From eef65b20fcb3408dad11ecc79cd5c914993e8ed2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Felf=C3=B6ldi=20Zsolt?= <zsfelfoldi@gmail.com>
Date: Mon, 6 Aug 2018 14:46:30 +0200
Subject: [PATCH] p2p: use safe atomic operations when changing connFlags
 (#17325)

---
 p2p/server.go | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/p2p/server.go b/p2p/server.go
index 669ef740d..8f3a511f3 100644
--- a/p2p/server.go
+++ b/p2p/server.go
@@ -258,13 +258,18 @@ func (c *conn) is(f connFlag) bool {
 }
 
 func (c *conn) set(f connFlag, val bool) {
-	flags := connFlag(atomic.LoadInt32((*int32)(&c.flags)))
-	if val {
-		flags |= f
-	} else {
-		flags &= ^f
+	for {
+		oldFlags := connFlag(atomic.LoadInt32((*int32)(&c.flags)))
+		flags := oldFlags
+		if val {
+			flags |= f
+		} else {
+			flags &= ^f
+		}
+		if atomic.CompareAndSwapInt32((*int32)(&c.flags), int32(oldFlags), int32(flags)) {
+			return
+		}
 	}
-	atomic.StoreInt32((*int32)(&c.flags), int32(flags))
 }
 
 // Peers returns all connected peers.