From b7ece91825b2ad3090a027804f899d793314c16e Mon Sep 17 00:00:00 2001
From: Derek Collison <derek@nats.io>
Date: Thu, 21 Jun 2018 18:22:06 -0700
Subject: [PATCH] Avoid race by using conditional deep copy

Signed-off-by: Derek Collison <derek@nats.io>
---
 server/client.go |  2 +-
 server/route.go  |  2 +-
 server/server.go | 14 +++++++++++++-
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/server/client.go b/server/client.go
index 02266bff0c..6379dfc83b 100644
--- a/server/client.go
+++ b/server/client.go
@@ -908,7 +908,7 @@ func (c *client) processPing() {
 		// If there was a cluster update since this client was created,
 		// send an updated INFO protocol now.
 		if srv.lastCURLsUpdate >= c.start.UnixNano() {
-			c.sendInfo(c.generateClientInfoJSON(srv.info))
+			c.sendInfo(c.generateClientInfoJSON(srv.copyInfo()))
 		}
 		c.mu.Unlock()
 		srv.mu.Unlock()
diff --git a/server/route.go b/server/route.go
index 3e8fb16475..8234583d1a 100644
--- a/server/route.go
+++ b/server/route.go
@@ -389,7 +389,7 @@ func (s *Server) sendAsyncInfoToClients() {
 		if c.opts.Protocol >= ClientProtoInfo && c.flags.isSet(firstPongSent) {
 			// sendInfo takes care of checking if the connection is still
 			// valid or not, so don't duplicate tests here.
-			c.sendInfo(c.generateClientInfoJSON(s.info))
+			c.sendInfo(c.generateClientInfoJSON(s.copyInfo()))
 		}
 		c.mu.Unlock()
 	}
diff --git a/server/server.go b/server/server.go
index 081d1eb01a..f1cf44c71f 100644
--- a/server/server.go
+++ b/server/server.go
@@ -708,6 +708,18 @@ func (s *Server) HTTPHandler() http.Handler {
 	return s.httpHandler
 }
 
+// Perform a conditional deep copy due to reference nature of ClientConnectURLs.
+// If updates are made to Info, this function should be consulted and updated.
+// Assume lock is held.
+func (s *Server) copyInfo() Info {
+	info := s.info
+	if info.ClientConnectURLs != nil {
+		info.ClientConnectURLs = make([]string, len(s.info.ClientConnectURLs))
+		copy(info.ClientConnectURLs, s.info.ClientConnectURLs)
+	}
+	return info
+}
+
 func (s *Server) createClient(conn net.Conn) *client {
 	// Snapshot server options.
 	opts := s.getOpts()
@@ -716,7 +728,7 @@ func (s *Server) createClient(conn net.Conn) *client {
 
 	// Grab JSON info string
 	s.mu.Lock()
-	info := s.info
+	info := s.copyInfo()
 	s.totalClients++
 	s.mu.Unlock()