Per the RFC, disable IPv6 support unless specifically requested to enable it, even if the underlying system has the required include headers.

NOTE: the IPv6 support is currently marginally working and has problems when IPv6 headers are present but the interfaces are not configured to use that protocol, per several reports from users. It is unclear that anyone is willing/able to support this capability. Should that situation change, this change can be reconsidered.

This commit was SVN r22039.

config/opal_configure_options.m4

@@ -431,18 +431,18 @@ AC_DEFINE_UNQUOTED([OPAL_WANT_HOME_CONFIG_FILES], [$result],
      [Enable per-user config files])
 
 #
-# Do we want to disable IPv6 support?
+# Do we want to enable IPv6 support?
 #
 AC_MSG_CHECKING([if want IPv6 support])
 AC_ARG_ENABLE([ipv6],
-    [AC_HELP_STRING([--disable-ipv6],
+    [AC_HELP_STRING([--enable-ipv6],
-        [Disable IPv6 support (default: enabled, but only if the underlying system supports it)])])
+        [Enable IPv6 support, but only if the underlying system supports it (default: disabled)])])
-if test "$enable_ipv6" = "no"; then
+if test "$enable_ipv6" = "yes"; then
+    AC_MSG_RESULT([yes])
+    opal_want_ipv6=1
+else
     AC_MSG_RESULT([no])
     opal_want_ipv6=0
-else
-    AC_MSG_RESULT([yes (if underlying system supports it)])
-    opal_want_ipv6=1
 fi
 AC_DEFINE_UNQUOTED([OPAL_ENABLE_IPV6], [$opal_want_ipv6],
                    [Enable IPv6 support, but only if the underlying system supports it])