1 files changed, 137 insertions, 0 deletions
diff --git a/contrib/tcpdump/checksum.c b/contrib/tcpdump/checksum.c
new file mode 100644
index 0000000..f441be3
--- /dev/null
+++ b/contrib/tcpdump/checksum.c
@@ -0,0 +1,137 @@
+/*
+ * Copyright (c) 1998-2006 The TCPDUMP project
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that: (1) source code
+ * distributions retain the above copyright notice and this paragraph
+ * in its entirety, and (2) distributions including binary code include
+ * the above copyright notice and this paragraph in its entirety in
+ * the documentation or other materials provided with the distribution.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND
+ * WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT
+ * LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE.
+ *
+ * miscellaneous checksumming routines
+ *
+ * Original code by Hannes Gredler (hannes@juniper.net)
+ */
+
+#ifndef lint
+static const char rcsid[] _U_ =
+    "@(#) $Header: /tcpdump/master/tcpdump/checksum.c,v 1.4 2006-09-25 09:23:32 hannes Exp $";
+#endif
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <tcpdump-stdinc.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "interface.h"
+
+#define CRC10_POLYNOMIAL 0x633
+static u_int16_t crc10_table[256];
+
+static void
+init_crc10_table(void)
+{   
+    register int i, j;
+    register u_int16_t accum;
+    
+    for ( i = 0;  i < 256;  i++ )
+    {
+        accum = ((unsigned short) i << 2);
+        for ( j = 0;  j < 8;  j++ )
+        {
+            if ((accum <<= 1) & 0x400) accum ^= CRC10_POLYNOMIAL;
+        }
+        crc10_table[i] = accum;
+    }
+    return;
+}
+
+u_int16_t
+verify_crc10_cksum(u_int16_t accum, const u_char *p, int length)
+{
+    register int i;
+
+    for ( i = 0;  i < length;  i++ )
+    {
+        accum = ((accum << 8) & 0x3ff)
+            ^ crc10_table[( accum >> 2) & 0xff]
+            ^ *p++;
+    }
+    return accum;
+}
+
+/* precompute checksum tables */
+void
+init_checksum(void) {
+
+    init_crc10_table();
+
+}
+
+/*
+ * Creates the OSI Fletcher checksum. See 8473-1, Appendix C, section C.3.
+ * The checksum field of the passed PDU does not need to be reset to zero.
+ */
+u_int16_t
+create_osi_cksum (const u_int8_t *pptr, int checksum_offset, int length)
+{
+
+    int x;
+    int y;
+    u_int32_t mul;
+    u_int32_t c0;
+    u_int32_t c1;
+    u_int16_t checksum;
+    int index;
+
+    checksum = 0;
+
+    c0 = 0;
+    c1 = 0;
+
+    for (index = 0; index < length; index++) {
+        /*
+         * Ignore the contents of the checksum field.
+         */
+        if (index == checksum_offset ||
+            index == checksum_offset+1) {
+            c1 += c0;
+            pptr++;
+        } else {
+            c0 = c0 + *(pptr++);
+            c1 += c0;
+        } 
+    }
+
+    c0 = c0 % 255;
+    c1 = c1 % 255;
+
+    mul = (length - checksum_offset)*(c0);
+  
+    x = mul - c0 - c1;
+    y = c1 - mul - 1;
+
+    if ( y >= 0 ) y++;
+    if ( x < 0 ) x--;
+
+    x %= 255;
+    y %= 255;
+
+
+    if (x == 0) x = 255;
+    if (y == 0) y = 255;
+
+    y &= 0x00FF;
+    checksum = ((x << 8) | y);
+  
+    return checksum;
+}