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>
---
Changes in v2:
- Reword the commit message to reference the symmetry between
nsim_open() and nsim_stop() in regarding to carrier. (Andrew Lunn)
- Link to v1: https://lore.kernel.org/r/20251013-netdevsim_fix-v1-1-357b265dd9d0@debian.org
---
drivers/net/netdevsim/netdev.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index ebc3833e95b44..fa1d97885caaf 100644
--- 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;
}
---
base-commit: 0b4b77eff5f8cd9be062783a1c1e198d46d0a753
change-id: 20251013-netdevsim_fix-b9a8a5064f8f
Best regards,
--
Breno Leitao <leitao@debian.org>