Add aft encapsulation-headers

[dplore]

Change Scope

• Add AFT container representing next-hop encapsulation headers. A list of encap-headers is defined which is used to represent a stack of one or more packets added to any packet matching a next-hop.

• Add containers for GRE, IP, UDP and MPLS encapsulation

• Later we will deprecate the existing AFT encapsulation containers for ip-in-ip and gre and MPLS.

• Changes to decapsulation are not in scope of this PR as the operational use cases inspiring this PR are met with with existing decapsulation leaves.

Use cases

• One operational use case for these nexthops is for an SDN controller to use gRIBI to program match and action rules that cause packets to be encapsulated in MPLS in UDP packets. The SDN controller chooses the encapsulation stack.
• In another, future operational use case, policy-forwarding might be used to define encapsulations which are representing in the afts model upon instantiation into the forwarding tables of the system. (Note, at this moment, changes to the policy-forwarding model to support multiple, arbitrary encapsulations is not in scope for this PR.)

Platform Implementations

Regarding MPLS in UDP encapsulation (which is the operational use case inspiring this change) is defined by RFC and supported by the following implementations.

• RFC 7510 defines the MPLS in UDP feature specification.
• Cisco IOS XR supports MPLS in UDP.
• JunOS nexthop-based-dynamic-tunnels supports MPLS in UDP.

Tree view

we are at: /network-instances/network-instance/afts/

diff -U 10 ~/master-tree.txt ~/aft-encap-tree.txt
[... snip ...]
         |  |     +--ro ip-in-ip
         |  |     |  +--ro state
         |  |     |     +--ro src-ip?   oc-inet:ip-address
         |  |     |     +--ro dst-ip?   oc-inet:ip-address
         |  |     +--ro gre
         |  |     |  +--ro state
         |  |     |     +--ro src-ip?   oc-inet:ip-address
         |  |     |     +--ro dst-ip?   oc-inet:ip-address
         |  |     |     +--ro ttl?      uint8
+        |  |     +--ro encap-headers
+        |  |     |  +--ro encap-header* [index]
+        |  |     |     +--ro index     -> ../state/index
+        |  |     |     +--ro state
+        |  |     |     |  +--ro index?   uint8
+        |  |     |     |  +--ro type?    oc-aftt:encapsulation-header-type
+        |  |     |     +--ro gre
+        |  |     |     |  +--ro state
+        |  |     |     |     +--ro src-ip?   oc-inet:ip-address
+        |  |     |     |     +--ro dst-ip?   oc-inet:ip-address
+        |  |     |     |     +--ro ttl?      uint8
+        |  |     |     +--ro ipv4
+        |  |     |     |  +--ro state
+        |  |     |     |     +--ro src-ip?   oc-inet:ip-address
+        |  |     |     |     +--ro dst-ip?   oc-inet:ip-address
+        |  |     |     +--ro ipv6
+        |  |     |     |  +--ro state
+        |  |     |     |     +--ro src-ip?   oc-inet:ip-address
+        |  |     |     |     +--ro dst-ip?   oc-inet:ip-address
+        |  |     |     +--ro mpls
+        |  |     |     |  +--ro state
+        |  |     |     |     +--ro traffic-class?      oc-mplst:mpls-tc
+        |  |     |     |     +--ro mpls-label-stack*   oc-mplst:mpls-label
+        |  |     |     +--ro udp-v4
+        |  |     |     |  +--ro state
+        |  |     |     |     +--ro src-ip?         oc-inet:ip-address
+        |  |     |     |     +--ro dst-ip?         oc-inet:ip-address
+        |  |     |     |     +--ro dscp?           oc-inet:dscp
+        |  |     |     |     +--ro src-udp-port?   oc-inet:port-number
+        |  |     |     |     +--ro dst-udp-port?   oc-inet:port-number
+        |  |     |     |     +--ro ip-ttl?         uint8
+        |  |     |     +--ro udp-v6
+        |  |     |     |  +--ro state
+        |  |     |     |     +--ro src-ip?         oc-inet:ip-address
+        |  |     |     |     +--ro dst-ip?         oc-inet:ip-address
+        |  |     |     |     +--ro dscp?           oc-inet:dscp
+        |  |     |     |     +--ro src-udp-port?   oc-inet:port-number
+        |  |     |     |     +--ro dst-udp-port?   oc-inet:port-number
+        |  |     |     |     +--ro ip-ttl?         uint8
+        |  |     |     +--ro vxlan
+        |  |     |        +--ro state
+        |  |     |           +--ro vni-label?               oc-evpn-types:evi-id
+        |  |     |           +--ro tunnel-src-ip-address?   oc-inet:ip-address
         |  |     +--ro interface-ref
         |  |        +--ro state
         |  |           +--ro interface?      -> /oc-if:interfaces/interface/name
         |  |           +--ro subinterface?   -> /oc-if:interfaces/interface[oc-if:name=current()/../

[OpenConfigBot]

No major YANG version changes in commit c47f0c8

[dplore]

Last-call for comments! This is planned to merge on Sep 26,2024.

@rgwilton @nandanarista @earies @LimeHat for comments.

[nandanarista]

The overall hierarchy LGTM.

[vishnureddybadveli]

Overall changes looks good to me.

[nachikethas]

LGTM.

Specifically, approving that the existing ip-in-ip encap/decap structures will be deprecated in a future release. Re-iterating that we fully expect all vendors to support this until we've completed the migration.

[dplore]

Addressed comments

• do not add pop-top-level to encap-header/mpls container
• refactor mpls-label-stack to be a grouping instead of typdef
• update descriptions

[robshakir]

Thanks for addressing my comments!

LGTM.