From edc37a66e34396fb480bab54650436095b9ac678 Mon Sep 17 00:00:00 2001
From: "Alexander V. Chernikov" <melifaro@FreeBSD.org>
Date: Sun, 12 Jul 2020 11:18:09 +0000
Subject: [PATCH] Add destructor for the rib subscription system to simplify
 users code.

Subscriptions are planned to be used by modules such as route lookup engines.
In that case that's the module task to properly unsibscribe before detach.
However, the in-kernel customer - inet6 wants to track default route changes.
To avoid having inet6 store per-fib subscriptions, handle automatic
 destruction internally.

Differential Revision:	https://reviews.freebsd.org/D25614
---
 sys/net/route.c           |  4 +++-
 sys/net/route/route_ctl.c | 25 +++++++++++++++++++++++++
 sys/net/route/shared.h    |  4 ++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/sys/net/route.c b/sys/net/route.c
index 6c42e8f6eda5..0b7a0e2d55b6 100644
--- a/sys/net/route.c
+++ b/sys/net/route.c
@@ -348,7 +348,7 @@ rt_table_init(int offset, int family, u_int fibnum)
 	nhops_init_rib(rh);
 
 	/* Init subscription system */
-	CK_STAILQ_INIT(&rh->rnh_subscribers);
+	rib_init_subscriptions(rh);
 
 	/* Finally, set base callbacks */
 	rh->rnh_addaddr = rn_addroute;
@@ -383,6 +383,8 @@ rt_table_destroy(struct rib_head *rh)
 
 	nhops_destroy_rib(rh);
 
+	rib_destroy_subscriptions(rh);
+
 	/* Assume table is already empty */
 	RIB_LOCK_DESTROY(rh);
 	free(rh, M_RTABLE);
diff --git a/sys/net/route/route_ctl.c b/sys/net/route/route_ctl.c
index 6218b82a935a..a573a07178e4 100644
--- a/sys/net/route/route_ctl.c
+++ b/sys/net/route/route_ctl.c
@@ -847,3 +847,28 @@ destroy_subscription_epoch(epoch_context_t ctx)
 
 	free(rs, M_RTABLE);
 }
+
+void
+rib_init_subscriptions(struct rib_head *rnh)
+{
+
+	CK_STAILQ_INIT(&rnh->rnh_subscribers);
+}
+
+void
+rib_destroy_subscriptions(struct rib_head *rnh)
+{
+	struct rib_subscription *rs;
+	struct epoch_tracker et;
+
+	NET_EPOCH_ENTER(et);
+	RIB_WLOCK(rnh);
+	while ((rs = CK_STAILQ_FIRST(&rnh->rnh_subscribers)) != NULL) {
+		CK_STAILQ_REMOVE_HEAD(&rnh->rnh_subscribers, next);
+		epoch_call(net_epoch_preempt, destroy_subscription_epoch,
+		    &rs->epoch_ctx);
+	}
+	RIB_WUNLOCK(rnh);
+	NET_EPOCH_EXIT(et);
+}
+
diff --git a/sys/net/route/shared.h b/sys/net/route/shared.h
index ce5075896c96..4ea20c5e011e 100644
--- a/sys/net/route/shared.h
+++ b/sys/net/route/shared.h
@@ -67,6 +67,10 @@ int nhop_create_from_nhop(struct rib_head *rnh, const struct nhop_object *nh_ori
 void nhops_update_ifmtu(struct rib_head *rh, struct ifnet *ifp, uint32_t mtu);
 int nhops_dump_sysctl(struct rib_head *rh, struct sysctl_req *w);
 
+/* subscriptions */
+void rib_init_subscriptions(struct rib_head *rnh);
+void rib_destroy_subscriptions(struct rib_head *rnh);
+
 /* route */
 VNET_DECLARE(uma_zone_t, rtzone);		/* Routing table UMA zone. */
 #define	V_rtzone	VNET(rtzone)