKrJana requested changes Sep 15, 2025

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anjan-keysight and others added 10 commits September 17, 2025 03:53

Add one more hirarchy in ipv6 ext header

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update ipv6 SR TLVs array with choice

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apratimmukherjee reviewed Sep 18, 2025

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alakendu reviewed Sep 18, 2025

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anjan-keysight and others added 8 commits September 18, 2025 11:29

update based on comments

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anjan-keysight and others added 5 commits September 22, 2025 11:08

update based on comments

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anjan-keysight mentioned this pull request Sep 23, 2025

Ipv6 srh no tlv #445

Merged

Ipv6 routing header merge #442

Are you sure you want to change the base?

Ipv6 routing header merge #442

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anjan-keysight commented Sep 12, 2025 • edited by Vibaswan Loading Uh oh! There was an error while loading. Please reload this page.

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anjan-keysight commented Sep 12, 2025 •

edited by Vibaswan

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