wsutil/inet_cidr.c

   1 /* ipv4.c
   2  *
   3  * Wireshark - Network traffic analyzer
   4  * By Gerald Combs <gerald@wireshark.org>
   5  * Copyright 1998 Gerald Combs
   6  *
   7  * SPDX-License-Identifier: GPL-2.0-or-later
   8  */
   9
  10 #include "inet_cidr.h"
  11
  12
  13 uint32_t
  14 ws_ipv4_get_subnet_mask(const uint32_t mask_length)
  15 {
  16         static const uint32_t masks[33] = {
  17                 0x00000000,
  18                 0x80000000, 0xc0000000, 0xe0000000, 0xf0000000,
  19                 0xf8000000, 0xfc000000, 0xfe000000, 0xff000000,
  20                 0xff800000, 0xffc00000, 0xffe00000, 0xfff00000,
  21                 0xfff80000, 0xfffc0000, 0xfffe0000, 0xffff0000,
  22                 0xffff8000, 0xffffc000, 0xffffe000, 0xfffff000,
  23                 0xfffff800, 0xfffffc00, 0xfffffe00, 0xffffff00,
  24                 0xffffff80, 0xffffffc0, 0xffffffe0, 0xfffffff0,
  25                 0xfffffff8, 0xfffffffc, 0xfffffffe, 0xffffffff,
  26         };
  27
  28         ws_assert(mask_length <= 32);
  29
  30         return masks[mask_length];
  31 }
  32
  33 static int
  34 compare_ipv4(const ipv4_addr_and_mask *a, const ipv4_addr_and_mask *b)
  35 {
  36     uint32_t addr_a, addr_b, nmask;
  37
  38     nmask = MIN(a->nmask, b->nmask);
  39     addr_a = a->addr & nmask;
  40     addr_b = b->addr & nmask;
  41     if (addr_a < addr_b)
  42         return -1;
  43     if (addr_a > addr_b)
  44         return 1;
  45     return 0;
  46 }
  47
  48 void
  49 ws_ipv4_addr_and_mask_init(ipv4_addr_and_mask *dst, ws_in4_addr src_addr, int src_bits)
  50 {
  51     dst->addr = g_ntohl(src_addr);
  52     dst->nmask = ws_ipv4_get_subnet_mask(src_bits);
  53 }
  54
  55 bool
  56 ws_ipv4_addr_and_mask_contains(const ipv4_addr_and_mask *ipv4, const ws_in4_addr *in_addr)
  57 {
  58     ipv4_addr_and_mask addr_and_mask;
  59
  60     addr_and_mask.addr = g_ntohl(*in_addr);
  61     addr_and_mask.nmask = ws_ipv4_get_subnet_mask(32);
  62     return compare_ipv4(ipv4, &addr_and_mask) == 0;
  63 }
  64
  65 static const uint8_t bitmasks[9] =
  66     { 0x00, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe, 0xff };
  67
  68 static int
  69 compare_ipv6(const ipv6_addr_and_prefix *a, const ipv6_addr_and_prefix *b)
  70 {
  71     uint32_t prefix;
  72     int pos = 0;
  73
  74     prefix = MIN(a->prefix, b->prefix); /* MIN() like IPv4 */
  75     prefix = MIN(prefix, 128);          /* sanitize, max prefix is 128 */
  76
  77     while (prefix >= 8) {
  78         int byte_a = (int) (a->addr.bytes[pos]);
  79         int byte_b = (int) (b->addr.bytes[pos]);
  80
  81         if (byte_a != byte_b) {
  82             return byte_a - byte_b;
  83         }
  84
  85         prefix -= 8;
  86         pos++;
  87     }
  88
  89     if (prefix != 0) {
  90         int byte_a = (int) (a->addr.bytes[pos] & (bitmasks[prefix]));
  91         int byte_b = (int) (b->addr.bytes[pos] & (bitmasks[prefix]));
  92
  93         if (byte_a != byte_b) {
  94             return byte_a - byte_b;
  95         }
  96     }
  97
  98     return 0;
  99 }
 100
 101
 102 bool
 103 ws_ipv6_addr_and_prefix_contains(const ipv6_addr_and_prefix *ipv6, const ws_in6_addr *in_addr)
 104 {
 105     ipv6_addr_and_prefix addr_and_mask;
 106
 107     addr_and_mask.addr = *in_addr;
 108     addr_and_mask.prefix = 128;
 109     return compare_ipv6(ipv6, &addr_and_mask) == 0;
 110 }