netdev - RE: [patch net-next] ipv6: allow userspace to create address with IFLA_F

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Date:	Wed, 6 Nov 2013 09:23:05 -0000
From:	"David Laight" <David.Laight@...LAB.COM>
To:	"Hannes Frederic Sowa" <hannes@...essinduktion.org>
Cc:	<nicolas.dichtel@...nd.com>, "David Miller" <davem@...emloft.net>,
	<jiri@...nulli.us>, <vyasevich@...il.com>,
	<netdev@...r.kernel.org>, <kuznet@....inr.ac.ru>,
	<jmorris@...ei.org>, <yoshfuji@...ux-ipv6.org>, <kaber@...sh.net>,
	<thaller@...hat.com>, <stephen@...workplumber.org>
Subject: RE: [patch net-next] ipv6: allow userspace to create address with IFLA_F_TEMPORARY flag

> By the way:
> Although dhclient uses an AF_PACKET socket, it never does request
> additional multicast addresses or promisc mode. So the only overhead is
> that we have to run the socket filter on each incoming packet.

Just creating the AF_PACKET socket requires that every receive
frame be duplicated.
On Linux this is a reference counted but the cost is still non-zero.
On some other OS (I first saw this with VxWorks) it is a full data copy.

	David