[PATCH] Propagate NCSI channel carrier loss/gain events to the kernel

[Johnathan Mantey <johnathanx.mantey@intel.com>]

From 76d99782ec897b010ba507895d60d27dca8dca44 Mon Sep 17 00:00:00 2001
From: Johnathan Mantey <johnathanx.mantey@intel.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.

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@intel.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;
-- 
2.24.1