From 3f66787605ef3b4f3cd141529dba3d32ccd06f98 Mon Sep 17 00:00:00 2001
From: russor <russor@whatsapp.com>
Date: Mon, 18 Apr 2016 13:47:14 -0700
Subject: [PATCH] fix placement of zeros when running alternate udp checksum

---
 net.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net.c b/net.c
index bdc5f85..05d707e 100644
--- a/net.c
+++ b/net.c
@@ -259,7 +259,8 @@ int udp_checksum(void *pheader, void *udata, int psize, int dsize, int alt_check
   char csumpacket[tsize];
   memset(csumpacket, (unsigned char) abs(bitpattern), abs(tsize));
   if (alt_checksum && dsize >= 2) {
-    csumpacket[psize] = csumpacket[psize + 1] = 0;
+    csumpacket[psize + sizeof(struct UDPHeader)] = 0;
+    csumpacket[psize + sizeof(struct UDPHeader) + 1] = 0;
   }
 
   struct UDPv4PHeader *prepend = (struct UDPv4PHeader *) csumpacket;
-- 
2.47.2