linux-kernel - RE: [PATCH] Hyperv: Trigger DHCP renew after host hibernation

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Date:	Thu, 14 Aug 2014 05:19:12 +0000
From:	Dexuan Cui <decui@...rosoft.com>
To:	Dan Williams <dcbw@...hat.com>, Tom Gundersen <teg@...m.no>
CC:	Greg KH <gregkh@...uxfoundation.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	Richard Weinberger <richard.weinberger@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Shao <huishao@...rosoft.com>,
	"Yue Zhang (OSTC DEV)" <yuezha@...rosoft.com>,
	"David Miller" <davem@...emloft.net>,
	Stephen Hemminger <stephen@...workplumber.org>
Subject: RE: [PATCH] Hyperv: Trigger DHCP renew after host hibernation

> -----Original Message-----
> From: Dan Williams
> > > e.g., on a bare metal host with Ubuntu 14.04, when I plug the RJ45 cable
> > > out of the network card and then plug the cable back into the network card
> > > quickly -- in ~3 seconds, networkd doesn't trigger DHCP renew request: in
> > > /var/log/syslog, we see
> > > Aug 12 11:07:07 decui-lin NetworkManager[828]: <info> (eth0): carrier
> now OFF (device state 100, deferring action for 4 seconds)
> > > Aug 12 11:07:07 decui-lin kernel: [  246.975453] e1000e: eth0 NIC Link is
> Down
> > > Aug 12 11:07:10 decui-lin NetworkManager[828]: <info> (eth0): carrier
> now ON (device state 100)
> > > Aug 12 11:07:10 decui-lin kernel: [  250.028533] e1000e: eth0 NIC Link is
> Up 100 Mbps Full Duplex, Flow Control: Rx/Tx
> > >
> > > It looks there is a delay of 4s.
> > > I'm going to find out if there is a configurable parameter for this.
> >
> > Just to avoid any confusion: you are referring to "networkd" (and so
> > did my comments), but the above logs are from "NetworkManager".
> 
> And yes, NM does have a 4-second delay before processing a carrier down
> event, and NM currently does not renew DHCP on link changes, but that's
> certainly something we can/should change.
> 
> Dan

Hi Tom, Dan,
Thanks a lot for the clarification!
So the 4s delay comes from NM rather than networkd.

Thanks,
-- Dexuan