finished self-implementation of DNS resolver recursion; will now remove all that!

[pingcheck] / src / dns / dnsmaster.cpp

/*
 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
 */

#include "dns/dnsmaster.h"

#include <logfunc.hpp>
#include <boost/bind.hpp>
#include <boost/asio/placeholders.hpp>

#include "dns/ippseudoresolver.h"
#include "dns/dnsresolver.h"

using boost::bind;
using I2n::Logger::GlobalLogger;


DnsMasterItem DnsMaster::TheOnlyInstance;

void DnsMaster::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)
{
    if (TheOnlyInstance)
    {
        GlobalLogger.warning()
            << "Blocking attempt to create another DnsMaster instance!";
        return;
    }

    GlobalLogger.info() << "Creating DNS Cache and Master";
    DnsCacheItem cache( new DnsCache(io_serv, cache_file) );
    TheOnlyInstance.reset( new DnsMaster(io_serv,
                                         default_name_server,
                                         resolved_ip_ttl_threshold,
                                         max_address_resolution_attempts,
                                         cache)
                         );
}


DnsMaster::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)
    : IoService( io_serv )
    , DefaultNameServer( default_name_server )
    , ResolvedIpTtlThreshold( resolved_ip_ttl_threshold )
    , MaxAddressResolutionAttempts( max_address_resolution_attempts )
    , Cache(cache)
    , ResolverMap()
{
}


DnsMasterItem& DnsMaster::get_instance()
{
    if ( !TheOnlyInstance )
        GlobalLogger.error()
            << "Request to return DnsMaster instance before creating it!";
    return TheOnlyInstance;
}

DnsMaster::~DnsMaster()
{
    GlobalLogger.info() << "DnsMaster is being destructed";

    if (DnsMaster::TheOnlyInstance)
    {    // just to be sure ...
        GlobalLogger.warning() << "DnsMaster is being destructed that is not "
                               << "singleton instance TheOnlyInstance!";
        DnsMaster::TheOnlyInstance.reset();
    }

    // Items in ResolverMap and the DnsCache might still be referenced by
    // Resolvers and are smart pointers, anyway --> nothing to do here
}



ResolverItem& DnsMaster::get_resolver_for( const std::string &hostname,
                                           const PingProtocol &ping_protocol )
{
    // find suitable DnsIpProtocol for ping protocol
    DnsIpProtocol protocol = ping2dns_protocol(ping_protocol);
    return get_resolver_for(hostname, protocol);
}


ResolverItem& DnsMaster::get_resolver_for(const std::string &hostname,
                                          const DnsIpProtocol &protocol)
{
    // create key to ResolverMap
    resolver_key_type key(hostname, protocol);
    if ( ResolverMap.count(key) == 0 )
    {   // need to create a resolver

        // check if it is an ip address, so can create a simple pseudo resolver
        if ( is_ip(hostname) )
        {
            boost::asio::ip::address ip
                              = boost::asio::ip::address::from_string(hostname);
            if ( (protocol == DNS_IPv4 && !ip.is_v4()) ||
                 (protocol == DNS_IPv6 && !ip.is_v6()) )
                GlobalLogger.warning() << "Asked to create a DNS resolver "
                                       << "for wrong IP protocol: v4 != v6! "
                                       << "We will comply.";
            GlobalLogger.info() << "Creating PseudoResolver for IP " << ip;
            ResolverItem new_resolver( new IpPseudoResolver(IoService,
                                                            hostname,
                                                            Cache) );
            ResolverMap[key] = new_resolver;
        }
        else
        {
            GlobalLogger.info() << "DnsMaster: Creating Resolver for host "
                << hostname << " and protocol " << to_string(protocol);
            ResolverItem new_resolver( new DnsResolver(IoService,
                                                       hostname,
                                                       protocol,
                                                       Cache,
                                                       DefaultNameServer) );
            ResolverMap[key] = new_resolver;
        }
    }
    return ResolverMap[key];
}

// create resolver but do not remember it in ResolverMap
ResolverItem DnsMaster::get_recursor_for(const std::string &hostname,
                                         const DnsIpProtocol &protocol,
                                    const boost::asio::ip::address &name_server)
{
    resolver_key_type key(hostname, protocol);
    if ( !ResolverMap[key] )
        GlobalLogger.warning() << "DnsMaster: requesting recursor for host "
            << hostname << " and protocol " << to_string(protocol)
            << " but have no regular resolver for this combination!";
    else
        GlobalLogger.warning() << "DnsMaster: requesting recursor for host "
            << hostname << " and protocol " << to_string(protocol);

    ResolverItem new_resolver( new DnsResolver(IoService,
                                               hostname,
                                               protocol,
                                               Cache,
                                               name_server) );
    return new_resolver;
}

/**
 * return true if given hostname string actually is an IP
 *
 * delegates decision to boost::asio::ip::address::from_string
 */
bool DnsMaster::is_ip(const std::string &hostname) const
{
    try
    {
        boost::asio::ip::address ip = boost::asio::ip::address::from_string(
                                                                      hostname);
        return ip.is_v4() || ip.is_v6();
    }
    catch ( const std::exception &ex )
    {
        return false;
    }
}


DnsIpProtocol DnsMaster::ping2dns_protocol(const PingProtocol& pprot)
{
    switch (pprot)
    {
        case PingProtocol_ICMP:     return DNS_IPv4; break;
        case PingProtocol_ICMPv6:   return DNS_IPv6; break;
        case PingProtocol_TCP:      return DNS_IPv4; break;
        case PingProtocol_TCP_IPv6: return DNS_IPv6; break;
        default:
            GlobalLogger.warning() << "Unexpected ping protocol: "
                                   << static_cast<int>(pprot);
            return DNS_IPALL;
            break;
    }
}

/*boost::asio::ip::address &DnsMaster::get_name_server() const
{
    return NameServer;
}*/

int DnsMaster::get_resolved_ip_ttl_threshold() const
{
    return ResolvedIpTtlThreshold;
}

int DnsMaster::get_max_address_resolution_attempts() const
{
    return MaxAddressResolutionAttempts;
}

std::string to_string(const DnsIpProtocol &protocol)
{
    switch (protocol)
    {
        case DNS_IPv4:  return "IPv4"; break;
        case DNS_IPv6:  return "IPv6"; break;
        case DNS_IPALL: return "IPv4/6"; break;
        default: GlobalLogger.warning() << "Unexpected protocol in to_string!";
                 return "Unexpected Protocol"; break;
    }
}
// (created using vim -- the world's best text editor)