path: root/src/bin/d2/d2_config.h

// Copyright (C) 2013-2014 Internet Systems Consortium, Inc. ("ISC")
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
// PERFORMANCE OF THIS SOFTWARE.

#ifndef D2_CONFIG_H
#define D2_CONFIG_H

#include <cc/data.h>
#include <d2/d2_asio.h>
#include <d2/d_cfg_mgr.h>
#include <dhcpsrv/dhcp_parsers.h>
#include <exceptions/exceptions.h>

#include <boost/foreach.hpp>

#include <stdint.h>
#include <string>

namespace isc {
namespace d2 {

/// @file d2_config.h
/// @brief A collection of classes for housing and parsing the application
/// configuration necessary for the DHCP-DDNS application (aka D2).
///
/// This file contains the class declarations for the class hierarchy created
/// from the D2 configuration and the parser classes used to create it.
/// The application configuration consists of a set of scalar parameters,
/// a list of TSIG keys, and two managed lists of domains: one list for
/// forward domains and one list for reverse domains.
///
/// The key list consists of one or more TSIG keys, each entry described by
/// a name, the algorithm method name, and its secret key component.
///
/// @todo  NOTE that TSIG configuration parsing is functional, the use of
/// TSIG Keys during the actual DNS update transactions is not.  This will be
/// implemented in a future release.
///
/// Each managed domain list consists of a list one or more domains and is
/// represented by the class DdnsDomainListMgr.
///
/// Each domain consists of a set of scalars parameters and a list of DNS
/// servers which support that domain. Among its scalars, is key_name, which
/// is the name of the TSIG Key to use for with this domain.  This value should
/// map to one of the TSIG Keys in the key list.  Domains are represented by
/// the class, DdnsDomain.
///
/// Each server consists of a set of scalars used to describe the server such
/// that the application can carry out DNS update exchanges with it. Servers
/// are represented by the class, DnsServerInfo.
///
/// The configuration specification for use with BIND10 is detailed in the file
/// dhcp-ddns.spec.
///
/// The parsing class hierarchy reflects this same scheme.  Working top down:
///
/// A DdnsDomainListMgrParser parses a managed domain list entry. It handles
/// any scalars which belong to the manager as well as creating and invoking a
/// DdnsDomainListParser to parse its list of domain entries.
///
/// A DdnsDomainLiatParser creates and invokes DdnsDomainListParser for each
/// domain entry in its list.
///
/// A DdnsDomainParser handles the scalars which belong to the domain as well as
/// creating and invoking a DnsSeverInfoListParser to parse its list of server
/// entries.
///
/// A DnsServerInfoListParser creates and invokes a DnsServerInfoParser for
/// each server entry in its list.
///
/// A DdnsServerInfoParser handles the scalars which belong to the server.
/// The following is sample configuration in JSON form with extra spacing
/// for clarity:
///
/// @code
/// {
///  "interface" : "eth1" ,
///  "ip_address" : "192.168.1.33" ,
///  "port" : 88 ,
///  "tsig_keys":
//// [
///    {
///     "name": "d2_key.tmark.org" ,
///     "algorithm": "md5" ,
///     "secret": "0123456989"
///    }
///  ],
///  "forward_ddns" :
///  {
///    "ddns_domains":
///    [
///      {
///        "name": "tmark.org." ,
///        "key_name": "d2_key.tmark.org" ,
///        "dns_servers" :
///        [
///          { "hostname": "fserver.tmark.org" },
///          { "hostname": "f2server.tmark.org" }
///        ]
///      },
///      {
///        "name": "pub.tmark.org." ,
///        "key_name": "d2_key.tmark.org" ,
///        "dns_servers" :
///        [
///          { "hostname": "f3server.tmark.org" }
///        ]
///      }
///    ]
///  },
///  "reverse_ddns" :
///  {
///    "ddns_domains":
///    [
///      {
///        "name": " 0.168.192.in.addr.arpa." ,
///        "key_name": "d2_key.tmark.org" ,
///        "dns_servers" :
///        [
///          { "ip_address": "127.0.0.101" , "port": 100 }
///        ]
///      }
///    ]
///  }
/// }
/// @endcode

/// @brief Exception thrown when the error during configuration handling
/// occurs.
class D2CfgError : public isc::Exception {
public:
    D2CfgError(const char* file, size_t line, const char* what) :
        isc::Exception(file, line, what) { };
};

/// @brief Represents a TSIG Key.
///
/// Currently, this is simple storage class containing the basic attributes of
/// a TSIG Key.  It is intended primarily as a reference for working with
/// actual keys and may eventually be replaced by isc::dns::TSIGKey.  TSIG Key
/// functionality at this stage is strictly limited to configuration parsing.
/// @todo full functionality for using TSIG during DNS updates will be added
/// in a future release.
class TSIGKeyInfo {
public:

    /// @brief Constructor
    ///
    /// @param name the unique label used to identify this key
    /// @param algorithm the name of the encryption alogirthm this key uses.
    /// (@todo This will be a fixed list of choices)
    ///
    /// @param secret the secret component of this key
    TSIGKeyInfo(const std::string& name, const std::string& algorithm,
                const std::string& secret);

    /// @brief Destructor
    virtual ~TSIGKeyInfo();

    /// @brief Getter which returns the key's name.
    ///
    /// @return returns the name as as std::string.
    const std::string getName() const {
        return (name_);
    }

    /// @brief Getter which returns the key's algorithm.
    ///
    /// @return returns the algorithm as as std::string.
    const std::string getAlgorithm() const {
        return (algorithm_);
    }

    /// @brief Getter which returns the key's secret.
    ///
    /// @return returns the secret as as std::string.
    const std::string getSecret() const {
        return (secret_);
    }

private:
    /// @brief The name of the key.
    ///
    /// This value is the unique identifeir thay domains use to
    /// to specify which TSIG key they need.
    std::string name_;

    /// @brief The algorithm that should be used for this key.
    std::string algorithm_;

    /// @brief The secret value component of this key.
    std::string secret_;
};

/// @brief Defines a pointer for TSIGKeyInfo instances.
typedef boost::shared_ptr<TSIGKeyInfo> TSIGKeyInfoPtr;

/// @brief Defines a map of TSIGKeyInfos, keyed by the name.
typedef std::map<std::string, TSIGKeyInfoPtr> TSIGKeyInfoMap;

/// @brief Defines a iterator pairing of name and TSIGKeyInfo
typedef std::pair<std::string, TSIGKeyInfoPtr> TSIGKeyInfoMapPair;

/// @brief Defines a pointer to map of TSIGkeyInfos
typedef boost::shared_ptr<TSIGKeyInfoMap> TSIGKeyInfoMapPtr;


/// @brief Represents a specific DNS Server.
/// It provides information about the server's network identity and typically
/// belongs to a list of servers supporting DNS for a given domain. It will
/// be used to establish communications with the server to carry out DNS
/// updates.
class DnsServerInfo {
public:

    /// @brief defines DNS standard port value
    static const uint32_t STANDARD_DNS_PORT = 53;

    /// @brief defines an "empty" string version of an ip address.
    static const char* EMPTY_IP_STR;


    /// @brief Constructor
    ///
    /// @param hostname is the resolvable name of the server. If not blank,
    /// then the server address should be resolved at runtime.
    /// @param ip_address is the static IP address of the server. If hostname
    /// is blank, then this address should be used to connect to the server.
    /// @param port is the port number on which the server listens.
    /// primarily meant for testing purposes.  Normally, DNS traffic is on
    /// is port 53. (NOTE the constructing code is responsible for setting
    /// the default.)
    /// @param enabled is a flag that indicates whether this server is
    /// enabled for use. It defaults to true.
    DnsServerInfo(const std::string& hostname,
                  isc::asiolink::IOAddress ip_address,
                  uint32_t port = STANDARD_DNS_PORT,
                  bool enabled=true);

    /// @brief Destructor
    virtual ~DnsServerInfo();

    /// @brief Getter which returns the server's hostname.
    ///
    /// @return returns the hostname as as std::string.
    const std::string getHostname() const {
        return (hostname_);
    }

    /// @brief Getter which returns the server's port number.
    ///
    /// @return returns the port number as a unsigned integer.
    uint32_t getPort() const {
        return (port_);
    }

    /// @brief Getter which returns the server's ip_address.
    ///
    /// @return returns the address as an IOAddress reference.
    const isc::asiolink::IOAddress& getIpAddress() const {
        return (ip_address_);
    }

    /// @brief Convenience method which returns whether or not the
    /// server is enabled.
    ///
    /// @return returns true if the server is enabled, false otherwise.
    bool isEnabled() const {
        return (enabled_);
    }

    /// @brief Sets the server's enabled flag to true.
    void enable() {
        enabled_ = true;
    }

    /// @brief Sets the server's enabled flag to false.
    void disable() {
        enabled_ = false;
    }

    /// @brief Returns a text representation for the server.
    std::string toText() const;


private:
    /// @brief The resolvable name of the server. If not blank, then the
    /// server's IP address should be dynamically resolved at runtime.
    std::string hostname_;

    /// @brief The static IP address of the server. When hostname is blank,
    /// then this address should be used to connect to the server.
    isc::asiolink::IOAddress ip_address_;

    /// @brief The port number on which the server listens for DNS traffic.
    uint32_t port_;

    /// @param enabled is a flag that indicates whether this server is
    /// enabled for use. It defaults to true.
    bool enabled_;
};

std::ostream&
operator<<(std::ostream& os, const DnsServerInfo& server);

/// @brief Defines a pointer for DnsServerInfo instances.
typedef boost::shared_ptr<DnsServerInfo> DnsServerInfoPtr;

/// @brief Defines a storage container for DnsServerInfo pointers.
typedef std::vector<DnsServerInfoPtr> DnsServerInfoStorage;

/// @brief Defines a pointer to DnsServerInfo storage containers.
typedef boost::shared_ptr<DnsServerInfoStorage> DnsServerInfoStoragePtr;


/// @brief Represents a DNS domain that is may be updated dynamically.
/// This class specifies a DNS domain and the list of DNS servers that support
/// it.  It's primary use is to map a domain to the DNS server(s) responsible
/// for it.
/// @todo Currently the name entry for a domain is just an std::string. It
/// may be worthwhile to change this to a dns::Name for purposes of better
/// validation and matching capabilities.
class DdnsDomain {
public:
    /// @brief Constructor
    ///
    /// @param name is the domain name of the domain.
    /// @param key_name is the TSIG key name for use with this domain.
    /// @param servers is the list of server(s) supporting this domain.
    DdnsDomain(const std::string& name, const std::string& key_name,
               DnsServerInfoStoragePtr servers);

    /// @brief Destructor
    virtual ~DdnsDomain();

    /// @brief Getter which returns the domain's name.
    ///
    /// @return returns the name in an std::string.
    const std::string getName() const {
        return (name_);
    }

    /// @brief Getter which returns the domain's TSIG key name.
    ///
    /// @return returns the key name in an std::string.
    const std::string getKeyName() const {
        return (key_name_);
    }

    /// @brief Getter which returns the domain's list of servers.
    ///
    /// @return returns the pointer to the server storage.
    const DnsServerInfoStoragePtr& getServers() {
        return (servers_);
    }

private:
    /// @brief The domain name of the domain.
    std::string name_;

    /// @brief The name of the TSIG key for use with this domain.
    std::string key_name_;

    /// @brief The list of server(s) supporting this domain.
    DnsServerInfoStoragePtr servers_;
};

/// @brief Defines a pointer for DdnsDomain instances.
typedef boost::shared_ptr<DdnsDomain> DdnsDomainPtr;

/// @brief Defines a map of DdnsDomains, keyed by the domain name.
typedef std::map<std::string, DdnsDomainPtr> DdnsDomainMap;

/// @brief Defines a iterator pairing domain name and DdnsDomain
typedef std::pair<std::string, DdnsDomainPtr> DdnsDomainMapPair;

/// @brief Defines a pointer to DdnsDomain storage containers.
typedef boost::shared_ptr<DdnsDomainMap> DdnsDomainMapPtr;

/// @brief Provides storage for and management of a list of DNS domains.
/// In addition to housing the domain list storage, it provides domain matching
/// services.  These services are used to match a FQDN to a domain.  Currently
/// it supports a single matching service, which will return the matching
/// domain or a wild card domain if one is specified.  The wild card domain is
/// specified as a domain whose name is "*".  The wild card domain will match
/// any entry and is provided for flexibility in FQDNs  If for instance, all
/// forward requests are handled by the same servers, the configuration could
/// specify the wild card domain as the only forward domain. All forward DNS
/// updates would be sent to that one list of servers, regardless of the FQDN.
/// As matching capabilities evolve this class is expected to expand.
class DdnsDomainListMgr {
public:
    /// @brief defines the domain name for denoting the wildcard domain.
    static const char* wildcard_domain_name_;

    /// @brief Constructor
    ///
    /// @param name is an arbitrary label assigned to this manager.
    DdnsDomainListMgr(const std::string& name);

    /// @brief Destructor
    virtual ~DdnsDomainListMgr ();

    /// @brief Matches a given name to a domain based on a longest match
    /// scheme.
    ///
    /// Given a FQDN, search the list of domains, successively removing a
    /// sub-domain from the FQDN until a match is found.  If no match is found
    /// and the wild card domain is present in the list, then return it as the
    /// match.  If the wild card domain is the only domain in the list, then
    /// it will be returned immediately for any FQDN.
    ///
    /// @param fqdn is the name for which to look.
    /// @param domain receives the matching domain. If no match is found its
    /// contents will be unchanged.
    ///
    /// @return returns true if a match is found, false otherwise.
    /// @todo This is a very basic match method, which expects valid FQDNs
    /// both as input and for the DdnsDomain::getName().  Currently both are
    /// simple strings and there is no normalization (i.e. added trailing dots
    /// if missing).
    virtual bool matchDomain(const std::string& fqdn, DdnsDomainPtr& domain);

    /// @brief Fetches the manager's name.
    ///
    /// @return returns a std::string containing the name of the manager.
    const std::string getName() const {
        return (name_);
    }

    /// @brief Returns the number of domains in the domain list.
    ///
    /// @brief returns an unsigned int containing the domain count.
    uint32_t size() const {
        return (domains_->size());
    }

    /// @brief Fetches the wild card domain.
    ///
    /// @return returns a pointer reference to the domain.  The pointer will
    /// empty if the wild card domain is not present.
    const DdnsDomainPtr& getWildcardDomain() {
        return (wildcard_domain_);
    }

    /// @brief Fetches the domain list.
    ///
    /// @return returns a pointer reference to the list of domains.
    const DdnsDomainMapPtr &getDomains() {
        return (domains_);
    }

    /// @brief Sets the manger's domain list to the given list of domains.
    /// This method will scan the inbound list for the wild card domain and
    /// set the internal wild card domain pointer accordingly.
    void setDomains(DdnsDomainMapPtr domains);

private:
    /// @brief An arbitrary label assigned to this manager.
    std::string name_;

    /// @brief Map of the domains, keyed by name.
    DdnsDomainMapPtr domains_;

    /// @brief Pointer to the wild card domain.
    DdnsDomainPtr wildcard_domain_;
};

/// @brief Defines a pointer for DdnsDomain instances.
typedef boost::shared_ptr<DdnsDomainListMgr> DdnsDomainListMgrPtr;

/// @brief Storage container for scalar configuration parameters.
///
/// This class is useful for implementing parsers for more complex configuration
/// elements (e.g. those of item type "map").  It provides a convenient way to
/// add storage to the parser for an arbitrary number and variety of scalar
/// configuration items (e.g. ints, bools, strings...) without explicitly adding
/// storage for each individual type needed by the parser.
///
/// This class implements a concrete version of the base class by supplying a
/// "clone" method.
class DScalarContext : public DCfgContextBase {
public:

    /// @brief Constructor
    DScalarContext() {
    };

    /// @brief Destructor
    virtual ~DScalarContext() {
    }

    /// @brief Creates a clone of a DStubContext.
    ///
    /// @return returns a pointer to the new clone.
    virtual DCfgContextBasePtr clone() {
        return (DCfgContextBasePtr(new DScalarContext(*this)));
    }

protected:
    /// @brief Copy constructor
    DScalarContext(const DScalarContext& rhs) : DCfgContextBase(rhs) {
    }

private:
    /// @brief Private assignment operator, not implemented.
    DScalarContext& operator=(const DScalarContext& rhs);
};

/// @brief Defines a pointer for DScalarContext instances.
typedef boost::shared_ptr<DScalarContext> DScalarContextPtr;

/// @brief Parser for  TSIGKeyInfo
///
/// This class parses the configuration element "tsig_key" defined in
/// src/bin/d2/dhcp-ddns.spec and creates an instance of a TSIGKeyInfo.
class TSIGKeyInfoParser : public  isc::dhcp::DhcpConfigParser {
public:
    /// @brief Constructor
    ///
    /// @param entry_name is an arbitrary label assigned to this configuration
    /// definition. Since servers are specified in a list this value is likely
    /// be something akin to "key:0", set during parsing.
    /// @param keys is a pointer to the storage area to which the parser
    /// should commit the newly created TSIGKeyInfo instance.
    TSIGKeyInfoParser(const std::string& entry_name, TSIGKeyInfoMapPtr keys);

    /// @brief Destructor
    virtual ~TSIGKeyInfoParser();

    /// @brief Performs the actual parsing of the given  "tsig_key" element.
    ///
    /// The results of the parsing are retained internally for use during
    /// commit.
    ///
    /// @param key_config is the "tsig_key" configuration to parse
    virtual void build(isc::data::ConstElementPtr key_config);

    /// @brief Creates a parser for the given "tsig_key" member element id.
    ///
    /// The key elements currently supported are(see dhcp-ddns.spec):
    ///   1. name
    ///   2. algorithm
    ///   3. secret
    ///
    /// @param config_id is the "item_name" for a specific member element of
    /// the "tsig_key" specification.
    ///
    /// @return returns a pointer to newly created parser.
    virtual isc::dhcp::ParserPtr createConfigParser(const std::string&
                                                    config_id);

    /// @brief Instantiates a DnsServerInfo from internal data values
    /// saves it to the storage area pointed to by servers_.
    virtual void commit();

private:
    /// @brief Arbitrary label assigned to this parser instance.
    /// Since servers are specified in a list this value is likely be something
    /// akin to "key:0", set during parsing.  Primarily here for diagnostics.
    std::string entry_name_;

    /// @brief Pointer to the storage area to which the parser should commit
    /// the newly created TSIGKeyInfo instance. This is given to us as a
    /// constructor argument by an upper level.
    TSIGKeyInfoMapPtr keys_;

    /// @brief Local storage area for scalar parameter values. Use to hold
    /// data until time to commit.
    DScalarContext local_scalars_;
};

/// @brief Parser for a list of TSIGKeyInfos
///
/// This class parses a list of "tsig_key" configuration elements.
/// (see src/bin/d2/dhcp-ddns.spec). The TSIGKeyInfo instances are added
/// to the given storage upon commit.
class TSIGKeyInfoListParser : public isc::dhcp::DhcpConfigParser {
public:

    /// @brief Constructor
    ///
    /// @param list_name is an arbitrary label assigned to this parser instance.
    /// @param keys is a pointer to the storage area to which the parser
    /// should commit the newly created TSIGKeyInfo instance.
    TSIGKeyInfoListParser(const std::string& list_name, TSIGKeyInfoMapPtr keys);

    /// @brief Destructor
    virtual ~TSIGKeyInfoListParser();

    /// @brief Performs the parsing of the given list "tsig_key" elements.
    ///
    /// It iterates over each key entry in the list:
    ///   1. Instantiate a TSIGKeyInfoParser for the entry
    ///   2. Pass the element configuration to the parser's build method
    ///   3. Add the parser instance to local storage
    ///
    /// The net effect is to parse all of the key entries in the list
    /// prepping them for commit.
    ///
    /// @param key_list_config is the list of "tsig_key" elements to parse.
    virtual void build(isc::data::ConstElementPtr key_list_config);

    /// @brief Iterates over the internal list of TSIGKeyInfoParsers,
    /// invoking commit on each.  This causes each parser to instantiate a
    /// TSIGKeyInfo from its internal data values and add that key
    /// instance to the local key storage area, local_keys_.   If all of the
    /// key parsers commit cleanly, then update the context key map (keys_)
    /// with the contents of local_keys_.  This is done to allow for duplicate
    /// key detection while parsing the keys, but not get stumped by it
    /// updating the context with a valid list.
    virtual void commit();

private:
    /// @brief Arbitrary label assigned to this parser instance.
    std::string list_name_;

    /// @brief Pointer to the storage area to which the parser should commit
    /// the list of newly created TSIGKeyInfo instances. This is given to us
    /// as a constructor argument by an upper level.
    TSIGKeyInfoMapPtr keys_;
    
    /// @brief Local storage area to which individual key parsers commit.
    TSIGKeyInfoMapPtr local_keys_;

    /// @brief Local storage of TSIGKeyInfoParser instances
    isc::dhcp::ParserCollection parsers_;
};

/// @brief Parser for  DnsServerInfo
///
/// This class parses the configuration element "dns_server" defined in
/// src/bin/d2/dhcp-ddns.spec and creates an instance of a DnsServerInfo.
class DnsServerInfoParser : public  isc::dhcp::DhcpConfigParser {
public:
    /// @brief Constructor
    ///
    /// @param entry_name is an arbitrary label assigned to this configuration
    /// definition. Since servers are specified in a list this value is likely
    /// be something akin to "server:0", set during parsing.
    /// @param servers is a pointer to the storage area to which the parser
    /// should commit the newly created DnsServerInfo instance.
    DnsServerInfoParser(const std::string& entry_name,
                        DnsServerInfoStoragePtr servers);

    /// @brief Destructor
    virtual ~DnsServerInfoParser();

    /// @brief Performs the actual parsing of the given  "dns_server" element.
    /// The results of the parsing are retained internally for use during
    /// commit.
    ///
    /// @param server_config is the "dns_server" configuration to parse
    virtual void build(isc::data::ConstElementPtr server_config);

    /// @brief Creates a parser for the given "dns_server" member element id.
    ///
    /// The server elements currently supported are(see dhcp-ddns.spec):
    ///   1. hostname
    ///   2. ip_address
    ///   3. port
    ///
    /// @param config_id is the "item_name" for a specific member element of
    /// the "dns_server" specification.
    ///
    /// @return returns a pointer to newly created parser.
    virtual isc::dhcp::ParserPtr createConfigParser(const std::string&
                                                    config_id);

    /// @brief Instantiates a DnsServerInfo from internal data values
    /// saves it to the storage area pointed to by servers_.
    virtual void commit();

private:
    /// @brief Arbitrary label assigned to this parser instance.
    /// Since servers are specified in a list this value is likely be something
    /// akin to "server:0", set during parsing.  Primarily here for diagnostics.
    std::string entry_name_;

    /// @brief Pointer to the storage area to which the parser should commit
    /// the newly created DnsServerInfo instance. This is given to us as a
    /// constructor argument by an upper level.
    DnsServerInfoStoragePtr servers_;

    /// @brief Local storage area for scalar parameter values. Use to hold
    /// data until time to commit.
    DScalarContext local_scalars_;
};

/// @brief Parser for a list of DnsServerInfos
///
/// This class parses a list of "dns_server" configuration elements.
/// (see src/bin/d2/dhcp-ddns.spec). The DnsServerInfo instances are added
/// to the given storage upon commit.
class DnsServerInfoListParser : public isc::dhcp::DhcpConfigParser {
public:

    /// @brief Constructor
    ///
    /// @param list_name is an arbitrary label assigned to this parser instance.
    /// @param servers is a pointer to the storage area to which the parser
    /// should commit the newly created DnsServerInfo instance.
    DnsServerInfoListParser(const std::string& list_name,
                            DnsServerInfoStoragePtr servers);

    /// @brief Destructor
    virtual ~DnsServerInfoListParser();

    /// @brief Performs the actual parsing of the given list "dns_server"
    /// elements.
    /// It iterates over each server entry in the list:
    ///   1. Instantiate a DnsServerInfoParser for the entry
    ///   2. Pass the element configuration to the parser's build method
    ///   3. Add the parser instance to local storage
    ///
    /// The net effect is to parse all of the server entries in the list
    /// prepping them for commit.
    ///
    /// @param server_list_config is the list of "dns_server" elements to parse.
    virtual void build(isc::data::ConstElementPtr server_list_config);

    /// @brief Iterates over the internal list of DnsServerInfoParsers,
    /// invoking commit on each.  This causes each parser to instantiate a
    /// DnsServerInfo from its internal data values and add that that server
    /// instance to the storage area, servers_.
    virtual void commit();

private:
    /// @brief Arbitrary label assigned to this parser instance.
    std::string list_name_;

    /// @brief Pointer to the storage area to which the parser should commit
    /// the list of newly created DnsServerInfo instances. This is given to us
    /// as a constructor argument by an upper level.
    DnsServerInfoStoragePtr servers_;

    /// @brief Local storage of DnsServerInfoParser instances
    isc::dhcp::ParserCollection parsers_;
};

/// @brief Parser for  DdnsDomain
///
/// This class parses the configuration element "ddns_domain" defined in
/// src/bin/d2/dhcp-ddns.spec and creates an instance of a DdnsDomain.
class DdnsDomainParser : public isc::dhcp::DhcpConfigParser {
public:
    /// @brief Constructor
    ///
    /// @param entry_name is an arbitrary label assigned to this configuration
    /// definition. Since domains are specified in a list this value is likely
    /// be something akin to "forward_ddns:0", set during parsing.
    /// @param domains is a pointer to the storage area to which the parser
    /// @param keys is a pointer to a map of the defined TSIG keys.
    /// should commit the newly created DdnsDomain instance.
    DdnsDomainParser(const std::string& entry_name, DdnsDomainMapPtr domains,
                     TSIGKeyInfoMapPtr keys);

    /// @brief Destructor
    virtual ~DdnsDomainParser();

    /// @brief Performs the actual parsing of the given  "ddns_domain" element.
    /// The results of the parsing are retained internally for use during
    /// commit.
    ///
    /// @param domain_config is the "ddns_domain" configuration to parse
    virtual void build(isc::data::ConstElementPtr domain_config);

    /// @brief Creates a parser for the given "ddns_domain" member element id.
    ///
    /// The domain elements currently supported are(see dhcp-ddns.spec):
    ///   1. name
    ///   2. key_name
    ///   3. dns_servers
    ///
    /// @param config_id is the "item_name" for a specific member element of
    /// the "ddns_domain" specification.
    ///
    /// @return returns a pointer to newly created parser.
    virtual isc::dhcp::ParserPtr createConfigParser(const std::string&
                                                    config_id);

    /// @brief Instantiates a DdnsDomain from internal data values
    /// saves it to the storage area pointed to by domains_.
    virtual void commit();

private:

    /// @brief Arbitrary label assigned to this parser instance.
    std::string entry_name_;

    /// @brief Pointer to the storage area to which the parser should commit
    /// the newly created DdnsDomain instance. This is given to us as a
    /// constructor argument by an upper level.
    DdnsDomainMapPtr domains_;

    /// @brief Pointer to the map of defined TSIG keys.
    /// This map is passed into us and contains all of the TSIG keys defined
    /// for this configuration.  It is used to validate the key name entry of
    /// DdnsDomains that specify one.
    TSIGKeyInfoMapPtr keys_;

    /// @brief Local storage for DnsServerInfo instances. This is passed into
    /// DnsServerInfoListParser(s), which in turn passes it into each
    /// DnsServerInfoParser.  When the DnsServerInfoParsers "commit" they add
    /// their server instance to this storage.
    DnsServerInfoStoragePtr local_servers_;

    /// @brief Local storage area for scalar parameter values. Use to hold
    /// data until time to commit.
    DScalarContext local_scalars_;
};

/// @brief Parser for a list of DdnsDomains
///
/// This class parses a list of "ddns_domain" configuration elements.
/// (see src/bin/d2/dhcp-ddns.spec). The DdnsDomain instances are added
/// to the given storage upon commit.
class DdnsDomainListParser : public isc::dhcp::DhcpConfigParser {
public:

    /// @brief Constructor
    ///
    /// @param list_name is an arbitrary label assigned to this parser instance.
    /// @param domains is a pointer to the storage area to which the parser
    /// @param keys is a pointer to a map of the defined TSIG keys.
    /// should commit the newly created DdnsDomain instance.
    DdnsDomainListParser(const std::string& list_name,
                         DdnsDomainMapPtr domains, TSIGKeyInfoMapPtr keys);

    /// @brief Destructor
    virtual ~DdnsDomainListParser();

    /// @brief Performs the actual parsing of the given list "ddns_domain"
    /// elements.
    /// It iterates over each server entry in the list:
    ///   1. Instantiate a DdnsDomainParser for the entry
    ///   2. Pass the element configuration to the parser's build method
    ///   3. Add the parser instance to local storage
    ///
    /// The net effect is to parse all of the domain entries in the list
    /// prepping them for commit.
    ///
    /// @param domain_list_config is the list of "ddns_domain" elements to
    /// parse.
    virtual void build(isc::data::ConstElementPtr domain_list_config);

    /// @brief Iterates over the internal list of DdnsDomainParsers, invoking
    /// commit on each.  This causes each parser to instantiate a DdnsDomain
    /// from its internal data values and add that domain instance to the
    /// storage area, domains_.
    virtual void commit();

private:
    /// @brief Arbitrary label assigned to this parser instance.
    std::string list_name_;

    /// @brief Pointer to the storage area to which the parser should commit
    /// the list of newly created DdnsDomain instances. This is given to us
    /// as a constructor argument by an upper level.
    DdnsDomainMapPtr domains_;

    /// @brief Pointer to the map of defined TSIG keys.
    /// This map is passed into us and contains all of the TSIG keys defined
    /// for this configuration.  It is used to validate the key name entry of
    /// DdnsDomains that specify one.
    TSIGKeyInfoMapPtr keys_;

    /// @brief Local storage of DdnsDomainParser instances
    isc::dhcp::ParserCollection parsers_;
};

/// @brief Parser for DdnsDomainListMgr
///
/// This class parses the configuration elements "forward_ddns" and
/// "reverse_ddns" as defined in src/bin/d2/dhcp-ddns.spec.  It populates the
/// given DdnsDomainListMgr with parsed information upon commit.  Note that
/// unlike other parsers, this parser does NOT instantiate the final object
/// during the commit phase, it populates it.  It must pre-exist.
class DdnsDomainListMgrParser : public isc::dhcp::DhcpConfigParser {
public:
    /// @brief Constructor
    ///
    /// @param entry_name is an arbitrary label assigned to this configuration
    /// definition.
    /// @param mgr is a pointer to the DdnsDomainListMgr to populate.
    /// @param keys is a pointer to a map of the defined TSIG keys.
    /// @throw throws D2CfgError if mgr pointer is empty.
    DdnsDomainListMgrParser(const std::string& entry_name,
                     DdnsDomainListMgrPtr mgr, TSIGKeyInfoMapPtr keys);

    /// @brief Destructor
    virtual ~DdnsDomainListMgrParser();

    /// @brief Performs the actual parsing of the given manager element.
    /// The results of the parsing are retained internally for use during
    /// commit.
    ///
    /// @param mgr_config is the manager configuration to parse
    virtual void build(isc::data::ConstElementPtr mgr_config);

    /// @brief Creates a parser for the given manager member element id.
    ///
    /// The manager elements currently supported are (see dhcp-ddns.spec):
    ///     1. ddns_domains
    ///
    /// @param config_id is the "item_name" for a specific member element of
    /// the manager specification.
    ///
    /// @return returns a pointer to newly created parser.
    virtual isc::dhcp::ParserPtr createConfigParser(const std::string&
                                                    config_id);

    /// @brief Populates the DdnsDomainListMgr from internal data values
    /// set during parsing.
    virtual void commit();

private:
    /// @brief Arbitrary label assigned to this parser instance.
    std::string entry_name_;

    /// @brief Pointer to manager instance to which the parser should commit
    /// the parsed data. This is given to us as a constructor argument by an
    /// upper level.
    DdnsDomainListMgrPtr mgr_;

    /// @brief Pointer to the map of defined TSIG keys.
    /// This map is passed into us and contains all of the TSIG keys defined
    /// for this configuration.  It is used to validate the key name entry of
    /// DdnsDomains that specify one.
    TSIGKeyInfoMapPtr keys_;

    /// @brief Local storage for DdnsDomain instances. This is passed into a
    /// DdnsDomainListParser(s), which in turn passes it into each
    /// DdnsDomainParser.  When the DdnsDomainParsers "commit" they add their
    /// domain instance to this storage.
    DdnsDomainMapPtr local_domains_;

    /// @brief Local storage area for scalar parameter values. Use to hold
    /// data until time to commit.
    /// @todo Currently, the manager has no scalars but this is likely to
    /// change as matching capabilities expand.
    DScalarContext local_scalars_;
};


}; // end of isc::d2 namespace
}; // end of isc namespace

#endif // D2_CONFIG_H