From e700bef2dc85fb4318d32ea5d3afd0335435c95e Mon Sep 17 00:00:00 2001
From: Marcelo Araujo <araujo@FreeBSD.org>
Date: Fri, 16 Sep 2016 04:22:21 +0000
Subject: [PATCH] Add an option called "random" that combined with "ether" can
 generate a random MAC address for an Ethernet interface.

PR:		211984
Submitted by:	pi@
Reviewed by:	gnn, cem, jhb, lidl, rpokala, wblock
Approved by:	wblock (manpages)
---
 sbin/ifconfig/af_link.c  | 24 +++++++++++++++++-------
 sbin/ifconfig/ifconfig.8 | 16 +++++++++++-----
 2 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/sbin/ifconfig/af_link.c b/sbin/ifconfig/af_link.c
index c96cbd2ce92e..361c82e50fe2 100644
--- a/sbin/ifconfig/af_link.c
+++ b/sbin/ifconfig/af_link.c
@@ -90,13 +90,23 @@ link_getaddr(const char *addr, int which)
 
 	if (which != ADDR)
 		errx(1, "can't set link-level netmask or broadcast");
-	if ((temp = malloc(strlen(addr) + 2)) == NULL)
-		errx(1, "malloc failed");
-	temp[0] = ':';
-	strcpy(temp + 1, addr);
-	sdl.sdl_len = sizeof(sdl);
-	link_addr(temp, &sdl);
-	free(temp);
+	if (!strcmp(addr, "random")) {
+		sdl.sdl_len = sizeof(sdl);
+		sdl.sdl_alen = ETHER_ADDR_LEN;
+		sdl.sdl_nlen = 0;
+		sdl.sdl_family = AF_LINK;
+		arc4random_buf(&sdl.sdl_data, ETHER_ADDR_LEN);
+		/* Non-multicast and claim it is a hardware address */
+		sdl.sdl_data[0] &= 0xfc;
+	} else {
+		if ((temp = malloc(strlen(addr) + 2)) == NULL)
+			errx(1, "malloc failed");
+		temp[0] = ':';
+		strcpy(temp + 1, addr);
+		sdl.sdl_len = sizeof(sdl);
+		link_addr(temp, &sdl);
+		free(temp);
+	}
 	if (sdl.sdl_alen > sizeof(sa->sa_data))
 		errx(1, "malformed link-level address");
 	sa->sa_family = AF_LINK;
diff --git a/sbin/ifconfig/ifconfig.8 b/sbin/ifconfig/ifconfig.8
index e8db561f45a0..fe5016346d6f 100644
--- a/sbin/ifconfig/ifconfig.8
+++ b/sbin/ifconfig/ifconfig.8
@@ -28,7 +28,7 @@
 .\"     From: @(#)ifconfig.8	8.3 (Berkeley) 1/5/94
 .\" $FreeBSD$
 .\"
-.Dd June 8, 2016
+.Dd September 17, 2016
 .Dt IFCONFIG 8
 .Os
 .Sh NAME
@@ -145,6 +145,12 @@ is specified as a series of colon-separated hex digits.
 This can be used to, for example,
 set a new MAC address on an Ethernet interface, though the
 mechanism used is not Ethernet specific.
+Use the
+.Pq Dq random
+keyword to set a randomly generated MAC address.
+A randomly-generated MAC address might be the same as one already in use
+in the network.
+Such duplications are extremely unlikely.
 If the interface is already
 up when this option is used, it will be briefly brought down and
 then brought back up again in order to ensure that the receive
@@ -254,7 +260,7 @@ Display subnet masks in dotted quad notation, for example:
 .br
 255.255.0.0 or 255.255.255.192
 .It Sy hex
-Display subnet masks in hexidecimal, for example:
+Display subnet masks in hexadecimal, for example:
 .br
 0xffff0000 or 0xffffffc0
 .El
@@ -2615,13 +2621,13 @@ and
 .Cm vlandev
 must both be set at the same time.
 .It Cm vlanpcp Ar priority_code_point
-Priority code point 
+Priority code point
 .Pq Dv PCP
 is an 3-bit field which refers to the IEEE 802.1p
 class of service and maps to the frame priority level.
 .Pp
 Values in order of priority are:
-.Cm 1 
+.Cm 1
 .Pq Dv Background (lowest) ,
 .Cm 0
 .Pq Dv Best effort (default) ,
@@ -2759,7 +2765,7 @@ interface to send the frame directly to the remote host instead of
 broadcasting the frame to the multicast group.
 This is the default.
 .It Fl vxlanlearn
-The forwarding table is not populated by recevied packets.
+The forwarding table is not populated by received packets.
 .It Cm vxlanflush
 Delete all dynamically-learned addresses from the forwarding table.
 .It Cm vxlanflushall