netdevsim: set the carrier when the device goes up

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>

diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index ebc3833e95b4403f90e79be6292083e4f765be6b..fa1d97885caaf2c8a4ee59e4ade47ee3fb8f16f2 100644 (file)
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -545,6 +545,7 @@ 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;
 
        netdev_assert_locked(dev);
@@ -555,6 +556,12 @@ 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;
 }