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// Copyright (C) 2013-2022 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 OPTION4_CLIENT_FQDN_H
#define OPTION4_CLIENT_FQDN_H
#include <dhcp/option.h>
#include <dns/name.h>
#include <string>
#include <utility>
namespace isc {
namespace dhcp {
/// @brief Exception thrown when invalid flags have been specified for
/// DHCPv4 Client FQDN %Option.
class InvalidOption4FqdnFlags : public Exception {
public:
InvalidOption4FqdnFlags(const char* file, size_t line, const char* what) :
isc::Exception(file, line, what) {}
};
/// @brief Exception thrown when invalid domain name is specified.
class InvalidOption4FqdnDomainName : public Exception {
public:
InvalidOption4FqdnDomainName(const char* file, size_t line,
const char* what) :
isc::Exception(file, line, what) {}
};
/// Forward declaration to implementation of @c Option4ClientFqdn class.
class Option4ClientFqdnImpl;
/// @brief Represents DHCPv4 Client FQDN %Option (code 81).
///
/// This option has been defined in the RFC 4702 and it has a following
/// structure:
/// - Code (1 octet) - option code (always equal to 81).
/// - Len (1 octet) - a length of the option.
/// - Flags (1 octet) - a field carrying "NEOS" flags described below.
/// - RCODE1 (1 octet) - deprecated field which should be set to 0 by the client
/// and set to 255 by the server.
/// - RCODE2 (1 octet) - deprecated, should be used in the same way as RCODE1.
/// - 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|E|O|S|
/// +-+-+-+-+-+-+-+-+
/// @endcode
/// where:
/// - N flag specifies whether server should (0) or should not (1) perform DNS
/// Update,
/// - E flag specifies encoding of the Domain Name field. If this flag is set
/// to 1 it indicates canonical wire format without compression. 0 indicates
/// the deprecated ASCII format.
/// - 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 DHCPv4 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 (or lack of dot at the end, in
/// case of ASCII encoding). 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.
///
/// @warning: The RFC4702 section 2.3.1 states that the clients and servers
/// should use character sets specified in RFC952, section 2.1 for ASCII-encoded
/// domain-names. This class doesn't detect the character set violation for
/// ASCII-encoded domain-name. It could be implemented in the future but it is
/// not important now for two reasons:
/// - ASCII encoding is deprecated
/// - clients SHOULD obey restrictions but if they don't, server may still
/// process the option
///
/// RFC 4702 mandates that the DHCP client sets RCODE1 and RCODE2 to 0 and that
/// server sets them to 255. This class allows to set the value for these
/// fields and both fields are always set to the same value. There is no way
/// to set them separately (e.g. set different value for RCODE1 and RCODE2).
/// However, there are no use cases which would require it.
///
/// <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 Option4ClientFqdn : public Option {
public:
///
/// @name A set of constants used to identify and set bits in the flags field
//@{
static const uint8_t FLAG_S = 0x01; ///< Bit S
static const uint8_t FLAG_O = 0x02; ///< Bit O
static const uint8_t FLAG_E = 0x04; ///< Bit E
static const uint8_t FLAG_N = 0x08; ///< Bit N
//@}
/// @brief Mask which zeroes MBZ flag bits.
static const uint8_t FLAG_MASK = 0xF;
/// @brief Represents the value of one of the RCODE1 or RCODE2 fields.
///
/// Typically, RCODE values are set to 255 by the server and to 0 by the
/// clients (as per RFC 4702).
class Rcode {
public:
Rcode(const uint8_t rcode)
: rcode_(rcode) { }
/// @brief Returns the value of the RCODE.
///
/// Returned value can be directly used to create the on-wire format
/// of the DHCPv4 Client FQDN %Option.
uint8_t getCode() const {
return (rcode_);
}
private:
uint8_t rcode_;
};
/// @brief Type of the domain-name: partial or full.
enum DomainNameType {
PARTIAL,
FULL
};
/// @brief The size in bytes of the fixed fields within DHCPv4 Client Fqdn
/// %Option.
///
/// The fixed fields are:
/// - Flags
/// - RCODE1
/// - RCODE2
static const uint16_t FIXED_FIELDS_LEN = 3;
/// @brief Constructor, creates option instance using flags and domain name.
///
/// This constructor is used to create an instance of the option which will
/// be included in outgoing messages.
///
/// Note that the RCODE values are encapsulated by the Rcode object (not a
/// simple uint8_t value). This helps to prevent a caller from confusing the
/// flags value with rcode value (both are uint8_t values). For example:
/// if caller swaps the two, it will be detected in the compilation time.
/// Also, this API encourages the caller to use two predefined functions:
/// @c RCODE_SERVER and @c RCODE_CLIENT to set the value of RCODE. These
/// functions generate objects which represent the only valid values to be
/// be passed to the constructor (255 and 0 respectively). Other
/// values should not be used. However, it is still possible that the other
/// entity (client or server) sends the option with invalid value. Although,
/// the RCODE values are ignored, there should be a way to represent such
/// invalid RCODE value. The Rcode class is capable of representing it.
///
/// @param flags a combination of flags to be stored in flags field.
/// @param rcode @c Rcode object representing a value for RCODE1 and RCODE2
/// fields of the option. Both fields are assigned the same value
/// encapsulated by the parameter.
/// @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.
/// @throw InvalidOption4FqdnFlags if value of the flags field is wrong.
/// @throw InvalidOption4FqdnDomainName if the domain-name is invalid.
explicit Option4ClientFqdn(const uint8_t flags,
const Rcode& rcode,
const std::string& domain_name,
const DomainNameType domain_name_type = FULL);
/// @brief Constructor, creates option instance with empty domain name.
///
/// This constructor creates an instance of the option with empty
/// domain-name. This domain-name is marked partial.
///
/// @param flags a combination of flags to be stored in flags field.
/// @param rcode @c Rcode object representing a value for RCODE1 and RCODE2
/// fields. Both fields are assigned the same value encapsulated by this
/// parameter.
/// @throw InvalidOption4FqdnFlags if value of the flags field is invalid.
Option4ClientFqdn(const uint8_t flags, const Rcode& rcode);
/// @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.
/// @throw InvalidOption4FqdnFlags if value of the flags field is invalid.
/// @throw InvalidOption4FqdnDomainName if the domain-name carried by the
/// option is invalid.
/// @throw OutOfRange if the option is truncated.
explicit Option4ClientFqdn(OptionBufferConstIter first,
OptionBufferConstIter last);
/// @brief Copy constructor
Option4ClientFqdn(const Option4ClientFqdn& source);
/// @brief Copies this option and returns a pointer to the copy.
virtual OptionPtr clone() const;
/// @brief Destructor
virtual ~Option4ClientFqdn();
/// @brief Assignment operator
Option4ClientFqdn& operator=(const Option4ClientFqdn& source);
/// @brief Checks if the specified flag of the DHCPv4 Client FQDN %Option
/// is set.
///
/// @param flag A value specifying a bit within flags field to be checked.
/// It must be one of the following @c FLAG_S, @c FLAG_E, @c FLAG_O,
/// @c FLAG_N.
///
/// @return true if the bit of the specified flags bit is set, false
/// otherwise.
/// @throw InvalidOption4ClientFlags if specified flag which value is to be
/// returned is invalid (is not one of the FLAG_S, FLAG_N, FLAG_O).
bool getFlag(const uint8_t flag) const;
/// @brief Modifies the value of the specified DHCPv4 Client Fqdn %Option
/// flag.
///
/// @param flag A value specifying a bit within flags field to be set. It
/// must be one of the following @c FLAG_S, @c FLAG_E, @c FLAG_O, @c FLAG_N.
/// @param set a boolean value which indicates whether flag should be
/// set (true), or cleared (false).
/// @throw InvalidOption4ClientFlags if specified flag which value is to be
/// set is invalid (is not one of the FLAG_S, FLAG_N, FLAG_O).
void setFlag(const uint8_t flag, const bool set);
/// @brief Sets the flag field value to 0.
void resetFlags();
/// @brief Returns @c Rcode objects representing value of RCODE1 and RCODE2.
///
/// @return Pair of Rcode objects of which first is the RCODE1 and the
/// second is RCODE2.
std::pair<Rcode, Rcode> getRcode() const;
/// @brief Set Rcode value.
///
/// @param rcode An @c Rcode object representing value of RCODE1 and RCODE2.
/// Both fields are assigned the same value.
void setRcode(const Rcode& rcode);
/// @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.
/// @throw InvalidOption4FqdnDomainName if the specified domain-name is
/// invalid.
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 DHCPv4 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 +
/// DHCPv4 option header).
///
/// @return length of the option.
virtual uint16_t len() const;
///
/// @name Well known Rcode declarations for DHCPv4 Client FQDN %Option
///
//@{
/// @brief Rcode being set by the server.
inline static const Rcode& RCODE_SERVER() {
static Rcode rcode(255);
return (rcode);
}
/// @brief Rcode being set by the client.
inline static const Rcode& RCODE_CLIENT() {
static Rcode rcode(0);
return (rcode);
}
//@}
private:
/// @brief A pointer to the implementation.
Option4ClientFqdnImpl* impl_;
};
/// A pointer to the @c Option4ClientFqdn object.
typedef boost::shared_ptr<Option4ClientFqdn> Option4ClientFqdnPtr;
} // namespace isc::dhcp
} // namespace isc
#endif // OPTION4_CLIENT_FQDN_H
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