RFR [9] 8058216: NetworkInterface.getHardwareAddress can return zero length byte array when run with preferIPv4Stack

[Chris Hegarty]

On 11/09/14 14:42, Chris Hegarty wrote:
> A small issue was found when running JCK tests on modern Windows platforms, that have IPv6 enabled, but forced to run with the IPv4 Stack, -Djava.net.preferIPv4Stack=true. NetworkInterface.getHardwareAddress() can return a zero length byte array, where is should, and is specified to, return null.
>
> The solution is to only create the byte array if the physical address is known. Running an existing regression test with -Djava.net.preferIPv4Stack=true covers this issue.

As was pointed out to me off list, the test should include this bug Id 
too. It is now added, and some more context around the diffs, for easier 
review.

---
diff --git a/src/java.base/windows/native/libnet/NetworkInterface.c 
b/src/java.base/windows/native/libnet/NetworkInterface.c
--- a/src/java.base/windows/native/libnet/NetworkInterface.c
+++ b/src/java.base/windows/native/libnet/NetworkInterface.c
@@ -975,39 +975,41 @@
  JNIEXPORT jbyteArray JNICALL Java_java_net_NetworkInterface_getMacAddr0
      (JNIEnv *env, jclass class, jbyteArray addrArray, jstring name, 
jint index) {
    jbyteArray ret = NULL;
    int len;
    MIB_IFROW *ifRowP;

    // Retained for now to support IPv4 only stack, java.net.preferIPv4Stack
    if (ipv6_available()) {
      return Java_java_net_NetworkInterface_getMacAddr0_XP(env, class, 
name, index);
    } else {
      ifRowP = getIF(index);
      if (ifRowP != NULL) {
        switch(ifRowP->dwType) {
        case MIB_IF_TYPE_ETHERNET:
        case MIB_IF_TYPE_TOKENRING:
        case MIB_IF_TYPE_FDDI:
        case IF_TYPE_IEEE80211:
          len = ifRowP->dwPhysAddrLen;
-        ret = (*env)->NewByteArray(env, len);
-        if (!IS_NULL(ret)) {
-          (*env)->SetByteArrayRegion(env, ret, 0, len, (jbyte *) 
ifRowP->bPhysAddr);
+        if (len > 0) {
+            ret = (*env)->NewByteArray(env, len);
+            if (!IS_NULL(ret)) {
+              (*env)->SetByteArrayRegion(env, ret, 0, len, (jbyte *) 
ifRowP->bPhysAddr);
+            }
          }
          break;
        }
        free(ifRowP);
      }
      return ret;
    }
  }

$ hg diff test/java/net/NetworkInterface/Test.javadiff --git 
a/test/java/net/NetworkInterface/Test.java 
b/test/java/net/NetworkInterface/Test.java
--- a/test/java/net/NetworkInterface/Test.java
+++ b/test/java/net/NetworkInterface/Test.java
@@ -22,7 +22,9 @@
   */

  /* @test
- * @bug 4405354 6594296
+ * @bug 4405354 6594296 8058216
+ * @run main Test
+ * @run main/othervm -Djava.net.preferIPv4Stack=true Test
   * @summary Basic tests for NetworkInterface
   */
  import java.net.NetworkInterface;

-Chris.