Refactor must restriction behavior for BGP MED policies

[earies]

• (M) release/models/bgp/openconfig-bgp-policy.yang
  • Relocate must restrictions at a container level and specify
    behavior for the MED type 'IGP' and associated actions
  • Increment version to 8.2.0

Change Scope

Relocate circular must statements from leafs to the encapsulating containers.
Clarify behavior when the BGP MED is set to 'IGP' and enforce conditional
actions.

Runtime behavior should not be affected by this change. While it could
classify as a YANG backwards incompatible change, this should likely be treated
as backwards compatible thus incrementing only the minor version here.

Without this change, implementations are subject to interpretation differences
and out-of-schema handling must be applied.

Platform Implementations

N/A: Clarify behavior of mandatory actions when BGP MED is set in addition to
when the MED is set to 'IGP'

Follow on commit from: #1165

[earies]

Schema validation examples:

Pass:

{
  "openconfig-routing-policy:routing-policy": {
    "policy-definitions": {
      "policy-definition": [
        {
          "name": "pd1",
          "config": {
            "name": "pd1"
          },
          "statements": {
            "statement": [
              {
                "name": "s1",
                "config": {
                  "name": "s1"
                },
                "conditions": {
                  "match-prefix-set": {
                    "state": {
                      "match-set-options": "ANY"
                    }
                  },
                  "match-neighbor-set": {
                    "state": {
                      "match-set-options": "ANY"
                    }
                  },
                  "match-tag-set": {
                    "state": {
                      "match-set-options": "ANY"
                    }
                  },
                  "openconfig-bgp-policy:bgp-conditions": {
                    "match-as-path-set": {
                      "state": {
                        "match-set-options": "ANY"
                      }
                    },
                    "match-community-set": {
                      "state": {
                        "match-set-options": "ANY"
                      }
                    },
                    "match-ext-community-set": {
                      "state": {
                        "match-set-options": "ANY"
                      }
                    }
                  }
                },
                "actions": {
                  "state": {
                    "policy-result": "NEXT_STATEMENT"
                  },
                  "openconfig-bgp-policy:bgp-actions": {
                    "config": {
                      "set-med": "IGP",
                      "set-med-action": "SET"
                    },
                    "state": {
                      "set-med": "IGP",
                      "set-med-action": "SET"
                    }
                  }
                }
              }
            ]
          }
        }
      ]
    }
  }
}

Pass:

{
  "openconfig-routing-policy:routing-policy": {
    "policy-definitions": {
      "policy-definition": [
        {
          "name": "pd1",
          "config": {
            "name": "pd1"
          },
          "statements": {
            "statement": [
              {
                "name": "s1",
                "config": {
                  "name": "s1"
                },
                "conditions": {
                  "match-prefix-set": {
                    "state": {
                      "match-set-options": "ANY"
                    }
                  },
                  "match-neighbor-set": {
                    "state": {
                      "match-set-options": "ANY"
                    }
                  },
                  "match-tag-set": {
                    "state": {
                      "match-set-options": "ANY"
                    }
                  },
                  "openconfig-bgp-policy:bgp-conditions": {
                    "match-as-path-set": {
                      "state": {
                        "match-set-options": "ANY"
                      }
                    },
                    "match-community-set": {
                      "state": {
                        "match-set-options": "ANY"
                      }
                    },
                    "match-ext-community-set": {
                      "state": {
                        "match-set-options": "ANY"
                      }
                    }
                  }
                },
                "actions": {
                  "state": {
                    "policy-result": "NEXT_STATEMENT"
                  },
                  "openconfig-bgp-policy:bgp-actions": {
                    "config": {
                      "set-med": 100,
                      "set-med-action": "ADD"
                    },
                    "state": {
                      "set-med": 100,
                      "set-med-action": "ADD"
                    }
                  }
                }
              }
            ]
          }
        }
      ]
    }
  }
}

Fail:

{
    "openconfig-routing-policy:routing-policy": {
        "policy-definitions": {
            "policy-definition": [
                {
                    "name": "pd1",
                    "config": {
                        "name": "pd1"
                    },
                    "statements": {
                        "statement": [
                            {
                                "name": "s1",
                                "config": {
                                    "name": "s1"
                                },
                                "actions": {
                                    "openconfig-bgp-policy:bgp-actions": {
                                        "config": {
                                            "set-med": "IGP",
                                            "set-med-action": "ADD"
                                        },
                                        "state": {
                                            "set-med": "IGP",
                                            "set-med-action": "ADD"
                                        }
                                    }
                                }
                            }
                        ]
                    }
                }
            ]
        }
    }
}

libyang err : set-med-action must be set to 'SET' when set-med = 'IGP', otherwise any action must be specified if set-med is an integer value. (/openconfig-routing-policy:routing-policy/policy-definitions/policy-definition[name='pd1']/statements/statement[name='s1']/actions/openconfig-bgp-policy:bgp-actions/config)
libyang err : set-med-action must be set to 'SET' when set-med = 'IGP', otherwise any action must be specified if set-med is an integer value. (/openconfig-routing-policy:routing-policy/policy-definitions/policy-definition[name='pd1']/statements/statement[name='s1']/actions/openconfig-bgp-policy:bgp-actions/state)

Fail:

{
    "openconfig-routing-policy:routing-policy": {
        "policy-definitions": {
            "policy-definition": [
                {
                    "name": "pd1",
                    "config": {
                        "name": "pd1"
                    },
                    "statements": {
                        "statement": [
                            {
                                "name": "s1",
                                "config": {
                                    "name": "s1"
                                },
                                "actions": {
                                    "openconfig-bgp-policy:bgp-actions": {
                                        "config": {
                                            "set-med": 100
                                        },
                                        "state": {
                                            "set-med": 100
                                        }
                                    }
                                }
                            }
                        ]
                    }
                }
            ]
        }
    }
}

libyang err : set-med-action must be set to 'SET' when set-med = 'IGP', otherwise any action must be specified if set-med is an integer value. (/openconfig-routing-policy:routing-policy/policy-definitions/policy-definition[name='pd1']/statements/statement[name='s1']/actions/openconfig-bgp-policy:bgp-actions/config)
libyang err : set-med-action must be set to 'SET' when set-med = 'IGP', otherwise any action must be specified if set-med is an integer value. (/openconfig-routing-policy:routing-policy/policy-definitions/policy-definition[name='pd1']/statements/statement[name='s1']/actions/openconfig-bgp-policy:bgp-actions/state)

[rgwilton]

I've checked with our BGP team and we support making this change.