netdev - [PATCH net-2.6] [NEIGH] [resend] Updating affected neighbours when about MAC address change in arp_netdev

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Message-ID: <31436f4a0712230551g4b394e13k87a9320fad4ae9b0@mail.gmail.com>
Date:	Sun, 23 Dec 2007 15:51:57 +0200
From:	"David Shwatrz" <dshwatrz@...il.com>
To:	davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH net-2.6] [NEIGH] [resend] Updating affected neighbours when about MAC address change in arp_netdev_event()

Hello,

This is a resend of the patch according to Yoshifuji comment. I will
send a patch for IPv6 later.

 We know that changes in MAC addresses are not frequent but
we are working on a special, highly advanced networking Linux based project
in our LABs, where we do change MAC addresses of an interface quite frequently.
(We do not go totally wild; the MAC addresses we are changing into are
from a set of given MAC addresses).

Normally, when we change a MAC address of some interface, the
relevant neighbours in the LAN which have entries with the previous MAC
address are not sent any update notification; instead, it is there
regular timers mechanisms which update the MAC address to the new
one in their ARP tables.

I had written a small patch to neigh_changeaddr() in net/ipv4/arp.c
against the 2.6 git net tree, which sends a gratuitous ARP to update
the list of
all the involved neighbours with the change of MAC address.
The patch is for arp_netdev_event() only.

This patch was tested and it does work in my LAB; if such a patch is
not needed,
I wonder why ?
It seems to me that it could not cause any troubles.
BTW, I had noticed that in irlan driver, there is such a mechanism
of sending a gratuitous ARP to update all the
neighbours when a MAC address is changed.

Signed-off-by: David Shwartz <dshwatrz@...il.com>

View attachment "patch.txt" of type "text/plain" (967 bytes)