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

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Date:	Mon, 28 Jun 2010 23:58:09 +0200
From:	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>
To:	Mitchell Erblich <erblichs@...thlink.net>
Cc:	David Miller <davem@...emloft.net>,
	Eric Dumazet <eric.dumazet@...il.com>, netdev@...r.kernel.org,
	Stephen Hemminger <shemminger@...tta.com>
Subject: Re: [PATCH net-next-2.6] ipv4: sysctl to block responding on down interface

Mitchell Erblich <erblichs@...thlink.net> wrote on 2010/06/28 23:28:29:
>
>
> 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
> >
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe netdev" in
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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?

No idea, but if so, does it need to process IP pkgs destined for
the IP address in question and pass these up to user space?

 Jocke

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