From e7aa4cd04bda4365c112fba075931aab9c0d4a3c Mon Sep 17 00:00:00 2001
From: Qian Wang <cbeuw.andy@gmail.com>
Date: Wed, 7 Aug 2019 13:59:27 +0100
Subject: [PATCH] Fix a stuck mutex

---
 internal/multiplex/switchboard.go | 8 +++-----
 internal/server/TLS.go            | 6 ------
 2 files changed, 3 insertions(+), 11 deletions(-)

diff --git a/internal/multiplex/switchboard.go b/internal/multiplex/switchboard.go
index c4bb416..fc4edd1 100644
--- a/internal/multiplex/switchboard.go
+++ b/internal/multiplex/switchboard.go
@@ -58,10 +58,10 @@ func (sb *switchboard) removeConn(connId uint32) {
 
 // a pointer to connId is passed here so that the switchboard can reassign it
 func (sb *switchboard) send(data []byte, connId *uint32) (int, error) {
-	var conn net.Conn
 	sb.connsM.RLock()
+	defer sb.connsM.RUnlock()
+	var conn net.Conn
 	conn, ok := sb.conns[*connId]
-	sb.connsM.RUnlock()
 	if ok {
 		return conn.Write(data)
 	} else {
@@ -72,13 +72,11 @@ func (sb *switchboard) send(data []byte, connId *uint32) (int, error) {
 		// in particular if newConnId is removed between the RUnlock and RLock, conns[newConnId] will return
 		// a nil pointer. To prevent this we must get newConnId and the reference to conn itself in one single mutex
 		// protection
-		sb.connsM.RLock()
 		if atomic.LoadUint32(&sb.broken) == 1 || len(sb.conns) == 0 {
 			return 0, errBrokenSwitchboard
 		}
 		newConnId := rand.Intn(len(sb.conns))
 		conn = sb.conns[uint32(newConnId)]
-		sb.connsM.RUnlock()
 		return conn.Write(data)
 	}
 
@@ -86,11 +84,11 @@ func (sb *switchboard) send(data []byte, connId *uint32) (int, error) {
 
 func (sb *switchboard) assignRandomConn() (uint32, error) {
 	sb.connsM.RLock()
+	defer sb.connsM.RUnlock()
 	if atomic.LoadUint32(&sb.broken) == 1 || len(sb.conns) == 0 {
 		return 0, errBrokenSwitchboard
 	}
 	connId := rand.Intn(len(sb.conns))
-	sb.connsM.RUnlock()
 	return uint32(connId), nil
 }
 
diff --git a/internal/server/TLS.go b/internal/server/TLS.go
index 7302141..58af276 100644
--- a/internal/server/TLS.go
+++ b/internal/server/TLS.go
@@ -161,12 +161,6 @@ func parseClientHello(data []byte) (ret *ClientHello, err error) {
 	return
 }
 
-func xor(a []byte, b []byte) {
-	for i := range a {
-		a[i] ^= b[i]
-	}
-}
-
 func composeServerHello(sessionId []byte, sharedSecret []byte, sessionKey []byte) ([]byte, error) {
 	nonce := make([]byte, 12)
 	rand.Read(nonce)