JDK-8200719: Cannot connect to IPv6 host when exists any active network interface without IPv6 address

[Joel Peláez Jorge]

Hi,

I am new in the OpenJDK Community and I contribute with a fix for the bug 
8200719 related to networking in macOS system.

I wrote a minimal patch that only set the scope id when the address is 
link-local or multicast. This change avoid send IPv6 packets on a wrong 
interface.

Bug: https://bugs.openjdk.java.net/browse/JDK-8200719

Patch:

diff -r f088ec60bed5 src/java.base/unix/native/libnet/net_util_md.c
--- a/src/java.base/unix/native/libnet/net_util_md.c Mon Apr 09 10:39:29 2018 
-0700
+++ b/src/java.base/unix/native/libnet/net_util_md.c Mon Apr 09 16:50:18 2018 
-0500
@@ -89,7 +89,8 @@
     }
     int defaultIndex;
     struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)him;
-    if (sin6->sin6_family == AF_INET6 && (sin6->sin6_scope_id == 0)) {
+    if (sin6->sin6_family == AF_INET6 && (sin6->sin6_scope_id == 0) &&
+        (IN6_IS_ADDR_LINKLOCAL(&sin6->sin6_addr) || 
IN6_IS_ADDR_MULTICAST(&sin6->sin6_addr))) {
         defaultIndex = (*env)->GetStaticIntField(env, ni_class,
                                                  ni_defaultIndexID);
         sin6->sin6_scope_id = defaultIndex;


Thanks,
Joel