bonding: Add independent control state machine

Add support for the independent control state machine per IEEE
802.1AX-2008 5.4.15 in addition to the existing implementation of the
coupled control state machine.

Introduces two new states, AD_MUX_COLLECTING and AD_MUX_DISTRIBUTING in
the LACP MUX state machine for separated handling of an initial
Collecting state before the Collecting and Distributing state. This
enables a port to be in a state where it can receive incoming packets
while not still distributing. This is useful for reducing packet loss when
a port begins distributing before its partner is able to collect.

Added new functions such as bond_set_slave_tx_disabled_flags and
bond_set_slave_rx_enabled_flags to precisely manage the port's collecting
and distributing states. Previously, there was no dedicated method to
disable TX while keeping RX enabled, which this patch addresses.

Note that the regular flow process in the kernel's bonding driver remains
unaffected by this patch. The extension requires explicit opt-in by the
user (in order to ensure no disruptions for existing setups) via netlink
support using the new bonding parameter coupled_control. The default value
for coupled_control is set to 1 so as to preserve existing behaviour.

Signed-off-by: Aahil Awatramani <aahila@google.com>
Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20240202175858.1573852-1-aahila@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

4 files changed, 194 insertions, 8 deletions

diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c
index c99ffe6c683a..f2942e8c6c91 100644
--- a/drivers/net/bonding/bond_3ad.c
+++ b/drivers/net/bonding/bond_3ad.c
@@ -106,6 +106,9 @@ static void ad_agg_selection_logic(struct aggregator *aggregator,
 static void ad_clear_agg(struct aggregator *aggregator);
 static void ad_initialize_agg(struct aggregator *aggregator);
 static void ad_initialize_port(struct port *port, int lacp_fast);
+static void ad_enable_collecting(struct port *port);
+static void ad_disable_distributing(struct port *port,
+				    bool *update_slave_arr);
 static void ad_enable_collecting_distributing(struct port *port,
 					      bool *update_slave_arr);
 static void ad_disable_collecting_distributing(struct port *port,
@@ -172,8 +175,37 @@ static inline int __agg_has_partner(struct aggregator *agg)
 }
 
 /**
+ * __disable_distributing_port - disable the port's slave for distributing.
+ * Port will still be able to collect.
+ * @port: the port we're looking at
+ *
+ * This will disable only distributing on the port's slave.
+ */
+static void __disable_distributing_port(struct port *port)
+{
+	bond_set_slave_tx_disabled_flags(port->slave, BOND_SLAVE_NOTIFY_LATER);
+}
+
+/**
+ * __enable_collecting_port - enable the port's slave for collecting,
+ * if it's up
+ * @port: the port we're looking at
+ *
+ * This will enable only collecting on the port's slave.
+ */
+static void __enable_collecting_port(struct port *port)
+{
+	struct slave *slave = port->slave;
+
+	if (slave->link == BOND_LINK_UP && bond_slave_is_up(slave))
+		bond_set_slave_rx_enabled_flags(slave, BOND_SLAVE_NOTIFY_LATER);
+}
+
+/**
  * __disable_port - disable the port's slave
  * @port: the port we're looking at
+ *
+ * This will disable both collecting and distributing on the port's slave.
  */
 static inline void __disable_port(struct port *port)
 {
@@ -183,6 +215,8 @@ static inline void __disable_port(struct port *port)
 /**
  * __enable_port - enable the port's slave, if it's up
  * @port: the port we're looking at
+ *
+ * This will enable both collecting and distributing on the port's slave.
  */
 static inline void __enable_port(struct port *port)
 {
@@ -193,10 +227,27 @@ static inline void __enable_port(struct port *port)
 }
 
 /**
- * __port_is_enabled - check if the port's slave is in active state
+ * __port_move_to_attached_state - check if port should transition back to attached
+ * state.
+ * @port: the port we're looking at
+ */
+static bool __port_move_to_attached_state(struct port *port)
+{
+	if (!(port->sm_vars & AD_PORT_SELECTED) ||
+	    (port->sm_vars & AD_PORT_STANDBY) ||
+	    !(port->partner_oper.port_state & LACP_STATE_SYNCHRONIZATION) ||
+	    !(port->actor_oper_port_state & LACP_STATE_SYNCHRONIZATION))
+		port->sm_mux_state = AD_MUX_ATTACHED;
+
+	return port->sm_mux_state == AD_MUX_ATTACHED;
+}
+
+/**
+ * __port_is_collecting_distributing - check if the port's slave is in the
+ * combined collecting/distributing state
  * @port: the port we're looking at
  */
-static inline int __port_is_enabled(struct port *port)
+static int __port_is_collecting_distributing(struct port *port)
 {
 	return bond_is_active_slave(port->slave);
 }
@@ -942,6 +993,7 @@ static int ad_marker_send(struct port *port, struct bond_marker *marker)
  */
 static void ad_mux_machine(struct port *port, bool *update_slave_arr)
 {
+	struct bonding *bond = __get_bond_by_port(port);
 	mux_states_t last_state;
 
 	/* keep current State Machine state to compare later if it was
@@ -999,9 +1051,13 @@ static void ad_mux_machine(struct port *port, bool *update_slave_arr)
 			if ((port->sm_vars & AD_PORT_SELECTED) &&
 			    (port->partner_oper.port_state & LACP_STATE_SYNCHRONIZATION) &&
 			    !__check_agg_selection_timer(port)) {
-				if (port->aggregator->is_active)
-					port->sm_mux_state =
-					    AD_MUX_COLLECTING_DISTRIBUTING;
+				if (port->aggregator->is_active) {
+					int state = AD_MUX_COLLECTING_DISTRIBUTING;
+
+					if (!bond->params.coupled_control)
+						state = AD_MUX_COLLECTING;
+					port->sm_mux_state = state;
+				}
 			} else if (!(port->sm_vars & AD_PORT_SELECTED) ||
 				   (port->sm_vars & AD_PORT_STANDBY)) {
 				/* if UNSELECTED or STANDBY */
@@ -1019,11 +1075,45 @@ static void ad_mux_machine(struct port *port, bool *update_slave_arr)
 			}
 			break;
 		case AD_MUX_COLLECTING_DISTRIBUTING:
+			if (!__port_move_to_attached_state(port)) {
+				/* if port state hasn't changed make
+				 * sure that a collecting distributing
+				 * port in an active aggregator is enabled
+				 */
+				if (port->aggregator->is_active &&
+				    !__port_is_collecting_distributing(port)) {
+					__enable_port(port);
+					*update_slave_arr = true;
+				}
+			}
+			break;
+		case AD_MUX_COLLECTING:
+			if (!__port_move_to_attached_state(port)) {
+				if ((port->sm_vars & AD_PORT_SELECTED) &&
+				    (port->partner_oper.port_state & LACP_STATE_SYNCHRONIZATION) &&
+				    (port->partner_oper.port_state & LACP_STATE_COLLECTING)) {
+					port->sm_mux_state = AD_MUX_DISTRIBUTING;
+				} else {
+					/* If port state hasn't changed, make sure that a collecting
+					 * port is enabled for an active aggregator.
+					 */
+					struct slave *slave = port->slave;
+
+					if (port->aggregator->is_active &&
+					    bond_is_slave_rx_disabled(slave)) {
+						ad_enable_collecting(port);
+						*update_slave_arr = true;
+					}
+				}
+			}
+			break;
+		case AD_MUX_DISTRIBUTING:
 			if (!(port->sm_vars & AD_PORT_SELECTED) ||
 			    (port->sm_vars & AD_PORT_STANDBY) ||
+			    !(port->partner_oper.port_state & LACP_STATE_COLLECTING) ||
 			    !(port->partner_oper.port_state & LACP_STATE_SYNCHRONIZATION) ||
 			    !(port->actor_oper_port_state & LACP_STATE_SYNCHRONIZATION)) {
-				port->sm_mux_state = AD_MUX_ATTACHED;
+				port->sm_mux_state = AD_MUX_COLLECTING;
 			} else {
 				/* if port state hasn't changed make
 				 * sure that a collecting distributing
@@ -1031,7 +1121,7 @@ static void ad_mux_machine(struct port *port, bool *update_slave_arr)
 				 */
 				if (port->aggregator &&
 				    port->aggregator->is_active &&
-				    !__port_is_enabled(port)) {
+				    !__port_is_collecting_distributing(port)) {
 					__enable_port(port);
 					*update_slave_arr = true;
 				}
@@ -1082,6 +1172,20 @@ static void ad_mux_machine(struct port *port, bool *update_slave_arr)
 							  update_slave_arr);
 			port->ntt = true;
 			break;
+		case AD_MUX_COLLECTING:
+			port->actor_oper_port_state |= LACP_STATE_COLLECTING;
+			port->actor_oper_port_state &= ~LACP_STATE_DISTRIBUTING;
+			port->actor_oper_port_state |= LACP_STATE_SYNCHRONIZATION;
+			ad_enable_collecting(port);
+			ad_disable_distributing(port, update_slave_arr);
+			port->ntt = true;
+			break;
+		case AD_MUX_DISTRIBUTING:
+			port->actor_oper_port_state |= LACP_STATE_DISTRIBUTING;
+			port->actor_oper_port_state |= LACP_STATE_SYNCHRONIZATION;
+			ad_enable_collecting_distributing(port,
+							  update_slave_arr);
+			break;
 		default:
 			break;
 		}
@@ -1907,6 +2011,45 @@ static void ad_initialize_port(struct port *port, int lacp_fast)
 }
 
 /**
+ * ad_enable_collecting - enable a port's receive
+ * @port: the port we're looking at
+ *
+ * Enable @port if it's in an active aggregator
+ */
+static void ad_enable_collecting(struct port *port)
+{
+	if (port->aggregator->is_active) {
+		struct slave *slave = port->slave;
+
+		slave_dbg(slave->bond->dev, slave->dev,
+			  "Enabling collecting on port %d (LAG %d)\n",
+			  port->actor_port_number,
+			  port->aggregator->aggregator_identifier);
+		__enable_collecting_port(port);
+	}
+}
+
+/**
+ * ad_disable_distributing - disable a port's transmit
+ * @port: the port we're looking at
+ * @update_slave_arr: Does slave array need update?
+ */
+static void ad_disable_distributing(struct port *port, bool *update_slave_arr)
+{
+	if (port->aggregator &&
+	    !MAC_ADDRESS_EQUAL(&port->aggregator->partner_system,
+			       &(null_mac_addr))) {
+		slave_dbg(port->slave->bond->dev, port->slave->dev,
+			  "Disabling distributing on port %d (LAG %d)\n",
+			  port->actor_port_number,
+			  port->aggregator->aggregator_identifier);
+		__disable_distributing_port(port);
+		/* Slave array needs an update */
+		*update_slave_arr = true;
+	}
+}
+
+/**
  * ad_enable_collecting_distributing - enable a port's transmit/receive
  * @port: the port we're looking at
  * @update_slave_arr: Does slave array need update?
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 4e0600c7b050..ae9d32c0faf4 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -6306,6 +6306,7 @@ static int __init bond_check_params(struct bond_params *params)
 	params->ad_actor_sys_prio = ad_actor_sys_prio;
 	eth_zero_addr(params->ad_actor_system);
 	params->ad_user_port_key = ad_user_port_key;
+	params->coupled_control = 1;
 	if (packets_per_slave > 0) {
 		params->reciprocal_packets_per_slave =
 			reciprocal_value(packets_per_slave);
diff --git a/drivers/net/bonding/bond_netlink.c b/drivers/net/bonding/bond_netlink.c
index cfa74cf8bb1a..29b4c3d1b9b6 100644
--- a/drivers/net/bonding/bond_netlink.c
+++ b/drivers/net/bonding/bond_netlink.c
@@ -122,6 +122,7 @@ static const struct nla_policy bond_policy[IFLA_BOND_MAX + 1] = {
 	[IFLA_BOND_PEER_NOTIF_DELAY]    = NLA_POLICY_FULL_RANGE(NLA_U32, &delay_range),
 	[IFLA_BOND_MISSED_MAX]		= { .type = NLA_U8 },
 	[IFLA_BOND_NS_IP6_TARGET]	= { .type = NLA_NESTED },
+	[IFLA_BOND_COUPLED_CONTROL]	= { .type = NLA_U8 },
 };
 
 static const struct nla_policy bond_slave_policy[IFLA_BOND_SLAVE_MAX + 1] = {
@@ -549,6 +550,16 @@ static int bond_changelink(struct net_device *bond_dev, struct nlattr *tb[],
 			return err;
 	}
 
+	if (data[IFLA_BOND_COUPLED_CONTROL]) {
+		int coupled_control = nla_get_u8(data[IFLA_BOND_COUPLED_CONTROL]);
+
+		bond_opt_initval(&newval, coupled_control);
+		err = __bond_opt_set(bond, BOND_OPT_COUPLED_CONTROL, &newval,
+				     data[IFLA_BOND_COUPLED_CONTROL], extack);
+		if (err)
+			return err;
+	}
+
 	return 0;
 }
 
@@ -615,6 +626,7 @@ static size_t bond_get_size(const struct net_device *bond_dev)
 						/* IFLA_BOND_NS_IP6_TARGET */
 		nla_total_size(sizeof(struct nlattr)) +
 		nla_total_size(sizeof(struct in6_addr)) * BOND_MAX_NS_TARGETS +
+		nla_total_size(sizeof(u8)) +	/* IFLA_BOND_COUPLED_CONTROL */
 		0;
 }
 
@@ -774,6 +786,10 @@ static int bond_fill_info(struct sk_buff *skb,
 		       bond->params.missed_max))
 		goto nla_put_failure;
 
+	if (nla_put_u8(skb, IFLA_BOND_COUPLED_CONTROL,
+		       bond->params.coupled_control))
+		goto nla_put_failure;
+
 	if (BOND_MODE(bond) == BOND_MODE_8023AD) {
 		struct ad_info info;
 
diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
index f3f27f0bd2a6..4cdbc7e084f4 100644
--- a/drivers/net/bonding/bond_options.c
+++ b/drivers/net/bonding/bond_options.c
@@ -84,7 +84,8 @@ static int bond_option_ad_user_port_key_set(struct bonding *bond,
 					    const struct bond_opt_value *newval);
 static int bond_option_missed_max_set(struct bonding *bond,
 				      const struct bond_opt_value *newval);
-
+static int bond_option_coupled_control_set(struct bonding *bond,
+					   const struct bond_opt_value *newval);
 
 static const struct bond_opt_value bond_mode_tbl[] = {
 	{ "balance-rr",    BOND_MODE_ROUNDROBIN,   BOND_VALFLAG_DEFAULT},
@@ -232,6 +233,12 @@ static const struct bond_opt_value bond_missed_max_tbl[] = {
 	{ NULL,		-1,	0},
 };
 
+static const struct bond_opt_value bond_coupled_control_tbl[] = {
+	{ "on",  1,  BOND_VALFLAG_DEFAULT},
+	{ "off", 0,  0},
+	{ NULL,  -1, 0},
+};
+
 static const struct bond_option bond_opts[BOND_OPT_LAST] = {
 	[BOND_OPT_MODE] = {
 		.id = BOND_OPT_MODE,
@@ -496,6 +503,15 @@ static const struct bond_option bond_opts[BOND_OPT_LAST] = {
 		.desc = "Delay between each peer notification on failover event, in milliseconds",
 		.values = bond_peer_notif_delay_tbl,
 		.set = bond_option_peer_notif_delay_set
+	},
+	[BOND_OPT_COUPLED_CONTROL] = {
+		.id = BOND_OPT_COUPLED_CONTROL,
+		.name = "coupled_control",
+		.desc = "Opt into using coupled control MUX for LACP states",
+		.unsuppmodes = BOND_MODE_ALL_EX(BIT(BOND_MODE_8023AD)),
+		.flags = BOND_OPTFLAG_IFDOWN,
+		.values = bond_coupled_control_tbl,
+		.set = bond_option_coupled_control_set,
 	}
 };
 
@@ -1692,3 +1708,13 @@ static int bond_option_ad_user_port_key_set(struct bonding *bond,
 	bond->params.ad_user_port_key = newval->value;
 	return 0;
 }
+
+static int bond_option_coupled_control_set(struct bonding *bond,
+					   const struct bond_opt_value *newval)
+{
+	netdev_info(bond->dev, "Setting coupled_control to %s (%llu)\n",
+		    newval->string, newval->value);
+
+	bond->params.coupled_control = newval->value;
+	return 0;
+}