changed how dns deals with cnames and recursion: remember cnames and implement recurs...

[pingcheck] / src / dns / dnsmaster.h

/*
 The software in this package is distributed under the GNU General
 Public License version 2 (with a special exception described below).

 A copy of GNU General Public License (GPL) is included in this distribution,
 in the file COPYING.GPL.

 As a special exception, if other files instantiate templates or use macros
 or inline functions from this file, or you compile this file and link it
 with other works to produce a work based on this file, this file
 does not by itself cause the resulting work to be covered
 by the GNU General Public License.

 However the source code for this file must still be made available
 in accordance with section (3) of the GNU General Public License.

 This exception does not invalidate any other reasons why a work based
 on this file might be covered by the GNU General Public License.

 Christian Herdtweck, Intra2net AG 2015
 */

/**
 * Two in one: a DNS resolver factory and a DNS cache
 *
 * Put these two things into one class because it is easier this way to avoid
 *   sync problems if e.g. there are 2 resolvers for the same host name
 *
 * This class is a Singleton. In case there are problems with this approach,
 * there is an alternative:
 * give every ResolverBase object a DnsMasterItem as variable, that is set
 *   during construction and call update / get_cached_results on that instance
 */

#ifndef DNS_MASTER_H
#define DNS_MASTER_H

#include <map>
#include <utility>   // pair

#include <boost/shared_ptr.hpp>
#include <boost/noncopyable.hpp>
#include <boost/net/dns.hpp>

#include "host/pinger.h"    // for IoserviceItem
#include "host/pingprotocol.h"
#include "dns/dnscache.h"
#include "dns/resolverbase.h"

class DnsMaster;

typedef boost::shared_ptr<DnsMaster> DnsMasterItem;

typedef boost::net::dns::type_t DnsIpProtocol;
const DnsIpProtocol DNS_IPv4 = boost::net::dns::type_a;
const DnsIpProtocol DNS_IPv6 = boost::net::dns::type_a6;
const DnsIpProtocol DNS_IPALL = boost::net::dns::type_all;

typedef std::pair<std::string, DnsIpProtocol> resolver_key_type;
typedef std::map<resolver_key_type, ResolverItem> resolver_map_type;


class DnsMaster : boost::noncopyable
{
// Resolver factory
public:
    ResolverItem& get_resolver_for(const std::string &hostname,
                                   const PingProtocol &ping_protocol);
    ResolverItem& get_resolver_for(const std::string &hostname,
                                   const DnsIpProtocol &protocol)
    ResolverItem get_recursor_for(const std::string &hostname,
                                  const DnsIpProtocol &protocol,
                                  const boost::asio::ip::address &name_server);

// implementation of singleton
private:
    static DnsMasterItem TheOnlyInstance;

    DnsMaster(const IoServiceItem &io_serv,
              const boost::asio::ip::address &default_name_server,
              const int resolved_ip_ttl_threshold,
              const int max_address_resolution_attempts,
              const DnsCacheItem &cache);
public:
    static void create_master(const IoServiceItem &io_serv,
                            const boost::asio::ip::address &default_name_server,
                            const int resolved_ip_ttl_threshold,
                            const int max_address_resolution_attempts,
                            const std::string &cache_file);
    static DnsMasterItem& get_instance();
    ~DnsMaster();

// storage of global variables
public:
    //boost::asio::ip::address &get_name_server() const;  // currently unused
    int get_resolved_ip_ttl_threshold() const;
    int get_max_address_resolution_attempts() const;

// variables
private:
    IoServiceItem IoService;
    const boost::asio::ip::address DefaultNameServer;
    const int ResolvedIpTtlThreshold;
    const int MaxAddressResolutionAttempts;
    DnsCacheItem Cache;
    resolver_map_type ResolverMap;

// internal helper functions
private:
    bool is_ip(const std::string &hostname) const;
    static DnsIpProtocol ping2dns_protocol(const PingProtocol& pprot);
};

#endif

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