nfs: introduce NFS4Client#getOwnerId

Motivation:
client's long-hand owner id is a client side identifier which is used by
server identify client on initial EXCHANGE_ID or SETCLIENT_ID (v4.0).
Moreover, during reboot recovery server uses owner id to find records
associated with a previous instance of the server.

Modification:
add NFS4Client#getOwnerId to make it possible to get client's owner id.
Remove NFS4Client#isOwner.

Result:
Client's long-hand owner id is available for later use.

Acked-by: Marina Sahakyan
Target: master

core/src/main/java/org/dcache/nfs/v4/NFS4Client.java

@@ -86,17 +86,15 @@ public class NFS4Client {
      */
 
     /**
-     * The client identifier string, from the eia_clientowner structure
-     * of the EXCHANGE_ID4args structure
+     * Variable length string that uniquely defines the client.
      */
     private final byte[] _ownerId;
 
     /**
-     * A client-specific value used to indicate reboots, from
-     * the eia_clientowner structure of the EXCHANGE_ID4args structure
+     * Verifier that is used to detect client reboots.
      */
-
     private final verifier4 _verifier;
+
     /**
      * The RPCSEC_GSS principal sent via the RPC headers.
      */
@@ -192,7 +190,7 @@ public NFS4Client(NFSv4StateHandler stateHandler, clientid4 clientId, int minorV
             byte[] ownerID, verifier4 verifier, Principal principal, long leaseTime, boolean calbackNeeded) {
 
         _stateHandler = stateHandler;
-        _ownerId = ownerID;
+        _ownerId = Arrays.copyOf(ownerID, ownerID.length);
         _verifier = verifier;
         _principal = principal;
         _clientId = clientId;
@@ -222,12 +220,11 @@ public int getMinorVersion() {
     }
 
     /**
-     * Check whatever client belongs to the provider owner.
-     * @param other client owner to test.
-     * @return <tt>true</tt> iff client belongs to the provider owner.
+     * Get client's long-hand unique identifier.
+     * @return client's unique identifier.
      */
-    public boolean isOwner(byte[] other) {
-        return Arrays.equals(_ownerId, other);
+    public byte[] getOwnerId() {
+        return _ownerId;
     }
 
     /**

core/src/main/java/org/dcache/nfs/v4/NFSv4StateHandler.java

@@ -24,6 +24,7 @@
 
 import java.net.InetSocketAddress;
 import java.security.Principal;
+import java.util.Arrays;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -186,11 +187,17 @@ public synchronized NFS4Client getClient(sessionid4 id) throws ChimeraNFSExcepti
         return client;
     }
 
+    /**
+     * Get existing, possibly not valid, client record that matches given client side generated long-hand owner identifier.
+     * @param ownerid client side generated long-hand owner identifier.
+     *
+     * @return an existing client record or null, if not matching record found.
+     */
     public synchronized NFS4Client clientByOwner(byte[] ownerid) {
         return _clientsByServerId.entries()
                 .stream()
                 .map(CacheElement::getObject)
-                .filter(c -> c.isOwner(ownerid))
+                .filter(c -> Arrays.equals(c.getOwnerId(), ownerid))
                 .findAny()
                 .orElse(null);
     }