src/base/net/reverseresolution.cpp

   1 /*
   2  * Bittorrent Client using Qt and libtorrent.
   3  * Copyright (C) 2006  Christophe Dumez <chris@qbittorrent.org>
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License
   7  * as published by the Free Software Foundation; either version 2
   8  * of the License, or (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  18  *
  19  * In addition, as a special exception, the copyright holders give permission to
  20  * link this program with the OpenSSL project's "OpenSSL" library (or with
  21  * modified versions of it that use the same license as the "OpenSSL" library),
  22  * and distribute the linked executables. You must obey the GNU General Public
  23  * License in all respects for all of the code used other than "OpenSSL".  If you
  24  * modify file(s), you may extend this exception to your version of the file(s),
  25  * but you are not obligated to do so. If you do not wish to do so, delete this
  26  * exception statement from your version.
  27  */
  28
  29 #include "reverseresolution.h"
  30
  31 #include <QHostInfo>
  32 #include <QString>
  33
  34 const int CACHE_SIZE = 2048;
  35
  36 using namespace Net;
  37
  38 namespace
  39 {
  40     bool isUsefulHostName(const QString &hostname, const QHostAddress &ip)
  41     {
  42         return (!hostname.isEmpty() && (hostname != ip.toString()));
  43     }
  44 }
  45
  46 ReverseResolution::ReverseResolution(QObject *parent)
  47     : QObject(parent)
  48 {
  49     m_cache.setMaxCost(CACHE_SIZE);
  50 }
  51
  52 ReverseResolution::~ReverseResolution()
  53 {
  54     // abort on-going lookups instead of waiting them
  55     for (auto iter = m_lookups.cbegin(); iter != m_lookups.cend(); ++iter)
  56         QHostInfo::abortHostLookup(iter.key());
  57 }
  58
  59 void ReverseResolution::resolve(const QHostAddress &ip)
  60 {
  61     const QString *hostname = m_cache.object(ip);
  62     if (hostname)
  63     {
  64         emit ipResolved(ip, *hostname);
  65         return;
  66     }
  67
  68     // do reverse lookup: IP -> hostname
  69     const int lookupId = QHostInfo::lookupHost(ip.toString(), this, &ReverseResolution::hostResolved);
  70     m_lookups.insert(lookupId, ip);
  71 }
  72
  73 void ReverseResolution::hostResolved(const QHostInfo &host)
  74 {
  75     const QHostAddress ip = m_lookups.take(host.lookupId());
  76
  77     if (host.error() != QHostInfo::NoError)
  78     {
  79         emit ipResolved(ip, {});
  80         return;
  81     }
  82
  83     const QString hostname = isUsefulHostName(host.hostName(), ip)
  84         ? host.hostName()
  85         : QString();
  86     m_cache.insert(ip, new QString(hostname));
  87     emit ipResolved(ip, hostname);
  88 }