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

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Date:	Fri, 18 Jul 2014 15:40:53 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Yue Zhang <yuezha@...rosoft.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	driverdev-devel@...uxdriverproject.org,
	LKML <linux-kernel@...r.kernel.org>,
	Greg KH <gregkh@...uxfoundation.org>,
	"olaf@...fle.de" <olaf@...fle.de>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"David S. Miller" <davem@...emloft.net>, haiyangz@...rosoft.com,
	"K. Y. Srinivasan" <kys@...rosoft.com>, huishao@...rosoft.com,
	decui@...rosoft.com
Subject: Re: [PATCH] Hyperv: Trigger DHCP renew after host hibernation

On Fri, Jul 18, 2014 at 12:55 PM, Yue Zhang <yuezha@...rosoft.com> wrote:
> From: Yue Zhang <yuezha@...rosoft.com>
>
> This patch addresses the comment from Olaf Hering and Greg KH
> for a previous commit 3a494e710367 ("hyperv: Add handler for
> RNDIS_STATUS_NETWORK_CHANGE event")
>
> In previous solution, the driver calls "network restart" to
> force a DHCP renew when the host is back from hibernation.
>
> In this fix, the driver will keep network carrier offline for
> 10 seconds and then bring it back. So that ifplugd daemon will
> notice this change and refresh DHCP lease.
>
> Cc: Haiyang Zhang <haiyangz@...rosoft.com>
> Cc: K. Y. Srinivasan <kys@...rosoft.com>
>
> Signed-off-by: Yue Zhang <yuezha@...rosoft.com>
> ---
>  drivers/net/hyperv/netvsc_drv.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index a9c5eaa..559c97d 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -33,6 +33,7 @@
>  #include <linux/if_vlan.h>
>  #include <linux/in.h>
>  #include <linux/slab.h>
> +#include <linux/delay.h>
>  #include <net/arp.h>
>  #include <net/route.h>
>  #include <net/sock.h>
> @@ -792,8 +793,7 @@ static void netvsc_link_change(struct work_struct *w)
>         struct netvsc_device *net_device;
>         struct rndis_device *rdev;
>         bool notify, refresh = false;
> -       char *argv[] = { "/etc/init.d/network", "restart", NULL };
> -       char *envp[] = { "HOME=/", "PATH=/sbin:/usr/sbin:/bin:/usr/bin", NULL };
> +       int delay;
>
>         rtnl_lock();
>
> @@ -816,8 +816,21 @@ static void netvsc_link_change(struct work_struct *w)
>
>         rtnl_unlock();
>
> -       if (refresh)
> -               call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
> +       if (refresh) {
> +               /*
> +                * Keep the carrier offline for 10 seconds
> +                * to notify ifplugd daemon network change
> +                */

Why 10? Is this a random number which works by accident for ifplugd?
What about other networking implementations, is 10 also ok for them?

> +               for (delay = 0; delay < 10; delay++) {
> +                       rtnl_lock();
> +                       netif_carrier_off(net);
> +                       rtnl_unlock();
> +                       ssleep(1);
> +               }
> +               rtnl_lock();
> +               netif_carrier_on(net);
> +               rtnl_unlock();
> +       }
>
>         if (notify)
>                 netdev_notify_peers(net);
> --
> 1.9.1
>
> --
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-- 
Thanks,
//richard
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