From 4bdcbcdbebbe667e0f6f72347788459c3287c521 Mon Sep 17 00:00:00 2001
From: xtaci <daniel820313@gmail.com>
Date: Tue, 28 Mar 2017 14:25:48 +0800
Subject: [PATCH] only allocate extra buffer when extra header is required

---
 sess.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/sess.go b/sess.go
index c308dba..8cea0fa 100644
--- a/sess.go
+++ b/sess.go
@@ -122,7 +122,6 @@ func newUDPSession(conv uint32, dataShards, parityShards int, l *Listener, conn
 	sess.l = l
 	sess.block = block
 	sess.recvbuf = make([]byte, mtuLimit)
-	sess.ext = make([]byte, mtuLimit)
 
 	// FEC initialization
 	sess.fecDecoder = newFECDecoder(rxFECMulti*(dataShards+parityShards), dataShards, parityShards)
@@ -140,6 +139,12 @@ func newUDPSession(conv uint32, dataShards, parityShards int, l *Listener, conn
 		sess.headerSize += fecHeaderSizePlus2
 	}
 
+	// only allocate extended packet buffer
+	// when the extra header is required
+	if sess.headerSize > 0 {
+		sess.ext = make([]byte, mtuLimit)
+	}
+
 	sess.kcp = NewKCP(conv, func(buf []byte, size int) {
 		if size >= IKCP_OVERHEAD {
 			sess.output(buf[:size])