netdev - Re: IPv6: autoconfiguration and suspend/resume or link down/up

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Date:	Tue, 19 Jul 2011 12:42:09 -0700
From:	Stephen Hemminger <stephen.hemminger@...tta.com>
To:	Jiri Bohac <jbohac@...e.cz>, netdev@...r.kernel.org
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	" David S. Miller" <davem@...emloft.net>,
	stephen hemminger <shemminger@...tta.com>
Subject: Re: IPv6: autoconfiguration and suspend/resume or link down/up

bridge forwarding table; route cache; and neighbor table could have same problem. I thought carrier is supposed to toggle on suspend or hibernate

Jiri Bohac <jbohac@...e.cz> wrote:

>Hi,
>
>I came over a surprising behaviour with IPv6 autoconfiguration,
>which I think is a bug, but I would first like to hear other
>people's opinions before trying to fix this:
>
>Problem 1: all the address/route lifetimes are kept in jiffies
>and jiffies don't get incremented on resume. So when a
>route/address lifetime is 30 minutes and the system resumes after
>1 hour, the route/address should be considered expired, but it is
>not.
>
>Problem 2: when a system is moved to a new network a RS is not
>sent. Thus, IPv6 does not autoconfigure until the router sends a
>periodic RA. This can occur both while the system is alive and
>while it is suspended. I think the autoconfigured state should be
>discarded when the kernel suspects the system could have been
>moved to a different network.
>
>When the cable is unplugged and plugged in again, we already get
>notified through linkwatch -> netdev_state_change ->
>  -> call_netdevice_notifiers(NETDEV_CHANGE, ...)
>However, if the device has already been autoconfigured,
>addrconf_notify() only handles this event by printing a
>message.
>
>So my idea was to:
>- handle link up/down in addrconf_notify() similarly to
>  NETDEV_UP/NETDEV_DOWN
>
>- on suspend, faking a link down event; on resume, faking a link up event
>  (or better, having a special event type for suspend/resume)
>
>This would cause autoconfiguration to be restarted on resume as
>well as cable plug/unplug, solving both the above problems.
>
>Or do we want to completely rely on userspace tools
>(networkmanager/ifplug) and expect them to do NETDEV_DOWN on
>unplug/suspend and NETDEV_UP on plug/resume?
>
>Any thoughts?
>
>-- 
>Jiri Bohac <jbohac@...e.cz>
>SUSE Labs, SUSE CZ
>