From 95af085073221d13b9ed15cceb269fea8a578fb5 Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Tue, 14 Oct 2025 02:17:25 -0700 Subject: [PATCH] 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 Fixes: 3762ec05a9fbda ("netdevsim: add NAPI support") Reviewed-by: Andrew Lunn Link: https://patch.msgid.link/20251014-netdevsim_fix-v2-1-53b40590dae1@debian.org Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- 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 ee2a7b2f6268..e2d92295ad33 100644 --- 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; }