4 // Fraunhofer Institute for Open Communication Systems (FOKUS)
5 // Competence Center NETwork research (NET), St. Augustin, GERMANY
6 // Stefan Bund <g0dil@berlios.de>
8 // This program is free software; you can redistribute it and/or modify
9 // it under the terms of the GNU General Public License as published by
10 // the Free Software Foundation; either version 2 of the License, or
11 // (at your option) any later version.
13 // This program is distributed in the hope that it will be useful,
14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 // GNU General Public License for more details.
18 // You should have received a copy of the GNU General Public License
19 // along with this program; if not, write to the
20 // Free Software Foundation, Inc.,
21 // 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
23 /** \mainpage The SENF Packet Library
25 The SENF Packet library provides facilities to analyze, manipulate and create structured packet
26 oriented data (e.g. network packets).
31 \section packet_intro_arch Introduction
32 \seechapter \ref packet_arch
34 The Packet library consists of several components:
36 \li The \ref packet_module manages the packet data and provides the framework for handling the
37 chain of packet headers. The visible interface is provided by the Packet class.
38 \li \ref packetparser provides the framework for interpreting packet data. It handles
39 parsing the packet information into meaningful values.
40 \li The \ref protocolbundles provide concrete implementations for interpreting packets of
41 some protocol. The Protocol Bundles are built on top of the basic packet library.
43 All these components work together to provide a hopefully simple and intuitive interface to
44 packet parsing and creation.
47 \section packet_intro_usage Tutorial
48 \seechapter \ref packet_usage
50 This chapter discusses the usage of the packet library from a high level view.
53 \section packet_intro_api The packet API
55 The packet library API is divided into three areas
57 \li the \ref senf::PacketData API for accessing the raw data container
58 \li the packet interpreter chain providing \ref packet_module
59 \li and \ref packetparser which provides access to protocol specific packet fields.
62 \section protocolbundles Supported packet types (protocols)
64 Each protocol bundle provides a collection of related concrete packet classes for a group of
67 \li \ref protocolbundle_default : Some basic default protocols: Ethernet, Ip, TCP, UDP
68 \li \ref protocolbundle_mpegdvb : MPEG and DVB protocols
69 \li \ref protocolbundle_80211 : 802.11 protocols
71 There are two ways to link with a bundle
73 \li If you only work with known packets which you explicitly reference you may just link with
74 the corresponding library.
75 \li If you need to parse unknown packets and want those to be parsed as complete as possible
76 without explicitly referencing the packet type, you will need to link against the combined
77 object file built for every bundle. This way, all packets defined in the bundle will be
78 included whether they are explicitly referenced or not (and they will all automatically be
82 \section packet_intro_new Defining new packet types
83 \seechapter \ref packet_new
85 The packet library provides the framework which allows to define arbitrary packet types. There
86 is quite some information needed to completely specify a specific type of packet.
90 /** \page packet_arch Overall Packet library Architecture
92 The packet library handles network packets of a large number of protocols. We work with a packet
98 \section packet_arch_handle The Packet handle
100 Whenever we are using a Packet, we are talking about a senf::Packet (or a
101 senf::ConcretePacket). This class is a \e handle referencing an internally managed packet data
102 structure. So even though we pass senf::Packet instances around by value, they work like
103 references. The packet library automatically manages all required memory resources using
106 Different Packet handles may really internally share one Packet data structure if they both
107 point to the same packet.
110 \section packet_arch_data The Packet as a 'bunch of bytes'
112 From the outside, a packet is just a bunch of bytes just as it is read from (or will be
113 written to) the wire. At this low-level view, we can access the data in it's raw form but
114 have no further information about what kind of packet we have.
116 The packet library provides a consistent container interface for this representation.
121 // Change first byte of packet to 0
124 // Copy packet data into a vector
125 std::vector<char> data (p.data().size());
126 std::copy(p.data().begin(), p.data().end(), data.begin());
129 This type of access is primarily needed when reading or writing packets (e.g. to/from the
132 \see senf::Packet::data() \n
136 \section packet_arch_chain The Interpreter Chain
138 On the next level, the packet is divided into a nested list of sub-packets (or headers) called
139 interpreters. Each senf::Packet handle internally points to an interpreter or header. This
140 allows us to access one and the same packet in different ways.
142 Consider an Ethernet Packet with an IP payload holding a UDP packet. We may reference either the
143 Ethernet packet as a whole or we may reference the IP or UDP interpreters (sub-packets or
144 headers). All handles really refer to the \e same data structure but provide access to a
145 different (sub-)range of the data in the packet.
147 We can navigate around this chained structure using appropriate members:
150 // eth, ip and udp all reference the same internal packet data albeit at different data ranges
152 Packet ip = eth.next();
153 Packet udp = ip.next();
155 eth.next() == ip // true
156 eth.next().is<IPv4Packet>() // true
157 eth.next().next() == udp // true
158 eth.next().is<UDPPacket>() // false
159 eth.find<UDPPacket>() == udp // true
161 udp.find<EthernetPacket>() // throws InvalidPacketChainException
162 udp.find<EthernetPacket>(senf::nothrow) // An in-valid() senf::Packet which tests as 'false'
163 udp.find<UDPPacket> == udp // true
164 udp.first<IPv4Packet>() // throws InvalidPacketChainException
166 udp.prev() == ip // true
167 udp.prev<EthernetPacket>() // throws InvalidPacketChainException
170 \see \ref packet_module
173 \section packet_arch_parser Parsing specific Protocols
175 On the next level, the packet library allows us to parse the individual protocols. This gives us
176 access to the protocol specific data members of a packet and allows us to access or manipulate a
177 packet in a protocol specific way.
179 To access this information, we need to use a protocol specific handle, the senf::ConcretePacket
180 which takes as a template argument the specific type of packet to be interpreted. This allows us
181 to easily interpret or create packets. Here an example on how to create a new Ethernet / IP / UDP
182 / Payload packet interpreter chain:
185 // EthernetPacket, IPv4Packet, UDPPacket and DataPacket are typedefs for corresponding
186 // ConcretePacket instantiations
187 senf::EthernetPacket eth (senf::EthernetPacket::create());
188 senf::IPv4Packet ip (senf::IPv4Packet ::createAfter(eth));
189 senf::UDPPacket udp (senf::UDPPacket ::createAfter(ip));
190 senf::DataPacket payload (senf::DataPacket ::createAfter(udp,
191 std::string("Hello, world!")));
193 udp->source() = 2000u;
194 udp->destination() = 2001u;
196 ip->source() = senf::INet4Address::from_string("192.168.0.1");
197 ip->destination() = senf::INet4Address::from_string("192.168.0.2");
198 eth->source() = senf::MACAddress::from_string("00:11:22:33:44:55");
199 eth->destination() = senf::MACAddress::from_string("00:11:22:33:44:66");
204 Again, realize, that \a eth, \a ip, \a udp and \a payload share the same internal packet
205 data structure (the respective \c data() members all provide access to the same underlying
206 container however at different byte ranges): The complete packet can be accessed at
207 <tt>eth.data()</tt> whereas <tt>payload.data()</tt> only holds UDP payload (in this case the
208 string "Hello, world!").
210 \see \ref packetparser \n
214 /** \page packet_usage Using the packet library
218 \section packet_usage_intro Includes
220 To use the library, you need to include the appropriate header files. This will probably happen
221 automatically when including the specific protocol headers. If needed, you may explicitly use
224 #include "Packets.hh"
229 \warning Never include any other Packets library header directly, only include \c
230 Packets.hh or one (or several) protocol headers from the protocol bundles.
232 Most every use of the packet library starts with some concrete packet typedef. Some fundamental
233 packet types are provided by \ref protocolbundle_default.
236 \section packet_usage_create Creating a new packet
238 Building on those packet types, this example will build a complex packet: This will be an
239 Ethernet packet containing an IPv4 UDP packet. We begin by building the raw packet skeleton:
242 #include "Packets/DefaultBundle/EthernetPacket.hh"
243 #include "Packets/DefaultBundle/IPv4Packet.hh"
244 #include "Packets/DefaultBundle/UDPPacket.hh"
246 senf::EthernetPacket eth (senf::EthernetPacket::create());
247 senf::IPv4Packet ip (senf::IPv4Packet ::createAfter(eth));
248 senf::UDPPacket udp (senf::UDPPacket ::createAfter(ip));
249 senf::DataPacket payload (senf::DataPacket ::createAfter(udp,
250 std::string("Hello, world!")));
253 These commands create what is called an interpreter chain. This chain consists of four
254 interpreters. All interpreters reference the same data storage. This data storage is a random
255 access sequence which contains the data bytes of the packet.
257 \note The data structures allocated are automatically managed using reference counting. In this
258 example we have four packet references each referencing the same underlying data
259 structure. This data structure will be freed when the last reference to it goes out of
262 The packet created above already has the correct UDP payload (The string "Hello, world!")
263 however all protocol fields are empty. We need to set those protocol fields:
266 udp->source() = 2000u;
267 udp->destination() = 2001u;
269 ip->source() = senf::INet4Address::from_string("192.168.0.1");
270 ip->destination() = senf::INet4Address::from_string("192.168.0.2");
271 eth->source() = senf::MACAddress::from_string("00:11:22:33:44:55");
272 eth->destination() = senf::MACAddress::from_string("00:11:22:33:44:66");
277 As seen above, packet fields are accessed using the <tt>-></tt> operator whereas other packet
278 facilities (like \c finalizeAll()) are directly accessed using the member operator. The field
279 values are simply set using appropriately named accessors. As a last step, the \c finalizeAll()
280 call will update all calculated fields (fields like next-protocol, header or payload length,
281 checksums etc). Now the packet is ready. We may now send it out using a packet socket
284 senf::PacketSocketHandle sock ("eth0");
285 sock.write(eth.data());
289 \section packet_usage_read Reading and parsing packets
291 The chain navigation functions are also used to parse a packet. Let's read an Ethernet packet
292 from a packet socket handle:
295 senf::PacketSocketHandle sock ("eth0");
296 senf::EthernetPacket packet (senf::EthernetPacket::create(senf::noinit));
297 sock.read(packet.data(),0u);
300 This first creates an uninitialized Ethernet packet and then reads into this packet. We can now
301 parse this packet. Let's find out, whether this is a UDP packet destined to port 2001:
305 senf::UDPPacket udp (packet.find<UDPPacket>());
306 if (udp->destination() == 2001u) {
309 } catch (senf::TruncatedPacketException &) {
310 std::cerr << "Ooops !! Broken packet received\n";
311 } catch (senf::InvalidPacketChainException &) {
312 std::cerr << "Not a udp packet\n";
316 TruncatedPacketException is thrown by <tt>udp->destination()</tt> if that field cannot be
317 accessed (that is it would be beyond the data read which means we have read a truncated
318 packet). More generally, whenever a field cannot be accessed because it would be out of bounds
319 of the data read, this exception is generated.
322 \section packet_usage_container The raw data container
324 Every packet is based internally on a raw data container holding the packet data. This container
325 is accessed via senf::Packet::data() member.
327 This container is a random access container. It can be used like an ordinary STL container and
328 supports all the standard container members.
333 // Insert 5 0x01 bytes
334 p.data().insert(p.data().begin()+5, 5, 0x01);
336 // Insert data from another container
337 p.data().insert(p.data().end(), other.begin(), other.end());
339 // Erase a single byte
340 p.data().erase(p.data().begin()+5);
342 // XOR byte 5 with 0xAA
346 A packet consists of a list of interpreters (packet headers or protocols) which all reference
347 the same data container at different byte ranges. Each packet consists of the protocol header \e
348 plus the packets payload. This means, that the data container ranges of successive packets from
349 a single interpreter chain are nested.
351 Example: The packet created above (the Ethernet-IP-UDP packet with payload "Hello, world!") has
352 4 Interpreters: Ethernet, IPv4, UDP and the UDP payload data. The nested data containers lead to
353 the following structure
356 // The ethernet header has a size of 14 bytes
357 eth.data().begin() + 14 == ip.data().begin()
358 eth.data().end() == ip.data().end()
360 // The IP header has a size of 20 bytes and therefore
361 ip.data().begin() + 20 == udp.data().begin()
362 ip.data().end() == udp.data().end()
364 // The UDP header has a size of 8 bytes and thus
365 udp.data().begin() + 8 == payload.data().begin()
366 udp.data().end() == payload.data().end()
369 This nesting will (and must) always hold: The data range of a subsequent packet will always be
370 within the range of it's preceding packet.
372 \warning It is forbidden to change the data of a subsequent packet interpreter from the
373 preceding packet even if the data container includes this data. If you do so, you may
374 corrupt the data structure (especially when changing it's size).
376 Every operation on a packet is considered to be \e within this packet and \e without and
377 following packet. When inserting or erasing data, the data ranges are all adjusted
378 accordingly. So the following are \e not the same even though \c eth.end(), \c ip.end() and \c
379 udp.end() are identical.
382 eth.data().insert(eth.data().end(), 5, 0x01);
383 assert( eth.data().end() == ip.data().end() + 5
384 && ip.data().end() == udp.data().end() );
386 // Or alternatively: (You could even use eth.data().end() here ... it's the same)
387 ip.data().insert(ip.data().end(), 5, 0x01);
388 assert( eth.data().end() == ip.data().end()
389 && ip.data().end() == udp.data().end() + 5 );
392 \warning When accessing the packet data via the container interface, you may easily build
393 invalid packets since the packet will not be validated against it's protocol.
396 \section packet_usage_fields Field access
398 When working with concrete protocols, the packet library provides direct access to all the
399 protocol information.
402 udp->source() = 2000u;
403 udp->destination() = 2001u;
405 ip->source() = senf::INet4Address::from_string("192.168.0.1");
406 ip->destination() = senf::INet4Address::from_string("192.168.0.2");
407 eth->source() = senf::MACAddress::from_string("00:11:22:33:44:55");
408 eth->destination() = senf::MACAddress::from_string("00:11:22:33:44:66");
411 The protocol field members above do \e not return references, they return parser instances.
412 Protocol fields are accessed via parsers. A parser is a very lightweight class which points into
413 the raw packet data and converts between raw data bytes and it's interpreted value: For example
414 a senf::UInt16Parser accesses 2 bytes (in network byte order) and converts them to or from a 16
415 bit integer. There are a few properties about parsers which need to be understood:
417 \li Parsers are created only temporarily when needed. They are created when accessing a protocol
418 field and are returned by value.
420 \li A parser never contains a value itself, it just references a packets data container.
422 \li Parsers can be built using other parsers and may have members which return further parsers.
424 The top-level interface to a packets protocol fields is provided by a protocol parser. This
425 protocol parser is a composite parser which has members to access the protocol fields (compare
426 with the example code above). Some protocol fields may be more complex than a simple value. In
427 this case, those accessors may return other composite parsers or collection parsers. Ultimately,
428 a value parser will be returned.
430 The simple value parsers which return plain values (integer numbers, network addresses etc) can
431 be used like those values and can also be assigned corresponding values. More complex parsers
432 don't allow simple assignment. However, they can always be copied from another parser <em>of the
433 same type</em> using the generalized parser assignment. This type of assignment also works for
434 simple parsers and is then identical to a normal assignment.
437 // Copy the complete udp parser from udp packet 2 to packet 1
438 udp1.parser() << udp2.parser();
441 Additionally, the parsers have a parser specific API which allows to manipulate or query the
444 This is a very abstract description of the parser structure. For a more concrete description, we
445 need to differentiate between the different parser types
447 \subsection packet_usage_fields_value Simple fields (Value parsers)
449 We have already seen value parsers: These are the lowest level building blocks witch parse
450 numbers, addresses etc. They return some type of value and can be assigned such a value. More
451 formally, they have a \c value_type typedef member which gives the type of value they accept and
452 they have an overloaded \c value() member which is used to read or set the value. Some parsers
453 have additional functionality: The numeric parser for Example provide conversion and arithmetic
454 operators so they can be used like a numeric value.
456 If you have a value parser \c valueParser with type \c ValueParser, the following will always be
459 // You can read the value and assign it to a variable of the corresponding value_type
460 ValueParser::value_type v (valueParser.value());
462 // You can assign that value to the parser
463 valueParser.value(v);
465 // The assignment can also be done using the generic parser assignment
470 \subsection packet_usage_fields_composite Composite and protocol parsers
472 A composite parser is a parser which just combines several other parsers into a structure: For
473 example, the senf::EthernetPacketParser has members \c destination(), \c source() and \c
474 type_length(). Those members return parsers again (in this case value parsers) to access the
477 Composite parsers can be nested; A composite parser may be returned by another composite
478 parser. The protocol parser is a composite parser which defines the field for a specific
479 protocol header like Ethernet.
481 \subsection packet_usage_fields_collection Collection parsers
483 Besides simple composites, the packet library has support for more complex collections.
485 \li The senf::ArrayParser allows to repeat an arbitrary parser a fixed number of times.
486 \li senf::VectorParser and senf::ListParser are two different types of lists with variable
488 \li The senf::VariantParser is a discriminated union: It will select one of several parsers
489 depending on the value of a discriminant.
492 \subsubsection packet_usage_collection_vector Vector and List Parsers
494 Remember, that a parser does \e not contain any data: It only points into the raw data
495 container. This is also true for the collection parsers. VectorParser and ListParser provide an
496 interface which looks like an STL container to access a sequence of elements.
498 We will use an \c MLDv2QueryPacket as an example (see <a
499 href="http://tools.ietf.org/html/rfc3810#section-5">RFC 3810</a>). Here an excerpt of the
502 <table class="fields">
503 <tr><td>nrOfSources</td><td>Integer</td><td>Number of multicast sources in this packet</td></tr>
504 <tr><td>sources</td><td>Vector of IPv6 Addresses</td><td>Multicast sources</td></tr>
507 To demonstrate nested collections, we use the \c MLDv2ReportPacket as an example. The relevant
508 fields of this packet are;
510 <table class="fields">
511 <tr><td>nrOfRecords</td><td>Integer</td><td>Number of multicast address records</td></tr>
512 <tr><td>records</td><td>List of Records</td><td>List of multicast groups and sources</td></tr>
515 Each Record is a composite with the following relevant fields:
517 <table class="fields">
518 <tr><td>nrOfSources</td><td>Integer</td><td>Number of sources in this record</td></tr>
519 <tr><td>sources</td><td>Vector of IPv6 Addresses</td><td>Multicast sources</td></tr>
522 The first example will iterate over the sources in a \c MLDv2QueryPacket:
525 MLDv2QueryPacket mld = ...;
527 // Instantiate a collection wrapper for the source list
528 MLDv2QueryPacket::Parser::sources_t::container sources (mld->sources());
530 // Iterate over all the addresses in that list
531 for (MLDv2QueryPacket::Parser::sources_t::container::iterator i (sources.begin());
532 i != sources.end(); ++i)
533 std::cout << *i << std::endl;
536 Beside other fields, the MLDv2Query consists of a list of source addresses. The \c sources()
537 member returns a VectorParser for these addresses. The collection parsers can only be accessed
538 completely using a container wrapper. The container wrapper type is available as the \c
539 container member of the collection parser, here it is \c
540 MLDv2QueryPacket::Parser::sources_t::container.
542 Using this wrapper, we can not only read the data, we can also manipulate the source list. Here
543 we copy a list of addresses from an \c std::vector into the packet:
546 std::vector<senf::INet6Address> addrs (...);
548 sources.resize(addrs.size());
549 std::copy(addrs.begin(), addrs.end(), sources.begin())
552 Collection parsers may be nested. To access a nested collection parser, a container wrapper must
553 be allocated for each level. An MLD Report (which is a composite parser) includes a list of
554 multicast address records called \c records(). Each record is again a composite which contains a
555 list of sources called \c sources():
558 MLDv2ReportPacket report = ...;
560 // Instantiate a collection wrapper for the list of records:
561 MLDv2ReportPacket::Parser::records_t::container records (report->records());
563 // Iterate over the multicast address records
564 for (MLDv2ReportPacket::Parser::records_t::container::iterator i (records.begin());
565 i != records.end(); ++i) {
566 // Allocate a collection wrapper for the multicast address record
567 typedef MLDv2ReportPacket::Parser::records_t::value_type::sources_t Sources;
568 Sources::container sources (i->sources());
570 // Iterate over the sources in this record
571 for (Sources::container::iterator i (sources.begin());
572 i != sources.end(); ++i)
573 std::cout << *i << std::endl;
577 In this example we also see how to find the type of a parser or container wrapper.
578 \li Composite parsers have typedefs for each their fields with a \c _t postfix
579 \li The vector or list parsers have a \c value_type typedef which gives the type of the
582 By traversing this hierarchical structure, the types of all the fields can be found.
584 The container wrapper is only temporary (even though it has a longer lifetime than a
585 parser). Any change made to the packet not via the collection wrapper has the potential to
586 invalidate the wrapper if it changes the packets size.
589 senf::VectorParser_Container Interface of the vector parser container wrapper \n
590 senf::ListParser_Container Interface of the list parser container wrapper
593 \subsubsection packet_usage_collection_variant The Variant Parser
595 The senf::VariantParser is a discriminated union of parsers. It is also used for optional fields
596 (using senf::VoidPacketParser as one possible variant which is a parser parsing nothing). A
597 senf::VariantParser is not really a collection in the strict sense: It only ever contains one
598 element, the \e type of which is determined by the discriminant.
600 For Example, we look at the DTCP HELLO Packet as defined in the UDLR Protocol (see <a
601 href="http://tools.ietf.org/html/rfc3077">RFC 3077</a>)
604 DTCPHelloPacket hello (...);
606 if (hello->ipVersion() == 4) {
607 typedef DTCPHelloPacket::Parser::v4fbipList_t FBIPList;
608 FBIPList::container fbips (hello->v4fbipList());
609 for (FBIPList::container::iterator i (fbips.begin()); i != fbips.end(); ++i)
610 std::cout << *i << std::endl;
612 else { // if (hello->ipVersion() == 6)
613 typedef DTCPHelloPacket::Parser::v6fbipList_t FBIPList;
614 FBIPList::container fbips (hello->v6fbipList());
615 for (FBIPList::container::iterator i (fbips.begin()); i != fbips.end(); ++i)
616 std::cout << *i << std::endl;
620 This packet has a field \c ipVersion() which has a value of 4 or 6. Depending on the version,
621 the packet contains a list of IPv4 or IPv6 addresses. Only one of the fields \c v4fbipList() and
622 \c v6fbipList() is available at a time. Which one is decided by the value of \c
623 ipVersion(). Trying to access the wrong one will provoke undefined behavior.
625 Here we have used the variants discriminant (the \c ipVersion() field) to select, which field to
626 parse. More generically, every variant field should have a corresponding member to test for it's
629 if (hello->has_v4fbipList()) {
632 else { // if (hello->has_v6fbipList())
637 A variant can have more than 2 possible types and you can be sure, that exactly one type will be
638 accessible at any time.
640 It is not possible to change a variant by simply changing the discriminant:
643 hello->ipVersion() = 6;
645 Instead, for each variant field there is a special member which switches the variant to that
646 type. After switching the type, the field will be in it's initialized (that is mostly zero)
649 std::vector<senf::INet6Address> addrs (...);
651 // Initialize the IPv6 list
652 hello->init_v6fbipList();
654 // Copy values into that list
655 DTCPHelloPacket::Parser::v6fbipList_t::container fbips (hello->v6fbipList());
656 fbips.resize(addrs.size());
657 std::copy(addrs.begin(), addrs.end(), fbips.begin());
660 \note Here we have documented the default variant interface as it is preferred. It is possible
661 to define variants in a different way giving other names to the special members (\c has_\e
662 name or \c init_\e name etc.). This must be documented with the composite or protocol parser
663 which defines the variant.
665 \section packet_usage_annotation Annotations
667 Sometimes we need to store additional data with a packet. Data, which is not part of the packet
668 itself but gives us some information about the packet: A timestamp, the interface the packet was
669 received on or other processing related information.
671 This type of information can be stored using the annotation interface. The following example
672 will read packet data and will store the read timestamp as a packet annotation.
676 senf::ClockService::clock_t value;
679 senf::EthernetPacket packet (senf::EthernetPacket::create(senf::noinit));
680 sock.read(packet.data(), 0u);
681 packet.annotation<Timestamp>().value = senf::ClockService::now();
684 In the same way, the annotation can be used later
687 if (senf::ClockService::now() - packet.annotation<Timestamp>().value
688 > senf::ClockService::seconds(1)) {
689 // Ouch ... this packet is to old
694 It is very important to define a specific structure (or class or enum) type for each type of
695 annotation. \e Never directly store a fundamental type as an annotation: The name of the type is
696 used to look up the annotation, so you can store only one annotation for each built-in type. \c
697 typedef does not help since \c typedef does not introduce new type names, it only defines an
700 Of course, the annotation structure can be arbitrary. However, one very important caveat: If the
701 annotation is not a POD type, it needs to inherit from senf::ComplexAnnotation. A type is POD,
702 if it is really just a bunch of bytes: No (non-static) members, no constructor or destructor and
703 no base classes and all it's members must be POD too. So the following annotation is complex
704 since \c std::string is not POD
707 struct ReadInfo : senf::ComplexAnnotation
709 std::string interface;
710 senf::ClockService::clock_t timestamp;
715 packet.annotation<ReadInfo>().interface = "eth0";
716 packet.annotation<ReadInfo>().timestamp = senf::ClockService::now();
718 // Or store a reference to the annotation for easier access
720 ReadInfo & info (packet.annotation<ReadInfo>());
722 if (info.interface == "eth0") {
727 Every annotation is automatically default-initialized, there is no way to query, whether a
728 packet holds a specific annotation -- every packet conceptually always holds all annotations.
730 You should use annotations economically: Every annotation type used in your program will
731 allocate an annotation slot in \e all packet data structures. So don't use hundreds of different
732 annotation types if this is not really necessary: Reuse annotation types where possible or
733 aggregate data into larger annotation structures. The best solution is to use annotations only
734 for a small number of packet specific informations. If you really need to manage a train-load of
735 data together with the packet consider some other way (e.g. place the packet into another class
736 which holds that data).
738 \see senf::Packet::annotation()
741 /** \page packet_new Defining new Packet types
743 Each packet is specified by the following two components:
745 \li A protocol parser which defines the protocol specific fields
746 \li A packet type class which is a policy class defining the packet
750 \see <a href="../../../HowTos/NewPacket/doc/html/index.html">NewPacket HowTo</a>
752 \section packet_new_parser The protocol parser
754 The protocol parser is simply a composite parser. It defines all the protocol
755 fields. Additionally, the protocol parser may have additional members which will then be
756 accessible via the \c -> operator of the packet. Possibilities here are e.g. checksum
757 calculation and validation, packet validation as a whole and so on.
759 Defining a protocol parser is quite simple:
761 struct EthernetPacketParser : public PacketParserBase
763 # include SENF_FIXED_PARSER()
765 SENF_PARSER_FIELD( destination, MACAddressParser );
766 SENF_PARSER_FIELD( source, MACAddressParser );
767 SENF_PARSER_FIELD( type_length, UInt16Parser );
769 SENF_PARSER_FINALIZE(EthernetPacketParser);
773 There are a lot of other possibilities to define fields. See \ref packetparsermacros for a
774 detailed description of the macro language which is used to define composite parsers.
777 \ref packetparsermacros
779 \section packet_new_type The packet type policy class
781 This is a class which provides all the information needed to integrate the new packet type into
784 \li It provides the type of the protocol parser to use
785 \li It provides information on how the next protocol can be found and where the payload resides
787 \li It provides methods to initialize a new packet and get information about the packet size
789 All this information is provided via static or typedef members.
792 struct EthernetPacketType
793 : public PacketTypeBase,
794 public PacketTypeMixin<EthernetPacketType, EtherTypes>
796 typedef PacketTypeMixin<EthernetPacketType, EtherTypes> mixin;
797 typedef ConcretePacket<EthernetPacketType> packet;
798 typedef EthernetPacketParser parser;
800 using mixin::nextPacketRange;
801 using mixin::initSize;
804 static factory_t nextPacketType(packet p);
805 static void dump(packet p, std::ostream & os);
806 static void finalize(packet p);
809 typedef EthernetPacketType::packet EthernetPacket;
812 The definition of senf::EthernetPacket is quite straight forward. This template works for most
815 \see \ref senf::PacketTypeMixin \n
816 \ref senf::PacketTypeBase \n
817 \ref senf::PacketRegistry
824 // c-file-style: "senf"
825 // indent-tabs-mode: nil
826 // ispell-local-dictionary: "american"
828 // compile-command: "scons -u doc"