[src/trunk]: src/sys/netinet ARP: Enable Address Defence again.

[roy <roy%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/b7bcc3752448
branches:  trunk
changeset: 456121:b7bcc3752448
user:      roy <roy%NetBSD.org@localhost>
date:      Wed Apr 24 10:20:36 2019 +0000

description:
ARP: Enable Address Defence again.

Revert the tentative/duplicated check and test for if it's been broadcast
or not. This reverts r1.245.

diffstat:

 sys/netinet/if_arp.c |  13 ++++++-------
 1 files changed, 6 insertions(+), 7 deletions(-)

diffs (37 lines):

diff -r 1cc8153d6343 -r b7bcc3752448 sys/netinet/if_arp.c
--- a/sys/netinet/if_arp.c      Wed Apr 24 09:35:54 2019 +0000
+++ b/sys/netinet/if_arp.c      Wed Apr 24 10:20:36 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_arp.c,v 1.278 2018/12/22 14:28:57 maxv Exp $        */
+/*     $NetBSD: if_arp.c,v 1.279 2019/04/24 10:20:36 roy Exp $ */
 
 /*
  * Copyright (c) 1998, 2000, 2008 The NetBSD Foundation, Inc.
@@ -68,7 +68,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_arp.c,v 1.278 2018/12/22 14:28:57 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_arp.c,v 1.279 2019/04/24 10:20:36 roy Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ddb.h"
@@ -1171,14 +1171,13 @@
         * Collision on sender address is always a duplicate.
         * Collision on target address is only a duplicate IF
         * the sender address is the null host (ie a DAD probe) AND
-        * our address is in the TENTATIVE state.
-        * DUPLICATED state is also checked so that processing stops here
-        * and an error can be logged.
+        * the message was broadcast - if it's unicast then it's
+        * a valid Unicast Poll from RFC 1122.
         */
        if (do_dad &&
            (in_hosteq(isaddr, myaddr) ||
-           (in_nullhost(isaddr) && in_hosteq(itaddr, myaddr)
-           && ia->ia4_flags & (IN_IFF_TENTATIVE | IN_IFF_DUPLICATED))))
+           (in_nullhost(isaddr) && in_hosteq(itaddr, myaddr) &&
+            m->m_flags & M_BCAST)))
        {
                arp_dad_duplicated((struct ifaddr *)ia,
                    lla_snprintf(llabuf, ar_sha(ah), ah->ar_hln));