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/*
* This program is is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License, version 2 of the
* License as published by the Free Software Foundation.
*
* 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., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
*/
/**
* $Id$
* @file net.c
* @brief Functions to parse raw packets.
*
* @author Arran Cudbard-Bell <a.cudbardb@freeradius.org>
* @copyright 2014-2015 Arran Cudbard-Bell <a.cudbardb@freeradius.org>
*/
#include <freeradius-devel/libradius.h>
#include <freeradius-devel/net.h>
/** Calculate UDP checksum
*
* Zero out UDP checksum in UDP header before calling fr_udp_checksum to get 'expected' checksum.
*
* @param data Pointer to the start of the UDP header
* @param len value of udp length field in host byte order. Must be validated to make
* sure it won't overrun data buffer.
* @param checksum current checksum, leave as 0 to just enable validation.
* @param src_addr in network byte order.
* @param dst_addr in network byte order.
* @return 0 if the checksum is correct, else another number.
*/
uint16_t fr_udp_checksum(uint8_t const *data, uint16_t len, uint16_t checksum,
struct in_addr const src_addr, struct in_addr const dst_addr)
{
uint64_t sum = 0; /* using 64bits avoids overflow check */
uint16_t const *p = (uint16_t const *)data;
uint16_t const *ip_src = (void const *) &src_addr.s_addr;
uint16_t const *ip_dst = (void const *) &dst_addr.s_addr;
uint16_t i;
sum += *(ip_src++);
sum += *ip_src;
sum += *(ip_dst++);
sum += *ip_dst;
sum += htons(IPPROTO_UDP);
sum += htons(len);
for (i = len; i > 1; i -= 2) {
sum += *p++;
}
if (i) {
sum += (0xff & *(uint8_t const *)p) << 8;
}
sum -= checksum;
while (sum >> 16) {
sum = (sum & 0xffff) + (sum >> 16);
}
return ((uint16_t) ~sum);
}
/** Calculate IP header checksum.
*
* Zero out IP header checksum in IP header before calling fr_iph_checksum to get 'expected' checksum.
*
* @param data Pointer to the start of the IP header
* @param ihl value of ip header length field (number of 32 bit words)
*/
uint16_t fr_iph_checksum(uint8_t const *data, uint8_t ihl)
{
uint64_t sum = 0;
uint16_t const *p = (uint16_t const *)data;
uint8_t nwords = (ihl << 1); /* number of 16-bit words */
for (sum = 0; nwords > 0; nwords--) {
sum += *p++;
}
sum = (sum >> 16) + (sum & 0xffff);
sum += (sum >> 16);
return ((uint16_t) ~sum);
}
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