1 files changed, 304 insertions, 0 deletions
diff --git a/bgpd/bgp_keepalives.c b/bgpd/bgp_keepalives.c
new file mode 100644
index 0000000..92123c2
--- /dev/null
+++ b/bgpd/bgp_keepalives.c
@@ -0,0 +1,304 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* BGP Keepalives.
+ * Implements a producer thread to generate BGP keepalives for peers.
+ * Copyright (C) 2017 Cumulus Networks, Inc.
+ * Quentin Young
+ */
+
+/* clang-format off */
+#include <zebra.h>
+#include <pthread.h>		// for pthread_mutex_lock, pthread_mutex_unlock
+
+#include "frr_pthread.h"        // for frr_pthread
+#include "hash.h"		// for hash, hash_clean, hash_create_size...
+#include "log.h"		// for zlog_debug
+#include "memory.h"		// for MTYPE_TMP, XFREE, XCALLOC, XMALLOC
+#include "monotime.h"		// for monotime, monotime_since
+
+#include "bgpd/bgpd.h"          // for peer, PEER_EVENT_KEEPALIVES_ON, peer...
+#include "bgpd/bgp_debug.h"	// for bgp_debug_neighbor_events
+#include "bgpd/bgp_packet.h"	// for bgp_keepalive_send
+#include "bgpd/bgp_keepalives.h"
+/* clang-format on */
+
+DEFINE_MTYPE_STATIC(BGPD, BGP_PKAT, "Peer KeepAlive Timer");
+DEFINE_MTYPE_STATIC(BGPD, BGP_COND, "BGP Peer pthread Conditional");
+DEFINE_MTYPE_STATIC(BGPD, BGP_MUTEX, "BGP Peer pthread Mutex");
+
+/*
+ * Peer KeepAlive Timer.
+ * Associates a peer with the time of its last keepalive.
+ */
+struct pkat {
+	/* the peer to send keepalives to */
+	struct peer *peer;
+	/* absolute time of last keepalive sent */
+	struct timeval last;
+};
+
+/* List of peers we are sending keepalives for, and associated mutex. */
+static pthread_mutex_t *peerhash_mtx;
+static pthread_cond_t *peerhash_cond;
+static struct hash *peerhash;
+
+static struct pkat *pkat_new(struct peer *peer)
+{
+	struct pkat *pkat = XMALLOC(MTYPE_BGP_PKAT, sizeof(struct pkat));
+	pkat->peer = peer;
+	monotime(&pkat->last);
+	return pkat;
+}
+
+static void pkat_del(void *pkat)
+{
+	XFREE(MTYPE_BGP_PKAT, pkat);
+}
+
+
+/*
+ * Callback for hash_iterate. Determines if a peer needs a keepalive and if so,
+ * generates and sends it.
+ *
+ * For any given peer, if the elapsed time since its last keepalive exceeds its
+ * configured keepalive timer, a keepalive is sent to the peer and its
+ * last-sent time is reset. Additionally, If the elapsed time does not exceed
+ * the configured keepalive timer, but the time until the next keepalive is due
+ * is within a hardcoded tolerance, a keepalive is sent as if the configured
+ * timer was exceeded. Doing this helps alleviate nanosecond sleeps between
+ * ticks by grouping together peers who are due for keepalives at roughly the
+ * same time. This tolerance value is arbitrarily chosen to be 100ms.
+ *
+ * In addition, this function calculates the maximum amount of time that the
+ * keepalive thread can sleep before another tick needs to take place. This is
+ * equivalent to shortest time until a keepalive is due for any one peer.
+ *
+ * @return maximum time to wait until next update (0 if infinity)
+ */
+static void peer_process(struct hash_bucket *hb, void *arg)
+{
+	struct pkat *pkat = hb->data;
+
+	struct timeval *next_update = arg;
+
+	static struct timeval elapsed;  // elapsed time since keepalive
+	static struct timeval ka = {0}; // peer->v_keepalive as a timeval
+	static struct timeval diff;     // ka - elapsed
+
+	static const struct timeval tolerance = {0, 100000};
+
+	uint32_t v_ka = atomic_load_explicit(&pkat->peer->v_keepalive,
+					     memory_order_relaxed);
+
+	/* 0 keepalive timer means no keepalives */
+	if (v_ka == 0)
+		return;
+
+	/* calculate elapsed time since last keepalive */
+	monotime_since(&pkat->last, &elapsed);
+
+	/* calculate difference between elapsed time and configured time */
+	ka.tv_sec = v_ka;
+	timersub(&ka, &elapsed, &diff);
+
+	int send_keepalive =
+		elapsed.tv_sec >= ka.tv_sec || timercmp(&diff, &tolerance, <);
+
+	if (send_keepalive) {
+		if (bgp_debug_keepalive(pkat->peer))
+			zlog_debug("%s [FSM] Timer (keepalive timer expire)",
+				   pkat->peer->host);
+
+		bgp_keepalive_send(pkat->peer);
+		monotime(&pkat->last);
+		memset(&elapsed, 0, sizeof(elapsed));
+		diff = ka;
+	}
+
+	/* if calculated next update for this peer < current delay, use it */
+	if (next_update->tv_sec < 0 || timercmp(&diff, next_update, <))
+		*next_update = diff;
+}
+
+static bool peer_hash_cmp(const void *f, const void *s)
+{
+	const struct pkat *p1 = f;
+	const struct pkat *p2 = s;
+
+	return p1->peer == p2->peer;
+}
+
+static unsigned int peer_hash_key(const void *arg)
+{
+	const struct pkat *pkat = arg;
+	return (uintptr_t)pkat->peer;
+}
+
+/* Cleanup handler / deinitializer. */
+static void bgp_keepalives_finish(void *arg)
+{
+	hash_clean_and_free(&peerhash, pkat_del);
+
+	pthread_mutex_unlock(peerhash_mtx);
+	pthread_mutex_destroy(peerhash_mtx);
+	pthread_cond_destroy(peerhash_cond);
+
+	XFREE(MTYPE_BGP_MUTEX, peerhash_mtx);
+	XFREE(MTYPE_BGP_COND, peerhash_cond);
+}
+
+/*
+ * Entry function for peer keepalive generation pthread.
+ */
+void *bgp_keepalives_start(void *arg)
+{
+	struct frr_pthread *fpt = arg;
+	fpt->master->owner = pthread_self();
+
+	struct timeval currtime = {0, 0};
+	struct timeval aftertime = {0, 0};
+	struct timeval next_update = {0, 0};
+	struct timespec next_update_ts = {0, 0};
+
+	/*
+	 * The RCU mechanism for each pthread is initialized in a "locked"
+	 * state. That's ok for pthreads using the frr_pthread,
+	 * event_fetch event loop, because that event loop unlocks regularly.
+	 * For foreign pthreads, the lock needs to be unlocked so that the
+	 * background rcu pthread can run.
+	 */
+	rcu_read_unlock();
+
+	peerhash_mtx = XCALLOC(MTYPE_BGP_MUTEX, sizeof(pthread_mutex_t));
+	peerhash_cond = XCALLOC(MTYPE_BGP_COND, sizeof(pthread_cond_t));
+
+	/* initialize mutex */
+	pthread_mutex_init(peerhash_mtx, NULL);
+
+	/* use monotonic clock with condition variable */
+	pthread_condattr_t attrs;
+	pthread_condattr_init(&attrs);
+	pthread_condattr_setclock(&attrs, CLOCK_MONOTONIC);
+	pthread_cond_init(peerhash_cond, &attrs);
+	pthread_condattr_destroy(&attrs);
+
+	/*
+	 * We are not using normal FRR pthread mechanics and are
+	 * not using fpt_run
+	 */
+	frr_pthread_set_name(fpt);
+
+	/* initialize peer hashtable */
+	peerhash = hash_create_size(2048, peer_hash_key, peer_hash_cmp, NULL);
+	pthread_mutex_lock(peerhash_mtx);
+
+	/* register cleanup handler */
+	pthread_cleanup_push(&bgp_keepalives_finish, NULL);
+
+	/* notify anybody waiting on us that we are done starting up */
+	frr_pthread_notify_running(fpt);
+
+	while (atomic_load_explicit(&fpt->running, memory_order_relaxed)) {
+		if (peerhash->count > 0)
+			pthread_cond_timedwait(peerhash_cond, peerhash_mtx,
+					       &next_update_ts);
+		else
+			while (peerhash->count == 0
+			       && atomic_load_explicit(&fpt->running,
+						       memory_order_relaxed))
+				pthread_cond_wait(peerhash_cond, peerhash_mtx);
+
+		monotime(&currtime);
+
+		next_update.tv_sec = -1;
+
+		hash_iterate(peerhash, peer_process, &next_update);
+		if (next_update.tv_sec == -1)
+			memset(&next_update, 0, sizeof(next_update));
+
+		monotime_since(&currtime, &aftertime);
+
+		timeradd(&currtime, &next_update, &next_update);
+		TIMEVAL_TO_TIMESPEC(&next_update, &next_update_ts);
+	}
+
+	/* clean up */
+	pthread_cleanup_pop(1);
+
+	return NULL;
+}
+
+/* --- thread external functions ------------------------------------------- */
+
+void bgp_keepalives_on(struct peer_connection *connection)
+{
+	struct peer *peer = connection->peer;
+
+	if (CHECK_FLAG(peer->thread_flags, PEER_THREAD_KEEPALIVES_ON))
+		return;
+
+	struct frr_pthread *fpt = bgp_pth_ka;
+	assert(fpt->running);
+
+	/* placeholder bucket data to use for fast key lookups */
+	static struct pkat holder = {0};
+
+	/*
+	 * We need to ensure that bgp_keepalives_init was called first
+	 */
+	assert(peerhash_mtx);
+
+	frr_with_mutex (peerhash_mtx) {
+		holder.peer = peer;
+		if (!hash_lookup(peerhash, &holder)) {
+			struct pkat *pkat = pkat_new(peer);
+			(void)hash_get(peerhash, pkat, hash_alloc_intern);
+			peer_lock(peer);
+		}
+		SET_FLAG(peer->thread_flags, PEER_THREAD_KEEPALIVES_ON);
+		/* Force the keepalive thread to wake up */
+		pthread_cond_signal(peerhash_cond);
+	}
+}
+
+void bgp_keepalives_off(struct peer_connection *connection)
+{
+	struct peer *peer = connection->peer;
+
+	if (!CHECK_FLAG(peer->thread_flags, PEER_THREAD_KEEPALIVES_ON))
+		return;
+
+	struct frr_pthread *fpt = bgp_pth_ka;
+	assert(fpt->running);
+
+	/* placeholder bucket data to use for fast key lookups */
+	static struct pkat holder = {0};
+
+	/*
+	 * We need to ensure that bgp_keepalives_init was called first
+	 */
+	assert(peerhash_mtx);
+
+	frr_with_mutex (peerhash_mtx) {
+		holder.peer = peer;
+		struct pkat *res = hash_release(peerhash, &holder);
+		if (res) {
+			pkat_del(res);
+			peer_unlock(peer);
+		}
+		UNSET_FLAG(peer->thread_flags, PEER_THREAD_KEEPALIVES_ON);
+	}
+}
+
+int bgp_keepalives_stop(struct frr_pthread *fpt, void **result)
+{
+	assert(fpt->running);
+
+	frr_with_mutex (peerhash_mtx) {
+		atomic_store_explicit(&fpt->running, false,
+				      memory_order_relaxed);
+		pthread_cond_signal(peerhash_cond);
+	}
+
+	pthread_join(fpt->thread, result);
+	return 0;
+}