Refactor non-compliant/overlapping YANG definition for BGP MED

release/models/bgp/openconfig-bgp-policy.yang

@@ -28,7 +28,14 @@ module openconfig-bgp-policy {
     It augments the base routing-policy module with BGP-specific
     options for conditions and actions.";
 
-  oc-ext:openconfig-version "7.1.0";
+  oc-ext:openconfig-version "8.0.0";
+
+  revision "2024-08-15" {
+    description
+      "Separate the ability to set the BGP MED into a distinct value
+      with optional action.";
+    reference "8.0.0";
+  }
 
   revision "2024-07-02" {
     description
@@ -210,23 +217,37 @@ module openconfig-bgp-policy {
   typedef bgp-set-med-type {
     type union {
       type uint32;
-      type string {
-        pattern '[+-][0-9]+';
-        oc-ext:posix-pattern '^[+-][0-9]+$';
-      }
       type enumeration {
         enum IGP {
-          description "set the MED value to the IGP cost toward the
-          next hop for the route";
+          description
+            "Set the MED value to the IGP cost toward the next hop for
+            the route";
         }
       }
     }
     description
-      "Type definition for specifying how the BGP MED can
-      be set in BGP policy actions. The three choices are to set
-      the MED directly using the uint32 type or increment/decrement
-      using +/- notation in the string type or setting it to
-      the IGP cost using the enum (predefined value).";
+      "Type definition for specifying how the BGP MED can be set in BGP
+      policy actions.  The MED can be specified as a direct integer
+      value or setting it to the IGP cost.  When set to the integer
+      value without a MED 'action', the value will be explicitly set.
+      If a MED 'action' is defined, the previous value will be modified
+      according to the action (e.g. ADD or SUBTRACT).";
+  }
+
+  typedef bgp-set-med-action {
+    type enumeration {
+      enum ADD {
+        description
+          "Action to increment the previous MED value.";
+      }
+      enum SUBTRACT {
+        description
+          "Action to decrement the previous MED value.";
+      }
+    }
+    description
+      "If specified, this action will alter a previous MED value by the
+      value defined by the bgp-set-med-type.";
   }
 
   // grouping statements
@@ -1345,8 +1366,17 @@ module openconfig-bgp-policy {
 
     leaf set-med {
       type bgp-set-med-type;
-      description "set the med metric attribute in the route
-      update";
+      description
+        "Set the MED metric attribute in the route update.  Can be used
+        in conjunction with 'set-med-action' in order to alter a
+        previous value by the value specified here.";
+    }
+
+    leaf set-med-action {
+      type bgp-set-med-action;
+      description
+        "Optionally used in conjunction with 'set-med' to alter a
+        previous value.";
     }
   }