Add ControllerGetNodeInfo RPC (alpha)

csi.proto

@@ -120,6 +120,11 @@ service Controller {
   rpc ControllerModifyVolume (ControllerModifyVolumeRequest)
     returns (ControllerModifyVolumeResponse) {
     }
+
+  rpc ControllerGetNodeInfo (ControllerGetNodeInfoRequest)
+    returns (ControllerGetNodeInfoResponse) {
+        option (alpha_method) = true;
+    }
 }
 
 service GroupController {
@@ -1205,6 +1210,62 @@ message ControllerModifyVolumeRequest {
 message ControllerModifyVolumeResponse {
 }
 
+message ControllerGetNodeInfoRequest {
+  option (alpha_message) = true;
+
+  // The identifier of the node as understood by the SP.
+  // This field is REQUIRED.
+  // This field MUST match the node_id returned by `NodeGetInfo`.
+  // This field overrides the general CSI size limit.
+  // The size of this field SHALL NOT exceed 256 bytes.
+  string node_id = 1;
+}
+
+message ControllerGetNodeInfoResponse {
+  option (alpha_message) = true;
+
+  message PublishedVolume {
+    // For volumes published by the CO, this MUST be the same volume_id
+    // value used in ControllerPublishVolume.
+    string volume_id = 1;
+  }
+
+  // Maximum number of volumes that controller can publish to the node.
+  // If value is not set or zero CO SHALL decide how many volumes of
+  // this type can be published by the controller to the node. The
+  // plugin MUST NOT set negative values here.
+  // This field is OPTIONAL.
+  int64 max_volumes_per_node = 1;
+
+  // Specifies where (regions, zones, racks, etc.) the node is
+  // accessible from.
+  // A plugin that returns this field MUST also set the
+  // VOLUME_ACCESSIBILITY_CONSTRAINTS plugin capability.
+  // COs MAY use this information along with the topology information
+  // returned in CreateVolumeResponse to ensure that a given volume is
+  // accessible from a given node when scheduling workloads.
+  // This field is OPTIONAL. If it is not specified, the CO MAY assume
+  // the node is not subject to any topological constraint, and MAY
+  // schedule workloads that reference any volume V, such that there are
+  // no topological constraints declared for V.
+  //
+  // Example 1:
+  //   accessible_topology =
+  //     {"region": "R1", "zone": "Z2"}
+  // Indicates the node exists within the "region" "R1" and the "zone"
+  // "Z2".
+  Topology accessible_topology = 2;
+
+  // The volumes that are currently published to this node.
+  // This MAY include volumes not published by the CO.
+  // max_volumes_per_node is the limit on the union of these volumes
+  // and the volumes published to the node by the CO.
+  // This field is OPTIONAL.
+  //
+  // The CO MUST NOT attempt to unpublish or otherwise operate on
+  // volumes it did not publish.
+  repeated PublishedVolume published_volumes = 3;
+}
 message GetCapacityRequest {
   // If specified, the Plugin SHALL report the capacity of the storage
   // that can be used to provision volumes that satisfy ALL of the
@@ -1355,6 +1416,13 @@ message ControllerServiceCapability {
       // A plugin which supports the LIST_VOLUME_HEALTH capability
       // MUST also support the GET_VOLUME_HEALTH capability.
       LIST_VOLUME_HEALTH = 17 [(alpha_enum_value) = true];
+
+      // Indicates the SP supports the ControllerGetNodeInfo RPC.
+      // This enables COs to fetch node topology and capacity
+      // information from the controller plugin, which may be able
+      // to access such information more securely than the node plugin.
+      // The SP MUST also support PUBLISH_UNPUBLISH_VOLUME.
+      GET_NODE_INFO = 18 [(alpha_enum_value) = true];
     }
 
     Type type = 1;
@@ -1942,8 +2010,16 @@ message NodeServiceCapability {
 
       // Indicates the SP supports the NodeGetStorageHealth RPC.
       // This enables COs to fetch health of entire storage subsystem
-	  // from node's perspective. 
+      // from node's perspective.
       GET_STORAGE_HEALTH = 8 [(alpha_enum_value) = true];
+
+      // Indicates the SP supports the controller_get_node_info field
+      // in NodeGetInfoRequest. When the CO sets that field, it will
+      // obtain accessible_topology and max_volumes_per_node via
+      // ControllerGetNodeInfo.
+      // If the SP supports NODE_INFO_FROM_CONTROLLER, it MUST also
+      // support the GET_NODE_INFO controller capability.
+      NODE_INFO_FROM_CONTROLLER = 9 [(alpha_enum_value) = true];
     }
 
     Type type = 1;
@@ -1955,6 +2031,17 @@ message NodeServiceCapability {
   }
 }
 message NodeGetInfoRequest {
+  // When true, the CO will obtain accessible_topology and
+  // max_volumes_per_node from the controller plugin using
+  // ControllerGetNodeInfo.
+  // The CO MUST ignore the accessible_topology and
+  // max_volumes_per_node in NodeGetInfoResponse if this field
+  // is true. The SP MAY omit those two fields from
+  // NodeGetInfoResponse and return only node_id in that case.
+  // The CO MUST NOT set this field to true unless the SP has the
+  // NODE_INFO_FROM_CONTROLLER node capability.
+  // This field is OPTIONAL.
+  bool controller_get_node_info = 1 [(alpha_field) = true];
 }
 
 message NodeGetInfoResponse {