netdevsim: set the carrier when the device goes up

[ Upstream commit 1a8fed52f7be14e45785e8e54d0d0b50fc17dbd8 ]

Bringing a linked netdevsim device down and then up causes communication
failure because both interfaces lack carrier. Basically a ifdown/ifup on
the interface make the link broken.

Commit 3762ec05a9fbda ("netdevsim: add NAPI support") added supported
for NAPI, calling netif_carrier_off() in nsim_stop(). This patch
re-enables the carrier symmetrically on nsim_open(), in case the device
is linked and the peer is up.

Signed-off-by: Breno Leitao <leitao@debian.org>
Fixes: 3762ec05a9fbda ("netdevsim: add NAPI support")
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20251014-netdevsim_fix-v2-1-53b40590dae1@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index ee2a7b2f6268deba4ad47c3f90fab753e3fae487..e2d92295ad33b22b48893a5323a8b88d53ec1617 100644 (file)
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -433,6 +433,7 @@ static void nsim_enable_napi(struct netdevsim *ns)
 static int nsim_open(struct net_device *dev)
 {
        struct netdevsim *ns = netdev_priv(dev);
+       struct netdevsim *peer;
        int err;
 
        err = nsim_init_napi(ns);
@@ -441,6 +442,12 @@ static int nsim_open(struct net_device *dev)
 
        nsim_enable_napi(ns);
 
+       peer = rtnl_dereference(ns->peer);
+       if (peer && netif_running(peer->netdev)) {
+               netif_carrier_on(dev);
+               netif_carrier_on(peer->netdev);
+       }
+
        return 0;
 }