From: russor <russor@whatsapp.com>
Date: Mon, 18 Apr 2016 22:22:50 +0000 (-0700)
Subject: correct checksum calculation when adding the overflow overflows
X-Git-Tag: v0.87~12^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F110%2Fhead;p=thirdparty%2Fmtr.git

correct checksum calculation when adding the overflow overflows

you can see this with a bit pattern of FF and a large packet length
---

diff --git a/net.c b/net.c
index f743492..60b2b68 100644
--- a/net.c
+++ b/net.c
@@ -247,8 +247,9 @@ int checksum(void *data, int sz)
   while (sz--) {
     sum += *(ch++);
   }
-  
-  sum = (sum >> 16) + (sum & 0xffff);  
+  while (sum >> 16) {
+    sum = (sum >> 16) + (sum & 0xffff);
+  }
 
   return (~sum & 0xffff);  
 }