linux-kernel - RE: [PATCH net-next] hyperv: Add handler for RNDIS_STATUS_NETWORK

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Message-ID: <BN1PR0301MB07707C038A4411BD4DF24DE3CA2F0@BN1PR0301MB0770.namprd03.prod.outlook.com>
Date:	Fri, 30 Oct 2015 22:03:31 +0000
From:	Haiyang Zhang <haiyangz@...rosoft.com>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>
CC:	Richard Weinberger <richard.weinberger@...il.com>,
	David Miller <davem@...emloft.net>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH net-next] hyperv: Add handler for
 RNDIS_STATUS_NETWORK_CHANGE event



> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@...hat.com]
> Sent: Friday, October 30, 2015 6:56 AM
> To: Haiyang Zhang <haiyangz@...rosoft.com>
> Cc: Richard Weinberger <richard.weinberger@...il.com>; David Miller
> <davem@...emloft.net>; olaf@...fle.de; jasowang@...hat.com; driverdev-
> devel@...uxdriverproject.org; LKML <linux-kernel@...r.kernel.org>;
> netdev@...r.kernel.org
> Subject: Re: [PATCH net-next] hyperv: Add handler for
> RNDIS_STATUS_NETWORK_CHANGE event
> 
> Haiyang Zhang <haiyangz@...rosoft.com> writes:
> 
> >> -----Original Message-----
> >> From: Richard Weinberger [mailto:richard.weinberger@...il.com]
> >> Sent: Tuesday, October 27, 2015 6:36 PM
> >> To: David Miller <davem@...emloft.net>
> >> Cc: Haiyang Zhang <haiyangz@...rosoft.com>; olaf@...fle.de; Greg
> Kroah-
> >> Hartman <greg@...ah.com>; netdev@...r.kernel.org; jasowang@...hat.com;
> >> driverdev-devel@...uxdriverproject.org; LKML <linux-
> >> kernel@...r.kernel.org>
> >> Subject: Re: [PATCH net-next] hyperv: Add handler for
> >> RNDIS_STATUS_NETWORK_CHANGE event
> >>
> >> On Mon, Jun 23, 2014 at 10:10 PM, David Miller <davem@...emloft.net>
> >> wrote:
> >> > From: Haiyang Zhang <haiyangz@...rosoft.com>
> >> > Date: Mon, 23 Jun 2014 16:09:59 +0000
> >> >
> >> >> So, what's the equivalent or similar command to "network restart"
> on
> >> SLES12? Could
> >> >> you update the command line for the usermodehelper when porting
> this
> >> patch to SLES
> >> >> 12?
> >> >
> >> > No, you are not going to keep the usermodehelper invocation in your
> >> driver
> >> > please remove it.  It is absolutely inappropriate, and I strictly
> do
> >> not want
> >> > to keep it in there because other people will copy it and then
> we'll
> >> have a
> >> > real mess on our hands.
> >>
> >> Sorry for digging up this old thread.
> >> While talking with some guys about usermodehelper abuses I came
> across
> >> this gem.
> >> Mainline still contains that "/etc/init.d/network restart" code.
> >> Haiyang, care to cleanup?
> >
> > Hi Richard and others,
> >
> > Thanks for the reminder. I will clean up the usermode helper.
> >
> > Do you have suggestions of trigger DHCP refresh from kernel mode? Any
> > sample code in the existing kernel code?
> >
> 
> I think it's wrong to call dhcp refresh from kernel. What happens when
> we reconnect normal hardware adapter to another network? Link goes down
> and then up and userspace is supposed to react accordingly. I think we
> should emulate something similar for RNDIS_STATUS_NETWORK_CHANGE.

When link is down physically for a few seconds, the DHCP will automatically 
refresh. I will add code to emulate this. There were some discussions around 
this and other possibilities previously... I agree emulating what happens 
with physically plug/unplug a cable is a reasonable way to trigger the DHCP 
refresh.

Thanks,
- Haiyang



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