nfs3: fix readdir entry size calculation

Motivation:
when estimating readdir reply size we should not forget about boolean
flag that indicates the presence of a next entry.

Modification:
fix entry overhead size.

Result:
The returned xdr doesn't overflow expected reply size.

Acked-by: Paul Millar
Target: master, 0.22
(cherry picked from commit ea6f71a)
Signed-off-by: Tigran Mkrtchyan <[email protected]>

core/src/main/java/org/dcache/nfs/v3/NfsServerV3.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009 - 2020 Deutsches Elektronen-Synchroton,
+ * Copyright (c) 2009 - 2021 Deutsches Elektronen-Synchroton,
  * Member of the Helmholtz Association, (DESY), HAMBURG, GERMANY
  *
  * This library is free software; you can redistribute it and/or modify
@@ -155,7 +155,18 @@
 public class NfsServerV3 extends nfs3_protServerStub {
 
     // needed to calculate replay size for READDIR3 and READDIRPLUS3
-    private static final int ENTRY3_SIZE = 24;
+    /*
+     * readdir entry size + overhead
+     * 8 (cookie) + 8 (file id) + 4 (name len) + 4 (smallest padded name) + 4 (boolean has next)
+     */
+    private static final int ENTRY3_SIZE = 28;
+
+    /*
+     * readdir_plus entry size + overhead, without file handle
+     * 8 (cookie) + 8 (file id) + 4 (name len) + 4 (smallest padded name) + 4 (boolean has next) +
+     * 4 (boolean attrs follow, always true) + 84 (fattr3) + 4 (boolean has handle, always true) +
+     * 4 (handle len)
+     */
     private static final int ENTRYPLUS3_SIZE = 124;
     private static final int READDIR3RESOK_SIZE = 104;
     private static final int READDIRPLUS3RESOK_SIZE = 104;

core/src/test/java/org/dcache/nfs/v3/NfsServerV3READDIRPLUS_3Test.java

@@ -24,6 +24,10 @@
 import org.junit.Before;
 import org.junit.Test;
 
+import static org.dcache.testutils.XdrHelper.calculateSize;
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.lessThanOrEqualTo;
 import static org.mockito.Mockito.*;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -177,7 +181,8 @@ public void testEofIfLastEntryDoesNotFit() throws Exception {
             n++;
         }
 
-        assertEquals("Not all antries returned", dirContents.size() - 1, n);
+        assertThat("reply overflow", calculateSize(result), is(lessThanOrEqualTo(3480)));
+        assertEquals("Not all entries returned", dirContents.size() - 1, n);
         assertFalse("The last entry is missed", result.resok.reply.eof);
     }
 }

core/src/test/java/org/dcache/nfs/v3/NfsServerV3READDIR_3Test.java

@@ -24,6 +24,10 @@
 import org.junit.Before;
 import org.junit.Test;
 
+import static org.dcache.testutils.XdrHelper.calculateSize;
+import static org.hamcrest.CoreMatchers.*;
+import static org.hamcrest.MatcherAssert.*;
+import static org.hamcrest.Matchers.lessThanOrEqualTo;
 import static org.mockito.Mockito.*;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
@@ -165,7 +169,7 @@ public void testEofIfLastEntryDoesNotFit() throws Exception {
         when(vfs.list(eq(dirInode), any(), anyLong())).thenReturn(new DirectoryStream(cookieVerifier, dirContents));
 
         RpcCall call = new RpcCallBuilder().from("1.2.3.4", "someHost.acme.com", 42).nfs3().noAuth().build();
-        READDIR3args args = NfsV3Ops.readDir(dirHandle, 0, cookieVerifier, 770); // only 22 entries will fit
+        READDIR3args args = NfsV3Ops.readDir(dirHandle, 0, cookieVerifier, 836); // only 22 entries will fit
         READDIR3res result = nfsServer.NFSPROC3_READDIR_3(call, args);
 
         int n = 0;
@@ -176,7 +180,8 @@ public void testEofIfLastEntryDoesNotFit() throws Exception {
             n++;
         }
 
-        assertEquals("Not all antries returned", dirContents.size() - 1, n);
+        assertThat("reply overflow", calculateSize(result), is(lessThanOrEqualTo(836)));
+        assertEquals("Not all entries returned", dirContents.size() - 1, n);
         assertFalse("The last entry is missed", result.resok.reply.eof);
     }
 }

core/src/test/java/org/dcache/nfs/v4/OperationREADDIRTest.java

@@ -27,8 +27,16 @@
 import org.junit.Test;
 import org.junit.Before;
 
+import static org.hamcrest.MatcherAssert.*;
 import static org.dcache.nfs.v4.NfsTestUtils.generateRpcCall;
-import static org.junit.Assert.*;
+import static org.dcache.testutils.XdrHelper.calculateSize;
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.Matchers.lessThanOrEqualTo;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.fail;
 import static org.mockito.Mockito.*;
 
 public class OperationREADDIRTest {
@@ -111,6 +119,7 @@ public void testEofIfLastEntryDoesNotFit() throws Exception {
 
         listed();
 
+        assertThat("reply overflow", calculateSize(result), is(lessThanOrEqualTo(1000)));
         assertEquals("Not all entries returned", dirEntries.length - 1, entryCount());
         assertFalse("The last entry is missed", result.opreaddir.resok4.reply.eof);
     }

core/src/test/java/org/dcache/testutils/XdrHelper.java

@@ -0,0 +1,21 @@
+package org.dcache.testutils;
+
+import org.dcache.oncrpc4j.xdr.Xdr;
+import org.dcache.oncrpc4j.xdr.XdrAble;
+
+public class XdrHelper {
+    private XdrHelper() {}
+
+
+    public static int calculateSize (XdrAble xdrAble) {
+        try {
+            Xdr xdr = new Xdr(128);
+            xdr.beginEncoding();
+            xdrAble.xdrEncode(xdr);
+            xdr.endEncoding();
+            return xdr.getBytes().length;
+        } catch (Exception e) {
+            throw new AssertionError("object does not survive xdr encoding", e);
+        }
+    }
+}