bgpd: batch peer connection error clearing

When peer connections encounter errors, attempt to batch some
of the clearing processing that occurs. Add a new batch object,
add multiple peers to it, if possible. Do one rib walk for the
batch, rather than one walk per peer. Use a handler callback
per batch to check and remove peers' path-infos, rather than
a work-queue and callback per peer. The original clearing code
remains; it's used for single peers.

Signed-off-by: Mark Stapp <mjs@cisco.com>

8 files changed, 613 insertions, 74 deletions

diff --git a/bgpd/bgp_fsm.c b/bgpd/bgp_fsm.c
index 764b6b8716..bc99f5fce2 100644
--- a/bgpd/bgp_fsm.c
+++ b/bgpd/bgp_fsm.c
@@ -1281,7 +1281,8 @@ void bgp_fsm_change_status(struct peer_connection *connection,
 		 * Clearing
 		 * (or Deleted).
 		 */
-		if (!work_queue_is_scheduled(peer->clear_node_queue) &&
+		if (!CHECK_FLAG(peer->flags, PEER_FLAG_CLEARING_BATCH) &&
+		    !work_queue_is_scheduled(peer->clear_node_queue) &&
 		    status != Deleted)
 			BGP_EVENT_ADD(connection, Clearing_Completed);
 	}
diff --git a/bgpd/bgp_memory.h b/bgpd/bgp_memory.h
index 1f76945da3..517e34feba 100644
--- a/bgpd/bgp_memory.h
+++ b/bgpd/bgp_memory.h
@@ -136,4 +136,6 @@ DECLARE_MTYPE(BGP_SOFT_VERSION);
 
 DECLARE_MTYPE(BGP_EVPN_OVERLAY);
 
+DECLARE_MTYPE(CLEARING_BATCH);
+
 #endif /* _QUAGGA_BGP_MEMORY_H */
diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index e279d18918..30fd6619c1 100644
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -4149,62 +4149,3 @@ void bgp_send_delayed_eor(struct bgp *bgp)
 	for (ALL_LIST_ELEMENTS(bgp->peer, node, nnode, peer))
 		bgp_write_proceed_actions(peer);
 }
-
-/*
- * Task callback in the main pthread to handle socket error
- * encountered in the io pthread. We avoid having the io pthread try
- * to enqueue fsm events or mess with the peer struct.
- */
-
-/* Max number of peers to process without rescheduling */
-#define BGP_CONN_ERROR_DEQUEUE_MAX 10
-
-void bgp_packet_process_error(struct event *thread)
-{
-	struct peer_connection *connection;
-	struct peer *peer;
-	struct bgp *bgp;
-	int counter = 0;
-	bool more_p = false;
-
-	bgp = EVENT_ARG(thread);
-
-	/* Dequeue peers from the error list */
-	while ((peer = bgp_dequeue_conn_err_peer(bgp, &more_p)) != NULL) {
-		connection = peer->connection;
-
-		if (bgp_debug_neighbor_events(peer))
-			zlog_debug("%s [Event] BGP error %d on fd %d",
-				   peer->host, peer->connection_errcode,
-				   connection->fd);
-
-		/* Closed connection or error on the socket */
-		if (peer_established(connection)) {
-			if ((CHECK_FLAG(peer->flags, PEER_FLAG_GRACEFUL_RESTART)
-			     || CHECK_FLAG(peer->flags,
-					   PEER_FLAG_GRACEFUL_RESTART_HELPER))
-			    && CHECK_FLAG(peer->sflags, PEER_STATUS_NSF_MODE)) {
-				peer->last_reset = PEER_DOWN_NSF_CLOSE_SESSION;
-				SET_FLAG(peer->sflags, PEER_STATUS_NSF_WAIT);
-			} else
-				peer->last_reset = PEER_DOWN_CLOSE_SESSION;
-		}
-
-		/* No need for keepalives, if enabled */
-		bgp_keepalives_off(connection);
-
-		bgp_event_update(connection, peer->connection_errcode);
-
-		counter++;
-		if (counter >= BGP_CONN_ERROR_DEQUEUE_MAX)
-			break;
-	}
-
-	/* Reschedule event if necessary */
-	if (more_p)
-		bgp_conn_err_reschedule(bgp);
-
-	if (bgp_debug_neighbor_events(NULL))
-		zlog_debug("%s: dequeued and processed %d peers", __func__,
-			   counter);
-}
diff --git a/bgpd/bgp_packet.h b/bgpd/bgp_packet.h
index 9ecbdc8b87..339e7520ba 100644
--- a/bgpd/bgp_packet.h
+++ b/bgpd/bgp_packet.h
@@ -82,8 +82,6 @@ extern void bgp_process_packet(struct event *event);
 
 extern void bgp_send_delayed_eor(struct bgp *bgp);
 
-/* Task callback to handle socket error encountered in the io pthread */
-void bgp_packet_process_error(struct event *thread);
 extern struct bgp_notify
 bgp_notify_decapsulate_hard_reset(struct bgp_notify *notify);
 extern bool bgp_has_graceful_restart_notification(struct peer *peer);
diff --git a/bgpd/bgp_route.c b/bgpd/bgp_route.c
index a7825165e7..95564bc0d8 100644
--- a/bgpd/bgp_route.c
+++ b/bgpd/bgp_route.c
@@ -80,6 +80,8 @@
 
 DEFINE_MTYPE_STATIC(BGPD, BGP_EOIU_MARKER_INFO, "BGP EOIU Marker info");
 DEFINE_MTYPE_STATIC(BGPD, BGP_METAQ, "BGP MetaQ");
+/* Memory for batched clearing of peers from the RIB */
+DEFINE_MTYPE(BGPD, CLEARING_BATCH, "Clearing batch");
 
 DEFINE_HOOK(bgp_snmp_update_stats,
 	    (struct bgp_dest *rn, struct bgp_path_info *pi, bool added),
@@ -6454,11 +6456,244 @@ void bgp_clear_route(struct peer *peer, afi_t afi, safi_t safi)
 		peer_unlock(peer);
 }
 
+/*
+ * Callback scheduled to process prefixes/dests for batch clearing; the
+ * dests were found via a rib walk.
+ * The one-peer version of this uses a per-peer workqueue to manage
+ * rescheduling, but we're just using a fixed limit here.
+ */
+
+/* Limit the number of dests we'll process per callback */
+#define BGP_CLEARING_BATCH_MAX_DESTS 100
+
+static void bgp_clear_batch_dests_task(struct event *event)
+{
+	struct bgp_clearing_info *cinfo = EVENT_ARG(event);
+	struct bgp_dest *dest;
+	struct bgp_path_info *pi, *next;
+	struct bgp_table *table;
+	struct bgp *bgp;
+	afi_t afi;
+	safi_t safi;
+	int counter = 0;
+
+	bgp = cinfo->bgp;
+
+next_dest:
+
+	dest = bgp_clearing_batch_next_dest(cinfo);
+	if (dest == NULL)
+		goto done;
+
+	table = bgp_dest_table(dest);
+	afi = table->afi;
+	safi = table->safi;
+
+	/* Have to check every path: it is possible that we have multiple paths
+	 * for a prefix from a peer if that peer is using AddPath.
+	 * Note that the clearing action may change the pi list; we try to do
+	 * a "safe" iteration.
+	 */
+	for (pi = bgp_dest_get_bgp_path_info(dest); pi; pi = next) {
+		next = pi ? pi->next : NULL;
+
+		if (!bgp_clearing_batch_check_peer(cinfo, pi->peer))
+			continue;
+
+		/* graceful restart STALE flag set. */
+		if (((CHECK_FLAG(pi->peer->sflags, PEER_STATUS_NSF_WAIT)
+		      && pi->peer->nsf[afi][safi])
+		     || CHECK_FLAG(pi->peer->af_sflags[afi][safi],
+				   PEER_STATUS_ENHANCED_REFRESH))
+		    && !CHECK_FLAG(pi->flags, BGP_PATH_STALE)
+		    && !CHECK_FLAG(pi->flags, BGP_PATH_UNUSEABLE))
+			bgp_path_info_set_flag(dest, pi, BGP_PATH_STALE);
+		else {
+			/* If this is an EVPN route, process for
+			 * un-import. */
+			if (safi == SAFI_EVPN)
+				bgp_evpn_unimport_route(
+					bgp, afi, safi,
+					bgp_dest_get_prefix(dest), pi);
+			/* Handle withdraw for VRF route-leaking and L3VPN */
+			if (SAFI_UNICAST == safi
+			    && (bgp->inst_type == BGP_INSTANCE_TYPE_VRF ||
+				bgp->inst_type == BGP_INSTANCE_TYPE_DEFAULT)) {
+				vpn_leak_from_vrf_withdraw(bgp_get_default(),
+							   bgp, pi);
+			}
+			if (SAFI_MPLS_VPN == safi &&
+			    bgp->inst_type == BGP_INSTANCE_TYPE_DEFAULT) {
+				vpn_leak_to_vrf_withdraw(pi);
+			}
+
+			bgp_rib_remove(dest, pi, pi->peer, afi, safi);
+		}
+	}
+
+	/* Unref this dest and table */
+	bgp_dest_unlock_node(dest);
+	bgp_table_unlock(table);
+
+	counter++;
+	if (counter < BGP_CLEARING_BATCH_MAX_DESTS)
+		goto next_dest;
+
+done:
+
+	/* If there are still dests to process, reschedule. */
+	if (bgp_clearing_batch_dests_present(cinfo)) {
+		if (bgp_debug_neighbor_events(NULL))
+			zlog_debug("%s: Batch %p: Rescheduled after processing %d dests",
+				   __func__, cinfo, counter);
+
+		event_add_event(bm->master, bgp_clear_batch_dests_task, cinfo,
+				0, &cinfo->t_sched);
+	} else {
+		if (bgp_debug_neighbor_events(NULL))
+			zlog_debug("%s: Batch %p: Done after processing %d dests",
+				   __func__, cinfo, counter);
+		bgp_clearing_batch_completed(cinfo);
+	}
+
+	return;
+}
+
+/*
+ * Walk a single table for batch peer clearing processing
+ */
+static void clear_batch_table_helper(struct bgp_clearing_info *cinfo,
+				     struct bgp_table *table)
+{
+	struct bgp_dest *dest;
+	bool force = (cinfo->bgp->process_queue == NULL);
+	uint32_t examined = 0, queued = 0;
+
+	for (dest = bgp_table_top(table); dest; dest = bgp_route_next(dest)) {
+		struct bgp_path_info *pi, *next;
+		struct bgp_adj_in *ain;
+		struct bgp_adj_in *ain_next;
+
+		examined++;
+
+		ain = dest->adj_in;
+		while (ain) {
+			ain_next = ain->next;
+
+			if (bgp_clearing_batch_check_peer(cinfo, ain->peer))
+				bgp_adj_in_remove(&dest, ain);
+
+			ain = ain_next;
+
+			assert(dest != NULL);
+		}
+
+		for (pi = bgp_dest_get_bgp_path_info(dest); pi; pi = next) {
+			next = pi->next;
+			if (!bgp_clearing_batch_check_peer(cinfo, pi->peer))
+				continue;
+
+			queued++;
+
+			if (force) {
+				bgp_path_info_reap(dest, pi);
+			} else {
+				/* Unlocked after processing */
+				bgp_table_lock(bgp_dest_table(dest));
+				bgp_dest_lock_node(dest);
+
+				bgp_clearing_batch_add_dest(cinfo, dest);
+				break;
+			}
+		}
+	}
+
+	if (examined > 0) {
+		if (bgp_debug_neighbor_events(NULL))
+			zlog_debug("%s: %s/%s: examined %u, queued %u",
+				   __func__, afi2str(table->afi),
+				   safi2str(table->safi), examined, queued);
+	}
+}
+
+/*
+ * RIB-walking helper for batch clearing work: walk all tables, identify
+ * dests that are affected by the peers in the batch, enqueue the dests for
+ * async processing.
+ */
+static void clear_batch_rib_helper(struct bgp_clearing_info *cinfo)
+{
+	afi_t afi;
+	safi_t safi;
+	struct bgp_dest *dest;
+	struct bgp_table *table;
+
+	FOREACH_AFI_SAFI (afi, safi) {
+		/* Identify table to be examined */
+		if (safi != SAFI_MPLS_VPN && safi != SAFI_ENCAP &&
+		    safi != SAFI_EVPN) {
+			table = cinfo->bgp->rib[afi][safi];
+			if (!table)
+				continue;
+
+			clear_batch_table_helper(cinfo, table);
+		} else {
+			for (dest = bgp_table_top(cinfo->bgp->rib[afi][safi]);
+			     dest; dest = bgp_route_next(dest)) {
+				table = bgp_dest_get_bgp_table_info(dest);
+				if (!table)
+					continue;
+
+				/* TODO -- record the tables we've seen
+				 * and don't repeat any?
+				 */
+
+				clear_batch_table_helper(cinfo, table);
+			}
+		}
+	}
+}
+
+/*
+ * Identify prefixes that need to be cleared for a batch of peers in 'cinfo'.
+ * The actual clearing processing will be done async...
+ */
+void bgp_clear_route_batch(struct bgp_clearing_info *cinfo)
+{
+	if (bgp_debug_neighbor_events(NULL))
+		zlog_debug("%s: BGP %s, batch %p", __func__,
+			   cinfo->bgp->name_pretty, cinfo);
+
+	/* Walk the rib, checking the peers in the batch */
+	clear_batch_rib_helper(cinfo);
+
+	/* If we found some prefixes, schedule a task to begin work. */
+	if (bgp_clearing_batch_dests_present(cinfo))
+		event_add_event(bm->master, bgp_clear_batch_dests_task, cinfo,
+				0, &cinfo->t_sched);
+
+	/* NB -- it's the caller's job to clean up, release refs, etc. if
+	 * we didn't find any dests
+	 */
+}
+
 void bgp_clear_route_all(struct peer *peer)
 {
 	afi_t afi;
 	safi_t safi;
 
+	/* We may be able to batch multiple peers' clearing work: check
+	 * and see.
+	 */
+	if (bgp_clearing_batch_add_peer(peer->bgp, peer)) {
+		if (bgp_debug_neighbor_events(peer))
+			zlog_debug("%s: peer %pBP batched", __func__, peer);
+		return;
+	}
+
+	if (bgp_debug_neighbor_events(peer))
+		zlog_debug("%s: peer %pBP", __func__, peer);
+
 	FOREACH_AFI_SAFI (afi, safi)
 		bgp_clear_route(peer, afi, safi);
 
diff --git a/bgpd/bgp_route.h b/bgpd/bgp_route.h
index 8932ff6407..5c10a865d1 100644
--- a/bgpd/bgp_route.h
+++ b/bgpd/bgp_route.h
@@ -779,6 +779,9 @@ extern void bgp_soft_reconfig_table_task_cancel(const struct bgp *bgp,
 extern bool bgp_soft_reconfig_in(struct peer *peer, afi_t afi, safi_t safi);
 extern void bgp_clear_route(struct peer *, afi_t, safi_t);
 extern void bgp_clear_route_all(struct peer *);
+/* Clear routes for a batch of peers */
+void bgp_clear_route_batch(struct bgp_clearing_info *cinfo);
+
 extern void bgp_clear_adj_in(struct peer *, afi_t, safi_t);
 extern void bgp_clear_stale_route(struct peer *, afi_t, safi_t);
 extern void bgp_set_stale_route(struct peer *peer, afi_t afi, safi_t safi);
diff --git a/bgpd/bgpd.c b/bgpd/bgpd.c
index 04b5af918f..cfd0b1fbca 100644
--- a/bgpd/bgpd.c
+++ b/bgpd/bgpd.c
@@ -89,7 +89,20 @@ DEFINE_HOOK(bgp_instance_state, (struct bgp *bgp), (bgp));
 DEFINE_HOOK(bgp_routerid_update, (struct bgp *bgp, bool withdraw), (bgp, withdraw));
 
 /* Peers with connection error/failure, per bgp instance */
-DECLARE_LIST(bgp_peer_conn_errlist, struct peer, conn_err_link);
+DECLARE_DLIST(bgp_peer_conn_errlist, struct peer, conn_err_link);
+
+/* List of info about peers that are being cleared from BGP RIBs in a batch */
+DECLARE_DLIST(bgp_clearing_info, struct bgp_clearing_info, link);
+
+/* List of dests that need to be processed in a clearing batch */
+DECLARE_LIST(bgp_clearing_destlist, struct bgp_clearing_dest, link);
+
+/* Hash of peers in clearing info object */
+static int peer_clearing_hash_cmp(const struct peer *p1, const struct peer *p2);
+static uint32_t peer_clearing_hashfn(const struct peer *p1);
+
+DECLARE_HASH(bgp_clearing_hash, struct peer, clear_hash_link,
+	     peer_clearing_hash_cmp, peer_clearing_hashfn);
 
 /* BGP process wide configuration.  */
 static struct bgp_master bgp_master;
@@ -3653,6 +3666,7 @@ peer_init:
 	/* Init peer connection error info */
 	pthread_mutex_init(&bgp->peer_errs_mtx, NULL);
 	bgp_peer_conn_errlist_init(&bgp->peer_conn_errlist);
+	bgp_clearing_info_init(&bgp->clearing_list);
 
 	return bgp;
 }
@@ -4036,11 +4050,12 @@ int bgp_delete(struct bgp *bgp)
 	struct bgp *bgp_to_proc = NULL;
 	struct bgp *bgp_to_proc_next = NULL;
 	struct bgp *bgp_default = bgp_get_default();
+	struct bgp_clearing_info *cinfo;
 
 	assert(bgp);
 
 	/*
-	 * Iterate the pending dest list and remove all the dest pertaininig to
+	 * Iterate the pending dest list and remove all the dest pertaining to
 	 * the bgp under delete.
 	 */
 	b_ann_cnt = zebra_announce_count(&bm->zebra_announce_head);
@@ -4086,6 +4101,10 @@ int bgp_delete(struct bgp *bgp)
 			   a_l3_cnt);
 	}
 
+	/* Cleanup for peer connection batching */
+	while ((cinfo = bgp_clearing_info_first(&bgp->clearing_list)) != NULL)
+		bgp_clearing_batch_completed(cinfo);
+
 	bgp_soft_reconfig_table_task_cancel(bgp, NULL, NULL);
 
 	/* make sure we withdraw any exported routes */
@@ -4241,6 +4260,10 @@ int bgp_delete(struct bgp *bgp)
 	/* Cancel peer connection errors event */
 	EVENT_OFF(bgp->t_conn_errors);
 
+	/* Cleanup for peer connection batching */
+	while ((cinfo = bgp_clearing_info_pop(&bgp->clearing_list)) != NULL)
+		bgp_clearing_batch_completed(cinfo);
+
 /* TODO - Other memory may need to be freed - e.g., NHT */
 
 #ifdef ENABLE_BGP_VNC
@@ -9012,8 +9035,303 @@ void bgp_gr_apply_running_config(void)
 	}
 }
 
+/* Hash of peers in clearing info object */
+static int peer_clearing_hash_cmp(const struct peer *p1, const struct peer *p2)
+{
+	if (p1 == p2)
+		return 0;
+	else if (p1 < p2)
+		return -1;
+	else
+		return 1;
+}
+
+static uint32_t peer_clearing_hashfn(const struct peer *p1)
+{
+	return (uint32_t)((intptr_t)p1 & 0xffffffffULL);
+}
+
+/*
+ * Free a clearing batch: this really just does the memory cleanup; the
+ * clearing code is expected to manage the peer, dest, table, etc refcounts
+ */
+static void bgp_clearing_batch_free(struct bgp *bgp,
+				    struct bgp_clearing_info **pinfo)
+{
+	struct bgp_clearing_info *cinfo = *pinfo;
+	struct bgp_clearing_dest *destinfo;
+
+	if (bgp_clearing_info_anywhere(cinfo))
+		bgp_clearing_info_del(&bgp->clearing_list, cinfo);
+
+	while ((destinfo = bgp_clearing_destlist_pop(&cinfo->destlist)) != NULL)
+		XFREE(MTYPE_CLEARING_BATCH, destinfo);
+
+	bgp_clearing_hash_fini(&cinfo->peers);
+
+	XFREE(MTYPE_CLEARING_BATCH, *pinfo);
+}
+
+/*
+ * Done with a peer that was part of a clearing batch
+ */
+static void bgp_clearing_peer_done(struct peer *peer)
+{
+	UNSET_FLAG(peer->flags, PEER_FLAG_CLEARING_BATCH);
+
+	/* Tickle FSM to start moving again */
+	BGP_EVENT_ADD(peer->connection, Clearing_Completed);
+
+	peer_unlock(peer); /* bgp_clear_route */
+}
+
+/*
+ * Initialize a new batch struct for clearing peer(s) from the RIB
+ */
+static void bgp_clearing_batch_begin(struct bgp *bgp)
+{
+	struct bgp_clearing_info *cinfo;
+
+	cinfo = XCALLOC(MTYPE_CLEARING_BATCH, sizeof(struct bgp_clearing_info));
+
+	cinfo->bgp = bgp;
+
+	/* Init hash of peers and list of dests */
+	bgp_clearing_hash_init(&cinfo->peers);
+	bgp_clearing_destlist_init(&cinfo->destlist);
+
+	/* Batch is open for more peers */
+	SET_FLAG(cinfo->flags, BGP_CLEARING_INFO_FLAG_OPEN);
+
+	bgp_clearing_info_add_head(&bgp->clearing_list, cinfo);
+}
+
+/*
+ * Close a batch of clearing peers, and begin working on the RIB
+ */
+static void bgp_clearing_batch_end(struct bgp *bgp)
+{
+	struct bgp_clearing_info *cinfo;
+
+	cinfo = bgp_clearing_info_first(&bgp->clearing_list);
+
+	assert(cinfo != NULL);
+	assert(CHECK_FLAG(cinfo->flags, BGP_CLEARING_INFO_FLAG_OPEN));
+
+	/* Batch is closed */
+	UNSET_FLAG(cinfo->flags, BGP_CLEARING_INFO_FLAG_OPEN);
+
+	/* If we have no peers to examine, just discard the batch info */
+	if (bgp_clearing_hash_count(&cinfo->peers) == 0) {
+		bgp_clearing_batch_free(bgp, &cinfo);
+		return;
+	}
+
+	/* Do a RIB walk for the current batch. If it finds dests/prefixes
+	 * to work on, this will schedule a task to process
+	 * the dests/prefixes in the batch.
+	 */
+	bgp_clear_route_batch(cinfo);
+
+	/* If we found no prefixes/dests, just discard the batch,
+	 * remembering that we're holding a ref for each peer.
+	 */
+	if (bgp_clearing_destlist_count(&cinfo->destlist) == 0) {
+		bgp_clearing_batch_completed(cinfo);
+	}
+}
+
+/* Check whether a dest's peer is relevant to a clearing batch */
+bool bgp_clearing_batch_check_peer(struct bgp_clearing_info *cinfo,
+				   const struct peer *peer)
+{
+	struct peer *p;
+
+	p = bgp_clearing_hash_find(&cinfo->peers, peer);
+	return (p != NULL);
+}
+
+/*
+ * Check whether a clearing batch has any dests to process
+ */
+bool bgp_clearing_batch_dests_present(struct bgp_clearing_info *cinfo)
+{
+	return (bgp_clearing_destlist_count(&cinfo->destlist) > 0);
+}
+
+/*
+ * Done with a peer clearing batch; deal with refcounts, free memory
+ */
+void bgp_clearing_batch_completed(struct bgp_clearing_info *cinfo)
+{
+	struct peer *peer;
+	struct bgp_dest *dest;
+	struct bgp_clearing_dest *destinfo;
+	struct bgp_table *table;
+
+	/* Ensure event is not scheduled */
+	event_cancel_event(bm->master, &cinfo->t_sched);
+
+	/* Remove all peers and un-ref */
+	while ((peer = bgp_clearing_hash_pop(&cinfo->peers)) != NULL)
+		bgp_clearing_peer_done(peer);
+
+	/* Remove any dests/prefixes and unlock */
+	destinfo = bgp_clearing_destlist_pop(&cinfo->destlist);
+	while (destinfo) {
+		dest = destinfo->dest;
+		XFREE(MTYPE_CLEARING_BATCH, destinfo);
+
+		table = bgp_dest_table(dest);
+		bgp_dest_unlock_node(dest);
+		bgp_table_unlock(table);
+
+		destinfo = bgp_clearing_destlist_pop(&cinfo->destlist);
+	}
+
+	/* Free memory */
+	bgp_clearing_batch_free(cinfo->bgp, &cinfo);
+}
+
+/*
+ * Add a prefix/dest to a clearing batch
+ */
+void bgp_clearing_batch_add_dest(struct bgp_clearing_info *cinfo,
+				 struct bgp_dest *dest)
+{
+	struct bgp_clearing_dest *destinfo;
+
+	destinfo = XCALLOC(MTYPE_CLEARING_BATCH,
+			   sizeof(struct bgp_clearing_dest));
+
+	destinfo->dest = dest;
+	bgp_clearing_destlist_add_tail(&cinfo->destlist, destinfo);
+}
+
+/*
+ * Return the next dest for batch clear processing
+ */
+struct bgp_dest *bgp_clearing_batch_next_dest(struct bgp_clearing_info *cinfo)
+{
+	struct bgp_clearing_dest *destinfo;
+	struct bgp_dest *dest = NULL;
+
+	destinfo = bgp_clearing_destlist_pop(&cinfo->destlist);
+	if (destinfo) {
+		dest = destinfo->dest;
+		XFREE(MTYPE_CLEARING_BATCH, destinfo);
+	}
+
+	return dest;
+}
+
+/* If a clearing batch is available for 'peer', add it and return 'true',
+ * else return 'false'.
+ */
+bool bgp_clearing_batch_add_peer(struct bgp *bgp, struct peer *peer)
+{
+	struct bgp_clearing_info *cinfo;
+
+	cinfo = bgp_clearing_info_first(&bgp->clearing_list);
+
+	if (cinfo && CHECK_FLAG(cinfo->flags, BGP_CLEARING_INFO_FLAG_OPEN)) {
+		if (!CHECK_FLAG(peer->flags, PEER_FLAG_CLEARING_BATCH)) {
+			/* Add a peer ref */
+			peer_lock(peer);
+
+			bgp_clearing_hash_add(&cinfo->peers, peer);
+			SET_FLAG(peer->flags, PEER_FLAG_CLEARING_BATCH);
+		}
+		return true;
+	}
+
+	return false;
+}
+
+/*
+ * Task callback in the main pthread to handle socket errors
+ * encountered in the io pthread. We avoid having the io pthread try
+ * to enqueue fsm events or mess with the peer struct.
+ */
+
+/* TODO -- should this be configurable? */
+/* Max number of peers to process without rescheduling */
+#define BGP_CONN_ERROR_DEQUEUE_MAX 10
+
+static void bgp_process_conn_error(struct event *event)
+{
+	struct bgp *bgp;
+	struct peer *peer;
+	struct peer_connection *connection;
+	int counter = 0;
+	size_t list_count = 0;
+	bool more_p = false;
+
+	bgp = EVENT_ARG(event);
+
+	frr_with_mutex (&bgp->peer_errs_mtx) {
+		peer = bgp_peer_conn_errlist_pop(&bgp->peer_conn_errlist);
+
+		list_count =
+			bgp_peer_conn_errlist_count(&bgp->peer_conn_errlist);
+	}
+
+	/* If we have multiple peers with errors, try to batch some
+	 * clearing work.
+	 */
+	if (list_count > 0)
+		bgp_clearing_batch_begin(bgp);
+
+	/* Dequeue peers from the error list */
+	while (peer != NULL) {
+		connection = peer->connection;
+
+		if (bgp_debug_neighbor_events(peer))
+			zlog_debug("%s [Event] BGP error %d on fd %d",
+				   peer->host, peer->connection_errcode,
+				   connection->fd);
+
+		/* Closed connection or error on the socket */
+		if (peer_established(connection)) {
+			if ((CHECK_FLAG(peer->flags, PEER_FLAG_GRACEFUL_RESTART)
+			     || CHECK_FLAG(peer->flags,
+					   PEER_FLAG_GRACEFUL_RESTART_HELPER))
+			    && CHECK_FLAG(peer->sflags, PEER_STATUS_NSF_MODE)) {
+				peer->last_reset = PEER_DOWN_NSF_CLOSE_SESSION;
+				SET_FLAG(peer->sflags, PEER_STATUS_NSF_WAIT);
+			} else
+				peer->last_reset = PEER_DOWN_CLOSE_SESSION;
+		}
+
+		/* No need for keepalives, if enabled */
+		bgp_keepalives_off(peer->connection);
+
+		/* Drive into state-machine changes */
+		bgp_event_update(connection, peer->connection_errcode);
+
+		counter++;
+		if (counter >= BGP_CONN_ERROR_DEQUEUE_MAX)
+			break;
+
+		peer = bgp_dequeue_conn_err_peer(bgp, &more_p);
+	}
+
+	/* Reschedule event if necessary */
+	if (more_p)
+		bgp_conn_err_reschedule(bgp);
+
+	/* Done with a clearing batch */
+	if (list_count > 0)
+		bgp_clearing_batch_end(bgp);
+
+	if (bgp_debug_neighbor_events(NULL))
+		zlog_debug("%s: dequeued and processed %d peers", __func__,
+			   counter);
+}
+
 /*
- * Enqueue a peer with a connection error to be handled in the main pthread
+ * Enqueue a peer with a connection error to be handled in the main pthread;
+ * this is called from the io pthread.
  */
 int bgp_enqueue_conn_err_peer(struct bgp *bgp, struct peer *peer, int errcode)
 {
@@ -9027,7 +9345,7 @@ int bgp_enqueue_conn_err_peer(struct bgp *bgp, struct peer *peer, int errcode)
 		}
 	}
 	/* Ensure an event is scheduled */
-	event_add_event(bm->master, bgp_packet_process_error, bgp, 0,
+	event_add_event(bm->master, bgp_process_conn_error, bgp, 0,
 			&bgp->t_conn_errors);
 	return 0;
 }
@@ -9061,7 +9379,7 @@ struct peer *bgp_dequeue_conn_err_peer(struct bgp *bgp, bool *more_p)
  */
 void bgp_conn_err_reschedule(struct bgp *bgp)
 {
-	event_add_event(bm->master, bgp_packet_process_error, bgp, 0,
+	event_add_event(bm->master, bgp_process_conn_error, bgp, 0,
 			&bgp->t_conn_errors);
 }
 
diff --git a/bgpd/bgpd.h b/bgpd/bgpd.h
index 069341456e..8489a1d535 100644
--- a/bgpd/bgpd.h
+++ b/bgpd/bgpd.h
@@ -386,32 +386,54 @@ struct bgp_mplsvpn_nh_label_bind_cache;
 PREDECL_RBTREE_UNIQ(bgp_mplsvpn_nh_label_bind_cache);
 
 /* List of peers that have connection errors in the io pthread */
-PREDECL_LIST(bgp_peer_conn_errlist);
+PREDECL_DLIST(bgp_peer_conn_errlist);
 
 /* List of info about peers that are being cleared from BGP RIBs in a batch */
-PREDECL_LIST(bgp_clearing_info);
+PREDECL_DLIST(bgp_clearing_info);
 
 /* Hash of peers in clearing info object */
 PREDECL_HASH(bgp_clearing_hash);
 
+/* List of dests that need to be processed in a clearing batch */
+PREDECL_LIST(bgp_clearing_destlist);
+
+struct bgp_clearing_dest {
+	struct bgp_dest *dest;
+	struct bgp_clearing_destlist_item link;
+};
+
 /* Info about a batch of peers that need to be cleared from the RIB.
  * If many peers need to be cleared, we process them in batches, taking
- * one walk through the RIB for each batch.
+ * one walk through the RIB for each batch. This is only used for "all"
+ * afi/safis, typically when processing peer connection errors.
  */
 struct bgp_clearing_info {
+	/* Owning bgp instance */
+	struct bgp *bgp;
+
 	/* Hash of peers */
 	struct bgp_clearing_hash_head peers;
 
+	/* Flags */
+	uint32_t flags;
+
+	/* List of dests - wrapped by a small wrapper struct */
+	struct bgp_clearing_destlist_head destlist;
+
 	/* Event to schedule/reschedule processing */
-	struct thread *t_sched;
+	struct event *t_sched;
+
+	/* TODO -- id, serial number, for debugging/logging? */
 
-	/* RIB dest for rescheduling */
-	struct bgp_dest *last_dest;
+	/* TODO -- info for rescheduling the RIB walk? future? */
 
-	/* Linkage for list of batches per-bgp */
+	/* Linkage for list of batches per bgp */
 	struct bgp_clearing_info_item link;
 };
 
+/* Batch is open, new peers can be added */
+#define BGP_CLEARING_INFO_FLAG_OPEN  (1 << 0)
+
 /* BGP instance structure.  */
 struct bgp {
 	/* AS number of this BGP instance.  */
@@ -1609,6 +1631,8 @@ struct peer {
 #define PEER_FLAG_EXTENDED_LINK_BANDWIDTH (1ULL << 39)
 #define PEER_FLAG_DUAL_AS		  (1ULL << 40)
 #define PEER_FLAG_CAPABILITY_LINK_LOCAL	  (1ULL << 41)
+/* Peer is part of a batch clearing its routes */
+#define PEER_FLAG_CLEARING_BATCH (1ULL << 42)
 
 	/*
 	 *GR-Disabled mode means unset PEER_FLAG_GRACEFUL_RESTART
@@ -2977,6 +3001,23 @@ extern void srv6_function_free(struct bgp_srv6_function *func);
 
 extern void bgp_session_reset_safe(struct peer *peer, struct listnode **nnode);
 
+/* If a clearing batch is available for 'peer', add it and return 'true',
+ * else return 'false'.
+ */
+bool bgp_clearing_batch_add_peer(struct bgp *bgp, struct peer *peer);
+/* Add a prefix/dest to a clearing batch */
+void bgp_clearing_batch_add_dest(struct bgp_clearing_info *cinfo,
+				 struct bgp_dest *dest);
+/* Check whether a dest's peer is relevant to a clearing batch */
+bool bgp_clearing_batch_check_peer(struct bgp_clearing_info *cinfo,
+				   const struct peer *peer);
+/* Check whether a clearing batch has any dests to process */
+bool bgp_clearing_batch_dests_present(struct bgp_clearing_info *cinfo);
+/* Returns the next dest for batch clear processing */
+struct bgp_dest *bgp_clearing_batch_next_dest(struct bgp_clearing_info *cinfo);
+/* Done with a peer clearing batch; deal with refcounts, free memory */
+void bgp_clearing_batch_completed(struct bgp_clearing_info *cinfo);
+
 #ifdef _FRR_ATTRIBUTE_PRINTFRR
 /* clang-format off */
 #pragma FRR printfrr_ext "%pBP" (struct peer *)