ifconfig: make interface address without mask an error

In commit d8237b9, as part of the deprecation of IPv4 address
classes, Mike Karels introduced a warning in ifconfig for setting an
address without a width or mask.  The commit message says "This will
hopefully be an error in the future."

As the warning has been included in releases from FreeBSD 13.1 on, and
sufficient time has passed, turn this into an error.

Reviewed by:	allanjude, olce, grembo, philip, gordon
Relnotes:	Yes
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D45585

UPDATING

@@ -27,6 +27,11 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 15.x IS SLOW:
 	world, or to merely disable the most expensive debugging functionality
 	at runtime, run "ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20240617:
+	ifconfig now treats IPv4 addresses without a width or mask as an error.
+	Specify the desired mask or width along with the IP address on the
+	ifconfig command line and in rc.conf.
+
 20240428:
 	OpenBSM auditing runtime (auditd, etc.) has been moved into the new
 	package FreeBSD-audit.  If you use OpenBSM auditing and pkgbase, you

sbin/ifconfig/af_inet.c

@@ -436,36 +436,13 @@ in_exec_nl(if_ctx *ctx, unsigned long action, void *data)
 
 	return (e.error);
 }
-
-static void
-in_setdefaultmask_nl(void)
-{
-	struct in_px *px = sintab_nl[ADDR];
-
-	in_addr_t i = ntohl(px->addr.s_addr);
-
-	/*
-	 * If netmask isn't supplied, use historical default.
-	 * This is deprecated for interfaces other than loopback
-	 * or point-to-point; warn in other cases.  In the future
-	 * we should return an error rather than warning.
-	 */
-	if (IN_CLASSA(i))
-		px->plen = 32 - IN_CLASSA_NSHIFT;
-	else if (IN_CLASSB(i))
-		px->plen = 32 - IN_CLASSB_NSHIFT;
-	else
-		px->plen = 32 - IN_CLASSC_NSHIFT;
-	px->maskset = true;
-}
 #endif
 
 static void
-warn_nomask(int ifflags)
+err_nomask(int ifflags)
 {
     if ((ifflags & (IFF_POINTOPOINT | IFF_LOOPBACK)) == 0) {
-	warnx("WARNING: setting interface address without mask "
-	    "is deprecated,\ndefault mask may not be correct.");
+	errx(1, "ERROR: setting interface address without mask is no longer supported.");
     }
 }
 
@@ -474,12 +451,11 @@ in_postproc(if_ctx *ctx __unused, int newaddr, int ifflags)
 {
 #ifdef WITHOUT_NETLINK
 	if (sintab[ADDR]->sin_len != 0 && sintab[MASK]->sin_len == 0 && newaddr) {
-		warn_nomask(ifflags);
+		err_nomask(ifflags);
 	}
 #else
 	if (sintab_nl[ADDR]->addrset && !sintab_nl[ADDR]->maskset && newaddr) {
-		warn_nomask(ifflags);
-	    in_setdefaultmask_nl();
+		err_nomask(ifflags);
 	}
 #endif
 }