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/*
This file is part of GNUnet.
(C) 2010 Christian Grothoff
GNUnet is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published
by the Free Software Foundation; either version 3, or (at your
option) any later version.
GNUnet 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 GNUnet; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
*/
/**
* @file vpn/gnunet-vpn-checksum.c
* @brief
* @author Philipp Toelke
*/
#include "gnunet-vpn-checksum.h"
uint32_t
calculate_checksum_update (uint32_t sum, uint16_t * hdr, short len)
{
for (; len >= 2; len -= 2)
sum += *(hdr++);
if (len == 1)
sum += *((unsigned char *) hdr);
return sum;
}
uint16_t
calculate_checksum_end (uint32_t sum)
{
while (sum >> 16)
sum = (sum >> 16) + (sum & 0xFFFF);
return ~sum;
}
/**
* Calculate the checksum of an IPv4-Header
*/
uint16_t
calculate_ip_checksum (uint16_t * hdr, short len)
{
uint32_t sum = calculate_checksum_update (0, hdr, len);
return calculate_checksum_end (sum);
}
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