Add GRE and MPLS encap-headers to network-instance/static

[dplore]

Change Scope

• Add GRE and MPLS encap-headers to network-instance/static
• This change is backwards compatible

Platform Implementations

While device implementations today widely support encapsulation of MPLS, GRE and MPLS into GRE packets this PR provides a method to configure a static next-hop-group for the purpose of encapsulation. Using static next-hops for MPLS in GRE encapsulation is a new feature being pursued from multiple device implementations to unify a single vendor neutral way to configure this encapsulation.

• Arista EOS supports MPLS in GRE encapsulation
• Cisco IOS XR supports MPLS in GRE encapsulation
• JunOS supports MPLS in GRE encapsulation

Tree view

         +--rw static
         |  +--rw next-hop-groups
         |  |  +--rw next-hop-group* [name]
         |  |     +--rw name         -> ../config/name
         |  |     +--rw config
         |  |     |  +--rw name?   string
         |  |     +--ro state
         |  |     |  +--ro name?   string
         |  |     +--rw next-hops
         |  |        +--rw next-hop* [index]
         |  |           +--rw index     -> ../config/index
         |  |           +--rw config
         |  |           |  +--rw index?   -> ../../../../../../next-hops/next-hop/index
         |  |           +--ro state
         |  |              +--ro index?   -> ../../../../../../next-hops/next-hop/index
         |  +--rw next-hops
         |     +--rw next-hop* [index]
         |        +--rw index            -> ../config/index
         |        +--rw config
         |        |  +--rw index?                   string
         |        |  +--rw next-network-instance?   -> /network-instances/network-instance/config/name
         |        |  +--rw next-hop?                union
         |        |  +--rw nh-network-instance?     -> /network-instances/network-instance/config/name
         |        |  +--rw recurse?                 boolean
         |        |  +--rw metric?                  uint32
         |        |  +--rw preference?              uint32
         |        +--ro state
         |        |  +--ro index?                   string
         |        |  +--ro next-network-instance?   -> /network-instances/network-instance/config/name
         |        |  +--ro next-hop?                union
         |        |  +--ro nh-network-instance?     -> /network-instances/network-instance/config/name
         |        |  +--ro recurse?                 boolean
         |        |  +--ro metric?                  uint32
         |        |  +--ro preference?              uint32
         |        +--rw encap-headers
         |           +--rw encap-header* [index]
         |              +--rw index     -> ../config/index
         |              +--rw config
         |              |  +--rw index?   uint8
         |              |  +--rw type?    oc-aftt:encapsulation-header-type
         |              +--ro state
         |              |  +--ro index?   uint8
         |              |  +--ro type?    oc-aftt:encapsulation-header-type
         |              +--rw udp-v4
         |              |  +--rw config
         |              |  |  +--rw src-ip?         oc-inet:ipv4-address
         |              |  |  +--rw dst-ip?         oc-inet:ipv4-address
         |              |  |  +--rw dscp?           oc-inet:dscp
         |              |  |  +--rw src-udp-port?   oc-inet:port-number
         |              |  |  +--rw dst-udp-port?   oc-inet:port-number
         |              |  |  +--rw ip-ttl?         uint8
         |              |  +--ro state
         |              |     +--ro src-ip?         oc-inet:ipv4-address
         |              |     +--ro dst-ip?         oc-inet:ipv4-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
+        |              +--rw gre
+        |              |  +--rw config
+        |              |  |  +--rw src-ip?   oc-inet:ip-address
+        |              |  |  +--rw dst-ip?   oc-inet:ip-address
+        |              |  |  +--rw ip-ttl?   oc-inet:ip-address
+        |              |  +--ro state
+        |              |     +--ro src-ip?   oc-inet:ip-address
+        |              |     +--ro dst-ip?   oc-inet:ip-address
+        |              |  |  +--rw ip-ttl?   oc-inet:ip-address
+        |              +--rw mpls
+        |                 +--rw config
+        |                 |  +--rw traffic-class?   oc-mplst:mpls-tc
+        |                 |  +--rw mpls-label?      oc-mplst:mpls-label
+        |                 +--ro state
+        |                 |  +--rw traffic-class?   oc-mplst:mpls-tc
+        |                 |  +--rw mpls-label?      oc-mplst:mpls-label

Example configuration for static next-hops with 1 MPLS label inside GRE encapsulation

{
  "next-hops": {
    "next-hop": [
      {
        "config": {
          "index": "Dest A-NH1",
          "metric": 10,
          "next-hop": "1.2.3.4"
        },
        "encap-headers": {
          "encap-header": [
            {
              "config": {
                "index": 1
                "type": "GRE",
              },
              "index": 1,
              "gre": {
                "config": {
                  "dst-ip": "1.1.1.1",
                  "src-ip": "2.2.2.2",
                  "dscp": 8,
                  "ttl": 32
                }
              }
            },
            {
              "config": {
                "index": 2
                "type": "MPLS",
              },
              "index": 2,
              "mpls": {
                "config": {
                  "label": 100,
                  "traffic-class": 1
                }
              }
            }
          ]
        },
        "index": "Dest A-NH1"
      }
    ]
  }
}

[OpenConfigBot]

No major YANG version changes in commit 05f35d9

[dplore]

Updated the PR description to show the tree.

[dplore]

@robshakir ready for your review

[ElodinLaarz]

Discussed in the meet (June 17th, 2025).

There are some changes to fix the example JSON config.
We still need to get some feedback from the vendors to see if the behavior mentioned in this comment thread is widely expected. (To be discussed at the community meet.)

Otherwise, seems good.

[dplore]

This will be reviewed on July 1, 2025 OC Operators meeting. Last call set for July 8, 2025

[ElodinLaarz]

Discussed at the July 1st OC Operators Meeting -- still have to address the minor change of JSON and get the workflow checks to be passing, but other than that sounds good.

[ElodinLaarz]

Once the checks are passing and a reviewer approves, this should be good. (we already reviewed at a previous meeting) - OC Operators Meeting July 8th.