add gnmirpc to oc paths (#3463)

* Add gnmirpc to oc paths to track per  gnmi RPC options supported/required per path

proto/ocpaths.proto

@@ -58,6 +58,10 @@ message OCPath {
   // A set of opaque tags that are used for this path. These tags can be used
   // to group paths according to use-case specific criteria.
   repeated string tags = 4;
+
+  // GNMIRpc describes expected (or supported) behavior for a particular
+  // Openconfig path.
+  GNMIRpc gnmi_rpc = 5;
 }
 
 // OCPathConstraint enumerates platform_types that are required to be supported
@@ -76,3 +80,39 @@ message OCPathConstraint {
     string platform_type = 1;
   }
 }
+
+// GNMIRpc describes expected (or supported) behavior for a particular
+// Openconfig path.
+message GNMIRpc {
+  bool get = 1;
+  bool set = 2;
+  bool subscribe = 3;
+
+  // SubscribeMode, describes how updates are triggered for the request.
+  enum SubscribeMode {
+    UNSPECIFIED_SUBSCRIBE_MODE = 0;
+    NO_READ_SUPPORT = 1;  // No requirement / support for path.
+    STREAM = 2;           // Values streamed by the target (Sec. 3.5.1.5.2).
+    ONCE = 3;  // Values sent once-off by the target (Sec. 3.5.1.5.1).
+    POLL = 4;  // Values sent in response to a poll request (Sec. 3.5.1.5.3).
+  }
+  repeated SubscribeMode sub_mode = 4;
+
+  // StreamMode is the mode of a streamed subscription, specifying how the
+  // target must return values for that subscription.
+  // Reference: gNMI Specification Section 3.5.1.3
+  enum StreamMode {
+    UNSPECIFIED_STREAM_MODE = 0;
+    NO_STREAMING_SUPPORT = 1;  // No requirement / support for streaming path.
+    TARGET_DEFINED = 2;        // The target selects for each element.
+    ON_CHANGE = 3;  // The target sends an update on element value change.
+    SAMPLE = 4;     // The target samples values according to the interval.
+  }
+  repeated StreamMode stream_mode = 5;
+
+  // If listed as part of a requirement, sample_interval_nanoseconds is the
+  // maximum allowable interval between updates.
+  // If listed as part of the description of level of support, it should be the
+  // smallest, recommended value.
+  uint64 sample_interval_nanoseconds = 6;
+}