[src/trunk]: src/sys/netinet ARP: Don't defend ARP probes.

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

details:   https://anonhg.NetBSD.org/src/rev/6940aa227451
branches:  trunk
changeset: 1004070:6940aa227451
user:      roy <roy%NetBSD.org@localhost>
date:      Fri Oct 11 13:32:46 2019 +0000

description:
ARP: Don't defend ARP probes.

We should let the nature of ARP takes it's course here when our address
is neither tentative nor duplicated.
This allows the host to work with ARP ping, which was broken in r1.279.

diffstat:

 sys/netinet/if_arp.c |  16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

diffs (41 lines):

diff -r afbe2a47c789 -r 6940aa227451 sys/netinet/if_arp.c
--- a/sys/netinet/if_arp.c      Fri Oct 11 11:05:41 2019 +0000
+++ b/sys/netinet/if_arp.c      Fri Oct 11 13:32:46 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_arp.c,v 1.288 2019/09/25 09:52:32 ozaki-r Exp $     */
+/*     $NetBSD: if_arp.c,v 1.289 2019/10/11 13:32:46 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 1.288 2019/09/25 09:52:32 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_arp.c,v 1.289 2019/10/11 13:32:46 roy Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_ddb.h"
@@ -1157,15 +1157,17 @@
        /*
         * DAD check, RFC 5227.
         * 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
-        * the message was broadcast - if it's unicast then it's
-        * a valid Unicast Poll from RFC 1122.
+        * Collision on target address is only a duplicate
+        * IF the sender address is the null host (ie a DAD probe)
+        * AND the message was broadcast
+        * AND our address is either tentative or duplicated
+        * If it was 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) &&
-            m->m_flags & M_BCAST)))
+            m->m_flags & M_BCAST &&
+            ia->ia4_flags & (IN_IFF_TENTATIVE | IN_IFF_DUPLICATED))))
        {
                struct sockaddr_dl sdl, *sdlp;