1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5
6#include <algorithm>
7#include <iterator>
8#include <map>
9
10#include <fcntl.h>
11#include <netdb.h>
12#include <net/if.h>
13#include <netinet/in.h>
14#include <arpa/inet.h>
15
16#include <string.h>
17
18#include "net_util.h"
19
20namespace net {
21
22#ifndef INET6_ADDRSTRLEN  /* for non IPv6 machines */
23#define INET6_ADDRSTRLEN 46
24#endif
25
26bool ParseIPLiteralToNumber(const std::string& ip_literal,
27                            IPAddressNumber* ip_number) {
28  char buf[sizeof(struct in6_addr)];
29  int size = sizeof(struct in_addr);
30  int mode = AF_INET;
31  if (ip_literal.find(':') != std::string::npos) {
32    mode = AF_INET6;
33    size = sizeof(struct in6_addr);
34  }
35  if (inet_pton(mode, ip_literal.c_str(), buf) != 1) {
36    return false;
37  }
38  ip_number->resize(size);
39  for (int i = 0; i < size; i++) {
40    (*ip_number)[i] = buf[i];
41  }
42  return true;
43}
44
45IPAddressNumber ConvertIPv4NumberToIPv6Number(
46    const IPAddressNumber& ipv4_number) {
47  // IPv4-mapped addresses are formed by:
48  // <80 bits of zeros>  + <16 bits of ones> + <32-bit IPv4 address>.
49  IPAddressNumber ipv6_number;
50  ipv6_number.reserve(16);
51  ipv6_number.insert(ipv6_number.end(), 10, 0);
52  ipv6_number.push_back(0xFF);
53  ipv6_number.push_back(0xFF);
54  ipv6_number.insert(ipv6_number.end(), ipv4_number.begin(), ipv4_number.end());
55  return ipv6_number;
56}
57
58bool ParseCIDRBlock(const std::string& cidr_literal,
59                    IPAddressNumber* ip_number,
60                    size_t* prefix_length_in_bits) {
61  // We expect CIDR notation to match one of these two templates:
62  //   <IPv4-literal> "/" <number of bits>
63  //   <IPv6-literal> "/" <number of bits>
64
65  std::vector<std::string> parts;
66  unsigned int split = cidr_literal.find('/');
67  if (split == std::string::npos)
68    return false;
69  parts.push_back(cidr_literal.substr(0, split));
70  parts.push_back(cidr_literal.substr(split + 1));
71  if (parts[1].find('/') != std::string::npos)
72    return false;
73
74  // Parse the IP address.
75  if (!ParseIPLiteralToNumber(parts[0], ip_number))
76    return false;
77
78  // Parse the prefix length.
79  int number_of_bits = atoi(parts[1].c_str());
80
81  // Make sure the prefix length is in a valid range.
82  if (number_of_bits < 0 ||
83      number_of_bits > static_cast<int>(ip_number->size() * 8))
84    return false;
85
86  *prefix_length_in_bits = static_cast<size_t>(number_of_bits);
87  return true;
88}
89
90bool IPNumberMatchesPrefix(const IPAddressNumber& ip_number,
91                           const IPAddressNumber& ip_prefix,
92                           size_t prefix_length_in_bits) {
93  // Both the input IP address and the prefix IP address should be
94  // either IPv4 or IPv6.
95
96  // In case we have an IPv6 / IPv4 mismatch, convert the IPv4 addresses to
97  // IPv6 addresses in order to do the comparison.
98  if (ip_number.size() != ip_prefix.size()) {
99    if (ip_number.size() == 4) {
100      return IPNumberMatchesPrefix(ConvertIPv4NumberToIPv6Number(ip_number),
101                                   ip_prefix, prefix_length_in_bits);
102    }
103    return IPNumberMatchesPrefix(ip_number,
104                                 ConvertIPv4NumberToIPv6Number(ip_prefix),
105                                 96 + prefix_length_in_bits);
106  }
107
108  // Otherwise we are comparing two IPv4 addresses, or two IPv6 addresses.
109  // Compare all the bytes that fall entirely within the prefix.
110  int num_entire_bytes_in_prefix = prefix_length_in_bits / 8;
111  for (int i = 0; i < num_entire_bytes_in_prefix; ++i) {
112    if (ip_number[i] != ip_prefix[i])
113      return false;
114  }
115
116  // In case the prefix was not a multiple of 8, there will be 1 byte
117  // which is only partially masked.
118  int remaining_bits = prefix_length_in_bits % 8;
119  if (remaining_bits != 0) {
120    unsigned char mask = 0xFF << (8 - remaining_bits);
121    int i = num_entire_bytes_in_prefix;
122    if ((ip_number[i] & mask) != (ip_prefix[i] & mask))
123      return false;
124  }
125
126  return true;
127}
128
129}  // namespace net
130