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Checksum computation

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This commit is contained in:
Michal Zima 2012-04-01 16:22:54 +02:00
parent aee57c680a
commit 19d5a22c18
3 changed files with 183 additions and 0 deletions
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1
src/Makefile.am
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@ -2,6 +2,7 @@ sbin_PROGRAMS = wrapsix-dnsproxy wrapsix-wrapper
wrapsix_dnsproxy_SOURCES = dnsproxy.c
wrapsix_wrapper_SOURCES = \
arp.c arp.h \
checksum.c checksum.h \
ipv6.c ipv6.h \
ipv4.h \
nat.c nat.h \

149
src/checksum.c Normal file
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@ -0,0 +1,149 @@
/*
* WrapSix
* Copyright (C) 2008-2012 Michal Zima <xhire@mujmalysvet.cz>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <netinet/in.h> /* htonl */
#include <stdio.h>
#include <stdlib.h> /* malloc */
#include <string.h> /* memcpy */
#include "checksum.h"
#include "ipv4.h"
#include "ipv6.h"
/**
* General checksum computation function
*
* @param data Pointer to data of which to compute the checksum
* @param length Length of the data (in bytes)
*
* @return Checksum
*/
unsigned short checksum(const void *data, int length)
{
const unsigned short *buf = data;
unsigned int sum = 0;
while (length >= 2) {
sum += *buf++;
if (sum & 0x80000000) {
sum = (sum & 0xffff) + (sum >> 16);
}
length -= 2;
}
if (length) {
unsigned char temp[2];
temp[0] = *(unsigned char *) buf;
temp[1] = 0;
sum += *(unsigned short *) temp;
}
while (sum >> 16) {
sum = (sum & 0xffff) + (sum >> 16);
}
return ~sum;
}
/**
* IPv4 checksum computation function
*
* @param ip_src Source IPv4 address
* @param ip_dest Destination IPv4 address
* @param length Length of the payload (in bytes)
* @param proto Protocol in the payload
* @param payload Pointer to payload data
*
* @return Checksum
*/
unsigned short checksum_ipv4(struct s_ipv4_addr ip_src,
struct s_ipv4_addr ip_dest,
unsigned short length, unsigned char proto,
unsigned char *payload)
{
unsigned char *buffer;
struct s_ipv4_pseudo *header;
unsigned short sum;
if ((buffer = malloc(sizeof(struct s_ipv4_pseudo) + length)) == NULL) {
fprintf(stderr, "[Error] Lack of free memory\n");
return 0;
}
header = (struct s_ipv4_pseudo *) buffer;
header->ip_src = ip_src;
header->ip_dest = ip_dest;
header->zeros = 0x0;
header->proto = proto;
header->len = htonl((unsigned int) length);
memcpy(buffer + sizeof(struct s_ipv4_pseudo), payload, (int) length);
sum = checksum(buffer, sizeof(struct s_ipv6_pseudo) + (int) length);
free(buffer);
return sum;
}
/**
* IPv6 checksum computation function
*
* @param ip_src Source IPv6 address
* @param ip_dest Destionation IPv6 address
* @param length Length of the payload (in bytes)
* @param proto Protocol in the payload
* @param payload Pointer to payload data
*
* @return Checksum
*/
unsigned short checksum_ipv6(struct s_ipv6_addr ip_src,
struct s_ipv6_addr ip_dest,
unsigned short length, unsigned char proto,
unsigned char *payload)
{
unsigned char *buffer;
struct s_ipv6_pseudo *header;
unsigned short sum;
if ((buffer = malloc(sizeof(struct s_ipv6_pseudo) + length)) == NULL) {
fprintf(stderr, "[Error] Lack of free memory\n");
return 0;
}
header = (struct s_ipv6_pseudo *) buffer;
header->ip_src = ip_src;
header->ip_dest = ip_dest;
header->len = htonl((unsigned int) length);
header->zeros = 0x0;
header->next_header = proto;
memcpy(buffer + sizeof(struct s_ipv6_pseudo), payload, (int) length);
sum = checksum(buffer, sizeof(struct s_ipv6_pseudo) + (int) length);
free(buffer);
return sum;
}

33
src/checksum.h Normal file
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@ -0,0 +1,33 @@
/*
* WrapSix
* Copyright (C) 2008-2012 Michal Zima <xhire@mujmalysvet.cz>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef CHECKSUM_H
#define CHECKSUM_H
#include "ipv4.h"
#include "ipv6.h"
unsigned short checksum(const void *data, int length);
unsigned short checksum_ipv4(struct s_ipv4_addr ip_src,
struct s_ipv4_addr ip_dest, unsigned short length,
unsigned char proto, unsigned char *payload);
unsigned short checksum_ipv6(struct s_ipv6_addr ip_src,
struct s_ipv6_addr ip_dest, unsigned short length,
unsigned char proto, unsigned char *payload);
#endif /* CHECKSUM_H */