8255264: Support for identifying the full range of IPv4 localhost addresses on Windows

Reviewed-by: alanb

Author: macarte

src/java.base/windows/native/libnet/net_util_md.h

@@ -90,24 +90,30 @@ struct ipv6bind {
 /**
  * With dual socket implementation the
  * IPv4 addresseses might be mapped as IPv6.
- * The IPv4 loopback adapter address will
- * be mapped as the following IPv6 ::ffff:127.0.0.1.
+ * The IPv4 loopback adapter address ranges (127.0.0.0 through 127.255.255.255) will
+ * be mapped as the following IPv6 ::ffff:127.0.0.0 through ::ffff:127.255.255.255.
  * For example, this is done by NET_InetAddressToSockaddr.
  */
 #define IN6_IS_ADDR_V4MAPPED_LOOPBACK(x) ( \
-    (((x)->s6_words[0] == 0)      &&  \
-     ((x)->s6_words[1] == 0)      &&  \
-     ((x)->s6_words[2] == 0)      &&  \
-     ((x)->s6_words[3] == 0)      &&  \
-     ((x)->s6_words[4] == 0)      &&  \
-     ((x)->s6_words[5] == 0xFFFF) &&  \
-     ((x)->s6_words[6] == 0x007F) &&  \
-     ((x)->s6_words[7] == 0x0100))    \
+    (((x)->s6_words[0] == 0)               &&  \
+     ((x)->s6_words[1] == 0)               &&  \
+     ((x)->s6_words[2] == 0)               &&  \
+     ((x)->s6_words[3] == 0)               &&  \
+     ((x)->s6_words[4] == 0)               &&  \
+     ((x)->s6_words[5] == 0xFFFF)          &&  \
+     (((x)->s6_words[6] & 0x00FF) == 0x007F)) \
+)
+
+/**
+ * Check for IPv4 loopback adapter address ranges (127.0.0.0 through 127.255.255.255)
+ */
+#define IN4_IS_ADDR_NETLONG_LOOPBACK(l) ( \
+    ((l & 0xFF000000) == 0x7F000000) \
 )
 
 #define IS_LOOPBACK_ADDRESS(x) ( \
     ((x)->sa.sa_family == AF_INET) ? \
-        (ntohl((x)->sa4.sin_addr.s_addr) == INADDR_LOOPBACK) : \
+        (IN4_IS_ADDR_NETLONG_LOOPBACK(ntohl((x)->sa4.sin_addr.s_addr))) : \
         ((IN6_IS_ADDR_LOOPBACK(&(x)->sa6.sin6_addr)) || \
          (IN6_IS_ADDR_V4MAPPED_LOOPBACK(&(x)->sa6.sin6_addr))) \
 )