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 <[e-mail]>
Reviewed-by: Hangbin Liu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

Documentation/networking/bonding.rst

···
 
 	The default value is 2, and the allowable range is 1 - 255.
 
+coupled_control
+
+    Specifies whether the LACP state machine's MUX in the 802.3ad mode
+    should have separate Collecting and Distributing states.
+
+    This is by implementing the independent control state machine per
+    IEEE 802.1AX-2008 5.4.15 in addition to the existing coupled control
+    state machine.
+
+    The default value is 1. This setting does not separate the Collecting
+    and Distributing states, maintaining the bond in coupled control.
+
 downdelay
 
 	Specifies the time, in milliseconds, to wait before disabling

drivers/net/bonding/bond_3ad.c

···
 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,
···
 }
 
 /**
+ * __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)
 {
···
 /**
  * __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)
 {
···
 }
 
 /**
- * __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 inline int __port_is_enabled(struct port *port)
+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 int __port_is_collecting_distributing(struct port *port)
 {
 	return bond_is_active_slave(port->slave);
 }
···
  */
 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
···
 			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 */
···
 			}
 			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
···
 				 */
 				if (port->aggregator &&
 				    port->aggregator->is_active &&
-				    !__port_is_enabled(port)) {
+				    !__port_is_collecting_distributing(port)) {
 					__enable_port(port);
 					*update_slave_arr = true;
 				}
···
 			ad_enable_collecting_distributing(port,
 							  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;
···
 		port->churn_partner_count = 0;
 
 		memcpy(&port->lacpdu, &lacpdu, sizeof(lacpdu));
+	}
+}
+
+/**
+ * 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;
 	}
 }
 

drivers/net/bonding/bond_main.c

···
 	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);

drivers/net/bonding/bond_netlink.c

···
 	[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] = {
···
 			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;
 }
 
···
 						/* 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;
 }
 
···
 
 	if (nla_put_u8(skb, IFLA_BOND_MISSED_MAX,
 		       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) {

drivers/net/bonding/bond_options.c

···
 					    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},
···
 	{ "maxval",	255,	BOND_VALFLAG_MAX},
 	{ "default",	2,	BOND_VALFLAG_DEFAULT},
 	{ 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] = {
···
 		.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,
 	}
 };
 
···
 		   newval->value);
 
 	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;
 }

include/net/bond_3ad.h

···
 	AD_MUX_DETACHED,	/* mux machine */
 	AD_MUX_WAITING,		/* mux machine */
 	AD_MUX_ATTACHED,	/* mux machine */
+	AD_MUX_COLLECTING,	/* mux machine */
+	AD_MUX_DISTRIBUTING,	/* mux machine */
 	AD_MUX_COLLECTING_DISTRIBUTING	/* mux machine */
 } mux_states_t;
 

include/net/bond_options.h

···
 	BOND_OPT_MISSED_MAX,
 	BOND_OPT_NS_TARGETS,
 	BOND_OPT_PRIO,
+	BOND_OPT_COUPLED_CONTROL,
 	BOND_OPT_LAST
 };
 

include/net/bonding.h

···
 #if IS_ENABLED(CONFIG_IPV6)
 	struct in6_addr ns_targets[BOND_MAX_NS_TARGETS];
 #endif
+	int coupled_control;
 
 	/* 2 bytes of padding : see ether_addr_equal_64bits() */
 	u8 ad_actor_system[ETH_ALEN + 2];
···
 	u8     backup:1,   /* indicates backup slave. Value corresponds with
 			      BOND_STATE_ACTIVE and BOND_STATE_BACKUP */
 	       inactive:1, /* indicates inactive slave */
+	       rx_disabled:1, /* indicates whether slave's Rx is disabled */
 	       should_notify:1, /* indicates whether the state changed */
 	       should_notify_link:1; /* indicates whether the link changed */
 	u8     duplex;
···
 		bond_set_slave_state(slave, BOND_STATE_BACKUP, notify);
 	if (!slave->bond->params.all_slaves_active)
 		slave->inactive = 1;
+	if (BOND_MODE(slave->bond) == BOND_MODE_8023AD)
+		slave->rx_disabled = 1;
+}
+
+static inline void bond_set_slave_tx_disabled_flags(struct slave *slave,
+						 bool notify)
+{
+	bond_set_slave_state(slave, BOND_STATE_BACKUP, notify);
 }
 
 static inline void bond_set_slave_active_flags(struct slave *slave,
···
 {
 	bond_set_slave_state(slave, BOND_STATE_ACTIVE, notify);
 	slave->inactive = 0;
+	if (BOND_MODE(slave->bond) == BOND_MODE_8023AD)
+		slave->rx_disabled = 0;
+}
+
+static inline void bond_set_slave_rx_enabled_flags(struct slave *slave,
+					       bool notify)
+{
+	slave->rx_disabled = 0;
 }
 
 static inline bool bond_is_slave_inactive(struct slave *slave)
 {
 	return slave->inactive;
+}
+
+static inline bool bond_is_slave_rx_disabled(struct slave *slave)
+{
+	return slave->rx_disabled;
 }
 
 static inline void bond_propose_link_state(struct slave *slave, int state)

include/uapi/linux/if_link.h

···
 	IFLA_BOND_AD_LACP_ACTIVE,
 	IFLA_BOND_MISSED_MAX,
 	IFLA_BOND_NS_IP6_TARGET,
+	IFLA_BOND_COUPLED_CONTROL,
 	__IFLA_BOND_MAX,
 };
 

tools/include/uapi/linux/if_link.h

···
 	IFLA_BOND_AD_LACP_ACTIVE,
 	IFLA_BOND_MISSED_MAX,
 	IFLA_BOND_NS_IP6_TARGET,
+	IFLA_BOND_COUPLED_CONTROL,
 	__IFLA_BOND_MAX,
 };