path: root/net/base/host_resolver.cc

// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/base/host_resolver.h"

#if defined(OS_WIN)
#include <ws2tcpip.h>
#include <wspiapi.h>  // Needed for Win2k compat.
#elif defined(OS_POSIX)
#include <netdb.h>
#include <sys/socket.h>
#endif

#include "base/message_loop.h"
#include "base/string_util.h"
#include "base/worker_pool.h"
#include "net/base/address_list.h"
#include "net/base/net_errors.h"

#if defined(OS_WIN)
#include "net/base/winsock_init.h"
#endif

namespace net {

//-----------------------------------------------------------------------------

static HostMapper* host_mapper;

std::string HostMapper::MapUsingPrevious(const std::string& host) {
  return previous_mapper_.get() ? previous_mapper_->Map(host) : host;
}

HostMapper* SetHostMapper(HostMapper* value) {
  std::swap(host_mapper, value);
  return value;
}

static int HostResolverProc(
    const std::string& host, const std::string& port, struct addrinfo** out) {
  struct addrinfo hints = {0};
  hints.ai_family = AF_UNSPEC;

  // DO NOT USE AI_ADDRCONFIG.
  //
  // The following comment in <winsock2.h> is the best documentation I found
  // on AI_ADDRCONFIG for Windows:
  //   Flags used in "hints" argument to getaddrinfo()
  //       - AI_ADDRCONFIG is supported starting with Vista
  //       - default is AI_ADDRCONFIG ON whether the flag is set or not
  //         because the performance penalty in not having ADDRCONFIG in
  //         the multi-protocol stack environment is severe;
  //         this defaulting may be disabled by specifying the AI_ALL flag,
  //         in that case AI_ADDRCONFIG must be EXPLICITLY specified to
  //         enable ADDRCONFIG behavior
  //
  // Not only is AI_ADDRCONFIG unnecessary, but it can be harmful.  If the
  // computer is not connected to a network, AI_ADDRCONFIG causes getaddrinfo
  // to fail with WSANO_DATA (11004) for "localhost", probably because of the
  // following note on AI_ADDRCONFIG in the MSDN getaddrinfo page:
  //   The IPv4 or IPv6 loopback address is not considered a valid global
  //   address.
  // See http://crbug.com/5234.
  hints.ai_flags = 0;

  // Restrict result set to only this socket type to avoid duplicates.
  hints.ai_socktype = SOCK_STREAM;

  int err = getaddrinfo(host.c_str(), port.c_str(), &hints, out);
  return err ? ERR_NAME_NOT_RESOLVED : OK;
}

static int ResolveAddrInfo(HostMapper* mapper, const std::string& host,
                           const std::string& port, struct addrinfo** out) {
  if (mapper) {
    std::string mapped_host = mapper->Map(host);

    if (mapped_host.empty())
      return ERR_NAME_NOT_RESOLVED;

    return HostResolverProc(mapped_host, port, out);
  } else {
    return HostResolverProc(host, port, out);
  }
}

//-----------------------------------------------------------------------------

class HostResolver::Request :
    public base::RefCountedThreadSafe<HostResolver::Request> {
 public:
  Request(HostResolver* resolver,
          const std::string& host,
          const std::string& port,
          AddressList* addresses,
          CompletionCallback* callback)
      : host_(host),
        port_(port),
        resolver_(resolver),
        addresses_(addresses),
        callback_(callback),
        origin_loop_(MessageLoop::current()),
        host_mapper_(host_mapper),
        error_(OK),
        results_(NULL) {
  }

  ~Request() {
    if (results_)
      freeaddrinfo(results_);
  }

  void DoLookup() {
    // Running on the worker thread
    error_ = ResolveAddrInfo(host_mapper_, host_, port_, &results_);

    Task* reply = NewRunnableMethod(this, &Request::DoCallback);

    // The origin loop could go away while we are trying to post to it, so we
    // need to call its PostTask method inside a lock.  See ~HostResolver.
    {
      AutoLock locked(origin_loop_lock_);
      if (origin_loop_) {
        origin_loop_->PostTask(FROM_HERE, reply);
        reply = NULL;
      }
    }

    // Does nothing if it got posted.
    delete reply;
  }

  void DoCallback() {
    // Running on the origin thread.
    DCHECK(error_ || results_);

    // We may have been cancelled!
    if (!resolver_)
      return;

    if (!error_) {
      addresses_->Adopt(results_);
      results_ = NULL;
    }

    // Drop the resolver's reference to us.  Do this before running the
    // callback since the callback might result in the resolver being
    // destroyed.
    resolver_->request_ = NULL;

    callback_->Run(error_);
  }

  void Cancel() {
    resolver_ = NULL;

    AutoLock locked(origin_loop_lock_);
    origin_loop_ = NULL;
  }

 private:
  // Set on the origin thread, read on the worker thread.
  std::string host_;
  std::string port_;

  // Only used on the origin thread (where Resolve was called).
  HostResolver* resolver_;
  AddressList* addresses_;
  CompletionCallback* callback_;

  // Used to post ourselves onto the origin thread.
  Lock origin_loop_lock_;
  MessageLoop* origin_loop_;

  // Hold an owning reference to the host mapper that we are going to use.
  // This may not be the current host mapper by the time we call
  // ResolveAddrInfo, but that's OK... we'll use it anyways, and the owning
  // reference ensures that it remains valid until we are done.
  scoped_refptr<HostMapper> host_mapper_;

  // Assigned on the worker thread, read on the origin thread.
  int error_;
  struct addrinfo* results_;
};

//-----------------------------------------------------------------------------

HostResolver::HostResolver() {
#if defined(OS_WIN)
  EnsureWinsockInit();
#endif
}

HostResolver::~HostResolver() {
  if (request_)
    request_->Cancel();
}

int HostResolver::Resolve(const std::string& hostname, int port,
                          AddressList* addresses,
                          CompletionCallback* callback) {
  DCHECK(!request_) << "resolver already in use";

  const std::string& port_str = IntToString(port);

  // Do a synchronous resolution.
  if (!callback) {
    struct addrinfo* results;
    int rv = ResolveAddrInfo(host_mapper, hostname, port_str, &results);
    if (rv == OK)
      addresses->Adopt(results);
    return rv;
  }

  request_ = new Request(this, hostname, port_str, addresses, callback);

  // Dispatch to worker thread...
  if (!WorkerPool::PostTask(FROM_HERE,
          NewRunnableMethod(request_.get(), &Request::DoLookup), true)) {
    NOTREACHED();
    request_ = NULL;
    return ERR_FAILED;
  }

  return ERR_IO_PENDING;
}

}  // namespace net