bfdd: tell peer when our control plane is dead

Simplify and fix the code that handles session teardown on control
plane shutdown (either failure or graceful).

- Don't move the `NULL` check inside `free` functions that expect
  data: it creates harder to understand flows.
- Add some new debug messages to aid visualizing session deletions.
- Add sanity check error message (if it ever happens).

Signed-off-by: Rafael Zalamena <rzalamena@opensourcerouting.org>

1 files changed, 51 insertions, 12 deletions

diff --git a/bfdd/ptm_adapter.c b/bfdd/ptm_adapter.c
index 7efbd2c7b..0d5183ed5 100644
--- a/bfdd/ptm_adapter.c
+++ b/bfdd/ptm_adapter.c
@@ -128,6 +128,35 @@ static void debug_printbpc(const struct bfd_peer_cfg *bpc, const char *fmt, ...)
 		   timers[0], timers[1], timers[2], cbit_str);
 }
 
+static void _ptm_bfd_session_del(struct bfd_session *bs, uint8_t diag)
+{
+	if (bglobal.debug_peer_event)
+		zlog_debug("session-delete: %s", bs_to_string(bs));
+
+	/* Change state and notify peer. */
+	bs->ses_state = PTM_BFD_DOWN;
+	bs->local_diag = diag;
+	ptm_bfd_snd(bs, 0);
+
+	/* Session reached refcount == 0, lets delete it. */
+	if (bs->refcount == 0) {
+		/*
+		 * Sanity check: if there is a refcount bug, we can't delete
+		 * the session a user configured manually. Lets leave a
+		 * message here so we can catch the bug if it exists.
+		 */
+		if (CHECK_FLAG(bs->flags, BFD_SESS_FLAG_CONFIG)) {
+			zlog_err(
+				"ptm-del-session: [%s] session refcount is "
+				"zero but it was configured by CLI",
+				bs_to_string(bs));
+		} else {
+			control_notify_config(BCM_NOTIFY_CONFIG_DELETE, bs);
+			bfd_session_free(bs);
+		}
+	}
+}
+
 static int _ptm_msg_address(struct stream *msg, int family, const void *addr)
 {
 	stream_putc(msg, family);
@@ -453,15 +482,20 @@ static void bfdd_dest_deregister(struct stream *msg, vrf_id_t vrf_id)
 
 	/* Unregister client peer notification. */
 	pcn = pcn_lookup(pc, bs);
-	pcn_free(pcn);
-	if (bs->refcount ||
-	    CHECK_FLAG(bs->flags, BFD_SESS_FLAG_CONFIG))
+	if (pcn != NULL) {
+		pcn_free(pcn);
 		return;
+	}
 
-	bs->ses_state = PTM_BFD_ADM_DOWN;
-	ptm_bfd_snd(bs, 0);
+	if (bglobal.debug_zebra)
+		zlog_debug("ptm-del-dest: failed to find BFD session");
 
-	ptm_bfd_sess_del(&bpc);
+	/*
+	 * XXX: We either got a double deregistration or the daemon who
+	 * created this is no longer around. Lets try to delete it anyway
+	 * and the worst case is the refcount will detain us.
+	 */
+	_ptm_bfd_session_del(bs, BD_NEIGHBOR_DOWN);
 }
 
 /*
@@ -503,6 +537,9 @@ static void bfdd_client_deregister(struct stream *msg)
 		return;
 	}
 
+	if (bglobal.debug_zebra)
+		zlog_debug("ptm-del-client: client pid %u", pid);
+
 	pc_free(pc);
 
 	return;
@@ -824,9 +861,6 @@ static void pc_free(struct ptm_client *pc)
 {
 	struct ptm_client_notification *pcn;
 
-	if (pc == NULL)
-		return;
-
 	TAILQ_REMOVE(&pcqueue, pc, pc_entry);
 
 	while (!TAILQ_EMPTY(&pc->pc_pcnqueue)) {
@@ -888,14 +922,19 @@ static void pcn_free(struct ptm_client_notification *pcn)
 	struct ptm_client *pc;
 	struct bfd_session *bs;
 
-	if (pcn == NULL)
-		return;
-
 	/* Handle session de-registration. */
 	bs = pcn->pcn_bs;
 	pcn->pcn_bs = NULL;
 	bs->refcount--;
 
+	/* Log modification to users. */
+	if (bglobal.debug_zebra)
+		zlog_debug("ptm-del-session: [%s] refcount=%" PRIu64,
+			   bs_to_string(bs), bs->refcount);
+
+	/* Set session down. */
+	_ptm_bfd_session_del(bs, BD_NEIGHBOR_DOWN);
+
 	/* Handle ptm_client deregistration. */
 	pc = pcn->pcn_pc;
 	pcn->pcn_pc = NULL;