Merge branch 'bonding-3ad-fix-carrier-state-with-no-usable-slaves'

Louis Scalbert says:

====================
bonding: 3ad: fix carrier state with no usable slaves

This series addresses a blackholing issue and a subsequent link-flapping
issue in the 802.3ad bonding driver when dealing with inactive slaves
and the `min_links` parameter.

When an 802.3ad (LACP) bonding interface has no slaves in the
collecting/distributing state, the bonding master still reports
carrier as up as long as at least 'min_links' slaves have carrier.

In this situation, only one slave is effectively used for TX/RX,
while traffic received on other slaves is dropped. Upper-layer
daemons therefore consider the interface operational, even though
traffic may be blackholed if the lack of LACP negotiation means
the partner is not ready to deal with traffic.

This patchset introduces an optional behavior, widely adopted across
the industry, to address this issue. It consists of bringing the
bonding master interface down to signal to upper-layer processes
that it is not usable.

This patchset depends on the following iproute2 change:
ip/bond: add lacp_strict support
Link: https://lore.kernel.org/netdev/20260408152409.276358-1-louis.scalbert@6wind.com/

Patch 1 adds the missing IFLA_BOND_BROADCAST_NEIGH in if_link
UAPI header.

Patch 2 adds missing broadcast-neigh to YAML rt-link specs.

Patch 3 introduces the lacp_strict configuration knob, which is
applied in the subsequent patch. The default (off) mode preserves
the existing behavior, while the strict mode (on) is intended to force
the bonding master carrier down in this situation.

Patch 4 addresses the core issue when lacp_strict is set to strict.
It ensures that carrier is asserted only when at least 'min_links'
slaves are in the Collecting/Distributing state.

Patch 5 fixes a side effect of the previous patch. Tightening the carrier
logic exposes a state persistence bug: when a physical link goes down,
the LACP collecting/distributing flags remain set. When the link returns,
the interface briefly hallucinates that it is ready, bounces the carrier
up, and then drops it again once LACP renegotiation starts. Fix by
resetting Collecting and Distributing state as soon as the link goes
down.

Patch 6 adds a test for bonding lacp_strict both modes.
====================

Link: https://patch.msgid.link/20260603150331.1919611-1-louis.scalbert@6wind.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 3 insertions, 0 deletions

diff --git a/include/net/bond_options.h b/include/net/bond_options.h
index e6eedf23aea1..52b966e92793 100644
--- a/include/net/bond_options.h
+++ b/include/net/bond_options.h
@@ -79,6 +79,7 @@ enum {
 	BOND_OPT_COUPLED_CONTROL,
 	BOND_OPT_BROADCAST_NEIGH,
 	BOND_OPT_ACTOR_PORT_PRIO,
+	BOND_OPT_LACP_STRICT,
 	BOND_OPT_LAST
 };
 
diff --git a/include/net/bonding.h b/include/net/bonding.h
index edd1942dcd73..2c54a36a8477 100644
--- a/include/net/bonding.h
+++ b/include/net/bonding.h
@@ -129,6 +129,7 @@ struct bond_params {
 	int peer_notif_delay;
 	int lacp_active;
 	int lacp_fast;
+	int lacp_strict;
 	unsigned int min_links;
 	int ad_select;
 	char primary[IFNAMSIZ];
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 363526549a01..43cecca49f01 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -1603,6 +1603,7 @@ enum {
 	IFLA_BOND_NS_IP6_TARGET,
 	IFLA_BOND_COUPLED_CONTROL,
 	IFLA_BOND_BROADCAST_NEIGH,
+	IFLA_BOND_LACP_STRICT,
 	__IFLA_BOND_MAX,
 };