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, 350 insertions, 0 deletions

diff --git a/tools/include/uapi/linux/if_link.h b/tools/include/uapi/linux/if_link.h
index 7e46ca4cd31b..757ce5e9426e 100644
--- a/tools/include/uapi/linux/if_link.h
+++ b/tools/include/uapi/linux/if_link.h
@@ -1526,6 +1526,8 @@ enum {
 	IFLA_BOND_MISSED_MAX,
 	IFLA_BOND_NS_IP6_TARGET,
 	IFLA_BOND_COUPLED_CONTROL,
+	IFLA_BOND_BROADCAST_NEIGH,
+	IFLA_BOND_LACP_STRICT,
 	__IFLA_BOND_MAX,
 };
 
diff --git a/tools/testing/selftests/drivers/net/bonding/Makefile b/tools/testing/selftests/drivers/net/bonding/Makefile
index 9af5f84edd37..be130bf585a4 100644
--- a/tools/testing/selftests/drivers/net/bonding/Makefile
+++ b/tools/testing/selftests/drivers/net/bonding/Makefile
@@ -8,6 +8,7 @@ TEST_PROGS := \
 	bond-lladdr-target.sh \
 	bond_ipsec_offload.sh \
 	bond_lacp_prio.sh \
+	bond_lacp_strict.sh \
 	bond_macvlan_ipvlan.sh \
 	bond_options.sh \
 	bond_passive_lacp.sh \
diff --git a/tools/testing/selftests/drivers/net/bonding/bond_lacp_strict.sh b/tools/testing/selftests/drivers/net/bonding/bond_lacp_strict.sh
new file mode 100755
index 000000000000..f1a93a1d952f
--- /dev/null
+++ b/tools/testing/selftests/drivers/net/bonding/bond_lacp_strict.sh
@@ -0,0 +1,347 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Testing if bond lacp_strict works
+#
+#          Partner (p_ns)
+#  +--------------------------+
+#  |          bond0           |
+#  |            +             |
+#  |      eth0  |  eth1       |
+#  |        +---+---+         |
+#  |        |       |         |
+#  +--------------------------+
+#  |        | eth0  | eth1    |
+#  |        |       |         |
+#  |(br_ns) | br0   | br1     |
+#  |        |       |         |
+#  |        | eth2  | eth3    |
+#  +--------------------------+
+#  |        |       |         |
+#  |        +---+---+         |
+#  |      eth0  |  eth1       |
+#  |            +             |
+#  |          bond0           |
+#  +--------------------------+
+#         Dut (d_ns)
+
+lib_dir=$(dirname "$0")
+# shellcheck disable=SC1090
+source "$lib_dir"/../../../net/lib.sh
+
+COLLECTING_DISTRIBUTING_MASK=48
+COLLECTING_DISTRIBUTING=48
+FAILED=0
+
+setup_links()
+{
+	# shellcheck disable=SC2154
+	ip -n "${p_ns}" link add eth0 type veth peer name eth0 netns "${br_ns}"
+	ip -n "${p_ns}" link add eth1 type veth peer name eth1 netns "${br_ns}"
+	ip -n "${d_ns}" link add eth0 type veth peer name eth2 netns "${br_ns}"
+	ip -n "${d_ns}" link add eth1 type veth peer name eth3 netns "${br_ns}"
+
+	ip -n "${br_ns}" link add br0 type bridge
+	ip -n "${br_ns}" link add br1 type bridge
+
+	ip -n "${br_ns}" link set dev br0 type bridge stp_state 0
+	ip -n "${br_ns}" link set dev br1 type bridge stp_state 0
+
+	ip -n "${br_ns}" link set eth0 master br0
+	ip -n "${br_ns}" link set eth2 master br0
+	ip -n "${br_ns}" link set eth1 master br1
+	ip -n "${br_ns}" link set eth3 master br1
+
+	# Allow LACP trames forwarding on bridge ports
+	ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br0/brif/eth0/group_fwd_mask"
+	ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br1/brif/eth1/group_fwd_mask"
+	ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br0/brif/eth2/group_fwd_mask"
+	ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br1/brif/eth3/group_fwd_mask"
+
+	ip -n "${br_ns}" link set eth0 up
+	ip -n "${br_ns}" link set eth2 up
+	ip -n "${br_ns}" link set eth1 up
+	ip -n "${br_ns}" link set eth3 up
+
+	ip -n "${br_ns}" link set br0 up
+	ip -n "${br_ns}" link set br1 up
+
+	ip -n "${d_ns}" link add bond0 type bond mode 802.3ad miimon 100 \
+		lacp_rate fast min_links 1
+	ip -n "${p_ns}" link add bond0 type bond mode 802.3ad miimon 100 \
+		lacp_rate fast min_links 1
+
+	ip -n "${d_ns}" link set eth0 master bond0
+	ip -n "${d_ns}" link set eth1 master bond0
+	ip -n "${p_ns}" link set eth0 master bond0
+	ip -n "${p_ns}" link set eth1 master bond0
+
+	ip -n "${d_ns}" link set bond0 up
+	ip -n "${p_ns}" link set bond0 up
+}
+
+test_master_carrier() {
+	local expected=$1
+	local mode_name=$2
+	local carrier
+
+	carrier=$(ip netns exec "${d_ns}" cat /sys/class/net/bond0/carrier)
+	[ "$carrier" == "1" ] && carrier="up" || carrier="down"
+
+	[ "$carrier" == "$expected" ] && return
+
+	echo "FAIL: Expected carrier $expected in lacp_strict $mode_name mode, got $carrier"
+
+	RET=1
+
+}
+
+compare_state() {
+	local actual_state=$1
+	local expected_state=$2
+	local iface=$3
+	local last_attempt=$4
+
+    [ $((actual_state & COLLECTING_DISTRIBUTING_MASK)) -eq "$expected_state" ] \
+		&& return 0
+
+	[ "$last_attempt" -ne 1 ] && return 1
+
+	printf "FAIL: Expected LACP %s actor state to " "$iface"
+	if [ "$expected_state" -eq $COLLECTING_DISTRIBUTING ]; then
+		echo "be in Collecting/Distributing state"
+	else
+		echo "have neither Collecting nor Distributing set."
+	fi
+
+	return 1
+}
+
+_test_lacp_port_state() {
+	local interface=$1
+	local expected=$2
+	local last_attempt=$3
+	local eth0_actor_state eth1_actor_state
+	local ret=0
+
+	# shellcheck disable=SC2016
+	while IFS='=' read -r k v; do
+		printf -v "$k" '%s' "$v"
+	done < <(
+		ip netns exec "${d_ns}" awk '
+		/^Slave Interface: / { iface=$3 }
+		/details actor lacp pdu:/ { ctx="actor" }
+		/details partner lacp pdu:/ { ctx="partner" }
+		/^[[:space:]]+port state: / {
+			if (ctx == "actor") {
+				gsub(":", "", iface)
+				printf "%s_%s_state=%s\n", iface, ctx, $3
+			}
+		}
+		' /proc/net/bonding/bond0
+	)
+
+	if [ "$interface" == "eth0" ] || [ "$interface" == "both" ]; then
+		compare_state "$eth0_actor_state" "$expected" eth0 "$last_attempt" || ret=1
+	fi
+
+	if [ "$interface" == "eth1" ] || [ "$interface" == "both" ]; then
+		compare_state "$eth1_actor_state" "$expected" eth1 "$last_attempt" || ret=1
+	fi
+
+	return $ret
+}
+
+test_lacp_port_state() {
+	local interface=$1
+	local expected=$2
+	local retry=$3
+	local last_attempt=0
+	local attempt=1
+	local ret=1
+
+	while [ $attempt -le $((retry + 1)) ]; do
+		[ $attempt -eq $((retry + 1)) ] && last_attempt=1
+		_test_lacp_port_state "$interface" "$expected" "$last_attempt" && return
+		((attempt++))
+		sleep 1
+	done
+
+	RET=1
+}
+
+
+trap cleanup_all_ns EXIT
+setup_ns d_ns p_ns br_ns
+setup_links
+
+# Initial state
+RET=0
+mode=off
+test_lacp_port_state both $COLLECTING_DISTRIBUTING 3
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 up"
+
+# partner eth0 down, eth1 up
+# (replicate eth0 state to dut eth0 by shutting a bridge port)
+RET=0
+ip -n "${p_ns}" link set eth0 down
+ip -n "${br_ns}" link set eth2 down
+test_lacp_port_state eth0 $FAILED 5
+test_lacp_port_state eth1 $COLLECTING_DISTRIBUTING 1
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 down"
+
+# partner eth0 and eth1 down
+RET=0
+ip -n "${p_ns}" link set eth1 down
+ip -n "${br_ns}" link set eth3 down
+test_lacp_port_state both $FAILED 5
+test_master_carrier down $mode # down because of min_links
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 down"
+
+# partner eth0 up, eth1 down
+RET=0
+ip -n "${p_ns}" link set eth0 up
+ip -n "${br_ns}" link set eth2 up
+test_lacp_port_state eth0 $COLLECTING_DISTRIBUTING 60
+test_lacp_port_state eth1 $FAILED 1
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 up, eth1 down"
+
+# partner eth0 and eth1 up
+RET=0
+ip -n "${p_ns}" link set eth1 up
+ip -n "${br_ns}" link set eth3 up
+test_lacp_port_state both $COLLECTING_DISTRIBUTING 60
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 up"
+
+# partner eth0 stops LACP and eth1 up
+RET=0
+ip netns exec "${br_ns}" sh -c "echo 0 > /sys/class/net/br0/brif/eth0/group_fwd_mask"
+ip netns exec "${br_ns}" sh -c "echo 0 > /sys/class/net/br0/brif/eth2/group_fwd_mask"
+test_lacp_port_state eth0 $FAILED 5
+test_lacp_port_state eth1 $COLLECTING_DISTRIBUTING 1
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 stopped sending LACP"
+
+# partner eth0 and eth1 stop LACP
+RET=0
+ip netns exec "${br_ns}" sh -c "echo 0 > /sys/class/net/br1/brif/eth1/group_fwd_mask"
+ip netns exec "${br_ns}" sh -c "echo 0 > /sys/class/net/br1/brif/eth3/group_fwd_mask"
+test_lacp_port_state both $FAILED 5
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 stopped sending LACP"
+
+# switch to lacp_strict on
+RET=0
+mode=on
+ip -n "${d_ns}" link set dev bond0 type bond lacp_strict $mode
+test_lacp_port_state both $FAILED 1
+test_master_carrier down $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 stopped sending LACP"
+
+# switch back to lacp_strict off mode
+RET=0
+mode=off
+ip -n "${d_ns}" link set dev bond0 type bond lacp_strict $mode
+test_lacp_port_state both $FAILED 1
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 stopped sending LACP"
+
+# eth0 recovers LACP
+RET=0
+ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br0/brif/eth0/group_fwd_mask"
+ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br0/brif/eth2/group_fwd_mask"
+test_lacp_port_state eth0 $COLLECTING_DISTRIBUTING 60
+test_lacp_port_state eth1 $FAILED 1
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 recovered and eth1 stopped sending LACP"
+
+# eth1 recovers LACP
+RET=0
+ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br1/brif/eth1/group_fwd_mask"
+ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br1/brif/eth3/group_fwd_mask"
+test_lacp_port_state both $COLLECTING_DISTRIBUTING 60
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 recovered LACP"
+
+# switch to lacp_strict on
+RET=0
+mode=on
+ip -n "${d_ns}" link set dev bond0 type bond lacp_strict $mode
+test_lacp_port_state both $COLLECTING_DISTRIBUTING 1
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 up"
+
+# partner eth0 down, eth1 up
+RET=0
+ip -n "${p_ns}" link set eth0 down
+ip -n "${br_ns}" link set eth2 down
+test_lacp_port_state eth0 $FAILED 5
+test_lacp_port_state eth1 $COLLECTING_DISTRIBUTING 1
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 down"
+
+# partner eth0 and eth1 down
+RET=0
+ip -n "${p_ns}" link set eth1 down
+ip -n "${br_ns}" link set eth3 down
+test_lacp_port_state both $FAILED 5
+test_master_carrier down $mode # down because of min_links
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 down"
+
+# partner eth0 up, eth1 down
+RET=0
+ip -n "${p_ns}" link set eth0 up
+ip -n "${br_ns}" link set eth2 up
+test_lacp_port_state eth0 $COLLECTING_DISTRIBUTING 60
+test_lacp_port_state eth1 $FAILED 1
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 up, eth1 down"
+
+# partner eth0 and eth1 up
+RET=0
+ip -n "${p_ns}" link set eth1 up
+ip -n "${br_ns}" link set eth3 up
+test_lacp_port_state both $COLLECTING_DISTRIBUTING 60
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 up"
+
+# partner eth0 stops LACP and eth1 up
+RET=0
+ip netns exec "${br_ns}" sh -c "echo 0 > /sys/class/net/br0/brif/eth0/group_fwd_mask"
+ip netns exec "${br_ns}" sh -c "echo 0 > /sys/class/net/br0/brif/eth2/group_fwd_mask"
+test_lacp_port_state eth0 $FAILED 5
+test_lacp_port_state eth1 $COLLECTING_DISTRIBUTING 1
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 stopped sending LACP"
+
+# partner eth0 and eth1 stop LACP
+RET=0
+ip netns exec "${br_ns}" sh -c "echo 0 > /sys/class/net/br1/brif/eth1/group_fwd_mask"
+ip netns exec "${br_ns}" sh -c "echo 0 > /sys/class/net/br1/brif/eth3/group_fwd_mask"
+test_lacp_port_state both $FAILED 5
+test_master_carrier down $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 stopped sending LACP"
+
+# eth0 recovers LACP
+RET=0
+ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br0/brif/eth0/group_fwd_mask"
+ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br0/brif/eth2/group_fwd_mask"
+test_lacp_port_state eth0 $COLLECTING_DISTRIBUTING 60
+test_lacp_port_state eth1 $FAILED 1
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 recovered and eth1 stopped sending LACP"
+
+# eth1 recovers LACP
+# shellcheck disable=SC2034
+RET=0
+ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br1/brif/eth1/group_fwd_mask"
+ip netns exec "${br_ns}" sh -c "echo 4 > /sys/class/net/br1/brif/eth3/group_fwd_mask"
+test_lacp_port_state both $COLLECTING_DISTRIBUTING 60
+test_master_carrier up $mode
+log_test "bond LACP" "lacp_strict $mode - eth0 and eth1 recovered LACP"
+
+exit "${EXIT_STATUS}"