From 2a3cbb6c8954b71ee5bcd49cd2d05e41b960975d Mon Sep 17 00:00:00 2001
From: "Alexander V. Chernikov" <melifaro@FreeBSD.org>
Date: Sat, 30 Jan 2021 21:52:44 +0000
Subject: [PATCH] MFC dd9163003cb1: Add rib_subscribe_locked() and
 rib_unsubsribe_locked()  to support subscriptions during RIB modifications.
 Add new subscriptions to the beginning of the lists instead of  the end. This
 fixes the situation when new subscription is created  int the callback for
 the existing subscription, leading to the  subscription notification handler
 pick it.

---
 sys/net/route/route_ctl.c | 34 +++++++++++++++++++++++++++++++++-
 sys/net/route/route_ctl.h |  3 +++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/sys/net/route/route_ctl.c b/sys/net/route/route_ctl.c
index 955b1df9029..6b0869196d1 100644
--- a/sys/net/route/route_ctl.c
+++ b/sys/net/route/route_ctl.c
@@ -1407,13 +1407,31 @@ rib_subscribe_internal(struct rib_head *rnh, rib_subscription_cb_t *f, void *arg
 
 	NET_EPOCH_ENTER(et);
 	RIB_WLOCK(rnh);
-	CK_STAILQ_INSERT_TAIL(&rnh->rnh_subscribers, rs, next);
+	CK_STAILQ_INSERT_HEAD(&rnh->rnh_subscribers, rs, next);
 	RIB_WUNLOCK(rnh);
 	NET_EPOCH_EXIT(et);
 
 	return (rs);
 }
 
+struct rib_subscription *
+rib_subscribe_locked(struct rib_head *rnh, rib_subscription_cb_t *f, void *arg,
+    enum rib_subscription_type type)
+{
+	struct rib_subscription *rs;
+
+	NET_EPOCH_ASSERT();
+	RIB_WLOCK_ASSERT(rnh);
+
+	if ((rs = allocate_subscription(f, arg, type, false)) == NULL)
+		return (NULL);
+	rs->rnh = rnh;
+
+	CK_STAILQ_INSERT_HEAD(&rnh->rnh_subscribers, rs, next);
+
+	return (rs);
+}
+
 /*
  * Remove rtable subscription @rs from the routing table.
  * Needs to be run in network epoch.
@@ -1433,6 +1451,20 @@ rib_unsibscribe(struct rib_subscription *rs)
 	    &rs->epoch_ctx);
 }
 
+void
+rib_unsibscribe_locked(struct rib_subscription *rs)
+{
+	struct rib_head *rnh = rs->rnh;
+
+	NET_EPOCH_ASSERT();
+	RIB_WLOCK_ASSERT(rnh);
+
+	CK_STAILQ_REMOVE(&rnh->rnh_subscribers, rs, rib_subscription, next);
+
+	epoch_call(net_epoch_preempt, destroy_subscription_epoch,
+	    &rs->epoch_ctx);
+}
+
 /*
  * Epoch callback indicating subscription is safe to destroy
  */
diff --git a/sys/net/route/route_ctl.h b/sys/net/route/route_ctl.h
index ecbc9ee91dc..bd256e9f083 100644
--- a/sys/net/route/route_ctl.h
+++ b/sys/net/route/route_ctl.h
@@ -144,6 +144,9 @@ struct rib_subscription *rib_subscribe(uint32_t fibnum, int family,
 struct rib_subscription *rib_subscribe_internal(struct rib_head *rnh,
     rib_subscription_cb_t *f, void *arg, enum rib_subscription_type type,
     bool waitok);
+struct rib_subscription *rib_subscribe_locked(struct rib_head *rnh,
+    rib_subscription_cb_t *f, void *arg, enum rib_subscription_type type);
 void rib_unsibscribe(struct rib_subscription *rs);
+void rib_unsibscribe_locked(struct rib_subscription *rs);
 
 #endif