// $Id$
//
-// Copyright (C) 2007
-// Fraunhofer Institute for Open Communication Systems (FOKUS)
-// Competence Center NETwork research (NET), St. Augustin, GERMANY
+// Copyright (C) 2007
+// Fraunhofer Institute for Open Communication Systems (FOKUS)
+// Competence Center NETwork research (NET), St. Augustin, GERMANY
// Stefan Bund <g0dil@berlios.de>
//
// This program is free software; you can redistribute it and/or modify
tethereal. The application uses a packet socket to read Ethernet packets from the \c eth0
interface and dumps the parsed packets out to the standard output.
- To try out the example application, check out the library, go to the \c Sniffer
+ To try out the example application, check out the library, go to the \c %Sniffer
directory and execute
<pre>
< Hit Ctrl-C when you've seen enough >
</pre>
- We will now look at the code which is found in \c Sniffer.cc in the \c Sniffer directory. The
- code starts out by including the necessary headers
+ We will now look at the code which is found in \c Sniffer.cc in the <tt>Examples/%Sniffer</tt>
+ directory. The code starts out by including the necessary headers
\skip // Custom includes
- \until membind
+ \until #include <senf/Scheduler/Scheduler.hh>
- (The additional includes found in the source but not shown here are part of a short-time fix
- which will be removed as soon as possible). The example application now contains a helper
- routine to produce a packet hexdump. We will skip this routine here. The example includes two
- implementations, one using blocking calls and a while loop, the other using the senf::Scheduler
- for asynchronous event notification. They are implemented in \c loop_main() and \c
- scheduler_main(). They will be documented below. For now, we skip these implementations and go
- straight to the \c main() function
+ The example includes two implementations, one using blocking calls and a while loop, the other
+ using the senf::Scheduler for asynchronous event notification. They are implemented in
+ \c loop_main() and \c scheduler_main(). They will be documented below. For now, we skip these
+ implementations and go straight to the \c main() function
\skip int main(
\until return 1;
the application, it might be better to let the exception \c abort the execution so you can get a
backtrace of the exception origin in the debugger.
- We now create a packet socket and bind it to the \c eth0 interface. A packet socket is a linux
- specific type of socket which returns ethernet packets directly from the network wire. By
- uncommenting the last line, you may switch the interface into promiscuous mode.
+ We create a packet socket and bind it to the interface given as second command line argument. A
+ packet socket is a linux specific type of socket which returns ethernet packets directly from
+ the network wire. By uncommenting the last line, you may switch the interface into promiscuous
+ mode.
\until //
We will now read packets from the socket forever, that is until the user hits Ctrl-C
\skip while
- \until read
+ \until while
The next step is, to parse the data read from the socket as an Ethernet packet
- \until ;
+ \until sock.read
+
+ There are several ways to read and parse a packet with different tradeoffs between efficiency
+ and simplicity. The Version we use here is already quite efficient.
- Lets digest this line step by step: We declare a variable named \c packet as a smart pointer to
- an \c EthernetPacket instance. \c ptr is a typedef member of all Packet classes for the
- corresponding smart pointer type. We then initialize this pointer with a call to the static \c
- create member of the \c Packet class. This member takes the type of Packet to parse as a
- template argument. We pass \c EthernetPacket here. The function takes an iterator range as an
- argument, and we pass it the complete packet just read by giving the range \c begin() to \c
- end() of our just read \c data string.
+ We begin by pre-declaring an uninitialized senf::EthernetPacket instance. By uninitialized we
+ mean, that the instance is not parseable and has a length of 0 bytes. This differs from a
+ default-constructed packet instance which may have initial content and \e is parseable.
+
+ We then tell the socket to read as much data as is available into the packet. The second arg to
+ read specifies the maximum number of bytes to read or 0 to read as much as possible. We pass
+ <tt>packet.data()</tt> to <tt>socket.read</tt> which is an STL compatible container holding the
+ data bytes of our previously created senf::EthernetPacket instance (which is currently empty).
The next step is to write out the packet to the standard output
The \c prettyName function from the \c Utils library is used, to get a nice, printable
representation of the \e dynamic type of the exception instance. It is an interface to the g++
- demangler. This is necessary since the \c name member of the C++ \c type_info instance is a
+ de-mangler. This is necessary since the \c name member of the C++ \c type_info instance is a
mangled name in \c g++.
-
- That's it for the simple blocking implementation.
+
+ That's it for the simple blocking implementation.
\section example_scheduler Using the Scheduler
- However, we have another one which uses the Scheduler. We do this as it will be most of the
- time: We define a class which manages reading the packets and dumping them out.
+ However, we have another one which uses the Scheduler.
\until }
- The class constructor binds the socket defined as a data member to the correct interface.
+ The class constructor binds the socket defined as a data member to the correct interface. To
+ tell the scheduler to call us back whenever data is available on the socket, we add a
+ senf::scheduler::FdEvent instance to out class.
- \until add
-
- The public \c run() member is called to run the sniffer. It first adds the socket to the
- Scheduler. The \c add() call takes two Arguments, the socket to bind to (which can be a lot of
- things and must not necessarily be a socket instance) and callback to call, whenever there is an
- event on that socket. A third argument may be specified to restrict the events, on which the
- function is called, here we have left out this argument which defaults to
- senf::Scheduler::EV_ALL.
-
- The callback is specified as a <a
- href="http://www.boost.org/doc/html/function.html">Boost.Function</a> object. We use the \c
- senf::membind helper from the Utils library to build such a function object. This helper takes
- an arbitrary class member and binds it to a specific instance.
+ The senf::scheduler::FdEvent constructor takes several arguments:
+ \li a string describing the event.
+ \li the callback to call whenever the event occurs. The callback is specified as a <a
+ href="http://www.boost.org/doc/libs/release/doc/html/function.html">Boost.Function</a>
+ object. We use the \c senf::membind helper from the Utils library to build such a
+ function object. This helper takes an arbitrary class member and binds it to a specific
+ instance.
+ \li the handle or file descriptor to monitor.
+ \li and the events to watch for.
\until }
- Calling the Schedulers \c process() method will start the event loop. This call does not return
- (ok, it does return in special cases if \c senf::Scheduler::terminate() is called which does not
- apply here).
-
+ The public \c run() member is called to run the sniffer. Here we just forward the call to the
+ scheduler. Calling the Schedulers \c process() method will start the event loop. This call does
+ not return (ok, that's a lie. It does return when \c senf::scheduler::terminate() is called
+ which does not apply here).
+
\until {
The \c dumpPacket() member is called by the scheduler whenever an event on the socket is
- encountered. The scheduler always passes two arguments: The socket and an event id which
- identifies the type of event which triggered the call.
+ encountered. The scheduler calls this function with a mask of the events which triggered the
+ call.
\until };
implementation. However, the scheduler guarantees, that a read on the socket will not block if
the socket is triggered to be readable (even if the socket is not set to non-blocking mode).
- We now only need to provide the \c scheduler_main() function to run this code
+ What's left is the \c scheduler_main() function to utilize this code
\until 0;
\until }
- This function is straight forward. The exception handling is the same as in \c loop_main(). The
- code then just creates a \c Sniffer instance and calls it's \c run() member.
+ This function is straight forward. The exception handling is the same as in \c loop_main().
\see \ref senf_components \n
\ref senf_build \n
- <a href="../../../../Socket/doc/html/index.html"><b>libSocket API reference</b></a> \n
- <a href="../../../../Packets/doc/html/index.html"><b>libPackets API reference</b></a> \n
- <a href="../../../../Utils/doc/html/index.html"><b>libUtils API reference</b></a>
+ <a href="../../../../senf/Socket/doc/html/index.html"><b>libSocket API reference</b></a> \n
+ <a href="../../../../senf/Packets/doc/html/index.html"><b>libPackets API reference</b></a> \n
+ <a href="../../../../senf/Utils/doc/html/index.html"><b>libUtils API reference</b></a>
*/
\f
// c-file-style: "senf"
// indent-tabs-mode: nil
// ispell-local-dictionary: "american"
-// compile-command: "scons -u test"
-// mode: flyspell
+// compile-command: "scons -u doc"
// mode: auto-fill
// End:
projects / senf.git / blobdiff