Index: usr.sbin/mountd/exports.5
===================================================================
--- usr.sbin/mountd/exports.5
+++ usr.sbin/mountd/exports.5
@@ -338,9 +338,10 @@
 option, or by using a separate
 .Fl mask
 option.
-If the mask is not specified, it will default to the mask for that network
-class (A, B or C; see
+If the mask is not specified, it will default to the historical mask
+for that network class (A, B or C; see
 .Xr inet 4 ) .
+This usage is deprecated, and will elicit a warning log message.
 See the
 .Sx EXAMPLES
 section below.
Index: usr.sbin/mountd/mountd.c
===================================================================
--- usr.sbin/mountd/mountd.c
+++ usr.sbin/mountd/mountd.c
@@ -3418,6 +3418,9 @@
 		    (opt_flags & OP_MASK) == 0) {
 			in_addr_t addr;
 
+			syslog(LOG_WARNING,
+			    "WARNING: No mask specified for %s, "
+			    "using out-of-date default", name);
 			addr = ((struct sockaddr_in *)sa)->sin_addr.s_addr;
 			if (IN_CLASSA(addr))
 				preflen = 8;
@@ -3425,7 +3428,7 @@
 				preflen = 16;
 			else if (IN_CLASSC(addr))
 				preflen = 24;
-			else if (IN_CLASSD(addr))
+			else if (IN_CLASSD(addr))	/* XXX Multicast??? */
 				preflen = 28;
 			else
 				preflen = 32;	/* XXX */