5.15-stable review patch. If anyone has any objections, please let me know.
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From: Ido Schimmel idosch@nvidia.com
[ Upstream commit 3d05b24429e1de7a17c8fdccb04a04dbc8ad297b ]
If a backup port is configured for a bridge port, the bridge will redirect known unicast traffic towards the backup port when the primary port is administratively up but without a carrier. This is useful, for example, in MLAG configurations where a system is connected to two switches and there is a peer link between both switches. The peer link serves as the backup port in case one of the switches loses its connection to the multi-homed system.
In order to avoid flooding when the primary port loses its carrier, the bridge does not flush dynamic FDB entries pointing to the port upon STP disablement, if the port has a backup port.
The above means that known unicast traffic destined to the primary port will be blackholed when the port is put administratively down, until the FDB entries pointing to it are aged-out.
Given that the current behavior is quite weird and unlikely to be depended on by anyone, amend the bridge to redirect to the backup port also when the primary port is administratively down and not only when it does not have a carrier.
The change is motivated by a report from a user who expected traffic to be redirected to the backup port when the primary port was put administratively down while debugging a network issue.
Reviewed-by: Petr Machata petrm@nvidia.com Signed-off-by: Ido Schimmel idosch@nvidia.com Acked-by: Nikolay Aleksandrov razor@blackwall.org Link: https://patch.msgid.link/20250812080213.325298-2-idosch@nvidia.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/bridge/br_forward.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c index 1b66c276118a3..aec5ab772a69d 100644 --- a/net/bridge/br_forward.c +++ b/net/bridge/br_forward.c @@ -148,7 +148,8 @@ void br_forward(const struct net_bridge_port *to, goto out;
/* redirect to backup link if the destination port is down */ - if (rcu_access_pointer(to->backup_port) && !netif_carrier_ok(to->dev)) { + if (rcu_access_pointer(to->backup_port) && + (!netif_carrier_ok(to->dev) || !netif_running(to->dev))) { struct net_bridge_port *backup_port;
backup_port = rcu_dereference(to->backup_port);