| /* |
| * It has originally been taken from the FreeBSD project. |
| * |
| * Copyright (c) 2001 Charles Mott <cm@linktel.net> |
| * Copyright (c) 2008 coresystems GmbH |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND |
| * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| * SUCH DAMAGE. |
| */ |
| |
| #include <stddef.h> |
| #include <stdint.h> |
| |
| uint16_t ipchecksum(const void *_ptr, size_t nbytes, uint16_t _sum) |
| { |
| uint32_t sum = (uint16_t)~_sum; |
| const uint16_t *ptr = _ptr; |
| |
| while (nbytes > 1) { |
| sum += *ptr++; |
| nbytes -= 2; |
| } |
| if (nbytes) |
| sum += (uint32_t)*(uint8_t *)ptr; |
| while (sum > 0xffff) |
| sum = (sum >> 16) + (sum & 0xffff); |
| return ~sum; |
| } |