netdev - Re: [PATCH net-next-2.6] ipv4: sysctl to block responding on down interface

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Message-Id: <D1C84781-4EC6-42D0-AE3E-258BE8BAA4BC@earthlink.net>
Date:	Mon, 28 Jun 2010 14:28:29 -0700
From:	Mitchell Erblich <erblichs@...thlink.net>
To:	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	Stephen Hemminger <shemminger@...tta.com>
Subject: Re: [PATCH net-next-2.6] ipv4: sysctl to block responding on down interface


On Jun 28, 2010, at 2:09 PM, Joakim Tjernlund wrote:

> Eric Dumazet <eric.dumazet@...il.com> wrote on 2010/06/28 21:42:01:
>> 
>> Le lundi 28 juin 2010 à 21:03 +0200, Joakim Tjernlund a écrit :
>>> Stephen Hemminger <shemminger@...tta.com> wrote on 2010/06/11 17:48:54:
>>>> 
>>>> When Linux is used as a router, it is undesirable for the kernel to process
>>>> incoming packets when the address assigned to the interface is down.
>>>> The initial problem report was for a management application that used ICMP
>>>> to check link availability.
>>>> 
>>>> The default is disabled to maintain compatibility with previous behavior.
>>>> This is not recommended for server systems because it makes fail over more
>>>> difficult, and does not account for configurations where multiple interfaces
>>>> have the same IP address.
>>>> 
>>>> Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
>>> 
>>> Ping David et. all?
>>> I too want this.
>> 
>> You probably missed David reply
>> 
>> http://permalink.gmane.org/gmane.linux.network/164494
> 
> Sure did, don't know how that happened, sorry.
> 
> Reading David's reply I do wonder about the current behaviour. Why
> is it so important to keep responding to an IP address when the
> admin has put the interface holding that IP address into administratively
> down state? I don't think the weak host model stipulates that it must be so, does it?
> 
> To me it "ifconfig eth0 down" means not only to stop using the I/F but
> also any IP address associated with the I/F. I was rather surprised that
> it didn't work that way. I don't see any way to make Linux stop responding to
> that IP other that removing it completely from the system, which is rather
> awkward.
> 
> Note, I don't mean that the same should be applied for the No Carrier case, just
> ifconfig down.
> 
> Jocke
> 
> 
> --
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Hey guys, isn't the support of magic pkts/ Energy star require the receipt
of pkts while the intf is down?

Mitchell Erblich--
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