From bbc5135f29e70508f8540ecbb9329707a8036ae5 Mon Sep 17 00:00:00 2001
From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Mon, 25 Feb 2019 22:56:40 +0100
Subject: peer: only synchronize_rcu_bh and traverse trie once when removing
 all peers

---
 src/device.c |  1 -
 src/peer.c   | 61 +++++++++++++++++++++++++++++++++++++++++-------------------
 2 files changed, 42 insertions(+), 20 deletions(-)

diff --git a/src/device.c b/src/device.c
index 15911b2..2866dd9 100644
--- a/src/device.c
+++ b/src/device.c
@@ -237,7 +237,6 @@ static void wg_destruct(struct net_device *dev)
 	mutex_lock(&wg->device_update_lock);
 	wg->incoming_port = 0;
 	wg_socket_reinit(wg, NULL, NULL);
-	wg_allowedips_free(&wg->peer_allowedips, &wg->device_update_lock);
 	/* The final references are cleared in the below calls to destroy_workqueue. */
 	wg_peer_remove_all(wg);
 	destroy_workqueue(wg->handshake_receive_wq);
diff --git a/src/peer.c b/src/peer.c
index b786381..6a33df0 100644
--- a/src/peer.c
+++ b/src/peer.c
@@ -87,16 +87,8 @@ struct wg_peer *wg_peer_get_maybe_zero(struct wg_peer *peer)
 	return peer;
 }
 
-/* We have a separate "remove" function make sure that all active places where
- * a peer is currently operating will eventually come to an end and not pass
- * their reference onto another context.
- */
-void wg_peer_remove(struct wg_peer *peer)
+static void peer_make_dead(struct wg_peer *peer)
 {
-	if (unlikely(!peer))
-		return;
-	lockdep_assert_held(&peer->device->device_update_lock);
-
 	/* Remove from configuration-time lookup structures. */
 	list_del_init(&peer->peer_list);
 	wg_allowedips_remove_by_peer(&peer->device->peer_allowedips, peer,
@@ -105,7 +97,13 @@ void wg_peer_remove(struct wg_peer *peer)
 
 	/* Mark as dead, so that we don't allow jumping contexts after. */
 	WRITE_ONCE(peer->is_dead, true);
-	synchronize_rcu_bh();
+
+	/* The caller must now synchronize_rcu_bh() for this to take effect. */
+}
+
+static void peer_remove_after_dead(struct wg_peer *peer)
+{
+	WARN_ON(!peer->is_dead);
 
 	/* No more keypairs can be created for this peer, since is_dead protects
 	 * add_new_keypair, so we can now destroy existing ones.
@@ -161,6 +159,40 @@ void wg_peer_remove(struct wg_peer *peer)
 	wg_peer_put(peer);
 }
 
+/* We have a separate "remove" function make sure that all active places where
+ * a peer is currently operating will eventually come to an end and not pass
+ * their reference onto another context.
+ */
+void wg_peer_remove(struct wg_peer *peer)
+{
+	if (unlikely(!peer))
+		return;
+	lockdep_assert_held(&peer->device->device_update_lock);
+
+	peer_make_dead(peer);
+	synchronize_rcu_bh();
+	peer_remove_after_dead(peer);
+}
+
+void wg_peer_remove_all(struct wg_device *wg)
+{
+	struct list_head dead_peers = LIST_HEAD_INIT(dead_peers);
+	struct wg_peer *peer, *temp;
+
+	lockdep_assert_held(&wg->device_update_lock);
+
+	/* Avoid having to traverse individually for each one. */
+	wg_allowedips_free(&wg->peer_allowedips, &wg->device_update_lock);
+
+	list_for_each_entry_safe(peer, temp, &wg->peer_list, peer_list) {
+		peer_make_dead(peer);
+		list_add_tail(&peer->peer_list, &dead_peers);
+	}
+	synchronize_rcu_bh();
+	list_for_each_entry_safe(peer, temp, &dead_peers, peer_list)
+		peer_remove_after_dead(peer);
+}
+
 static void rcu_release(struct rcu_head *rcu)
 {
 	struct wg_peer *peer = container_of(rcu, struct wg_peer, rcu);
@@ -204,12 +236,3 @@ void wg_peer_put(struct wg_peer *peer)
 		return;
 	kref_put(&peer->refcount, kref_release);
 }
-
-void wg_peer_remove_all(struct wg_device *wg)
-{
-	struct wg_peer *peer, *temp;
-
-	lockdep_assert_held(&wg->device_update_lock);
-	list_for_each_entry_safe(peer, temp, &wg->peer_list, peer_list)
-		wg_peer_remove(peer);
-}
-- 
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