net/dns/dns_config_watcher_mac.cc

   1 // Copyright 2014 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 #include "net/dns/dns_config_watcher_mac.h"
   6
   7 #include <dlfcn.h>
   8
   9 #include "base/lazy_instance.h"
  10 #include "third_party/apple_apsl/dnsinfo.h"
  11
  12 namespace {
  13
  14 // dnsinfo symbols are available via libSystem.dylib, but can also be present in
  15 // SystemConfiguration.framework. To avoid confusion, load them explicitly from
  16 // libSystem.dylib.
  17 class DnsInfoApi {
  18  public:
  19   typedef const char* (*dns_configuration_notify_key_t)();
  20   typedef dns_config_t* (*dns_configuration_copy_t)();
  21   typedef void (*dns_configuration_free_t)(dns_config_t*);
  22
  23   DnsInfoApi()
  24       : dns_configuration_notify_key(NULL),
  25         dns_configuration_copy(NULL),
  26         dns_configuration_free(NULL) {
  27     handle_ = dlopen("/usr/lib/libSystem.dylib",
  28                      RTLD_LAZY | RTLD_NOLOAD);
  29     if (!handle_)
  30       return;
  31     dns_configuration_notify_key =
  32         reinterpret_cast<dns_configuration_notify_key_t>(
  33             dlsym(handle_, "dns_configuration_notify_key"));
  34     dns_configuration_copy =
  35         reinterpret_cast<dns_configuration_copy_t>(
  36             dlsym(handle_, "dns_configuration_copy"));
  37     dns_configuration_free =
  38         reinterpret_cast<dns_configuration_free_t>(
  39             dlsym(handle_, "dns_configuration_free"));
  40   }
  41
  42   ~DnsInfoApi() {
  43     if (handle_)
  44       dlclose(handle_);
  45   }
  46
  47   dns_configuration_notify_key_t dns_configuration_notify_key;
  48   dns_configuration_copy_t dns_configuration_copy;
  49   dns_configuration_free_t dns_configuration_free;
  50
  51  private:
  52   void* handle_;
  53 };
  54
  55 const DnsInfoApi& GetDnsInfoApi() {
  56   static base::LazyInstance<DnsInfoApi>::Leaky api = LAZY_INSTANCE_INITIALIZER;
  57   return api.Get();
  58 }
  59
  60 struct DnsConfigTDeleter {
  61   inline void operator()(dns_config_t* ptr) const {
  62     if (GetDnsInfoApi().dns_configuration_free)
  63       GetDnsInfoApi().dns_configuration_free(ptr);
  64   }
  65 };
  66
  67 }  // namespace
  68
  69 namespace net {
  70 namespace internal {
  71
  72 bool DnsConfigWatcher::Watch(
  73     const base::Callback<void(bool succeeded)>& callback) {
  74   if (!GetDnsInfoApi().dns_configuration_notify_key)
  75     return false;
  76   return watcher_.Watch(GetDnsInfoApi().dns_configuration_notify_key(),
  77                         callback);
  78 }
  79
  80 // static
  81 ConfigParsePosixResult DnsConfigWatcher::CheckDnsConfig() {
  82   if (!GetDnsInfoApi().dns_configuration_copy)
  83     return CONFIG_PARSE_POSIX_NO_DNSINFO;
  84   scoped_ptr<dns_config_t, DnsConfigTDeleter> dns_config(
  85       GetDnsInfoApi().dns_configuration_copy());
  86   if (!dns_config)
  87     return CONFIG_PARSE_POSIX_NO_DNSINFO;
  88
  89   // TODO(szym): Parse dns_config_t for resolvers rather than res_state.
  90   // DnsClient can't handle domain-specific unscoped resolvers.
  91   unsigned num_resolvers = 0;
  92   for (int i = 0; i < dns_config->n_resolver; ++i) {
  93     dns_resolver_t* resolver = dns_config->resolver[i];
  94     if (!resolver->n_nameserver)
  95       continue;
  96     if (resolver->options && !strcmp(resolver->options, "mdns"))
  97       continue;
  98     ++num_resolvers;
  99   }
 100   if (num_resolvers > 1)
 101     return CONFIG_PARSE_POSIX_UNHANDLED_OPTIONS;
 102   return CONFIG_PARSE_POSIX_OK;
 103 }
 104
 105 }  // namespace internal
 106 }  // namespace net