* ISO checksum related routines
*
* Copyright (C) 2001,2002 Sampo Saaristo
- * Tampere University of Technology
+ * Tampere University of Technology
* Institute of Communications Engineering
*
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public Licenseas published by the Free
- * Software Foundation; either version 2 of the License, or (at your option)
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public Licenseas published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
* any later version.
*
- * This program is distributed in the hope that it will be useful,but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * This program is distributed in the hope that it will be useful,but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
-
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <zebra.h>
#include "iso_checksum.h"
+#include "checksum.h"
/*
* Calculations of the OSI checksum.
* sum a (mod 255) = 0
* 1 i
*
- * L
+ * L
* sum (L-i+1)a (mod 255) = 0
* 1 i
*
* Based on Annex C.4 of ISO/IEC 8473
*/
-int
-iso_csum_verify (u_char * buffer, int len, uint16_t * csum)
-{
- u_int8_t *p;
- u_int32_t c0;
- u_int32_t c1;
- u_int16_t checksum;
- int i, partial_len;
-
- p = buffer;
- checksum = 0;
- c0 = *csum & 0xff00;
- c1 = *csum & 0x00ff;
-
- /*
- * If both are zero return correct
- */
- if (c0 == 0 && c1 == 0)
- return 0;
-
- /*
- * If either, but not both are zero return incorrect
- */
- if (c0 == 0 || c1 == 0)
- return 1;
-
- /*
- * Otherwise initialize to zero and calculate...
- */
- c0 = 0;
- c1 = 0;
-
- while (len)
- {
- partial_len = MIN(len, 5803);
-
- for (i = 0; i < partial_len; i++)
- {
- c0 = c0 + *(p++);
- c1 += c0;
- }
-
- c0 = c0 % 255;
- c1 = c1 % 255;
-
- len -= partial_len;
- }
-
- if (c0 == 0 && c1 == 0)
- return 0;
-
- return 1;
-}
-
-/*
- * Creates the checksum. *csum points to the position of the checksum in the
- * PDU.
- * Based on Annex C.4 of ISO/IEC 8473
- */
-#define FIXED_CODE
-u_int16_t
-iso_csum_create (u_char * buffer, int len, u_int16_t n)
+int iso_csum_verify(uint8_t *buffer, int len, uint16_t csum, int offset)
{
-
- u_int8_t *p;
- int x;
- int y;
- u_int32_t mul;
- u_int32_t c0;
- u_int32_t c1;
- u_int16_t checksum;
- u_int16_t *csum;
- int i, init_len, partial_len;
-
- checksum = 0;
-
- /*
- * Zero the csum in the packet.
- */
- csum = (u_int16_t *) (buffer + n);
- *(csum) = checksum;
-
- p = buffer;
- c0 = 0;
- c1 = 0;
- init_len = len;
-
- while (len != 0)
- {
- partial_len = MIN(len, 5803);
-
- for (i = 0; i < partial_len; i++)
- {
- c0 = c0 + *(p++);
- c1 += c0;
- }
-
- c0 = c0 % 255;
- c1 = c1 % 255;
-
- len -= partial_len;
- }
-
- mul = (init_len - n)*(c0);
-
-#ifdef FIXED_CODE
- 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 = 1;
-
- checksum = (y << 8) | (x & 0xFF);
-
-#else
- x = mul - c0 - c1;
- x %= 255;
-
- y = c1 - mul - 1;
- y %= 255;
-
- if (x == 0)
- x = 255;
- if (y == 0)
- y = 255;
-
- checksum = ((y << 8) | x);
-#endif
-
- /*
- * Now we write this to the packet
- */
- *(csum) = checksum;
-
- /* return the checksum for user usage */
- return checksum;
+ uint16_t checksum;
+ uint32_t c0;
+ uint32_t c1;
+
+ c0 = csum & 0xff00;
+ c1 = csum & 0x00ff;
+
+ /*
+ * If both are zero return correct
+ */
+ if (c0 == 0 && c1 == 0)
+ return 0;
+
+ /*
+ * If either, but not both are zero return incorrect
+ */
+ if (c0 == 0 || c1 == 0)
+ return 1;
+
+ checksum = fletcher_checksum(buffer, len, offset);
+ if (checksum == htons(csum))
+ return 0;
+ return 1;
}
projects / mirror_frr.git / blobdiff