net/checksum.c

   1 /*
   2  * This file was originally taken from the FreeBSD project.
   3  *
   4  * Copyright (c) 2001 Charles Mott <cm@linktel.net>
   5  * Copyright (c) 2008 coresystems GmbH
   6  * All rights reserved.
   7  *
   8  * SPDX-License-Identifier:     BSD-2-Clause
   9  */
  10
  11 #include <common.h>
  12 #include <net.h>
  13
  14 unsigned compute_ip_checksum(const void *vptr, unsigned nbytes)
  15 {
  16         int sum, oddbyte;
  17         const unsigned short *ptr = vptr;
  18
  19         sum = 0;
  20         while (nbytes > 1) {
  21                 sum += *ptr++;
  22                 nbytes -= 2;
  23         }
  24         if (nbytes == 1) {
  25                 oddbyte = 0;
  26                 ((u8 *)&oddbyte)[0] = *(u8 *)ptr;
  27                 ((u8 *)&oddbyte)[1] = 0;
  28                 sum += oddbyte;
  29         }
  30         sum = (sum >> 16) + (sum & 0xffff);
  31         sum += (sum >> 16);
  32         sum = ~sum & 0xffff;
  33
  34         return sum;
  35 }
  36
  37 unsigned add_ip_checksums(unsigned offset, unsigned sum, unsigned new)
  38 {
  39         unsigned long checksum;
  40
  41         sum = ~sum & 0xffff;
  42         new = ~new & 0xffff;
  43         if (offset & 1) {
  44                 /*
  45                  * byte-swap the sum if it came from an odd offset; since the
  46                  * computation is endian independant this works.
  47                  */
  48                 new = ((new >> 8) & 0xff) | ((new << 8) & 0xff00);
  49         }
  50         checksum = sum + new;
  51         if (checksum > 0xffff)
  52                 checksum -= 0xffff;
  53
  54         return (~checksum) & 0xffff;
  55 }
  56
  57 int ip_checksum_ok(const void *addr, unsigned nbytes)
  58 {
  59         return !(compute_ip_checksum(addr, nbytes) & 0xfffe);
  60 }