Retire most of the classful network behaviour of netstat -r output, for IPv4.

Without -n, we now only print a "network name" without the prefix length
 under the following conditions:
  1) the network address and mask matches a classful network prefix;
  2) getnetbyaddr(3) returns a network name for this network address.

 With -n, we unconditionally print the full unabbreviated CIDR network
 prefix in the form "a.b.c.d/p". 0.0.0.0/0 is still printed as "default".

This change is in preparation for changes such as equal-cost multipath, and
to more generally assist operational deployment of FreeBSD as a modern IPv4
router. There are currently no plans to backport this change.

Discussed on:	freebsd-net

UPDATING

@@ -21,6 +21,17 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 7.x IS SLOW:
 	developers choose to disable these features on build machines
 	to maximize performance.
 
+20070214:
+	The output of netstat -r has changed. Without -n, we now only
+	print a "network name" without the prefix length if the network
+	address and mask exactly match a Class A/B/C network, and an entry
+	exists in the nsswitch "networks" map.
+	With -n, we print the full unabbreviated CIDR network prefix in
+	the form "a.b.c.d/p". 0.0.0.0/0 is always printed as "default".
+	This change is in preparation for changes such as equal-cost
+	multipath, and to more generally assist operational deployment
+	of FreeBSD as a modern IPv4 router.
+
 20070210:
 	PIM has been turned on by default in the IPv4 multicast
 	routing code. The kernel option 'PIM' has now been removed.

usr.bin/netstat/route.c

@@ -134,7 +134,6 @@ static const char *fmt_sockaddr (struct sockaddr *sa, struct sockaddr *mask,
 static void p_flags (int, const char *);
 static const char *fmt_flags(int f);
 static void p_rtentry (struct rtentry *);
-static u_long forgemask (u_long);
 static void domask (char *, u_long, u_long);
 
 /*
@@ -801,26 +800,18 @@ routename(u_long in)
 	return (line);
 }
 
-static u_long
+#define	NSHIFT(m) (							\
-forgemask(u_long a)
+	(m) == IN_CLASSA_NET ? IN_CLASSA_NSHIFT :			\
-{
+	(m) == IN_CLASSB_NET ? IN_CLASSB_NSHIFT :			\
-	u_long m;
+	(m) == IN_CLASSC_NET ? IN_CLASSC_NSHIFT :			\
-
+	0)
-	if (IN_CLASSA(a))
-		m = IN_CLASSA_NET;
-	else if (IN_CLASSB(a))
-		m = IN_CLASSB_NET;
-	else
-		m = IN_CLASSC_NET;
-	return (m);
-}
 
 static void
 domask(char *dst, u_long addr, u_long mask)
 {
 	int b, i;
 
-	if (!mask || (forgemask(addr) == mask)) {
+	if (mask == 0 || (!numeric_addr && NSHIFT(mask) != 0)) {
 		*dst = '\0';
 		return;
 	}
@@ -853,62 +844,28 @@ netname(u_long in, u_long mask)
 	char *cp = 0;
 	static char line[MAXHOSTNAMELEN];
 	struct netent *np = 0;
-	u_long dmask;
 	u_long i;
 
-#define	NSHIFT(m) (							\
-	(m) == IN_CLASSA_NET ? IN_CLASSA_NSHIFT :			\
-	(m) == IN_CLASSB_NET ? IN_CLASSB_NSHIFT :			\
-	(m) == IN_CLASSC_NET ? IN_CLASSC_NSHIFT :			\
-	0)
-
 	i = ntohl(in);
-	dmask = forgemask(i);
 	if (!numeric_addr && i) {
 		np = getnetbyaddr(i >> NSHIFT(mask), AF_INET);
-		if (np == NULL && mask == 0)
-			np = getnetbyaddr(i >> NSHIFT(dmask), AF_INET);
 		if (np != NULL) {
 			cp = np->n_name;
 			trimdomain(cp, strlen(cp));
 		}
 	}
-#undef NSHIFT
 	if (cp != NULL) {
 		strncpy(line, cp, sizeof(line) - 1);
 		line[sizeof(line) - 1] = '\0';
 	} else {
-		switch (dmask) {
+		inet_ntop(AF_INET, (char *)&in, line, sizeof(line) - 1);
-		case IN_CLASSA_NET:
-			if ((i & IN_CLASSA_HOST) == 0) {
-				sprintf(line, "%lu", C(i >> 24));
-				break;
-			}
-			/* FALLTHROUGH */
-		case IN_CLASSB_NET:
-			if ((i & IN_CLASSB_HOST) == 0) {
-				sprintf(line, "%lu.%lu",
-					C(i >> 24), C(i >> 16));
-				break;
-			}
-			/* FALLTHROUGH */
-		case IN_CLASSC_NET:
-			if ((i & IN_CLASSC_HOST) == 0) {
-				sprintf(line, "%lu.%lu.%lu",
-					C(i >> 24), C(i >> 16), C(i >> 8));
-				break;
-			}
-			/* FALLTHROUGH */
-		default:
-			sprintf(line, "%lu.%lu.%lu.%lu",
-				C(i >> 24), C(i >> 16), C(i >> 8), C(i));
-			break;
-		}
 	}
 	domask(line + strlen(line), i, mask);
 	return (line);
 }
 
+#undef NSHIFT
+
 #ifdef INET6
 const char *
 netname6(struct sockaddr_in6 *sa6, struct in6_addr *mask)