1/*
2 * libjingle
3 * Copyright 2008, Google Inc.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are met:
7 *
8 *  1. Redistributions of source code must retain the above copyright notice,
9 *     this list of conditions and the following disclaimer.
10 *  2. Redistributions in binary form must reproduce the above copyright notice,
11 *     this list of conditions and the following disclaimer in the documentation
12 *     and/or other materials provided with the distribution.
13 *  3. The name of the author may not be used to endorse or promote products
14 *     derived from this software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
17 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
18 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
19 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
20 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
21 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
22 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
23 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
24 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
25 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 */
27
28#include "talk/base/nethelpers.h"
29
30#include "talk/base/byteorder.h"
31#include "talk/base/signalthread.h"
32
33namespace talk_base {
34
35#if defined(LINUX) || defined(ANDROID)
36static const size_t kInitHostentLen = 1024;
37static const size_t kMaxHostentLen = kInitHostentLen * 8;
38#endif
39
40// AsyncResolver
41
42AsyncResolver::AsyncResolver() : result_(NULL), error_(0) {
43}
44
45AsyncResolver::~AsyncResolver() {
46  FreeHostEnt(result_);
47}
48
49void AsyncResolver::DoWork() {
50  result_ = SafeGetHostByName(addr_.hostname().c_str(), &error_);
51}
52
53void AsyncResolver::OnWorkDone() {
54  if (result_) {
55    addr_.SetIP(NetworkToHost32(
56        *reinterpret_cast<uint32*>(result_->h_addr_list[0])));
57  }
58}
59
60// The functions below are used to do gethostbyname, but with an allocated
61// instead of a static buffer.
62hostent* SafeGetHostByName(const char* hostname, int* herrno) {
63  if (NULL == hostname || NULL == herrno) {
64    return NULL;
65  }
66  hostent* result = NULL;
67#if defined(WIN32)
68  // On Windows we have to allocate a buffer, and manually copy the hostent,
69  // along with its embedded pointers.
70  hostent* ent = gethostbyname(hostname);
71  if (!ent) {
72    *herrno = WSAGetLastError();
73    return NULL;
74  }
75
76  // Get the total number of bytes we need to copy, and allocate our buffer.
77  int num_aliases = 0, num_addrs = 0;
78  int total_len = sizeof(hostent);
79  total_len += strlen(ent->h_name) + 1;
80  while (ent->h_aliases[num_aliases]) {
81    total_len += sizeof(char*) + strlen(ent->h_aliases[num_aliases]) + 1;
82    ++num_aliases;
83  }
84  total_len += sizeof(char*);
85  while (ent->h_addr_list[num_addrs]) {
86    total_len += sizeof(char*) + ent->h_length;
87    ++num_addrs;
88  }
89  total_len += sizeof(char*);
90
91  result = static_cast<hostent*>(malloc(total_len));
92  if (NULL == result) {
93    return NULL;
94  }
95  char* p = reinterpret_cast<char*>(result) + sizeof(hostent);
96
97  // Copy the hostent into it, along with its embedded pointers.
98  result->h_name = p;
99  memcpy(p, ent->h_name, strlen(ent->h_name) + 1);
100  p += strlen(ent->h_name) + 1;
101
102  result->h_aliases = reinterpret_cast<char**>(p);
103  p += (num_aliases + 1) * sizeof(char*);
104  for (int i = 0; i < num_aliases; ++i) {
105    result->h_aliases[i] = p;
106    memcpy(p, ent->h_aliases[i], strlen(ent->h_aliases[i]) + 1);
107    p += strlen(ent->h_aliases[i]) + 1;
108  }
109  result->h_aliases[num_aliases] = NULL;
110
111  result->h_addrtype = ent->h_addrtype;
112  result->h_length = ent->h_length;
113
114  result->h_addr_list = reinterpret_cast<char**>(p);
115  p += (num_addrs + 1) * sizeof(char*);
116  for (int i = 0; i < num_addrs; ++i) {
117    result->h_addr_list[i] = p;
118    memcpy(p, ent->h_addr_list[i], ent->h_length);
119    p += ent->h_length;
120  }
121  result->h_addr_list[num_addrs] = NULL;
122
123  *herrno = 0;
124#elif defined(LINUX) || defined(ANDROID)
125  // gethostbyname() is not thread safe, so we need to call gethostbyname_r()
126  // which is a reentrant version of gethostbyname().
127  ASSERT(kInitHostentLen > sizeof(hostent));
128  size_t size = kInitHostentLen;
129  int ret;
130  void* buf = malloc(size);
131  if (NULL == buf) {
132    return NULL;
133  }
134  char* aux = static_cast<char*>(buf) + sizeof(hostent);
135  size_t aux_len = size - sizeof(hostent);
136  while ((ret = gethostbyname_r(hostname, reinterpret_cast<hostent*>(buf), aux,
137      aux_len, &result, herrno)) == ERANGE) {
138    size *= 2;
139    if (size > kMaxHostentLen) {
140      break;  // Just to be safe.
141    }
142    buf = realloc(buf, size);
143    if (NULL == buf) {
144      return NULL;
145    }
146    aux = static_cast<char*>(buf) + sizeof(hostent);
147    aux_len = size - sizeof(hostent);
148  }
149  if (ret != 0 || buf != result) {
150    free(buf);
151    return NULL;
152  }
153  *herrno = 0;
154#elif defined(OSX) || defined(IOS)
155  // Mac OS returns an object with everything allocated.
156  result = getipnodebyname(hostname, AF_INET, AI_DEFAULT, herrno);
157#else
158#error "I don't know how to do gethostbyname safely on your system."
159#endif
160  return result;
161}
162
163// This function should mirror the above function, and free any resources
164// allocated by the above.
165void FreeHostEnt(hostent* host) {
166#if defined(OSX) || defined(IOS)
167  freehostent(host);
168#elif defined(WIN32) || defined(POSIX)
169  free(host);
170#else
171#error "I don't know how to free a hostent on your system."
172#endif
173}
174
175}  // namespace talk_base
176