Index: sbin/ifconfig/af_inet.c
===================================================================
--- sbin/ifconfig/af_inet.c
+++ sbin/ifconfig/af_inet.c
@@ -54,6 +54,8 @@
 
 static struct in_aliasreq in_addreq;
 static struct ifreq in_ridreq;
+static int in_cidr;
+static int in_dotquad;
 
 static void
 in_status(int s __unused, const struct ifaddrs *ifa)
@@ -66,19 +68,34 @@
 	if (sin == NULL)
 		return;
 
-	printf("\tinet %s ", inet_ntoa(sin->sin_addr));
+	printf("\tinet %s", inet_ntoa(sin->sin_addr));
 
 	if (ifa->ifa_flags & IFF_POINTOPOINT) {
 		sin = (struct sockaddr_in *)ifa->ifa_dstaddr;
 		if (sin == NULL)
 			sin = &null_sin;
-		printf("--> %s ", inet_ntoa(sin->sin_addr));
+		printf(" --> %s ", inet_ntoa(sin->sin_addr));
 	}
 
 	sin = (struct sockaddr_in *)ifa->ifa_netmask;
 	if (sin == NULL)
 		sin = &null_sin;
-	printf("netmask 0x%lx ", (unsigned long)ntohl(sin->sin_addr.s_addr));
+	if (in_cidr) {
+		int cidr = 32;
+		unsigned long smask;
+
+		smask = ntohl(sin->sin_addr.s_addr);
+		while ((smask & 1) == 0) {
+			smask = smask >> 1;
+			cidr--;
+			if (cidr == 0)
+				break;
+		}
+		printf("/%d ", cidr);
+	} else if (in_dotquad)
+		printf(" netmask %s ", inet_ntoa(sin->sin_addr));
+	else
+		printf(" netmask 0x%lx ", (unsigned long)ntohl(sin->sin_addr.s_addr));
 
 	if (ifa->ifa_flags & IFF_BROADCAST) {
 		sin = (struct sockaddr_in *)ifa->ifa_broadaddr;
@@ -197,6 +214,28 @@
 	.af_addreq	= &in_addreq,
 };
 
+static void
+in_copt_cb(const char *optarg __unused)
+{
+	in_cidr++;	/* print IPv4 subnet mask in CIDR notation */
+}
+static struct option in_copt = {
+	.opt = "c",
+	.opt_usage = "[-c]",
+	.cb = in_copt_cb
+};
+
+static void
+in_sopt_cb(const char *optarg __unused)
+{
+	in_dotquad++;	/* print IPv4 subnet mask in dotted quad notation */
+}
+static struct option in_sopt = {
+	.opt = "s",
+	.opt_usage = "[-s]",
+	.cb = in_sopt_cb
+};
+
 static __constructor void
 inet_ctor(void)
 {
@@ -206,4 +245,6 @@
 		return;
 #endif
 	af_register(&af_inet);
+	opt_register(&in_copt);
+	opt_register(&in_sopt);
 }
Index: sbin/ifconfig/ifconfig.8
===================================================================
--- sbin/ifconfig/ifconfig.8
+++ sbin/ifconfig/ifconfig.8
@@ -28,7 +28,7 @@
 .\"     From: @(#)ifconfig.8	8.3 (Berkeley) 1/5/94
 .\" $FreeBSD$
 .\"
-.Dd Aug 12, 2015
+.Dd August 29, 2015
 .Dt IFCONFIG 8
 .Os
 .Sh NAME
@@ -36,6 +36,8 @@
 .Nd configure network interface parameters
 .Sh SYNOPSIS
 .Nm
+.Op Fl c
+.Op Fl s
 .Op Fl L
 .Op Fl k
 .Op Fl m
@@ -194,6 +196,17 @@
 List the interfaces in the given group.
 .El
 .Pp
+The following flags can be used to modify the output format of
+.Nm :
+.Bl -tag -width indent
+.It Fl c
+Display subnet masks in CIDR notation.
+For example 10.0.0.0/8 or 203.0.113.224/29
+.It Fl s
+Display subnet masks in dotted quad notation.
+For example 255.255.0.0 or 255.255.255.192
+.El
+.Pp
 The following parameters may be set with
 .Nm :
 .Bl -tag -width indent