2 // Fraunhofer Institut fuer offene Kommunikationssysteme (FOKUS)
3 // Kompetenzzentrum fuer Satelitenkommunikation (SatCom)
4 // Stefan Bund <g0dil@berlios.be>
6 // This program is free software; you can redistribute it and/or modify
7 // it under the terms of the GNU General Public License as published by
8 // the Free Software Foundation; either version 2 of the License, or
9 // (at your option) any later version.
11 // This program is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // You should have received a copy of the GNU General Public License
17 // along with this program; if not, write to the
18 // Free Software Foundation, Inc.,
19 // 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
22 \brief PacketParser public header */
24 /** \defgroup packetparser The PacketParser facility
26 The PacketParser facility provides a framework to implement very lightweight classes which parse
27 the raw content of a packet into meaningful values. PacketParsers are always passed around
28 <em>by value</em>, they can be understood as pointers into the packet data with added type
29 information providing parsing functions.
31 Parsers are built hierarchically. A high-level parser will return other parsers when accessing
32 an element (Example: Asking an EthernetParser for the ethertype field by calling the parsers \c
33 type() member will return an \c UInt16 parser). The lowest level building blocks then return the
34 values. This hierarchical structure greatly simplifies building complex parsers.
36 Since parsers are very lightweight and are passed by value, packet fields are accessed using the
37 corresponding accessor method:
42 // Assign new value to an integer parser
45 // Write out above value
46 std::cerr << p->someField() << "\n";
48 // Use the generic parser-assignment operator '<<' to copy field values
49 p->someVector()[1].someOtherField() << q->someField();
50 p->someVector() << q->someVector()
53 Here \c someField(), \c someOtherField() and \c someVector() are accessor methods named after
54 the field name. Each returns a parser object. Simple parsers can be used like their
55 corresponding basic type (e.g. a Parse_UInt16 field can be used like an unsigned integer), more
56 complex parsers provide type specific access members. Assigning a value to a parser will change
57 the underlying representation (the packet data).
59 More complex parsers (especially those representing a collection of values) provide an
60 additional wrapper class for mutating access (e.g. Parse_Vector provides a container wrapper
61 with am STL compatible random-access sequence interface). See the documentation of the specific
62 parser for the wrapper specification.
64 Every parser is derived from senf::PacketParserBase. This class provides the necessary
65 housekeeping information and provides the parsers with access to the data.
67 \warning Parsers are like iterators: They are invalidated <em>whenever the size of the packet's
68 data is changed</em>. You should not store a parser anywhere. If you want to keep a parser
69 reference, use the senf::SafePacketParser wrapper. You still will need to take extra care to
70 ensure the parser is not invalidated.
73 #ifndef HH_PacketParser_
74 #define HH_PacketParser_ 1
77 #include <boost/utility/enable_if.hpp>
78 #include <boost/type_traits.hpp>
79 #include <boost/optional.hpp>
80 #include "Utils/SafeBool.hh"
81 #include "PacketTypes.hh"
82 #include "PacketData.hh"
84 #include "PacketParser.mpp"
85 ///////////////////////////////hh.p////////////////////////////////////////
89 /** \brief Parser Base class
91 Parsers come in two favors: fixed and dynamically sized parsers. A <em>fixed size
92 parser</em> has a constant size, it will always parse a fixed number of bytes. The low-level
93 'final' parsers (like the integer parsers) are fixed size parsers as are composite parsers
94 built up only of fixed-size fields.
96 A <em>dynamically sized</em> parser on the other hand infers it's size from the contents of
97 the data parsed. Any parser containing at least one dynamically sized sub-parser will itself
100 Both kinds of parser need to derive from PacketParserBase and implement several required
101 members. Which members to implement depends on the parsers flavor. There are two ways how to
103 \li If the parser just consists of a simple sequence of consecutive fields (sub-parsers),
104 the \ref SENF_PACKET_PARSER_DEFINE_FIELDS and \ref
105 SENF_PACKET_PARSER_DEFINE_FIXED_FIELDS macros provide a simple and convenient way to
107 \li In more complex cases, you need to implement the necessary members manually.
109 This documentation is about the manual implementation. You should nevertheless read through
110 this to understand, what above macros are doing.
112 The following example documents the interface (which must be) provided by a parser:
114 struct FooParser : public PacketParserBase
116 FooParser(data_iterator i, state_type s) : PacketParserBase(i,s) {}
118 // If this parser has a fixed size, you must define this size here This definition
119 // allows the parser to be used within the list, vector and array parsers static
120 static const size_type fixed_bytes = some_constant_size;
122 // If the parser does not have a fixed size, you must implement the bytes() member to
123 // return the size. ONLY EVER DEFINE ONE OF fixed_bytes OR bytes().
124 size_type bytes() const;
126 // If you define bytes(), you also need to define the init_bytes. This is the number
127 // of bytes to allocate when creating a new object
128 static const size_type init_bytes = some_constant_size;
130 // You also may define an init() member. This will be called to initialize a newly
131 // created data object. The default implementation just does nothing.
134 // ////////////////////////////////////////////////////////////////////////
136 // Add here members returning (sub-)parsers for the fields. The 'parse' member is
137 // used to construct the sub-parsers. This member either takes an iterator to the
138 // data to be parsed or just an offset in bytes.
140 senf::Parse_UInt16 type() const { return parse<Parse_UInt16>( 0 ); }
141 senf::Parse_UInt16 size() const { return parse<Parse_UInt16>( 2 ); }
145 You should never call the \c bytes() member of a parser directly. Instead you should use the
146 freestanding senf::bytes() function. This function will return the correct size irrespective
147 of the parsers flavor. You may access \c fixed_bytes directly, however be aware that this
148 will restrict your code to fixed size parsers (which depending on the circumstances may be
149 exactly what you want).
151 In the same way, don't access \c init_bytes directly, always use the senf::init_bytes
152 meta-function class which correctly supports fixed size parsers.
154 \ingroup packetparser
156 class PacketParserBase
159 ///////////////////////////////////////////////////////////////////////////
162 typedef detail::packet::iterator data_iterator; ///< Raw data iterator type
163 typedef detail::packet::size_type size_type; ///< Unsigned integral type
164 typedef detail::packet::difference_type difference_type; ///< Signed integral type
165 typedef detail::packet::byte byte; ///< Unsigned 8bit value, the raw value type
166 typedef PacketData * state_type; ///< Type of the 'state' parameter
168 ///////////////////////////////////////////////////////////////////////////
169 ///\name Structors and default members
172 // no default constructor
174 // default destructor
175 // no conversion constructors
178 ///////////////////////////////////////////////////////////////////////////
180 data_iterator i() const; ///< Return beginning of data to parse
181 /**< The parser is expected to interpret the data beginning
182 here. The size of the interpreted is given by
183 <tt>senf::bytes(</tt><em>parser
184 instance</em><tt>)</tt>. */
185 state_type state() const; ///< Return state of this parser
186 /**< The value returned should be interpreted as an opaque
187 value provided just to be forwarded to other
189 PacketData & data() const; ///< Access the packets raw data container
190 /**< This member will return the raw data container holding
191 the data which is parsed by \c this parser. */
193 void init() const; ///< Default implementation
194 /**< This is just an empty default
195 implementation. Re-implement this member in your own
196 parsers if needed. */
199 PacketParserBase(data_iterator i, state_type s); ///< Standard constructor
200 /**< This is the constructor used by most parsers. The
201 parameters are just forwarded from the derived classes
202 constructor parameters. */
203 PacketParserBase(data_iterator i, state_type s, size_type size);
204 ///< Size checking constructor
205 /**< In addition to the standard constructor, this
206 constructor will validate, that there is enough data in
207 the raw data container to parse \a size bytes after \a
210 This constructor is called by all 'final' parsers
211 (e.g. the integer parsers) and \e only by those
212 parsers. Most parsers do \e not check the validity of
213 the iterator, this is delayed until the very last
214 parser. This allows to partial parse truncated
217 \throw TruncatedPacketException if the raw data
218 container does not hold at least \a size bytes
219 beginning at \a i. */
221 bool check(size_type size); ///< Check size of data container
222 /**< \returns \c true, if the data container holds at least
223 \a size beginning at i(), \c false otherwise. */
224 void validate(size_type size); ///< Validate size of data container
225 /**< \throws TruncatedPacketException if the raw data
226 container does not hold at least \a size bytes
229 template <class Parser> Parser parse(data_iterator i) const; ///< Create sub-parser
230 /**< Creates a new instance of \a Parser to parse data
231 beginning at \a i. Automatically passes \a state() to
233 template <class Parser> Parser parse(size_type n) const; ///< Create sub-parser
234 /**< Creates a new instance of \a Parser to parse data
235 * beginning at i()<tt> + </tt>\a n. Automatically passes \a
236 state() to the new parser. */
238 void defaultInit() const; ///< Default implementation
239 /**< This is just an empty default
240 implementation. Re-implement this member in your own
241 parsers if needed. */
249 template <class Parser> friend class SafePacketParser;
252 /** \brief Return raw size parsed by the given parser object
254 This function will either call <tt>p.bytes()</tt> or return <tt>Parser::fixed_bytes</tt>
255 depending on the type of parser.
257 The value returned does \e not take into account the amount of data actually available. So
258 you always need to validate this value against the packet size if you directly access the
259 data. The standard low-level parses all do this check automatically to guard against
262 \param[in] p Parser object to check
263 \returns number of bytes this parser expects to parser
264 \ingroup packetparser
266 template <class Parser>
267 PacketParserBase::size_type bytes(Parser p);
269 namespace detail { template <class Parser> class ParserInitBytes; }
271 /** \brief Return number of bytes to allocate to new object of given type
273 This meta-function is called like
275 senf::init_bytes<SomeParser>::value
278 This expression evaluates to a compile-time constant integral expression of type
279 senf::PacketParserBase::size_type. This meta-function will return \c Parser::fixed_bytes or
280 \c Parser::init_bytes depending on the type of parser.
282 \param[in] Parser The Parser to return init_bytes for
283 \returns Number of bytes to allocate to the new object
284 \ingroup packetparser
286 template <class Parser>
287 struct init_bytes : public detail::ParserInitBytes<Parser>
290 /** \brief Generic parser copying
292 This operator allows to copy the values of identical parsers. This operation does \e not
293 depend on the parsers detailed implementation, it will just replace the data bytes of the
294 target parser with those from the source parser. This allows to easily copy around complex
295 packet substructures.
297 This operation is different from the ordinary assignment operator: It does not change the \a
298 target parser, it changes the data referenced by the \a target parser.
300 \ingroup packetparser
302 template <class Parser>
303 typename boost::enable_if<
304 boost::is_base_of<PacketParserBase, Parser>,
306 operator<<(Parser target, Parser source);
308 /** \brief Generic parser value assignment
310 This operator allows to assign a value to parsers which implement a <tt>value(</tt>\a
311 value<tt>)</tt> member. This operator allows to use a common syntax for assigning values or
314 \ingroup packetparser
316 template <class Parser, class Value>
317 typename boost::enable_if_c <
318 boost::is_base_of<PacketParserBase, Parser>::value
319 && ! boost::is_base_of<PacketParserBase, Value>::value,
321 operator<<(Parser target, Value const & value);
323 /** \defgroup packetparsermacros Helper macros for defining new packet parsers
325 To simplify the definition of simple packet parsers, several macros are provided. Before
326 using these macros you should familiarize yourself with the packet parser interface as
327 described in senf::PacketParserBase.
329 These macros simplify providing the above defined interface. A typical packet declaration
330 using these macros has the following form (This is a concrete example from the definition of
331 the ethernet packet in <tt>DefaultBundle/EthernetPacket.hh</tt>)
333 \dontinclude EthernetPacket.hh
334 \skipline struct Parse_EthVLan : public PacketParserBase
337 The macros take care of the following:
338 \li They define the accessor functions returning parsers of the given type.
339 \li They automatically calculate the offset of the fields from the preceding fields.
340 \li The macros provide a definition for \c init()
341 \li The macros define the \c bytes(), \c fixed_bytes and \c init_bytes members as needed.
343 You may define either a fixed or a dynamically sized parser. Fixed size parsers are defined
344 using \ref SENF_PACKET_PARSER_DEFINE_FIXED_FIELDS, dynamically sized parsers are defined
345 using \ref SENF_PACKET_PARSER_DEFINE_FIELDS. The different members are implemented such
348 \li The needed parser constructor is defined
349 \li \c init() calls \c defaultInit(). \c defaultInit() is defined to call \c init() on each
351 \li \c bytes() (on dynamically sized parser) respectively \c fixed_bytes (on fixed size
352 parsers) is defined to return the sum of the sizes of all fields.
353 \li On dynamically sized parsers, \c init_bytes is defined to return the sum of the
354 \c init_size's of all fields
356 The central definition macros are \ref SENF_PACKET_PARSER_DEFINE_FIXED_FIELDS and \ref
357 SENF_PACKET_PARSER_DEFINE_FIELDS. The argument to both has the same structure. It is a
358 (boost preprocessor style) sequence of field definitions where each field definition
359 provides the builder macro to use and the name and type of the field to define:
361 SENF_PACKET_PARSER_DEFINE[_FIXED]_FIELDS(
362 (( <builder> )( <name>, <type> ))
367 For each field, this command will define
368 \li A method \a name() returning an instance of the \a type parser
369 \li \a name<tt>_t</tt> as a typedef for \a type, the fields value
370 \li \a name<tt>_offset</tt> to give the offset of the field from the beginning of the
371 parser. If the parser is a fixed size parser, this will be a static constant, otherwise
374 The \a builder argument selects, how the field is defined
375 \li <tt>Field</tt> defines a field and increments the current position by the size of the
377 \li <tt>OverlayField</tt> defines a field like <tt>Field</tt> but does \e not increment the
378 position. In the above example, this is used to overlay the different bitfield parsers:
379 All overlaying bitfield parser except the last one (the one with the highest bit
380 numbers) is marked as OverlayField.
382 The \a name argument defines the name of the accessor method.
384 The \a type argument is the parser to return for that field. Since none of the arguments may
385 contain a comma, <em>This argument cannot be a multi-parameter template</em>. Always use
386 typedefs to access templated parsers as shown above.
388 The \ref SENF_PACKET_PARSER_INIT macro defines the constructor and the \c init() member. If
389 you want to provide your own \c init() implementation, use \ref
390 SENF_PACKET_PARSER_NO_INIT. The first statement in your init method should probably to call
391 \c defaultInit(). This will call the \c init() member of all the fields. Afterwards you can
392 set up the field values as needed:
394 struct SomePacket : public senf::PacketParserBase
396 SENF_PACKET_PARSER_NO_INIT(SomePacket);
398 typedef senf::Parse_UInt8 Parse_Type;
399 typedef senf::Parse_Vector< senf::Parse_UInt32,
400 senf::SimpleVectorSizer<senf::Parse_UInt16>
403 SENF_PACKET_PARSER_DEFINE_FIELDS(
404 ((Field)( type, Parse_Type ))
405 ((Field)( elements, Parse_Elements ))
411 elements().push_back(0x01020304u);
416 \ingroup packetparser
419 /** \brief Define initialization members of a parser
421 This macro defines the packet parser constructor and the \c init() member. \c init() is
422 defined to just call \c defaultInit() which is defined by the other macros to call \c init()
423 on each of the parsers fields.
425 \ingroup packetparsermacros
428 # define SENF_PACKET_PARSER_INIT(name) \
429 name(data_iterator i, state_type s) : senf::PacketParserBase(i,s) {} \
430 void init() const { defaultInit(); }
432 /** \brief Define initialization members of a parser except init()
434 This macro is like SENF_PACKET_PARSER_INIT but does \e not define \c init(). This allows you
435 to provide your own implementation. You should call \c defaultInit() first before
436 initializing your data fields.
438 \ingroup packetparsermacros
441 # define SENF_PACKET_PARSER_NO_INIT(name) \
442 name(data_iterator i, state_type s) : senf::PacketParserBase(i,s) {}
444 /** \brief Define fields for a dynamically sized parser
446 Define the fields as specified in \a fields. This macro supports dynamically sized
447 subfields, the resulting parser will be dynamically sized.
449 \ingroup packetparsermacros
452 # define SENF_PACKET_PARSER_DEFINE_FIELDS(fields) \
453 SENF_PACKET_PARSER_I_DEFINE_FIELDS(0,fields)
455 /** \brief Define fields for a dynamically sized parser (with offset)
457 Define the fields as specified in \a fields. This macro supports dynamically sized
458 subfields, the resulting parser will be dynamically sized.
460 The \a offset argument gives the byte offset at which to start parsing the fields. This
461 helps defining extended parser deriving from a base parser:
463 struct ExtendedParser : public BaseParser
465 ExtendedParser(data_iterator i, state_type s) : BaseParser(i,s) {}
467 SENF_PACKET_PARSER_DEFINE_FIELDS_OFFSET(senf::bytes(BaseParser(*this)),
468 ( ... fields ... ) );
478 \ingroup packetparsermacros
481 # define SENF_PACKET_PARSER_DEFINE_FIELDS_OFFSET(offset,fields) \
482 SENF_PACKET_PARSER_I_DEFINE_FIELDS(offset,fields)
484 /** \brief Define fields for a fixed size parser
486 Define the fields as specified in \a fields. This macro only supports fixed size
487 subfields, the resulting parser will also be a fixed size parser.
489 \ingroup packetparsermacros
492 # define SENF_PACKET_PARSER_DEFINE_FIXED_FIELDS(fields) \
493 SENF_PACKET_PARSER_I_DEFINE_FIXED_FIELDS(0,fields)
495 /** \brief Define fields for a fixed size parser
497 Define the fields as specified in \a fields. This macro only supports fixed size
498 subfields, the resulting parser will also be a fixed size parser.
500 The \a offset argument gives the byte offset at which to start parsing the fields. This
501 helps defining extended parser deriving from a base parser:
503 struct ExtendedParser : public BaseParser
505 ExtendedParser(data_iterator i, state_type s) : BaseParser(i,s) {}
507 SENF_PACKET_PARSER_DEFINE_FIXED_FIELDS_OFFSET(BaseParser::fixed_bytes,
508 ( ... fields ... ) );
518 \ingroup packetparsermacros
521 # define SENF_PACKET_PARSER_DEFINE_FIXED_FIELDS_OFFSET(offset,fields) \
522 SENF_PACKET_PARSER_I_DEFINE_FIXED_FIELDS(offset,fields)
524 /** \brief Default parser parsing nothing
526 struct VoidPacketParser
527 : public PacketParserBase
529 SENF_PACKET_PARSER_INIT(VoidPacketParser);
532 /** \brief Iterator re-validating Parser wrapper
534 An ordinary parser will be invalidated whenever the raw data container's size is
535 changed. This can complicate some algorithms considerably.
537 This wrapper will update the parsers iterator (the value returned by the i() member) on
538 every access. This ensures that the iterator will stay valid.
540 \attention Beware however, if you insert or remove data before the safe wrapper, the
541 location will \e not be updated accordingly and therefore the parser will be
544 Additionally a SafePacketParser has an uninitialized state. The only allowed operations in
545 this state are the boolean test for validity and assigning another parser.
547 \ingroup packetparser
549 template <class Parser>
550 class SafePacketParser
551 : public SafeBool< SafePacketParser<Parser> >
554 ///////////////////////////////////////////////////////////////////////////
557 ///////////////////////////////////////////////////////////////////////////
558 ///\name Structors and default members
561 // default copy constructor
562 // default copy assignment
563 // default destructor
564 SafePacketParser(); ///< Create an empty uninitialized SafePacketParser
566 // conversion constructors
567 SafePacketParser(Parser parser); ///< Initialize SafePacketParser from \a parser
569 SafePacketParser & operator=(Parser parser); ///< Assign \a parser to \c this
572 ///////////////////////////////////////////////////////////////////////////
574 Parser operator*() const; ///< Access the stored parser
575 /**< On every access, the stored parsers iterator will be
576 updated / re-validated. */
577 Parser const * operator->() const; ///< Access the stored parser
578 /**< On every access, the stored parsers iterator will be
579 updated / re-validated. */
580 bool boolean_test() const; ///< Check validity
585 mutable boost::optional<Parser> parser_;
586 senf::safe_data_iterator i_;
591 ///////////////////////////////hh.e////////////////////////////////////////
593 #if !defined(SENF_PACKETS_DECL_ONLY) && !defined(HH_PacketParser_i_)
594 #define HH_PacketParser_i_
595 #include "PacketParser.cci"
596 #include "PacketParser.ct"
597 #include "PacketParser.cti"
604 // c-file-style: "senf"
605 // indent-tabs-mode: nil
606 // ispell-local-dictionary: "american"
607 // compile-command: "scons -u test"
608 // comment-column: 40