package/network/ipv6/6rd/src/6rdcalc.c

   1 /*
   2  * Utility used to calculate the 6rd subnet.
   3  *
   4  * Copyright 2012, Stéphan Kochen <stephan@kochen.nl>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version 2
   9  * of the License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19  */
  20
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/errno.h>
  25 #include <arpa/inet.h>
  26 #include <netinet/in.h>
  27
  28 #define INET_PREFIXSTRLEN (INET_ADDRSTRLEN+3)
  29 #define INET6_PREFIXSTRLEN (INET6_ADDRSTRLEN+4)
  30
  31 static void print_usage()
  32 {
  33         fprintf(stderr, "Usage: 6rdcalc <v6 prefix>/<mask> <v4 address>/<mask>\n");
  34         exit(1);
  35 }
  36
  37 static void print_error()
  38 {
  39         fprintf(stderr, "%s", strerror(errno));
  40         exit(1);
  41 }
  42
  43 static void parse_str(int af, char *str, void *addr, unsigned long *mask)
  44 {
  45         int ret;
  46         char *slash;
  47
  48         /* Split the address at the slash. */
  49         if ((slash = strchr(str, '/')) == NULL)
  50                 print_usage();
  51         *slash = '\0';
  52
  53         /* Parse the address. */
  54         if ((ret = inet_pton(af, str, addr)) != 1) {
  55                 if (ret == 0)
  56                         print_usage();
  57                 else
  58                         print_error();
  59         }
  60
  61         /* Parse the mask. */
  62         *mask = strtoul(slash+1, NULL, 10);
  63         if ((af == AF_INET  && *mask >  32) ||
  64                 (af == AF_INET6 && *mask > 128))
  65                 print_usage();
  66 }
  67
  68 int main(int argc, const char **argv)
  69 {
  70         char v6str[INET6_PREFIXSTRLEN], v4str[INET_PREFIXSTRLEN];
  71         struct in6_addr v6;
  72         struct in_addr v4;
  73         unsigned long v6it, v4it, mask;
  74         unsigned char *byte4, *byte6;
  75         unsigned char bit4, bit6;
  76
  77         /* Check parameters. */
  78         if (argc != 3)
  79                 print_usage();
  80
  81         /* Parse the v6 address. */
  82         strncpy(v6str, argv[1], INET6_PREFIXSTRLEN);
  83         v6str[INET6_PREFIXSTRLEN-1] = '\0';
  84         parse_str(AF_INET6, v6str, &v6, &v6it);
  85
  86         /* Parse the v4 address */
  87         strncpy(v4str, argv[2], INET_PREFIXSTRLEN);
  88         v6str[INET_PREFIXSTRLEN-1] = '\0';
  89         parse_str(AF_INET, v4str, &v4, &v4it);
  90
  91         /* Check if the combined mask is within bounds. */
  92         mask = (32 - v4it) + v6it;
  93         if (mask > 128)
  94                 print_usage();
  95
  96         /* Combine the addresses. */
  97         while (v4it < 32) {
  98                 byte6 = (unsigned char *)(&v6.s6_addr) + (v6it >> 3);
  99                 byte4 = (unsigned char *)(&v4.s_addr)  + (v4it >> 3);
 100                 bit6 = 128 >> (v6it & 0x07);
 101                 bit4 = 128 >> (v4it & 0x07);
 102
 103                 if (*byte4 & bit4)
 104                         *byte6 |= bit6;
 105                 else
 106                         *byte6 &= ~bit6;
 107
 108                 v4it++; v6it++;
 109         }
 110
 111         /* Clear remaining bits. */
 112         while (v6it < 128) {
 113                 byte6 = (unsigned char *)(&v6.s6_addr) + (v6it >> 2);
 114                 bit6 = 128 >> (v6it & 0x07);
 115
 116                 *byte6 &= ~bit6;
 117
 118                 v6it++;
 119         }
 120
 121         /* Print the subnet prefix. */
 122         if (inet_ntop(AF_INET6, &v6, v6str, sizeof(v6str)) == NULL)
 123                 print_error();
 124         printf("%s/%lu\n", v6str, mask);
 125         return 0;
 126 }