net/checksum.c

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