linux-kernel - Re: A kexec approach to hibernation

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Message-ID: <87r6oimqva.fsf@jbms.ath.cx>
Date:	Mon, 11 Jun 2007 11:51:21 -0400
From:	Jeremy Maitin-Shepard <jbms@....edu>
To:	Xavier Bestel <xavier.bestel@...e.fr>
Cc:	nigel@...el.suspend2.net, "Rafael J. Wysocki" <rjw@...k.pl>,
	linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...l.org>,
	Pavel Machek <pavel@....cz>
Subject: Re: A kexec approach to hibernation

Xavier Bestel <xavier.bestel@...e.fr> writes:

> On Mon, 2007-06-11 at 11:01 -0400, Jeremy Maitin-Shepard wrote:
>> >> You might claim then that the solution is to simply keep the network
>> >> driver quiesced or stopped.  But then it is impossible to write the
>> >> image over the network.  The way to get around this problem is to write
>> >> the image over the network using a fresh network stack.
>> 
>> > Or teach the driver stack about the difference/reset it. Remember that
>> > even if you get a fresh network stack, you'll still be getting packets
>> > for the old stack. Getting a new ip (assuming one is available) won't
>> > stop other connections getting killed, either because we send resets
>> > from the kexec'd kernel, or because they timeout looking for the old
>> > ip.
>> 
>> I could be mistaken, but I think that bringing up the network interface
>> with a different IP address would prevent it from reseting existing TCP
>> connections, because it would never receive the packets for those
>> existing connections.  

> That can't work. There are networks where the client must have a fixed
> IP, or must accept the adress given by dhcp in order to talk to
> fileservers. And you still have the same mac adress, which may cause
> problems.

I wasn't suggesting that using a different IP address would be a general
solution.  It might be a solution for a few people.

In general, I'd imagine that most people would not bring up the network
interface at all, and most of the people that do would bring it up with
the same IP address, causing some existing TCP connections to possibly
be reset.

I think that causing connections to be reset is, however, far better
than acking packets that are then silently thrown away.

-- 
Jeremy Maitin-Shepard
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