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Date:      Mon, 3 Oct 2016 19:02:22 +0000 (UTC)
From:      Eric van Gyzen <vangyzen@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r306652 - head/usr.sbin/arp
Message-ID:  <201610031902.u93J2MR8062236@repo.freebsd.org>

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Author: vangyzen
Date: Mon Oct  3 19:02:22 2016
New Revision: 306652
URL: https://svnweb.freebsd.org/changeset/base/306652

Log:
  Update arp(4) to document the net.link.ether.inet.garp_rexmit_count sysctl.
  
  Submitted by:	David A. Bright <david.a.bright@dell.com>
  Requested by:	markj
  Reviewed by:	markj, badger
  MFC after:	4 weeks
  X-MFC with:	r306577
  Sponsored by:	Dell EMC
  Differential Revision:	https://reviews.freebsd.org/D8136

Modified:
  head/usr.sbin/arp/arp.4

Modified: head/usr.sbin/arp/arp.4
==============================================================================
--- head/usr.sbin/arp/arp.4	Mon Oct  3 18:20:58 2016	(r306651)
+++ head/usr.sbin/arp/arp.4	Mon Oct  3 19:02:22 2016	(r306652)
@@ -28,7 +28,7 @@
 .\"	@(#)arp4.4	6.5 (Berkeley) 4/18/94
 .\" $FreeBSD$
 .\"
-.Dd November 5, 2013
+.Dd October 3, 2016
 .Dt ARP 4
 .Os
 .Sh NAME
@@ -126,6 +126,24 @@ the hardware address.
 Installing such entries is RFC 1812 violation, but some prorietary
 load balancing techniques require routers on network to do so.
 Turned off by default.
+.It Va garp_rexmit_count
+Should the kernel retransmit gratuitous ARP (GARP) packets when an IPv4 address
+is added to an interface.
+A GARP is always transmitted when an IPv4 address is added to an interface.
+A non-zero value of this sysctl will cause the GARP packet to be retransmitted
+the stated number of times.
+The interval between retransmissions is doubled each time, so the
+retransmission intervals are: {1, 2, 4, 8, 16, ...} (seconds).
+The default value of zero means only the initial GARP is sent; no
+additional GARP packets are retransmitted.
+The maximum value is sixteen.
+.Pp
+Although a single GARP packet (the default behavior) is usually sufficient, in
+some circumstances, such as when a shared address is passed between cluster
+nodes, this single GARP may be dropped or lost.
+This can lead to neighbors on the network link working with a stale ARP cache
+and sending packets destined for that address to the node that previously owned
+the address, which may not respond.
 .It Va log_arp_movements
 Should the kernel log movements of IP addresses from one hardware
 address to an other.



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