netdev - Re: [PATCH] Propagate NCSI channel carrier loss/gain events to the kernel

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Date:   Mon, 13 Jan 2020 16:43:13 -0800
From:   samjonas <sam@...dozajonas.com>
To:     Johnathan Mantey <johnathanx.mantey@...el.com>,
        netdev@...r.kernel.org
Cc:     davem@...emloft.net
Subject: Re: [PATCH] Propagate NCSI channel carrier loss/gain events to the
 kernel

On Fri, 2020-01-10 at 14:02 -0800, Johnathan Mantey wrote:
> From 76d99782ec897b010ba507895d60d27dca8dca44 Mon Sep 17 00:00:00
> 2001
> From: Johnathan Mantey <johnathanx.mantey@...el.com>
> Date: Fri, 10 Jan 2020 12:46:17 -0800
> Subject: [PATCH] Propagate NCSI channel carrier loss/gain events to
> the
> kernel
> 
> Problem statement:
> Insertion or removal of a network cable attached to a NCSI controlled
> network channel does not notify the kernel of the loss/gain of the
> network link.
> 
> The expectation is that /sys/class/net/eth(x)/carrier will change
> state after a pull/insertion event. In addition the carrier_up_count
> and carrier_down_count files should increment.
> 
> Change statement:
> Use the NCSI Asynchronous Event Notification handler to detect a
> change in a NCSI link.
> Add code to propagate carrier on/off state to the network interface.
> The on/off state is only modified after the existing code identifies
> if the network device HAD or HAS a link state change.

If we set the carrier state off until we successfully configured a
channel could we avoid this limitation?

Cheers,
Sam

> 
> Test procedure:
> Connected a L2 switch with only two ports connected.
> One port was a DHCP corporate net, the other port attached to the
> NCSI
> controlled NIC.
> 
> Starting with the L2 switch with DC on, check to make sure the NCSI
> link is operating.
> cat /sys/class/net/eth1/carrier
> 1
> cat /sys/class/net/eth1/carrier_up_count
> 0
> cat /sys/class/net/eth1/carrier_down_count
> 0
> 
> Remove DC from the L2 switch, and check link state
> cat /sys/class/net/eth1/carrier
> 0
> cat /sys/class/net/eth1/carrier_up_count
> 0
> cat /sys/class/net/eth1/carrier_down_count
> 1
> 
> Restore DC to the L2 switch, and check link state
> cat /sys/class/net/eth1/carrier
> 1
> cat /sys/class/net/eth1/carrier_up_count
> 1
> cat /sys/class/net/eth1/carrier_down_count
> 1
> 
> Signed-off-by: Johnathan Mantey <johnathanx.mantey@...el.com>
> ---
>  net/ncsi/ncsi-aen.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/net/ncsi/ncsi-aen.c b/net/ncsi/ncsi-aen.c
> index b635c194f0a8..274c415dcead 100644
> --- a/net/ncsi/ncsi-aen.c
> +++ b/net/ncsi/ncsi-aen.c
> @@ -89,6 +89,12 @@ static int ncsi_aen_handler_lsc(struct
> ncsi_dev_priv
> *ndp,
>      if ((had_link == has_link) || chained)
>          return 0;
>  
> +    if (had_link) {
> +        netif_carrier_off(ndp->ndev.dev);
> +    } else {
> +        netif_carrier_on(ndp->ndev.dev);
> +    }
> +
>      if (!ndp->multi_package && !nc->package->multi_channel) {
>          if (had_link) {
>              ndp->flags |= NCSI_DEV_RESHUFFLE;