netdev - Re: [RFC PATCH] powerpc/pseries/mobility: notify network peers after migration

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Date:   Wed, 06 Nov 2019 15:13:15 +1100
From:   Russell Currey <ruscur@...sell.cc>
To:     Thomas Falcon <tlfalcon@...ux.ibm.com>, linuxppc-dev@...abs.org
Cc:     nathanl@...ux.ibm.com, netdev@...r.kernel.org, msuchanek@...e.com,
        tyreld@...ux.ibm.com
Subject: Re: [RFC PATCH] powerpc/pseries/mobility: notify network peers
 after migration

On Tue, 2019-11-05 at 18:06 -0600, Thomas Falcon wrote:
> After a migration, it is necessary to send a gratuitous ARP
> from all running interfaces so that the rest of the network
> is aware of its new location. However, some supported network
> devices are unaware that they have been migrated. To avoid network
> interruptions and other unwanted behavior, force a GARP on all
> valid, running interfaces as part of the post_mobility_fixup
> routine.
> 
> Signed-off-by: Thomas Falcon <tlfalcon@...ux.ibm.com>

Hi Thomas,

> ---
>  arch/powerpc/platforms/pseries/mobility.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/arch/powerpc/platforms/pseries/mobility.c
> b/arch/powerpc/platforms/pseries/mobility.c
> index b571285f6c14..c1abc14cf2bb 100644
> --- a/arch/powerpc/platforms/pseries/mobility.c
> +++ b/arch/powerpc/platforms/pseries/mobility.c
> @@ -17,6 +17,9 @@
>  #include <linux/delay.h>
>  #include <linux/slab.h>
>  #include <linux/stringify.h>
> +#include <linux/netdevice.h>
> +#include <linux/rtnetlink.h>
> +#include <net/net_namespace.h>
>  
>  #include <asm/machdep.h>
>  #include <asm/rtas.h>
> @@ -331,6 +334,8 @@ void post_mobility_fixup(void)
>  {
>  	int rc;
>  	int activate_fw_token;
> +	struct net_device *netdev;
> +	struct net *net;
>  
>  	activate_fw_token = rtas_token("ibm,activate-firmware");
>  	if (activate_fw_token == RTAS_UNKNOWN_SERVICE) {
> @@ -371,6 +376,21 @@ void post_mobility_fixup(void)
>  	/* Possibly switch to a new RFI flush type */
>  	pseries_setup_rfi_flush();
>  
> +	/* need to force a gratuitous ARP on running interfaces */
> +	rtnl_lock();
> +	for_each_net(net) {
> +		for_each_netdev(net, netdev) {
> +			if (netif_device_present(netdev) &&
> +			    netif_running(netdev) &&
> +			    !(netdev->flags & (IFF_NOARP |
> IFF_LOOPBACK)))
> +				call_netdevice_notifiers(NETDEV_NOTIFY_
> PEERS,
> +							 netdev);

Without curly braces following the "if" statment, the second line
(below) will be executed unconditionally, which I assume with this
indentation isn't what you want.

(reported by snowpatch)

- Russell

> +				call_netdevice_notifiers(NETDEV_RESEND_
> IGMP,
> +							 netdev);
> +		}
> +	}
> +	rtnl_unlock();
> +
>  	return;
>  }
>