From f53eb22bfbe0959c449c03aa136f0e398813afd9 Mon Sep 17 00:00:00 2001
From: Miek Gieben <miek@miek.nl>
Date: Thu, 5 May 2016 16:56:17 +0100
Subject: [PATCH] Check length before packing OPT (#352)

fixes #351
---
 msg.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/msg.go b/msg.go
index 52afbc59..41b6e0da 100644
--- a/msg.go
+++ b/msg.go
@@ -596,7 +596,7 @@ func packStructValue(val reflect.Value, msg []byte, off int, compression map[str
 				for j := 0; j < val.Field(i).Len(); j++ {
 					element := val.Field(i).Index(j).Interface()
 					b, e := element.(EDNS0).pack()
-					if e != nil {
+					if e != nil || off+3 > lenmsg {
 						return lenmsg, &Error{err: "overflow packing opt"}
 					}
 					// Option code