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/*
* Utility used to calculate the 6rd subnet.
*
* Copyright 2012, Stéphan Kochen <stephan@kochen.nl>
*
* This program 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 2
* 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 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/errno.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#define INET_PREFIXSTRLEN (INET_ADDRSTRLEN+3)
#define INET6_PREFIXSTRLEN (INET6_ADDRSTRLEN+4)
static void print_usage()
{
fprintf(stderr, "Usage: 6rdcalc <v6 prefix>/<mask> <v4 address>/<mask>\n");
exit(1);
}
static void print_error()
{
fprintf(stderr, "%s", strerror(errno));
exit(1);
}
static void parse_str(int af, char *str, void *addr, unsigned long *mask)
{
int ret;
char *slash;
/* Split the address at the slash. */
if ((slash = strchr(str, '/')) == NULL)
print_usage();
*slash = '\0';
/* Parse the address. */
if ((ret = inet_pton(af, str, addr)) != 1) {
if (ret == 0)
print_usage();
else
print_error();
}
/* Parse the mask. */
*mask = strtoul(slash+1, NULL, 10);
if ((af == AF_INET && *mask > 32) ||
(af == AF_INET6 && *mask > 128))
print_usage();
}
int main(int argc, const char **argv)
{
char v6str[INET6_PREFIXSTRLEN], v4str[INET_PREFIXSTRLEN];
struct in6_addr v6;
struct in_addr v4;
unsigned long v6it, v4it, mask;
unsigned char *byte4, *byte6;
unsigned char bit4, bit6;
/* Check parameters. */
if (argc != 3)
print_usage();
/* Parse the v6 address. */
strncpy(v6str, argv[1], INET6_PREFIXSTRLEN);
v6str[INET6_PREFIXSTRLEN-1] = '\0';
parse_str(AF_INET6, v6str, &v6, &v6it);
/* Parse the v4 address */
strncpy(v4str, argv[2], INET_PREFIXSTRLEN);
v6str[INET_PREFIXSTRLEN-1] = '\0';
parse_str(AF_INET, v4str, &v4, &v4it);
/* Check if the combined mask is within bounds. */
mask = (32 - v4it) + v6it;
if (mask > 128)
print_usage();
/* Combine the addresses. */
while (v4it < 32) {
byte6 = (unsigned char *)(&v6.s6_addr) + (v6it >> 3);
byte4 = (unsigned char *)(&v4.s_addr) + (v4it >> 3);
bit6 = 128 >> (v6it & 0x07);
bit4 = 128 >> (v4it & 0x07);
if (*byte4 & bit4)
*byte6 |= bit6;
else
*byte6 &= ~bit6;
v4it++; v6it++;
}
/* Clear remaining bits. */
while (v6it < 128) {
byte6 = (unsigned char *)(&v6.s6_addr) + (v6it >> 2);
bit6 = 128 >> (v6it & 0x07);
*byte6 &= ~bit6;
v6it++;
}
/* Print the subnet prefix. */
if (inet_ntop(AF_INET6, &v6, v6str, sizeof(v6str)) == NULL)
print_error();
printf("%s/%lu\n", v6str, mask);
return 0;
}
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