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
70 There are two ways to link with a bundle
72 \li If you only work with known packets which you explicitly reference you may just link with
73 the corresponding library.
74 \li If you need to parse unknown packets and want those to be parsed as complete as possible
75 without explicitly referencing the packet type, you will need to link against the combined
76 object file built for every bundle. This way, all packets defined in the bundle will be
77 included whether they are explicitly referenced or not (and they will all automatically be
81 \section packet_intro_new Defining new packet types
82 \seechapter \ref packet_new
84 The packet library provides the framework which allows to define arbitrary packet types. There
85 is quite some information needed to completely specify a specific type of packet.
89 /** \page packet_arch Overall Packet library Architecture
91 The packet library handles network packets of a large number of protocols. We work with a packet
97 \section packet_arch_handle The Packet handle
99 Whenever we are using a Packet, we are talking about a senf::Packet (or a
100 senf::ConcretePacket). This class is a \e handle referencing an internally managed packet data
101 structure. So even though we pass senf::Packet instances around by value, they work like
102 references. The packet library automatically manages all required memory resources using
105 Different Packet handles may really internally share one Packet data structure if they both
106 point to the same packet.
109 \section packet_arch_data The Packet as a 'bunch of bytes'
111 From the outside, a packet is just a bunch of bytes just as it is read from (or will be
112 written to) the wire. At this low-level view, we can access the data in it's raw form but
113 have no further information about what kind of packet we have.
115 The packet library provides a consistent container interface for this representation.
120 // Change first byte of packet to 0
123 // Copy packet data into a vector
124 std::vector<char> data (p.data().size());
125 std::copy(p.data().begin(), p.data().end(), data.begin());
128 This type of access is primarily needed when reading or writing packets (e.g. to/from the
131 \see senf::Packet::data() \n
135 \section packet_arch_chain The Interpreter Chain
137 On the next level, the packet is divided into a nested list of sub-packets (or headers) called
138 interpreters. Each senf::Packet handle internally points to an interpreter or header. This
139 allows us to access one and the same packet in different ways.
141 Consider an Ethernet Packet with an IP payload holding a UDP packet. We may reference either the
142 Ethernet packet as a whole or we may reference the IP or UDP interpreters (sub-packets or
143 headers). All handles really refer to the \e same data structure but provide access to a
144 different (sub-)range of the data in the packet.
146 We can navigate around this chained structure using appropriate members:
149 // eth, ip and udp all reference the same internal packet data albeit at different data ranges
151 Packet ip = eth.next();
152 Packet udp = ip.next();
154 eth.next() == ip // true
155 eth.next().is<IPv4Packet>() // true
156 eth.next().next() == udp // true
157 eth.next().is<UDPPacket>() // false
158 eth.find<UDPPacket>() == udp // true
160 udp.find<EthernetPacket>() // throws InvalidPacketChainException
161 udp.find<EthernetPacket>(senf::nothrow) // An in-valid() senf::Packet which tests as 'false'
162 udp.find<UDPPacket> == udp // true
163 udp.first<IPv4Packet>() // throws InvalidPacketChainException
165 udp.prev() == ip // true
166 udp.prev<EthernetPacket>() // throws InvalidPacketChainException
169 \see \ref packet_module
172 \section packet_arch_parser Parsing specific Protocols
174 On the next level, the packet library allows us to parse the individual protocols. This gives us
175 access to the protocol specific data members of a packet and allows us to access or manipulate a
176 packet in a protocol specific way.
178 To access this information, we need to use a protocol specific handle, the senf::ConcretePacket
179 which takes as a template argument the specific type of packet to be interpreted. This allows us
180 to easily interpret or create packets. Here an example on how to create a new Ethernet / IP / UDP
181 / Payload packet interpreter chain:
184 // EthernetPacket, IPv4Packet, UDPPacket and DataPacket are typedefs for corresponding
185 // ConcretePacket instantiations
186 senf::EthernetPacket eth (senf::EthernetPacket::create());
187 senf::IPv4Packet ip (senf::IPv4Packet ::createAfter(eth));
188 senf::UDPPacket udp (senf::UDPPacket ::createAfter(ip));
189 senf::DataPacket payload (senf::DataPacket ::createAfter(udp,
190 std::string("Hello, world!")));
192 udp->source() = 2000u;
193 udp->destination() = 2001u;
195 ip->source() = senf::INet4Address::from_string("192.168.0.1");
196 ip->destination() = senf::INet4Address::from_string("192.168.0.2");
197 eth->source() = senf::MACAddress::from_string("00:11:22:33:44:55");
198 eth->destination() = senf::MACAddress::from_string("00:11:22:33:44:66");
203 Again, realize, that \a eth, \a ip, \a udp and \a payload share the same internal packet
204 data structure (the respective \c data() members all provide access to the same underlying
205 container however at different byte ranges): The complete packet can be accessed at
206 <tt>eth.data()</tt> whereas <tt>payload.data()</tt> only holds UDP payload (in this case the
207 string "Hello, world!").
209 \see \ref packetparser \n
213 /** \page packet_usage Using the packet library
217 \section packet_usage_intro Includes
219 To use the library, you need to include the appropriate header files. This will probably happen
220 automatically when including the specific protocol headers. If needed, you may explicitly use
223 #include "Packets.hh"
228 \warning Never include any other Packets library header directly, only include \c
229 Packets.hh or one (or several) protocol headers from the protocol bundles.
231 Most every use of the packet library starts with some concrete packet typedef. Some fundamental
232 packet types are provided by \ref protocolbundle_default.
235 \section packet_usage_create Creating a new packet
237 Building on those packet types, this example will build a complex packet: This will be an
238 Ethernet packet containing an IPv4 UDP packet. We begin by building the raw packet skeleton:
241 #include "Packets/DefaultBundle/EthernetPacket.hh"
242 #include "Packets/DefaultBundle/IPv4Packet.hh"
243 #include "Packets/DefaultBundle/UDPPacket.hh"
245 senf::EthernetPacket eth (senf::EthernetPacket::create());
246 senf::IPv4Packet ip (senf::IPv4Packet ::createAfter(eth));
247 senf::UDPPacket udp (senf::UDPPacket ::createAfter(ip));
248 senf::DataPacket payload (senf::DataPacket ::createAfter(udp,
249 std::string("Hello, world!")));
252 These commands create what is called an interpreter chain. This chain consists of four
253 interpreters. All interpreters reference the same data storage. This data storage is a random
254 access sequence which contains the data bytes of the packet.
256 \note The data structures allocated are automatically managed using reference counting. In this
257 example we have four packet references each referencing the same underlying data
258 structure. This data structure will be freed when the last reference to it goes out of
261 The packet created above already has the correct UDP payload (The string "Hello, world!")
262 however all protocol fields are empty. We need to set those protocol fields:
265 udp->source() = 2000u;
266 udp->destination() = 2001u;
268 ip->source() = senf::INet4Address::from_string("192.168.0.1");
269 ip->destination() = senf::INet4Address::from_string("192.168.0.2");
270 eth->source() = senf::MACAddress::from_string("00:11:22:33:44:55");
271 eth->destination() = senf::MACAddress::from_string("00:11:22:33:44:66");
276 As seen above, packet fields are accessed using the <tt>-></tt> operator whereas other packet
277 facilities (like \c finalizeAll()) are directly accessed using the member operator. The field
278 values are simply set using appropriately named accessors. As a last step, the \c finalizeAll()
279 call will update all calculated fields (fields like next-protocol, header or payload length,
280 checksums etc). Now the packet is ready. We may now send it out using a packet socket
283 senf::PacketSocketHandle sock ("eth0");
284 sock.write(eth.data());
288 \section packet_usage_read Reading and parsing packets
290 The chain navigation functions are also used to parse a packet. Let's read an Ethernet packet
291 from a packet socket handle:
294 senf::PacketSocketHandle sock ("eth0");
295 senf::EthernetPacket packet (senf::EthernetPacket::create(senf::noinit));
296 sock.read(packet.data(),0u);
299 This first creates an uninitialized Ethernet packet and then reads into this packet. We can now
300 parse this packet. Let's find out, whether this is a UDP packet destined to port 2001:
304 senf::UDPPacket udp (packet.find<UDPPacket>());
305 if (udp->destination() == 2001u) {
308 } catch (senf::TruncatedPacketException &) {
309 std::cerr << "Ooops !! Broken packet received\n";
310 } catch (senf::InvalidPacketChainException &) {
311 std::cerr << "Not a udp packet\n";
315 TruncatedPacketException is thrown by <tt>udp->destination()</tt> if that field cannot be
316 accessed (that is it would be beyond the data read which means we have read a truncated
317 packet). More generally, whenever a field cannot be accessed because it would be out of bounds
318 of the data read, this exception is generated.
321 \section packet_usage_container The raw data container
323 Every packet is based internally on a raw data container holding the packet data. This container
324 is accessed via senf::Packet::data() member.
326 This container is a random access container. It can be used like an ordinary STL container and
327 supports all the standard container members.
332 // Insert 5 0x01 bytes
333 p.data().insert(p.data().begin()+5, 5, 0x01);
335 // Insert data from another container
336 p.data().insert(p.data().end(), other.begin(), other.end());
338 // Erase a single byte
339 p.data().erase(p.data().begin()+5);
341 // XOR byte 5 with 0xAA
345 A packet consists of a list of interpreters (packet headers or protocols) which all reference
346 the same data container at different byte ranges. Each packet consists of the protocol header \e
347 plus the packets payload. This means, that the data container ranges of successive packets from
348 a single interpreter chain are nested.
350 Example: The packet created above (the Ethernet-IP-UDP packet with payload "Hello, world!") has
351 4 Interpreters: Ethernet, IPv4, UDP and the UDP payload data. The nested data containers lead to
352 the following structure
355 // The ethernet header has a size of 14 bytes
356 eth.data().begin() + 14 == ip.data().begin()
357 eth.data().end() == ip.data().end()
359 // The IP header has a size of 20 bytes and therefore
360 ip.data().begin() + 20 == udp.data().begin()
361 ip.data().end() == udp.data().end()
363 // The UDP header has a size of 8 bytes and thus
364 udp.data().begin() + 8 == payload.data().begin()
365 udp.data().end() == payload.data().end()
368 This nesting will (and must) always hold: The data range of a subsequent packet will always be
369 within the range of it's preceding packet.
371 \warning It is forbidden to change the data of a subsequent packet interpreter from the
372 preceding packet even if the data container includes this data. If you do so, you may
373 corrupt the data structure (especially when changing it's size).
375 Every operation on a packet is considered to be \e within this packet and \e without and
376 following packet. When inserting or erasing data, the data ranges are all adjusted
377 accordingly. So the following are \e not the same even though \c eth.end(), \c ip.end() and \c
378 udp.end() are identical.
381 eth.data().insert(eth.data().end(), 5, 0x01);
382 assert( eth.data().end() == ip.data().end() + 5
383 && ip.data().end() == udp.data().end() );
385 // Or alternatively: (You could even use eth.data().end() here ... it's the same)
386 ip.data().insert(ip.data().end(), 5, 0x01);
387 assert( eth.data().end() == ip.data().end()
388 && ip.data().end() == udp.data().end() + 5 );
391 \warning When accessing the packet data via the container interface, you may easily build
392 invalid packets since the packet will not be validated against it's protocol.
395 \section packet_usage_fields Field access
397 When working with concrete protocols, the packet library provides direct access to all the
398 protocol information.
401 udp->source() = 2000u;
402 udp->destination() = 2001u;
404 ip->source() = senf::INet4Address::from_string("192.168.0.1");
405 ip->destination() = senf::INet4Address::from_string("192.168.0.2");
406 eth->source() = senf::MACAddress::from_string("00:11:22:33:44:55");
407 eth->destination() = senf::MACAddress::from_string("00:11:22:33:44:66");
410 The protocol field members above do \e not return references, they return parser instances.
411 Protocol fields are accessed via parsers. A parser is a very lightweight class which points into
412 the raw packet data and converts between raw data bytes and it's interpreted value: For example
413 a senf::UInt16Parser accesses 2 bytes (in network byte order) and converts them to or from a 16
414 bit integer. There are a few properties about parsers which need to be understood:
416 \li Parsers are created only temporarily when needed. They are created when accessing a protocol
417 field and are returned by value.
419 \li A parser never contains a value itself, it just references a packets data container.
421 \li Parsers can be built using other parsers and may have members which return further parsers.
423 The top-level interface to a packets protocol fields is provided by a protocol parser. This
424 protocol parser is a composite parser which has members to access the protocol fields (compare
425 with the example code above). Some protocol fields may be more complex than a simple value. In
426 this case, those accessors may return other composite parsers or collection parsers. Ultimately,
427 a value parser will be returned.
429 The simple value parsers which return plain values (integer numbers, network addresses etc) can
430 be used like those values and can also be assigned corresponding values. More complex parsers
431 don't allow simple assignment. However, they can always be copied from another parser <em>of the
432 same type</em> using the generalized parser assignment. This type of assignment also works for
433 simple parsers and is then identical to a normal assignment.
436 // Copy the complete udp parser from udp packet 2 to packet 1
437 udp1.parser() << udp2.parser();
440 Additionally, the parsers have a parser specific API which allows to manipulate or query the
443 This is a very abstract description of the parser structure. For a more concrete description, we
444 need to differentiate between the different parser types
446 \subsection packet_usage_fields_value Simple fields (Value parsers)
448 We have already seen value parsers: These are the lowest level building blocks witch parse
449 numbers, addresses etc. They return some type of value and can be assigned such a value. More
450 formally, they have a \c value_type typedef member which gives the type of value they accept and
451 they have an overloaded \c value() member which is used to read or set the value. Some parsers
452 have additional functionality: The numeric parser for Example provide conversion and arithmetic
453 operators so they can be used like a numeric value.
455 If you have a value parser \c valueParser with type \c ValueParser, the following will always be
458 // You can read the value and assign it to a variable of the corresponding value_type
459 ValueParser::value_type v (valueParser.value());
461 // You can assign that value to the parser
462 valueParser.value(v);
464 // The assignment can also be done using the generic parser assignment
469 \subsection packet_usage_fields_composite Composite and protocol parsers
471 A composite parser is a parser which just combines several other parsers into a structure: For
472 example, the senf::EthernetPacketParser has members \c destination(), \c source() and \c
473 type_length(). Those members return parsers again (in this case value parsers) to access the
476 Composite parsers can be nested; A composite parser may be returned by another composite
477 parser. The protocol parser is a composite parser which defines the field for a specific
478 protocol header like Ethernet.
480 \subsection packet_usage_fields_collection Collection parsers
482 Besides simple composites, the packet library has support for more complex collections.
484 \li The senf::ArrayParser allows to repeat an arbitrary parser a fixed number of times.
485 \li senf::VectorParser and senf::ListParser are two different types of lists with variable
487 \li The senf::VariantParser is a discriminated union: It will select one of several parsers
488 depending on the value of a discriminant.
491 \subsubsection packet_usage_collection_vector Vector and List Parsers
493 Remember, that a parser does \e not contain any data: It only points into the raw data
494 container. This is also true for the collection parsers. VectorParser and ListParser provide an
495 interface which looks like an STL container to access a sequence of elements.
497 We will use an \c MLDv2QueryPacket as an example (see <a
498 href="http://tools.ietf.org/html/rfc3810#section-5">RFC 3810</a>). Here an excerpt of the
501 <table class="fields">
502 <tr><td>nrOfSources</td><td>Integer</td><td>Number of multicast sources in this packet</td></tr>
503 <tr><td>sources</td><td>Vector of IPv6 Addresses</td><td>Multicast sources</td></tr>
506 To demonstrate nested collections, we use the \c MLDv2ReportPacket as an example. The relevant
507 fields of this packet are;
509 <table class="fields">
510 <tr><td>nrOfRecords</td><td>Integer</td><td>Number of multicast address records</td></tr>
511 <tr><td>records</td><td>List of Records</td><td>List of multicast groups and sources</td></tr>
514 Each Record is a composite with the following relevant fields:
516 <table class="fields">
517 <tr><td>nrOfSources</td><td>Integer</td><td>Number of sources in this record</td></tr>
518 <tr><td>sources</td><td>Vector of IPv6 Addresses</td><td>Multicast sources</td></tr>
521 The first example will iterate over the sources in a \c MLDv2QueryPacket:
524 MLDv2QueryPacket mld = ...;
526 // Instantiate a collection wrapper for the source list
527 MLDv2QueryPacket::Parser::sources_t::container sources (mld->sources());
529 // Iterate over all the addresses in that list
530 for (MLDv2QueryPacket::Parser::sources_t::container::iterator i (sources.begin());
531 i != sources.end(); ++i)
532 std::cout << *i << std::endl;
535 Beside other fields, the MLDv2Query consists of a list of source addresses. The \c sources()
536 member returns a VectorParser for these addresses. The collection parsers can only be accessed
537 completely using a container wrapper. The container wrapper type is available as the \c
538 container member of the collection parser, here it is \c
539 MLDv2QueryPacket::Parser::sources_t::container.
541 Using this wrapper, we can not only read the data, we can also manipulate the source list. Here
542 we copy a list of addresses from an \c std::vector into the packet:
545 std::vector<senf::INet6Address> addrs (...);
547 sources.resize(addrs.size());
548 std::copy(addrs.begin(), addrs.end(), sources.begin())
551 Collection parsers may be nested. To access a nested collection parser, a container wrapper must
552 be allocated for each level. An MLD Report (which is a composite parser) includes a list of
553 multicast address records called \c records(). Each record is again a composite which contains a
554 list of sources called \c sources():
557 MLDv2ReportPacket report = ...;
559 // Instantiate a collection wrapper for the list of records:
560 MLDv2ReportPacket::Parser::records_t::container records (report->records());
562 // Iterate over the multicast address records
563 for (MLDv2ReportPacket::Parser::records_t::container::iterator i (records.begin());
564 i != records.end(); ++i) {
565 // Allocate a collection wrapper for the multicast address record
566 typedef MLDv2ReportPacket::Parser::records_t::value_type::sources_t Sources;
567 Sources::container sources (i->sources());
569 // Iterate over the sources in this record
570 for (Sources::container::iterator i (sources.begin());
571 i != sources.end(); ++i)
572 std::cout << *i << std::endl;
576 In this example we also see how to find the type of a parser or container wrapper.
577 \li Composite parsers have typedefs for each their fields with a \c _t postfix
578 \li The vector or list parsers have a \c value_type typedef which gives the type of the
581 By traversing this hierarchical structure, the types of all the fields can be found.
583 The container wrapper is only temporary (even though it has a longer lifetime than a
584 parser). Any change made to the packet not via the collection wrapper has the potential to
585 invalidate the wrapper if it changes the packets size.
588 senf::VectorParser_Container Interface of the vector parser container wrapper \n
589 senf::ListParser_Container Interface of the list parser container wrapper
592 \subsubsection packet_usage_collection_variant The Variant Parser
594 The senf::VariantParser is a discriminated union of parsers. It is also used for optional fields
595 (using senf::VoidPacketParser as one possible variant which is a parser parsing nothing). A
596 senf::VariantParser is not really a collection in the strict sense: It only ever contains one
597 element, the \e type of which is determined by the discriminant.
599 For Example, we look at the DTCP HELLO Packet as defined in the UDLR Protocol (see <a
600 href="http://tools.ietf.org/html/rfc3077">RFC 3077</a>)
603 DTCPHelloPacket hello (...);
605 if (hello->ipVersion() == 4) {
606 typedef DTCPHelloPacket::Parser::v4fbipList_t FBIPList;
607 FBIPList::container fbips (hello->v4fbipList());
608 for (FBIPList::container::iterator i (fbips.begin()); i != fbips.end(); ++i)
609 std::cout << *i << std::endl;
611 else { // if (hello->ipVersion() == 6)
612 typedef DTCPHelloPacket::Parser::v6fbipList_t FBIPList;
613 FBIPList::container fbips (hello->v6fbipList());
614 for (FBIPList::container::iterator i (fbips.begin()); i != fbips.end(); ++i)
615 std::cout << *i << std::endl;
619 This packet has a field \c ipVersion() which has a value of 4 or 6. Depending on the version,
620 the packet contains a list of IPv4 or IPv6 addresses. Only one of the fields \c v4fbipList() and
621 \c v6fbipList() is available at a time. Which one is decided by the value of \c
622 ipVersion(). Trying to access the wrong one will provoke undefined behavior.
624 Here we have used the variants discriminant (the \c ipVersion() field) to select, which field to
625 parse. More generically, every variant field should have a corresponding member to test for it's
628 if (hello->has_v4fbipList()) {
631 else { // if (hello->has_v6fbipList())
636 A variant can have more than 2 possible types and you can be sure, that exactly one type will be
637 accessible at any time.
639 It is not possible to change a variant by simply changing the discriminant:
642 hello->ipVersion() = 6;
644 Instead, for each variant field there is a special member which switches the variant to that
645 type. After switching the type, the field will be in it's initialized (that is mostly zero)
648 std::vector<senf::INet6Address> addrs (...);
650 // Initialize the IPv6 list
651 hello->init_v6fbipList();
653 // Copy values into that list
654 DTCPHelloPacket::Parser::v6fbipList_t::container fbips (hello->v6fbipList());
655 fbips.resize(addrs.size());
656 std::copy(addrs.begin(), addrs.end(), fbips.begin());
659 \note Here we have documented the default variant interface as it is preferred. It is possible
660 to define variants in a different way giving other names to the special members (\c has_\e
661 name or \c init_\e name etc.). This must be documented with the composite or protocol parser
662 which defines the variant.
664 \section packet_usage_annotation Annotations
666 Sometimes we need to store additional data with a packet. Data, which is not part of the packet
667 itself but gives us some information about the packet: A timestamp, the interface the packet was
668 received on or other processing related information.
670 This type of information can be stored using the annotation interface.
674 senf::ClockService::clock_t value;
677 senf::EthernetPacket packet (senf::EthernetPacket::create(senf::noinit));
678 sock.read(packet.data(), 0u);
679 packet.annotation<Timestamp>().value = senf::ClockService::now();
682 In the same way, the annotation can be used later
685 if (senf::ClockService::now() - packet.annotation<Timestamp>().value
686 > senf::ClockService::seconds(1)) {
687 // Ouch ... this packet is to old
692 It is very important to define a specific structure (or class) type for each type of
693 annotation. \e Never directly store a fundamental type as an annotation: The name of the type is
694 used to look up the annotation, so you can store only one annotation for each built-in type. \c
695 typedef does not help since \c typedef does not introduce new type names, it only defines an
698 Of course, the annotation structure can be arbitrary. However, one very important caveat: If the
699 annotation is not a POD type, it needs to inherit from senf::ComplexAnnotation. A type is POD,
700 if it is really just a bunch of bytes: No (non-static) members, no constructor or destructor and
701 no base classes and all it's members must be POD too. So the following annotation is complex
702 since \c std::string is not POD
705 struct ReadInfo : senf::ComplexAnnotation
707 std::string interface;
708 senf::ClockService::clock_t timestamp;
713 packet.annotation<ReadInfo>().interface = "eth0";
714 packet.annotation<ReadInfo>().timestamp = senf::ClockService::now();
716 // Or store a reference to the annotation for easier access
718 ReadInfo & info (packet.annotation<ReadInfo>());
720 if (info.interface == "eth0") {
725 You should use annotations economically: Every annotation type used in your program will
726 allocate an annotation slot in \e all packet data structures. So don't use hundreds of different
727 annotation types if this is not really necessary: Reuse annotation types where possible or
728 aggregate data into larger annotation structures. The best solution is to use annotations only
729 for a small number of packet specific informations. If you really need to manage a train-load of
730 data together with the packet consider some other way (e.g. place the packet into another class
731 which holds that data).
733 \see senf::Packet::annotation()
736 /** \page packet_new Defining new Packet types
738 Each packet is specified by the following two components:
740 \li A protocol parser which defines the protocol specific fields
741 \li A packet type class which is a policy class defining the packet
745 \see <a href="../../../HowTos/NewPacket/doc/html/index.html">NewPacket HowTo</a>
747 \section packet_new_parser The protocol parser
749 The protocol parser is simply a composite parser. It defines all the protocol
750 fields. Additionally, the protocol parser may have additional members which will then be
751 accessible via the \c -> operator of the packet. Possibilities here are e.g. checksum
752 calculation and validation, packet validation as a whole and so on.
754 Defining a protocol parser is quite simple:
756 struct EthernetPacketParser : public PacketParserBase
758 # include SENF_FIXED_PARSER()
760 SENF_PARSER_FIELD( destination, MACAddressParser );
761 SENF_PARSER_FIELD( source, MACAddressParser );
762 SENF_PARSER_FIELD( type_length, UInt16Parser );
764 SENF_PARSER_FINALIZE(EthernetPacketParser);
768 There are a lot of other possibilities to define fields. See \ref packetparsermacros for a
769 detailed description of the macro language which is used to define composite parsers.
772 \ref packetparsermacros
774 \section packet_new_type The packet type policy class
776 This is a class which provides all the information needed to integrate the new packet type into
779 \li It provides the type of the protocol parser to use
780 \li It provides information on how the next protocol can be found and where the payload resides
782 \li It provides methods to initialize a new packet and get information about the packet size
784 All this information is provided via static or typedef members.
787 struct EthernetPacketType
788 : public PacketTypeBase,
789 public PacketTypeMixin<EthernetPacketType, EtherTypes>
791 typedef PacketTypeMixin<EthernetPacketType, EtherTypes> mixin;
792 typedef ConcretePacket<EthernetPacketType> packet;
793 typedef EthernetPacketParser parser;
795 using mixin::nextPacketRange;
796 using mixin::initSize;
799 static factory_t nextPacketType(packet p);
800 static void dump(packet p, std::ostream & os);
801 static void finalize(packet p);
804 typedef EthernetPacketType::packet EthernetPacket;
807 The definition of senf::EthernetPacket is quite straight forward. This template works for most
810 \see \ref senf::PacketTypeMixin \n
811 \ref senf::PacketTypeBase \n
812 \ref senf::PacketRegistry
819 // c-file-style: "senf"
820 // indent-tabs-mode: nil
821 // ispell-local-dictionary: "american"
823 // compile-command: "scons -u doc"