src/cidr.c

   1 /* For terms of usage/redistribution/modification see the LICENSE file */
   2 /* For authors and contributors see the AUTHORS file */
   3
   4 #include "iptraf-ng-compat.h"
   5
   6 // TODO: full rewrite
   7
   8 /*
   9  * Returns a binary subnet mask based on the number of mask bits.  The
  10  * dotted-decimal notation may be obtained with inet_ntoa.
  11  */
  12 unsigned long cidr_get_mask(unsigned int maskbits)
  13 {
  14         struct in_addr mask;
  15
  16         if (maskbits == 0)
  17                 return 0;
  18
  19         inet_aton("255.255.255.255", &mask);
  20         mask.s_addr = htonl(mask.s_addr << (32 - maskbits));
  21
  22         return mask.s_addr;
  23 }
  24
  25 /*
  26  * Returns a subnet mask in dotted-decimal notation given the number of
  27  * 1-bits in the mask.
  28  */
  29 char *cidr_get_quad_mask(unsigned int maskbits)
  30 {
  31         struct in_addr addr;
  32
  33         addr.s_addr = cidr_get_mask(maskbits);
  34         return inet_ntoa(addr);
  35 }
  36
  37 /*
  38  * Returns the number of 1-bits in the given binary subnet mask in
  39  * network byte order.
  40  */
  41 unsigned int cidr_get_maskbits(unsigned long mask)
  42 {
  43         unsigned int i = 32;
  44
  45         if (mask == 0)
  46                 return 0;
  47
  48         mask = ntohl(mask);
  49         while (mask % 2 == 0) {
  50                 mask >>= 1;
  51                 i--;
  52         }
  53
  54         return i;
  55 }
  56
  57 /*
  58  * Parse and cut off mask from CIDR-style address/mask string. In case of
  59  * absent or invalid input in the mask, 255 is returned in *maskbits
  60  * (255 is invalid for an IPv4 address).
  61  */
  62 void cidr_split_address(char *cidr_addr, unsigned int *maskbits)
  63 {
  64         char *slashptr = strchr(cidr_addr, '/');
  65         if (slashptr == NULL) {
  66                 *maskbits = 255;
  67                 return;
  68         }
  69
  70         /*
  71          * Cut out the mask part and move past the slash
  72          */
  73         *slashptr = '\0';
  74         slashptr++;
  75
  76         if (*slashptr != '\0') {
  77                 unsigned long val;
  78                 char *endptr;
  79
  80                 val = strtoul(slashptr, &endptr, 10);
  81                 if (val > UINT_MAX)
  82                         val = UINT_MAX;
  83                 *maskbits = (unsigned int)val;
  84                 if (*endptr != '\0')
  85                         *maskbits = 255;
  86         } else
  87                 *maskbits = 255;
  88
  89         return;
  90 }