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Add STP loop guard support #88

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9 changes: 8 additions & 1 deletion include/stp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -94,6 +94,7 @@
#define g_stp_protect_mask stp_global.protect_mask
#define g_stp_protect_do_disable_mask stp_global.protect_do_disable_mask
#define g_stp_root_protect_mask stp_global.root_protect_mask
#define g_stp_loop_protect_mask stp_global.loop_protect_mask
#define g_stp_protect_disabled_mask stp_global.protect_disabled_mask
#define g_stp_enable_mask stp_global.enable_mask
#define g_stp_enable_config_mask stp_global.enable_admin_mask
Expand All @@ -120,6 +121,7 @@
#define STP_IS_PROTECT_DO_DISABLE_CONFIGURED(_port_) IS_MEMBER(stp_global.protect_do_disable_mask, (_port_))
#define STP_IS_PROTECT_DO_DISABLED(_port_) IS_MEMBER(stp_global.protect_disabled_mask, (_port_))
#define STP_IS_ROOT_PROTECT_CONFIGURED(_p_) IS_MEMBER(stp_global.root_protect_mask, (_p_))
#define STP_IS_LOOP_PROTECT_CONFIGURED(_p_) IS_MEMBER(stp_global.loop_protect_mask, (_p_))
#define STP_IS_PROTOCOL_ENABLED(mode) (stp_global.enable == true && stp_global.proto_mode == mode)

// _port_ is a pointer to either STP_PORT_CLASS or RSTP_PORT_CLASS
Expand Down Expand Up @@ -303,6 +305,8 @@ typedef struct
TIMER forward_delay_timer;
TIMER hold_timer;
TIMER root_protect_timer;
bool loop_guard_active;
bool loop_guard_synced;

UINT32 forward_transitions;
UINT32 rx_config_bpdu;
Expand Down Expand Up @@ -334,7 +338,8 @@ typedef struct
#define STP_PORT_CLASS_PORT_FAST_BIT 14
#define STP_PORT_CLASS_ROOT_PROTECT_BIT 15
#define STP_PORT_CLASS_BPDU_PROTECT_BIT 16
#define STP_PORT_CLASS_CLEAR_STATS_BIT 17
#define STP_PORT_CLASS_LOOP_PROTECT_BIT 17
#define STP_PORT_CLASS_CLEAR_STATS_BIT 18
UINT32 modified_fields;
} __attribute__((aligned(4))) STP_PORT_CLASS;

Expand Down Expand Up @@ -371,6 +376,7 @@ typedef struct
PORT_MASK *protect_do_disable_mask;
PORT_MASK *protect_disabled_mask;
PORT_MASK *root_protect_mask;
PORT_MASK *loop_protect_mask;
uint16_t root_protect_timeout;
L2_PROTO_MODE proto_mode;

Expand All @@ -391,6 +397,7 @@ typedef enum
STP_RAS_MES_AGE_TIMER_EXPIRY,
STP_RAS_ROOT_PROTECT_TIMER_EXPIRY,
STP_RAS_ROOT_PROTECT_VIOLATION,
STP_RAS_LOOP_PROTECT_VIOLATION,
STP_RAS_ROOT_ROLE,
STP_RAS_DESIGNATED_ROLE,
STP_RAS_MP_RX_DELAY_EVENT,
Expand Down
1 change: 1 addition & 0 deletions include/stp_dbsync.h
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,7 @@ typedef struct {
uint32_t tx_tcn_bpdu;
uint32_t rx_tcn_bpdu;
uint32_t root_protect_timer;
uint8_t loop_guard_active;

uint8_t clear_stats;
uint32_t modified_fields;
Expand Down
1 change: 1 addition & 0 deletions include/stp_ipc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -138,6 +138,7 @@ typedef struct STP_PORT_CONFIG_MSG
char intf_name[IFNAMSIZ];
uint8_t enabled;
uint8_t root_guard;
uint8_t loop_guard;
uint8_t bpdu_guard;
uint8_t bpdu_guard_do_disable;
uint8_t portfast;
Expand Down
25 changes: 23 additions & 2 deletions stp/stp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -491,7 +491,7 @@ void make_forwarding(STP_CLASS *stp_class, PORT_ID port_number)
{
STP_PORT_CLASS *stp_port_class = GET_STP_PORT_CLASS(stp_class, port_number);

if ((stp_port_class->state == BLOCKING) && (!is_timer_active(&stp_port_class->root_protect_timer)))
if ((stp_port_class->state == BLOCKING) && (!is_timer_active(&stp_port_class->root_protect_timer)) && (!stp_port_class->loop_guard_active))
{

stp_port_class->state = LISTENING;
Expand Down Expand Up @@ -726,6 +726,24 @@ void message_age_timer_expiry(STP_CLASS *stp_class, PORT_ID port_number)
stp_port_class = GET_STP_PORT_CLASS(stp_class, port_number);
stp_port_class->self_loop = false;

/* Loop Guard: if configured on a non-designated port, enter loop-inconsistent

@wajahatrazi wajahatrazi Jul 10, 2026

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What if a port has both loop_guard_active AND root_protect_timer active simultaneously? How does that being handled?

* state instead of allowing the port to become designated/forwarding */
if (STP_IS_LOOP_PROTECT_CONFIGURED(port_number) &&
!designated_port(stp_class, port_number))
{
stp_port_class->loop_guard_active = true;
stp_port_class->loop_guard_synced = false;
stp_port_class->state = BLOCKING;
stputil_set_port_state(stp_class, stp_port_class);
SET_BIT(stp_port_class->modified_fields, STP_PORT_CLASS_LOOP_PROTECT_BIT);
SET_BIT(stp_port_class->modified_fields, STP_PORT_CLASS_MEMBER_PORT_STATE_BIT);
STP_SYSLOG("STP: Loop Guard interface %s, VLAN %u loop-inconsistent (BPDUs lost)",
stp_intf_get_port_name(port_number), stp_class->vlan_id);
STP_LOG_INFO("STP_RAS_LOOP_PROTECT_VIOLATION I:%lu P:%lu V:%u",
GET_STP_INDEX(stp_class), port_number, stp_class->vlan_id);
return;
}

root = root_bridge(stp_class);
become_designated_port(stp_class, port_number);
configuration_update(stp_class);
Expand Down Expand Up @@ -876,6 +894,9 @@ void send_tcn_bpdu(STP_CLASS* stp_class, PORT_ID port_number)

if (stptimer_is_active(&stp_port_class->root_protect_timer))
return;


if (stp_port_class->loop_guard_active)
return;

stputil_send_pvst_bpdu(stp_class, port_number, TCN_BPDU_TYPE);
}
1 change: 1 addition & 0 deletions stp/stp_data.c
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@ int8_t stpdata_init_global_port_mask()
ret |= bmp_alloc(&g_stp_protect_mask, g_max_stp_port);
ret |= bmp_alloc(&g_stp_protect_do_disable_mask, g_max_stp_port);
ret |= bmp_alloc(&g_stp_root_protect_mask, g_max_stp_port);
ret |= bmp_alloc(&g_stp_loop_protect_mask, g_max_stp_port);
ret |= bmp_alloc(&g_stp_protect_disabled_mask, g_max_stp_port);

/* By default fast span is enabled on all ports */
Expand Down
6 changes: 6 additions & 0 deletions stp/stp_debug.c
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Expand Up @@ -118,13 +118,15 @@ void stpdm_global()
UINT8 enable_string[500], enable_admin_string[500];
UINT8 fastspan_string[500], fastspan_admin_string[500], fastuplink_admin_string[500];
UINT8 protect_string[500], protect_do_disable_string[500], protect_disabled_string[500], root_protect_string[500];
UINT8 loop_protect_string[500];

mask_to_string(g_stp_enable_mask, enable_string, 500);
mask_to_string(g_stp_enable_config_mask, enable_admin_string, 500);
mask_to_string(stp_global.protect_mask, protect_string, sizeof(protect_string));
mask_to_string(stp_global.protect_do_disable_mask, protect_do_disable_string, sizeof(protect_do_disable_string));
mask_to_string(stp_global.protect_disabled_mask, protect_disabled_string, sizeof(protect_disabled_string));
mask_to_string(stp_global.root_protect_mask, root_protect_string, sizeof(root_protect_string));
mask_to_string(stp_global.loop_protect_mask, loop_protect_string, sizeof(loop_protect_string));
mask_to_string(g_fastspan_mask, fastspan_string, 500);
mask_to_string(g_fastspan_config_mask, fastspan_admin_string, 500);
mask_to_string(g_fastuplink_mask, fastuplink_admin_string, 500);
Expand All @@ -151,6 +153,7 @@ void stpdm_global()
"protect_do_disable_mask= %s\n\t"
"protect_disabled_mask = %s\n\t"
"root_protect_mask = %s\n\t"
"loop_protect_mask = %s\n\t"
"root_protect_timeout = %u\n\t"
"fastspan_mask = %s\n\t"
"fastspan_admin_mask = %s\n\t"
Expand All @@ -176,6 +179,7 @@ void stpdm_global()
protect_do_disable_string,
protect_disabled_string,
root_protect_string,
loop_protect_string,
stp_global.root_protect_timeout,
fastspan_string,
fastspan_admin_string,
Expand Down Expand Up @@ -289,6 +293,7 @@ void stpdm_port_class(STP_CLASS *stp_class, PORT_ID port_number)
"forward_delay_timer = %s %d\n"
"hold timer = %s %d\n"
"root_protect_timer = %s %u\n"
"loop_guard_active = %s\n"
"forward_transitions = %d\n"
"rx_config_bpdu = %d\n"
"tx_config_bpdu = %d\n"
Expand All @@ -313,6 +318,7 @@ void stpdm_port_class(STP_CLASS *stp_class, PORT_ID port_number)
stp_port->hold_timer.value,
STP_TIMER_STRING(&stp_port->root_protect_timer),
stp_port->root_protect_timer.value,
stp_port->loop_guard_active ? "YES" : "NO",
stp_port->forward_transitions,
stp_port->rx_config_bpdu,
stp_port->tx_config_bpdu,
Expand Down
29 changes: 25 additions & 4 deletions stp/stp_mgr.c
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Expand Up @@ -295,6 +295,11 @@ void stpmgr_disable_port(STP_CLASS *stp_class, PORT_ID port_number)
stptimer_stop(&stp_port_class->root_protect_timer);
}

if (stp_port_class->loop_guard_active)
{
stp_port_class->loop_guard_active = false;
}

clear_mask_bit(stp_class->enable_mask, port_number);
configuration_update(stp_class);
port_state_selection(stp_class);
Expand Down Expand Up @@ -1249,6 +1254,20 @@ bool stpmgr_config_root_protect(PORT_ID port_id, bool enable)
return true;
}

/*****************************************************************************/
/* stpmgr_config_loop_protect: enables/disables loop-guard feature on the */
/* input port. */
/*****************************************************************************/
static bool stpmgr_config_loop_protect(PORT_ID port_id, bool enable)
{
if (enable)
set_mask_bit(stp_global.loop_protect_mask, port_id);
else
clear_mask_bit(stp_global.loop_protect_mask, port_id);

return true;
}

/*****************************************************************************/
/* stpmgr_config_root_protect_timeout: configures the timeout in seconds for */
/* which the violated stp port is kept in blocking state. */
Expand Down Expand Up @@ -1717,9 +1736,9 @@ static void stpmgr_process_intf_config_msg(void *msg)
return;
}

STP_LOG_INFO("op:%d, intf:%s, enable:%d, root_grd:%d, bpdu_grd:%d , do_dis:%d, cost:%d, pri:%d, portfast:%d, uplink_fast:%d, count:%d",
pmsg->opcode, pmsg->intf_name, pmsg->enabled, pmsg->root_guard, pmsg->bpdu_guard,
pmsg->bpdu_guard_do_disable, pmsg->path_cost, pmsg->priority,
STP_LOG_INFO("op:%d, intf:%s, enable:%d, root_grd:%d, loop_grd:%d, bpdu_grd:%d , do_dis:%d, cost:%d, pri:%d, portfast:%d, uplink_fast:%d, count:%d",
pmsg->opcode, pmsg->intf_name, pmsg->enabled, pmsg->root_guard, pmsg->loop_guard, pmsg->bpdu_guard,
pmsg->bpdu_guard_do_disable, pmsg->path_cost, pmsg->priority,
pmsg->portfast, pmsg->uplink_fast, pmsg->count);

port_id = stp_intf_get_port_id_by_name(pmsg->intf_name);
Expand Down Expand Up @@ -1771,8 +1790,9 @@ static void stpmgr_process_intf_config_msg(void *msg)
if (pmsg->enabled)
{
stpmgr_config_root_protect(port_id, pmsg->root_guard);
stpmgr_config_loop_protect(port_id, pmsg->loop_guard);

@qianqian-33 qianqian-33 Jul 10, 2026

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This PR currently implements only PVST. Could we consider implementing MSTP support as well?

stpmgr_config_protect(port_id, pmsg->bpdu_guard, pmsg->bpdu_guard_do_disable);

stpmgr_config_fastspan(port_id, pmsg->portfast);
stpmgr_config_fastuplink(port_id, pmsg->uplink_fast);
}
Expand All @@ -1788,6 +1808,7 @@ static void stpmgr_process_intf_config_msg(void *msg)
if (pmsg->opcode == STP_DEL_COMMAND || !pmsg->enabled)
{
stpmgr_config_root_protect(port_id, false);
stpmgr_config_loop_protect(port_id, false);
stpmgr_config_protect(port_id, false, false);

stpmgr_config_fastspan(port_id, true);
Expand Down
73 changes: 67 additions & 6 deletions stp/stp_util.c
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Expand Up @@ -498,6 +498,27 @@ static bool stputil_root_protect_violation(STP_CLASS *stp_class, PORT_ID port_nu
return true;
}


/*****************************************************************************/
/* stputil_loop_guard_bpdu_recovery: called when a BPDU is received on a */
/* loop-inconsistent port. clears the loop guard active flag, logs recovery, */
/* and marks the port state as modified. */
/*****************************************************************************/
static void stputil_loop_guard_bpdu_recovery(STP_CLASS *stp_class, PORT_ID port_number)
{
STP_PORT_CLASS *stp_port;

stp_port = GET_STP_PORT_CLASS(stp_class, port_number);

STP_SYSLOG("STP: Loop Guard interface %s, VLAN %u consistent (BPDU received)",
stp_intf_get_port_name(port_number), stp_class->vlan_id);

stp_port->loop_guard_active = false;
stp_port->loop_guard_synced = false;
SET_BIT(stp_port->modified_fields, STP_PORT_CLASS_LOOP_PROTECT_BIT);
SET_BIT(stp_port->modified_fields, STP_PORT_CLASS_MEMBER_PORT_STATE_BIT);
}

/*****************************************************************************/
/* stputil_root_protect_validate: routine validates the bpdu to see that it */
/* is conforming to the root protect configuration. */
Expand Down Expand Up @@ -779,6 +800,16 @@ void stputil_process_bpdu(STP_INDEX stp_index, PORT_ID port_number, void *buffer
return;
}

// Loop Guard: if port is in loop-inconsistent state and receives a BPDU, recover

@wajahatrazi wajahatrazi Jul 10, 2026

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What BPDU qualifies for recovery? Any BPDU?

if (STP_IS_LOOP_PROTECT_CONFIGURED(port_number))
{
STP_PORT_CLASS *stp_port_lg = GET_STP_PORT_CLASS(stp_class, port_number);
if (stp_port_lg->loop_guard_active)
{
stputil_loop_guard_bpdu_recovery(stp_class, port_number);
}
}

last_bpdu_rx_time = stp_class->last_bpdu_rx_time;
current_time = sys_get_seconds();
stp_class->last_bpdu_rx_time = current_time;
Expand Down Expand Up @@ -898,7 +929,12 @@ void stptimer_sync_port_class(STP_CLASS *stp_class, STP_PORT_CLASS * stp_port)
if(timer_value != 0 && stp_port->state == BLOCKING)
strcpy(stp_vlan_intf.port_state, "ROOT-INC");
else
strcpy(stp_vlan_intf.port_state, l2_port_state_to_string(stp_port->state, stp_port->port_id.number));
{
if(stp_port->loop_guard_active && stp_port->state == BLOCKING)
strcpy(stp_vlan_intf.port_state, "LOOP-INC");
else
strcpy(stp_vlan_intf.port_state, l2_port_state_to_string(stp_port->state, stp_port->port_id.number));
}

if (stp_port->state == DISABLED)
{
Expand Down Expand Up @@ -965,6 +1001,16 @@ void stptimer_sync_port_class(STP_CLASS *stp_class, STP_PORT_CLASS * stp_port)
stp_vlan_intf.root_protect_timer = -1;
}

if(IS_BIT_SET(stp_port->modified_fields, STP_PORT_CLASS_LOOP_PROTECT_BIT))
{
stp_vlan_intf.loop_guard_active = stp_port->loop_guard_active ? 1 : 0;
stp_port->loop_guard_synced = true;
}
else
{
stp_vlan_intf.loop_guard_active = -1;
}

if(IS_BIT_SET(stp_port->modified_fields, STP_PORT_CLASS_CLEAR_STATS_BIT))
{
stp_vlan_intf.clear_stats = 1;
Expand Down Expand Up @@ -1120,7 +1166,10 @@ void stputil_sync_port_counters(STP_CLASS *stp_class, STP_PORT_CLASS * stp_port)

if (is_timer_active(&stp_port->root_protect_timer))
SET_BIT(stp_port->modified_fields, STP_PORT_CLASS_ROOT_PROTECT_BIT);


if (stp_port->loop_guard_active && !stp_port->loop_guard_synced)
SET_BIT(stp_port->modified_fields, STP_PORT_CLASS_LOOP_PROTECT_BIT);

stptimer_sync_port_class(stp_class, stp_port);
}

Expand Down Expand Up @@ -1302,23 +1351,36 @@ void stptimer_update(STP_CLASS *stp_class)
(stp_port_class->root_protect_timer.active && !STP_IS_ROOT_PROTECT_CONFIGURED(port_number)))
{
stp_port_class->root_protect_timer.active = false;
stputil_root_protect_timer_expired(stp_class, port_number);
stputil_root_protect_timer_expired(stp_class, port_number);

if (debugGlobal.stp.enabled)
{
if (STP_DEBUG_VP(stp_class->vlan_id, port_number))
{
STP_LOG_INFO("I:%lu P:%u V:%u Ev:%d",GET_STP_INDEX(stp_class),port_number,
STP_LOG_INFO("I:%lu P:%u V:%u Ev:%d",GET_STP_INDEX(stp_class),port_number,
stp_class->vlan_id,STP_RAS_ROOT_PROTECT_TIMER_EXPIRY);
}
}
else
{
STP_LOG_INFO("I:%lu P:%u V:%u Ev:%d",GET_STP_INDEX(stp_class),port_number,
STP_LOG_INFO("I:%lu P:%u V:%u Ev:%d",GET_STP_INDEX(stp_class),port_number,
stp_class->vlan_id,STP_RAS_ROOT_PROTECT_TIMER_EXPIRY);
}
}

/* Loop guard config can be removed while the port is already loop-inconsistent.
* In that case, clear loop-guard state and run the same recovery path used on
* message-age expiry so the port can be re-evaluated immediately. */
if (stp_port_class->loop_guard_active && !STP_IS_LOOP_PROTECT_CONFIGURED(port_number))
{
stp_port_class->loop_guard_active = false;
stp_port_class->loop_guard_synced = false;
SET_BIT(stp_port_class->modified_fields, STP_PORT_CLASS_LOOP_PROTECT_BIT);
SET_BIT(stp_port_class->modified_fields, STP_PORT_CLASS_MEMBER_PORT_STATE_BIT);

message_age_timer_expiry(stp_class, port_number);
}

port_number = port_mask_get_next_port(stp_class->enable_mask, port_number);
}

Expand Down Expand Up @@ -1441,4 +1503,3 @@ void sys_assert(int status)
{
assert(status);
}

6 changes: 6 additions & 0 deletions stpsync/stp_sync.cpp
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Expand Up @@ -387,6 +387,12 @@ void StpSync::updateStpVlanInterfaceInfo(STP_VLAN_PORT_TABLE * stp_vlan_intf)
fvVector.push_back(rpt);
}

if(stp_vlan_intf->loop_guard_active != 0xFF)
{
FieldValueTuple lga("loop_guard_active", to_string(stp_vlan_intf->loop_guard_active));
fvVector.push_back(lga);
}

vlan = VLAN_PREFIX + to_string(stp_vlan_intf->vlan_id);
key = vlan + ":" + ifName;

Expand Down