8059309: network tests fail with "java.net.SocketException: Couldn't obtain phys addr" when run as "root"

The solaris specific code is changed to use the fallback mechanism if the DLPI interface returns an error indicating that the operation is unsupported. In addition, NetworkInterface::getHardwareAddress is changed to always return null for the loopback interface.

Reviewed-by: alanb

src/java.base/share/classes/java/net/NetworkInterface.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -523,6 +523,9 @@ public final class NetworkInterface {
                 }
             }
         }
+        if (isLoopback0(name, index)) {
+            return null;
+        }
         for (InetAddress addr : addrs) {
             if (addr instanceof Inet4Address) {
                 return getMacAddr0(((Inet4Address)addr).getAddress(), name, index);

src/java.base/unix/native/libnet/NetworkInterface.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -1884,6 +1884,7 @@ static int getMacFromDevice
     int fd;
     dl_phys_addr_req_t dlpareq;
     dl_phys_addr_ack_t *dlpaack;
+    dl_error_ack_t     *dlerack;
     struct strbuf msg;
     char buf[128];
     int flags = 0;
@@ -1920,6 +1921,19 @@ static int getMacFromDevice
         return -1;
     }
 
+    if (dlpaack->dl_primitive == DL_ERROR_ACK) {
+        dlerack = (dl_error_ack_t *)buf;
+        if (dlerack->dl_error_primitive != DL_PHYS_ADDR_REQ) {
+            JNU_ThrowByName(env, JNU_JAVANETPKG "SocketException",
+                           "Couldn't obtain physical address\n");
+            return -1;
+        }
+        if (dlerack->dl_errno == DL_UNSUPPORTED) {
+            // fallback to lookup in the ARP table
+            return 0;
+        }
+    }
+
     if (msg.len < DL_PHYS_ADDR_ACK_SIZE || dlpaack->dl_primitive != DL_PHYS_ADDR_ACK) {
         JNU_ThrowByName(env, JNU_JAVANETPKG "SocketException",
                         "Couldn't obtain phys addr\n");

test/jdk/java/net/NetworkInterface/NullMacAddress.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+ * @bug 8059309
+ * @summary Test that querrying the mac address of the loopback interface
+ *          returns null and doesn't throw a SocketException.
+ * @library /test/lib
+ * @run testng/othervm NullMacAddress
+ * @run testng/othervm -Djava.net.preferIPv6Addresses=true NullMacAddress
+ * @run testng/othervm -Djava.net.preferIPv4Stack=true NullMacAddress
+ */
+
+import org.testng.annotations.BeforeTest;
+import org.testng.annotations.Test;
+import static org.testng.Assert.*;
+
+import java.io.UncheckedIOException;
+import java.math.BigInteger;
+import java.net.NetworkInterface;
+import java.net.SocketException;
+import java.util.Locale;
+
+import jdk.test.lib.net.IPSupport;
+
+public class NullMacAddress {
+
+    @BeforeTest
+    void setup() {
+        IPSupport.throwSkippedExceptionIfNonOperational();
+    }
+
+    @Test
+    public void testNetworkInterfaces() throws SocketException {
+        NetworkInterface.networkInterfaces().forEach(this::testMacAddress);
+    }
+
+    private void testMacAddress(NetworkInterface ni) {
+        try {
+            var name = ni.getDisplayName();
+            System.out.println("Testing: " + name);
+            var loopback = ni.isLoopback();
+            var macAddress = ni.getHardwareAddress();
+            var hdr = macAddress == null ? "null"
+                    : "0x" + new BigInteger(1, macAddress)
+                    .toString(16).toUpperCase(Locale.ROOT);
+            System.out.println("   MAC address: " + hdr + (loopback ? " (loopback)" : ""));
+            if (loopback) {
+                assertNull(macAddress, "Loopback interface \""
+                        + name + "\" doesn't have a null MAC Address");
+            }
+        } catch (SocketException ex) {
+            throw new UncheckedIOException(ex);
+        }
+    }
+ }
+