From: ian <ian>
Date: Sun, 3 Mar 2002 14:03:34 +0000 (+0000)
Subject: Iteratively ones-c the checksum
X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=commitdiff_plain;h=02aa73e95e6c1c13994f278aee20e40cb31784c7;p=vinegar-ip.git

Iteratively ones-c the checksum
---

diff --git a/make-probes.tcl b/make-probes.tcl
index a23edff..3466cdb 100755
--- a/make-probes.tcl
+++ b/make-probes.tcl
@@ -49,7 +49,10 @@ proc packet-csum-ip {packet} {
 	set cs [expr "\$cs + 0x$this"]
 	debug 7 [format "0x%s 0x%08x" $this $cs]
     }
-    return [expr {(($cs & 0xffff) + (($cs >> 16) & 0xffff)) ^ 0xffff}]
+    while {$cs > 0xffff} {
+	set cs [expr {($cs & 0xffff) + (($cs >> 16) & 0xffff)}]
+    }
+    return [expr {$cs ^ 0xffff}]
 }
 
 proc packet-fromstring {s} {