// Copyright (C) 2013-2025 Internet Systems Consortium, Inc. ("ISC")

//

// This Source Code Form is subject to the terms of the Mozilla Public

// License, v. 2.0. If a copy of the MPL was not distributed with this

// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef OPTION6_CLIENT_FQDN_H

#define OPTION6_CLIENT_FQDN_H

#include <dhcp/option.h>

#include <dns/name.h>

#include <string>

namespace isc {

namespace dhcp {

/// @brief Exception thrown when invalid flags have been specified for

/// DHCPv6 Client Fqdn %Option.

class InvalidOption6FqdnFlags : public Exception {

public:

    InvalidOption6FqdnFlags(const char* file, size_t line, const char* what) :

        isc::Exception(file, line, what) {}

};

/// @brief Exception thrown when invalid domain name is specified.

class InvalidOption6FqdnDomainName : public Exception {

public:

    InvalidOption6FqdnDomainName(const char* file, size_t line,

                                const char* what) :

        isc::Exception(file, line, what) {}

};

/// Forward declaration to implementation of @c Option6ClientFqdn class.

class Option6ClientFqdnImpl;

/// @brief Represents DHCPv6 Client FQDN %Option (code 39).

///

/// This option has been defined in the RFC 4704 and it has a following

/// structure:

/// - option-code = 39 (2 octets)

/// - option-len (2 octets)

/// - flags (1 octet)

/// - domain-name - variable length field comprising partial or fully qualified

/// domain name.

///

/// The flags field has the following structure:

/// @code

///        0 1 2 3 4 5 6 7

///       +-+-+-+-+-+-+-+-+

///       |  MBZ    |N|O|S|

///       +-+-+-+-+-+-+-+-+

/// @endcode

/// where:

/// - N flag specifies whether server should (0) or should not (1) perform DNS

///  Update,

/// - O flag is set by the server to indicate that it has overridden client's

/// preference set with the S bit.

/// - S flag specifies whether server should (1) or should not (0) perform

/// forward (FQDN-to-address) updates.

///

/// This class exposes a set of functions to modify flags and check their

/// correctness.

///

/// Domain names being carried by DHCPv6 Client Fqdn %Option can be fully

/// qualified or partial. Partial domain names are encoded similar to the

/// fully qualified domain names, except that they lack terminating zero

/// at the end of their wire representation. It is also accepted to create an

/// instance of this option which has empty domain-name. Clients use empty

/// domain-names to indicate that server should generate complete fully

/// qualified domain-name.

///

/// Since domain names are case insensitive (see RFC 4343), this class

/// converts them to lower case format regardless if they are received over

/// the wire or created from strings.

///

/// <b>Design choice:</b> This class uses pimpl idiom to separate the interface

/// from implementation specifics. Implementations may use different approaches

/// to handle domain names (mostly validation of the domain-names). The existing

/// @c isc::dns::Name class is a natural (and the simplest) choice to handle

/// domain-names. Use of this class however, implies that libdhcp must be linked

/// with libdns. At some point these libraries may need to be separated, i.e. to

/// support compilation and use of standalone DHCP server. This will require

/// that the part of implementation which deals with domain-names is modified to

/// not use classes from libdns. These changes will be transparent for this

/// interface.

class Option6ClientFqdn : public Option {

public:

    ///

    ///@name A set of constants setting respective bits in 'flags' field

    //@{

    static const uint8_t FLAG_S = 0x01; ///< S bit.

    static const uint8_t FLAG_O = 0x02; ///< O bit.

    static const uint8_t FLAG_N = 0x04; ///< N bit.

    //@}

    /// @brief Mask which zeroes MBZ flag bits.

    static const uint8_t FLAG_MASK = 0x7;

    /// @brief The length of the flag field within DHCPv6 Client Fqdn %Option.

    static const uint16_t FLAG_FIELD_LEN = 1;

    /// @brief Type of the domain-name: partial or full.

    enum DomainNameType : uint16_t {

        PARTIAL,

        FULL

    };

    /// @brief Constructor, creates option instance using flags and domain name.

    ///

    /// This constructor is used to create instance of the option which will be

    /// included in outgoing messages.

    ///

    /// @param flags a combination of flag bits to be stored in flags field.

    /// @param domain_name a name to be stored in the domain-name field.

    /// @param domain_name_type indicates if the domain name is partial

    /// or full.

    explicit Option6ClientFqdn(const uint8_t flags,

                               const std::string& domain_name,

                               const DomainNameType domain_name_type = FULL);

    /// @brief Constructor, creates option instance using flags.

    ///

    /// This constructor creates an instance of the option with empty

    /// domain-name. This domain-name is marked partial.

    ///

    /// @param flags A combination of flag bits to be stored in flags field.

    Option6ClientFqdn(const uint8_t flags);

    /// @brief Constructor, creates an option instance from part of the buffer.

    ///

    /// This constructor is mainly used to parse options in the received

    /// messages. Function parameters specify buffer bounds from which the

    /// option should be created. The size of the buffer chunk, specified by

    /// the constructor's parameters should be equal or larger than the size

    /// of the option. Otherwise, constructor will throw an exception.

    ///

    /// @param first the lower bound of the buffer to create option from.

    /// @param last the upper bound of the buffer to create option from.

    explicit Option6ClientFqdn(OptionBufferConstIter first,

                               OptionBufferConstIter last);

    /// @brief Copy constructor

    Option6ClientFqdn(const Option6ClientFqdn& source);

    /// @brief Copies this option and returns a pointer to the copy.

    virtual OptionPtr clone() const;

    /// @brief Destructor

    virtual ~Option6ClientFqdn();

    /// @brief Assignment operator

    Option6ClientFqdn& operator=(const Option6ClientFqdn& source);

    /// @brief Checks if the specified flag of the DHCPv6 Client FQDN %Option

    /// is set.

    ///

    /// This method checks the single bit of flags field. Therefore, a caller

    /// should use one of the: @c FLAG_S, @c FLAG_N, @c FLAG_O constants as

    /// an argument of the function. Attempt to use any other value (including

    /// combinations of these constants) will result in exception.

    ///

    /// @param flag A value specifying the flags bit to be checked. It can be

    /// one of the following: @c FLAG_S, @c FLAG_N, @c FLAG_O.

    ///

    /// @return true if the bit of the specified flag is set, false otherwise.

    bool getFlag(const uint8_t flag) const;

    /// @brief Modifies the value of the specified DHCPv6 Client Fqdn %Option

    /// flag.

    ///

    /// This method sets the single bit of flags field. Therefore, a caller

    /// should use one of the: @c FLAG_S, @c FLAG_N, @c FLAG_O constants as

    /// an argument of the function. Attempt to use any other value (including

    /// combinations of these constants) will result in exception.

    ///

    /// @param flag A value specifying the flags bit to be modified. It can

    /// be one of the following: @c FLAG_S, @c FLAG_N, @c FLAG_O.

    /// @param set a boolean value which indicates whether flag should be

    /// set (true), or cleared (false).

    void setFlag(const uint8_t flag, const bool set);

    /// @brief Sets the flag field value to 0.

    void resetFlags();

    /// @brief Returns the domain-name in the text format.

    ///

    /// If domain-name is partial, it lacks the dot at the end (e.g. myhost).

    /// If domain-name is fully qualified, it has the dot at the end (e.g.

    /// myhost.example.com.).

    ///

    /// @return domain-name in the text format.

    std::string getDomainName() const;

    /// @brief Writes domain-name in the wire format into a buffer.

    ///

    /// The data being written are appended at the end of the buffer.

    ///

    /// @param [out] buf buffer where domain-name will be written.

    void packDomainName(isc::util::OutputBuffer& buf) const;

    /// @brief Set new domain-name.

    ///

    /// @param domain_name domain name field value in the text format.

    /// @param domain_name_type type of the domain name: partial or fully

    /// qualified.

    void setDomainName(const std::string& domain_name,

                       const DomainNameType domain_name_type);

    /// @brief Set empty domain-name.

    ///

    /// This function is equivalent to @c Option6ClientFqdn::setDomainName

    /// with empty partial domain-name. It is exception safe.

    void resetDomainName();

    /// @brief Returns enumerator value which indicates whether domain-name is

    /// partial or full.

    ///

    /// @return An enumerator value indicating whether domain-name is partial

    /// or full.

    DomainNameType getDomainNameType() const;

    /// @brief Writes option in the wire format into a buffer.

    ///

    /// @param [out] buf output buffer where option data will be stored.

    /// @param check if set to false, allows options larger than 255 for v4

    virtual void pack(isc::util::OutputBuffer& buf, bool check = true) const;

    /// @brief Parses option from the received buffer.

    ///

    /// Method creates an instance of the DHCPv6 Client FQDN %Option from the

    /// wire format. Parameters specify the bounds of the buffer to read option

    /// data from. The size of the buffer limited by the specified parameters

    /// should be equal or larger than size of the option (including its

    /// header). Otherwise exception will be thrown.

    ///

    /// @param first lower bound of the buffer to parse option from.

    /// @param last upper bound of the buffer to parse option from.

    virtual void unpack(OptionBufferConstIter first,

                        OptionBufferConstIter last);

    /// @brief Returns string representation of the option.

    ///

    /// The string returned by the method comprises the bit value of each

    /// option flag and the domain-name.

    ///

    /// @param indent number of spaces before printed text.

    ///

    /// @return string with text representation.

    virtual std::string toText(int indent = 0) const;

    /// @brief Returns length of the complete option (data length +

    /// DHCPv6 option header).

    ///

    /// @return length of the option.

    virtual uint16_t len() const;

private:

    /// @brief A pointer to the implementation.

    Option6ClientFqdnImpl* impl_;

};

/// A pointer to the @c Option6ClientFqdn object.

typedef boost::shared_ptr<Option6ClientFqdn> Option6ClientFqdnPtr;

} // namespace isc::dhcp

} // namespace isc

#endif // OPTION6_CLIENT_FQDN_H