Click Source Code Changes

This page, taken from the Click distribution's NEWS file, summarizes changes to the Click distribution since our first release.

• Drivers
  • The Click drivers, language, and tools support named configuration parameters, which can be set in configuration files or on the command line. See 'conf/test-ping.click' for an example.
  • click-install provides a --cpu option, to force Click to run on a given CPU (Beyers Cronje). Also, click-install provides a --user option, setting the uid/gid owning the Click file system.
  • Linux 2.6.19 support.
  • Improved support for recent FreeBSD kernels (Bruce Simpson).
  • ns-2.30 support, and ns-2.29 support removed. You will need to apply the ns-2.30-patch with this distribution; old patches are obsolete.
  • Improved stability for e1000-5.x drivers (Kevin Lahey), e1000-6.x drivers (Beyers Cronje, Adam Greenhalgh, Joonwoo Park), and e1000-7.x drivers (Max Poletto, Roman Chertov).
  • Improved stability for Linux kernel module.
  • Improved SMP Click. For instance, removed NotifierQueue race conditions. Thanks very much to Joonwoo Park.
  • click-viz is integrated into click-pretty.
  • click-fastclassifier and click-devirtualize work.
  • click-align's output is smaller; it generates output only for elements that require alignment information. The need for alignment information is indicated by the character A in flags().
• Elements
  • Linuxmodule elements FromDevice and PollDevice have a TIMESTAMP keyword argument, to force timestamps at device receive time. Recent kernels don't timestamp received packets most of the time.
  • Linuxmodule FromDevice, PollDevice, and ToDevice support the QUIET keyword argument. Another change makes it easier to use these elements when there are many devices with the same Ethernet address. Thanks to Cliff Frey.
  • Greatly improved IPsec elements from Dimitris Syrivelis and Ioannis Avramopoulos.
  • ToIPSummaryDump supports MD5 checksums (Vern Paxson request).
  • Add support for PlanetLab Privileged Operations (proper) packet sending and receiving (thanks, Mark Huang).
  • Script: The "run" handlers accepts arguments, which the script can refer to as $args, $1, $2, and so forth. "goto exit" works.
  • User-level FromDevice's SNIFFER argument now works. SNIFFER false automatically installs a firewall rule that prevents the kernel from processing FromDevice's packets. When Click stops, the rule is automatically removed. Works only on Linux at the moment.
  • More handlers for UDPIPEncap, ARPQuerier, ICMPPingSource, ICMPPingEncap, and others.
  • Linuxmodule: Add experimental FromUserDevice and ToUserDevice elements, for communicating between kernel configurations and user level via /dev. Only available if --enable-experimental was supplied to configure. Thanks to Roman Chertov.
  • Bug fixes, performance improvements, and extensions to many elements, including AddressTranslator, AverageCounter, BandwidthMeter, BeaconSource, ControlSocket, DSRRouteTable, DirectIPLookup, Discard, FromDevice, FromDump, FromNetFlowSummaryDump, FromSimDevice, HostEtherFilter, ICMPPingRewriter, ICMPRewriter, IP6Mirror, IPClassifier/IPFilter, IPEncap, IPMirror, IPNameInfo, InfiniteSource, KernelTap, KernelTun, LinuxIPLookup, RangeIPLookup, RawSocket, Reframe, Script, SetUDPChecksum, SimpleQueue, Socket, ToDevice, ToDump, ToHost, ToSimDevice, UDPIPEncap, UMLSwitch.
• Internals
  • Initial and very preliminary support for multithreading at user level. If one of your elements plans to fork a new thread, compile Click with --enable-user-multithread. Most of Click is still not thread safe, but this will fix some common problems, such as Packet reference counts.
  • Introduce new cp_va_kparse() functions with a better interface than cp_va_parse(). Document confparse functions.
  • Document and rewrite EWMA classes.
  • Important bug fixes in Task will make notification more stable.
  • Remove some deprecated member functions in String and Element (notify_ninputs() and notify_noutputs()).
  • Fix bugs in lexing, notification, and Linux kernel module locking and SMP support. Thanks especially to Joonwoo (Jason) Park for SMP patches and bug reports.
  • String and StringAccum objects use specialized memory allocation functions, allowing very large Strings and StringAccums in kernel space. So do Queues.
  • Compilation fixes for x86_64. Thanks, Puneet Sood.
  • A better hashcode() system uses templates and overloading, reducing the chance that an operator bool() will mistakenly be used as a hashcode(). Thanks, Andrew Ratin.
  • Use operator unspecified_bool_type() rather than operator bool() for similar reasons.
• Other bug fixes and improvements.
• Thanks to Nicola Arnoldi, Ioannis Avramopoulos, Salman Abdul Baset, Koen Beel, Kristian Beilke, Torquato Bertani, John Bicket, Bart Braem, Vladimir Bychkovsky, Marco Canini, Srivas Chennu, Szymon Chachulski, Roman Chertov, David Claffey, Beyers Cronje, Peter De Cleyn, Norbert Egi, Nick Feamster, Cliff Frey, Matt Gordon, Adam Greenhalgh, Mark Huang, Mathias Jeschke, Azeem Khan, Christian Kreibich, Mathias Kurth, Kevin Lahey, lastlijing yahoo com cn, Pierre-Emmanuel Le Roux, Nicolas Letor, Joe Maldonaldo, David Moore, Tim Morgan, Jim Mott-Smith, Jens Mueller, Arvid Nilsson, Joonwoo (Jason) Park, Vern Paxson, Max Poletto, Vivek Raghunathan, Roberto Riggio, Robert Ross, Bruce Simpson, Puneet Sood, Dimitris Syrivelis, Seiichi Tatsukawa, Andy Van Maele, Frederic Van Quickenborne, Wim Vandenberghe, Rob Wachol, and Mike Wilson, and anyone we inadvertently forgot to mention here.

• Linux 2.6.16.13 kernel module support, including support for packages.
• click-packages-1.5.0 supports SNMP and Netflow (donated by Mazu Networks) and multicast (preliminary).
• IP routing element improvements, including new, gloriously fast DirectIPLookup element (Marko Zec with kohler).
• Add new Script element, basically replacing PokeHandlers and DriverManager, with support for programmability and signal handling; check it out.
• New elements: ChangeUID, ListenEtherSwitch, RawSocket, Socket, Truncate, ARPPrint and CheckARPHeader (Jose Maria Gonzalez), many wifi elements.
• Deprecated elements: FromRawSocket, FromSocket, PokeHandlers, ToRawSocket, ToSocket.
• Polling version of Intel's e1000-5.7.6 driver.
• Bug fixes and extensions to many elements, including ARPQuerier, EtherSwitch, FromDAGDump, FromDevice (userlevel), ICMPPingSource, IPAddrRewriter, IPFilter/IPClassifier, IPPrint, LinkUnqueue, RandomBitErrors, RatedUnqueue, SetTimestamp, ToDevice (kernel and userlevel), ToIPSummaryDump.
• Integrated nsclick patch, and improved nsclick (Michael Voorhaen, Bart Braem, kohler).
• x86_64 support.
• Wifi (bicket)
  • Most wifi elements have been removed from the repository. They will be added back later as a separate package in click-packages.
• Internals
  • Initiate Doxygen documentation for important base types, such as Element, String, Notifier, and so forth. This project is not complete; as each class gets Doxygenated its interface tends to change, so be prepared.
  • Add new port_count() method, allowing elements to declare how many ports they support. This replaces Element::set_ninputs(), set_noutputs(), add_input(), add_output(), notify_ninputs(), and notify_noutputs(), which are all now deprecated.
  • Add RAW handler flag, for handlers whose output should not be modified (for example, no adding a courtesy newline).
  • Element::run_timer takes a Timer * argument. The old version is deprecated.
  • Add a new, general mechanism for named enumerations (such as IP protocols, TCP/UDP ports, addresses, and so forth), NameInfo/NameDB.
  • Add ELEMENT_LIBS support, so an element can pull in a static library.
  • Many bug fixes.
  • Diagram library improvements.
• Thanks to Dan Aguayo, Mark Allman, Bart Braem, Kristof Cauwel, Spencer Chang, YenJung Chang, Jacky Cheng, Beyers Cronje, Weidong Cui, Anne Dudfield, Brian Gallaway, Michael Gellman, Chema Gonzalez, Andrew Gorelik, Adam Greenhalgh, Jason Haas, Trevor Harrison, Felipe Huici, Bart Jooris, Srikanth Kandula, Bob Keyes, Kevin Lahey, Dagang Li, Nikitas Liogkas, Yun Mao, Ross Mcilroy, Alastair McKinley, Indian Mogul, Thomas Paine, Ruoming Pang, Juncheol Park, Vern Paxson, Michael Voorhaen, Michael Walfish, Nick Weaver, Qinghua Ye, Marko Zec, and anyone else whose name was forgotten.

• Remove bonehead linuxmodule compile error.

• BSD kernel module support! Implemented by Marko Zec, University of Zagreb.
• KernelTap is undeprecated. (jbicket)
• User-level Click has FromHost and ToHost elements, at least on Linux! (jbicket)
• Add FullNoteQueue option. FullNoteQueue informs upstream listeners when it's full. Queue now invokes FullNoteQueue by default. (kohler)
• New elements: Truncate, RandomSeed, IPAddrPairRewriter, SchedOrderTest.
• IPFilter/IPClassifier: Support "ip[POS:LEN]" and "transp[POS:LEN]" expressions. (kohler)
• Add support for new-format DAG dumps, and more encapsulation types for FromDump, including 802.11 and PPP. (kohler)
• ToIPSummaryDump will emit a dash for a field only if that field wasn't captured, rather than if the header wasn't captured. For example, if the first 8 bytes of the TCP header were captured, ToIPSummaryDump will happily print the source and destination ports, but not anything further. (kohler)
• DriverManager: Add "loop" instruction, available at user level. (kohler)
• Bug fixes, particularly to IPReassembler, click-fastclassifier, click-devirtualize (kohler), and fix the linuxmodule bug that led to errors like "wmem_alloc != 0" (jbicket).
• Fixes to wireless source routing elements (element/wifi/sr/) - gives each link a sequence number and age to prevent old linkstate from floating around in the network. Also more documentation. (jbicket)
• Add header (click_wifi_extra) to replace prism header. Communicates with the device driver (things like transmission status, bitrate, retries, etc). See ExtraEncap and ExtraDecap as well as FilterTX. (jbicket)
• Internal changes (kohler)
  • Handler class rewritten.
  • Timers are stored in a heap; thanks to Jonathan K. Lee for an initial implementation.
  • If you supply the --enable-task-heap option to ./configure, tasks will also be stored in a heap, rather than a linked list.
• Thanks to Peter De Cleyn, Holger Dreger, Thomer Gil, Jeff Gold, Bob Keyes, Peter Lippens, Nikitas Liogkas, Kevin Mitchell, Indian Mogul, Michele Mordenti, Vern Paxson, Marcel Poisot, Pavlin Radoslavov, Rick Stewart, Erik VandeKieft, Frederic Van Quickenborne, Erwin Van de Velde, Marko Zec.

• Added Element::static_initialize() and static_cleanup() methods. Elements use these methods to set up and tear down global state. See the programming manual (doc/click.info*) for details.
• Fix click-mkmindriver (reported by Harvey Jones).
• Fix IPInputCombo (reported by Jerry Parente).
• Grid/Wifi updates (John Bicket).
• Add /click/messages handler.
• Updates so that Click may be compiled by gcc-3.4.1.

• Elements
  • Major rearrangement of Grid/Wifi elements (John Bicket). Add "--enable-wifi" configuration option, to select the wifi elements. There are elements in the elements/wifi/ap directory that will allow you to build an access point. Also, There is a driver available at http://www.pdos.lcs.mit.edu/~jbicket/madwifi.stripped that works with Atheros-based 802.11a/b/g cars which sends/receives 802.11 packets. To compile with that driver, download the driver and then point configure at it using "--with-wifi=DIR". The elements WifiEncap and WifiDecap to encapsulate/decapsulate 802.3 packets into 802.11 before they go to FromDev and after they come from ToDev. Elements such as SetTXPower and SetTXRate allow per-packet transmit control and bit-rate control, respectively.
  • Add FromSocket, ToSocket, IPFlowRawSockets, FromRawSocket, and ToRawSocket elements from Mark Huang. These elements let user-level configurations talk to the network over raw sockets.
  • Add FromCapDump element, to support trace files generated by Mark Allman's cap tool.
  • Add AggregatePacketCounter, EraseIPPayload, StoreData, ComparePackets, Message elements.
  • Rename SortedTaskSched to BalancedThreadSched (the old name still works for now). Its implementation also changed; rather than sort *all* tasks, it repeatedly moves tasks from the most-oversubscribed thread to the most-undersubscribed thread (in sorted order).
  • DriverManager adds "save" and "append" instructions.
  • ICMPSendPings can keep ping statistics, like a standalone ping program.
  • AnonymizeIPAddr handles IP addresses in headers embedded within ICMP packets.
  • IPSummaryDump elements change the format for TCP SACK options; the new format is "sack:N1-N2".
  • Add syntax for bandwidths with units, such as "kb/s".
  • Other improvements to DriverManager, RatedUnqueue, DelayShaper, CycleCountAccum, From/ToIPSummaryDump, ControlSocket.
  • Bug fixes to StrideSched and others.
• Drivers
  • The user-level driver will quit immediately if given a configuration with no elements. It also supports the "--exit-handler" option.
• Bug fixes
  • Fix compound element parsing.
  • Fix race conditions on the task list.
  • Fix bugs with "atomic_uint32_t::operator{&=,|=}", and fix their definitions on ARM.
  • Fix user-level hotswapping.
  • Fix TCP/UDP checksum calculation in the presence of IP source routing options.
  • Support Click SMP again.
  • Improve Linux patches (to correct bugs in AX25 and similar headers), and add a linux-2.4.26 patch.
• Internal changes
  • Allow for multiple kinds of Notifiers, defined by name.
  • Renamed the uatomic32_t type to atomic_uint32_t.
  • Generate click-buildtool from click-buildtool.in.
  • Remove Element::clone() function.
  • Add more regression tests, improve 'testie'.

• Major changes
  • Huge Grid changes, bug fixes, new functionality, and restructuring into multiple directories.
  • Scheduling rewrite. Previously, each Router object had its own set of "threads". In the kernel, this meant many Click kernel threads might be active during a configuration change, limiting how fast you could change configurations. Now all Routers share a single set of "threads", so configuration changes are faster and hopefully more reliable. Bugs remain. We would so appreciate testing help it's not funny.
  • Userlevel driver: Support hotswapping. Hotswappable elements include ControlSocket, ChatterSocket, FromDump.

• New elements
  • Add many Grid elements.
  • Add FromNLANRDump (read directly from NLANR traces), FromTcpdump (read from ASCII tcpdump(1) output), LinkUnqueue (model a link including delay), SetTimestampDelta.
  • Add SourceIPHashMapper element (Max Krohn).
  • Add PortInfo and cp_tcpudp_port(): now you can refer to TCP/UDP ports by name in elements like UDPIPEncap.

• Element changes
  • ControlSocket supports LLRPCs.
  • IPClassifier and IPFilter support "ip hl", "ip id", and "ip vers"; arbitrary >, >=, <, and <= comparisons; and ?: expressions.
  • CheckIPHeader and friends accept packets with bad source addresses, as long as they are destined for the router. Added keyword arguments.
  • SetTCPChecksum implements the correct checksum.
  • ICMPError handles source-routed packets appropriately.
  • FromIPSummaryDump supports ip_opt, ip_ttl, ip_tos, and tcp_ntopt types.
  • Scheduler elements (such as StrideSched), packet dump elements (such as FromDump), and KernelTun use notification, reducing CPU overhead.
  • Updates to AggregateCounter, AggregateIP, AggregateIPFlows, DelayShaper, ICMPPingSource, InfiniteSource, KernelTun, StoreIPAddress, TCPRewriter.
  • SimpleQueue supports the (C++-only) yank() operation.
  • Linuxmodule: Fix race condition in FromHost.
  • Linuxmodule: ToHost watches for device up/down events.

• Language, configuration, and driver changes
  • Compound elements support keyword arguments and __REST__ arguments.
  • Add 'conf/click-mkclgw.pl', a script that reads a simple configuration file ('conf/example.clgw' for the format) and generates a NAT cluster gateway, supporting firewalls, reverse NAT mappings through the firewalls, and load-balanced clusters (Max Krohn).
  • Userlevel: Remove --stop option.
  • Userlevel: Use poll() instead of select() when available; supports more file descriptors.
  • Linuxmodule: Add --enable-kassert configure option to enable kernel assertion checking.
  • Support recursive element directories.
  • Tool cleanups.
  • Diagram macro updates.

• Internal changes
  • Standardize on a single HashMap template class, called HashMap.
  • String::c_str() is const.
  • Add String functionality based on 'const char *' iterators (STL-like).
  • Configuration fixes for Mac OS X.
  • DeQueues can grow arbitrarily large in the kernel.
  • Adjust startup sequence. Add click_static_initialize() to take care of common initialization steps.
  • Handlers: Change the way global handlers are called.
  • Add click_ether_vlan structure in <clicknet/ether.h>.
  • Add tests and bug fixes (including Packet::shrink_data, IPMapper).
  • ErrorHandler supports verbosity settings; other updates.
  • Timers that stop the router prevent later timers from running.
  • 'tickets' handlers are often writable.
  • Remove compatibility functions.
  • Add click_in_cksum_pseudohdr() function.

• Incompatible changes
  • The 'Queue' element is now a NotifierQueue. To access a queue without notification, use 'SimpleQueue'.
  • The semantics of IPFilter 'deny' arguments have changed. Now, 'deny' means the same thing as 'drop'. The old behavior was inappropriately surprising.
  • Deprecated KernelTap element in favor of KernelTun.
  • Renamed MergeByTimestamp to TimeSortedSched.
  • '--enable-clickfs' is the default. (Clickfs provides a symlink from /proc/click to /click to make upgrading easier.)
  • Removed elements deprecated in 1.2.4. This includes LookupIPRoute, LookupIPRouteLinux, FromLinux, ToLinux, ToLinuxSniffers, PeekHandlers, ProbSplitter, and RandomLossage.
  • Removed user-level Click driver's '--stop' option.
  • The 'void Element::run_scheduled()' method has been deprecated; use 'bool Element::run_task()' or 'void Element::run_timer()' instead. 'run_task()'s bool return value should be true iff the task managed to do some useful work. (This helps the adaptive scheduler.)
  • HandlerCall's interface has changed. So have the raw functions for accessing handlers from a Router object.
  • Element map files now use an XML format, and are called 'elementmap.xml' and 'elementmap-PACKAGE.xml', not 'elementmap' and 'elementmap.PACKAGE'.
  • LLRPCs now explicitly encode the amount of data they transfer to and from the caller, using the same mechanism as ioctl(). The local_llrpc() virtual method has been removed.
  • Removed deprecated header files like <click/click_ip.h> (use <clicknet/ip.h> and similar).
  • Changed ICMP structure and macro names in <clicknet/icmp.h>.
  • Removed deprecated Element methods and method signatures, including 'Element::uninitialize()', 'Element::configure(const Vector<String> &)', and 'Element::live_reconfigure(const Vector<String> &)'.
  • Click declarations and definitions are now surrounded with CLICK_DECLS and CLICK_ENDDECLS macros (see any source file for an example). These macros normally do nothing. In the 'ns' driver, though, they drop all Click declarations into a separate namespace.
  • Removed 'String::operator const char *()', which caused problems with newer GCCs.
• Drivers
  • Add an optional adaptive task scheduler, written initially by Petros Zerfos pzerfos@cs.ucla.edu. Give 'configure' the '--enable-adaptive' option to turn it on. The adaptive scheduler takes less CPU time when Click isn't busy, and lets you control the minimum and maximum shares that Click will take of the CPU. This is particularly useful for the Linux kernel module, on a uniprocessor, for running user-level programs (tcpdump, for instance) as well as Click. The adaptive scheduler provides access to its parameters via handlers; see click.o(8) for more information.
  • Integrated the 'nsclick' driver from the University of Colorado, and particularly by Michael Neufeld. This driver lets you integrate a Click router with an ns simulation; Click can accept ns packets and return packets to ns. See configure's '--enable-ns' option and the 'ns' subdirectory.
  • Add support for Linux 2.4.20 and a newer Intel E1000 driver (4.3.15).
  • Linux kernel module driver notices when other processes are waiting to access the task list (to unschedule a task, for example), and explicitly waits to give them a chance.
  • Various Linux kernel module bug fixes, including a serious one in the SKB manager (mismeasured packet sizes could cause a kernel crash eventually).
  • Add 'Task::strong_unschedule()', which moves tasks to the quiescent thread; that way, tasks will not run even if they are rescheduled. Useful in the presence of notification.
  • Improve performance of add_select() and remove_select() at user level.
• Elements
  • Add SetUDPChecksum, TimestampAccum, PaintSwitch, KernelTun, MixedQueue.
  • Add a set of elements for trace analysis via a new packet annotation, the aggregate annotation. Elements include AggregateIPFlows, ToIPFlowDumps, AggregateIP, AggregateLength, AggregateCounter, AggregateFilter, AggregateFirst, AggregateLast.
  • Added notification support to ToDevice, DelayUnqueue, Unqueue, ToIPSummaryDump, ToDump.
  • FromIPSummaryDump and ToIPSummaryDump: Add optional binary format to save space and speed processing. Add 'aggregate', 'tcp_opt', 'tcp_sack', 'tcp_window', 'first_timestamp', and 'ip_opt' content types. FromIPSummaryDump understands '!flowid' and '!aggregate' lines.
  • FromDump and friends support 802.11 link types and the IPv6 Ethernet type.
  • Extended or changed functionality for ToDump (optional output port), Counter (different keyword argument names), CycleCountAccum and PerfCountAccum (different handler names), ControlSocket (different select() plan for writes reduces needless spinning; READONLY is a keyword argument), DelayUnqueue (supports combination of long delays and fast rates), IPFragmenter (HONOR_DF is a keyword argument), SetIPAddress (supports live reconfiguration), UDPIPEncap (supports live reconfiguration), IPGWOptions (lazy packet copying and better behavior on bad options), ICMPError (accept mnemonic names for ICMP error types and codes), IPReassembler (optionally emit dead fragments to output 1).
  • Bug fixes to FromIPSummaryDump, ToIPSummaryDump, IPReassembler, FromDump, ICMPRewriter, ICMPPingRewriter, ProgressBar, TCPRewriter, AddressInfo, ARPResponder, ToHost, ToHostSniffers, Classifier, InfiniteSource, IPGWOptions, ICMPError, IPOutputCombo, SetTCPChecksum.
• Tools
  • Add click2xml tool, for translating a Click configuration into an XML format, and a preliminary version of xml2click, which goes the other way.
  • Changed meaning of click-mkmindriver's `-e' option. Now `-e' means `--expression' for consistency. `-E' means `--elements'.
  • click-install supports the BSD kernel module.
  • Bug fixes to click-devirtualize, click-install, click-xform, click-buildtool.
• Internals
  • Add 'typename' where required to support newer GCCs.
  • Add Packet::shrink_data(), Packet::icmp_header(), and some others.
  • Change interface to BigHashMap iterators and BigHashMap_Arenas.
  • At user-level, ErrorHandler supports '%[efgEFG]' conversions for doubles. To print an element declaration, say '%{element}' (not '%e').
  • Bug fixes to CLP, BigHashMap, ...
  • Compiles cleanly on machines with 64-bit longs.
• Acknowledgements
  • Thanks to AUTHORS, and (in no particular order) to YongKang Zhu, Filip Henderieckx, Vlemincx Koen, David Scott Page, Wang Po-Cheng, Adam Smith, Ryan Menezes, Gordon Lee, Chip Coldwell, Xiao Phong, Jose Vasconcellos, Tomasz Jaskolski, Bart Samwel, and anyone we've missed.

• Drivers
  • FreeBSD module updates from Luigi Rizzo.
  • The Linux kernel module can support its own /proc-like file system, "clickfs". This file system is faster and takes less memory than the default /proc/click filesystem, and it is not subject to arbitrary limits on the number of files. Generally you will mount it under /click. (Click-install takes care of file system mounting and unmounting.) Give ./configure the --enable-clickfs option to enable clickfs (and disable /proc/click). Currently, clickfs only works under Linux 2.2. In the next release, it will also work under Linux 2.4, and --enable-clickfs will be the default.
  • Fix several race conditions in the Linux kernel module.
  • The user-level driver works on Solaris. Thanks to David Scott Page page@cs.utexas.edu for patches and suggestions.
• Elements
  • Add notifier support. The NotifierQueue element acts like a Queue, but can reschedule downstream Tasks when packets arrive on a previously empty Queue. This can greatly reduce CPU usage. Several other elements listen for notification, including DelayUnqueue, Discard, and ToDevice.
  • Rename FromLinux, ToLinux, and ToLinuxSniffers to FromHost, ToHost, and ToHostSniffers. The old names are still available.
  • Classifier optimization algorithm changed. The new algorithm, based on dominators, is much faster for medium-to-large Classifiers.
  • Add FromDAGDump element in the analysis package. This element reads DAG dumps (see http://dag.cs.waikato.ac.nz/).
  • Add LinearIPLookup element, a version of StaticIPLookup that supports dynamically adding and removing routes.
  • Add SortedIPLookup element, a version of LinearIPLookup that sorts its routes.
  • Bug fixes and enhancements in AddressInfo, CheckIPHeader, DelayUnqueue, DriverManager, Linux FromDevice, FromDump, FromIPSummaryDump, FrontDropQueue, Grid elements, ICMPPingResponder, ICMPSendPings, IPAddrRewriter, IPFragmenter, IPPrint, IPReassembler, IPRewriter, IPRouteTable, RadixIPLookup, TCPRewriter, TimeFilter, ToIPSummaryDump, etc.
  • Add RandomSwitch element.
  • Add preliminary elements that support regression testing, in elements/test.
• Tools
  • Add click-pretty tool, which pretty-prints Click configuration files as HTML.
  • Click-install works for the FreeBSD kernel module.
  • Click-install exits with nonzero exit status if the configuration could not be initialized.
• Internals
  • The signatures for the `Element::configure()' and `Element::live_reconfigure()' methods have changed. Formerly, these methods took a `const Vector<String> &conf'. Now, they take a `Vector<String> &conf', and the methods may alter the `conf' argument however they'd like. The old signatures still work for backward compatibility, but they are deprecated, and will be removed in a future release.
  • Deprecated `Element::uninitialize()' in favor of a new method, `Element::cleanup(CleanupStage stage)'. The `stage' argument, an enumerated value, says how far the element was initialized: not at all (CLEANUP_NO_ROUTER), configure() failed (CLEANUP_CONFIGURE_FAILED), configure() succeeded but initialize() was not called (CLEANUP_CONFIGURED), initialize() failed (CLEANUP_INITIALIZE_FAILED), initialize() succeeded but the router as a whole failed (CLEANUP_INITIALIZED), and the router initialized successfully, including this element (CLEANUP_ROUTER_INITIALIZED). So `uninitialize()' corresponded to `stage >= CLEANUP_INITIALIZED'. `Element::uninitialize()' works for now, but it will be removed in a future release.
  • The signature for the `Element::configuration()' method has also changed. It no longer takes a `bool *' argument.
  • Add cp_va_parse_remove_keywords() function, which removes keywords from an argument list.
  • Moved network-header-structure #include files to include/clicknet. For instance, `#include <click/click_ip.h>' should now be written `#include <clicknet/ip.h>'. The old names still work, but will be removed in a future release.
  • Renamed `IPAddress::mask_more_specific()' method to `IPAddress::mask_as_specific()', to emphasize that it allows equality.
  • Changed click_ip6 header structure.
  • Tools substantially rewritten. The tool library is now much easier to deal with, so tools should be easier to write, debug, and understand.
  • Better handling of out-of-memory events.
  • Improved `Packet::uniqueify()' implementation: it now copies only the packet data, not both header and data.
  • Click identifiers can no longer end with a slash.
• Acknowledgements
  • Thanks to the usual suspects (AUTHORS), and to David Scott Page page@cs.utexas.edu, Luigi Rizzo rizzo@aciri.org, Eric Freudenthal eric.freudenthal@nyu.edu and Tao Zhao taozhao@cs.nyu.edu, and Jose Vasconcellos jvasco@bellatlantic.net.

• Drivers
  • Linux kernel module: Rename Click kernel threads to "kclick".
  • User-level driver: Add `-e' option.
  • Various Linux 2.4 improvements.
  • FreeBSD driver is coming along nicely. You should compile this version of the driver against an *unmodified* FreeBSD kernel (RELENG_4 branch, version 440002 or later). Thanks to Luigi Rizzo, some of the improvements in the Click kernel patch have been checked in to the latest FreeBSD source! Bug fixes: can handle chained mbufs, etc.
  • Better support for cross-compiling tools, via the `--enable-tools' configuration switch.
  • Linux kernel module: Bug fixes, from Mazu, for dynamic installation and removal of devices, and for receiving large packets.
• Elements
  • Added a collection of analysis-related elements; give `--enable-analysis' to ./configure. Elements include FromIPSummaryDump and ToIPSummaryDump (read and write ASCII summary files; see http://www.aciri.org/kohler/ipsumdump/), FromNetFlowSummaryDump (read ASCII NetFlow summary files), AnonymizeIPAddr (anonymize IP addresses while preserving prefixes), MergeByTimestamp (merge multiple time-sorted packet streams into a single time-sorted stream), TimeFilter (select packets by timestamp), and TimeRange (monitors packet timestamps).
  • New elements: StripToNetworkHeader, ProgressBar (prints an ultra-cool progress bar to standard error), etc.
  • CheckIPHeader and friends set the destination IP address annotation from the IP header's destination address.
  • IPClassifier/IPFilter supports more >/>=/</<= comparisons, and gives better error messages on comparisons it does not support.
  • RED handles long quiescent periods better. As a result, Queue and friends could remove their annoying _empty_jiffies member. Also, RED uses the Gentle variant recommended by the RED gods.
  • Added AdaptiveRED element, by Jitendra Padhye padhye@aciri.org.
  • FromDump can read from gzipped or bzipped tcpdump files.
  • Deprecate RandomLossage and ProbSplitter elements in favor of new RandomSample element.
  • Deprecate PeekHandlers in favor of PokeHandlers, whose syntax has been extended. The new PokeHandlers is incompatible with old PokeHandlers configuration strings.
  • Bug fixes in ARPQuerier, FromDevice, ToDevice, FromDump, ICMPPingResponder, ControlSocket, DriverManager, IPRewriter and friends, Grid elements, Classifier.
  • Added functionality to FromDevice, FromDump, Shaper, BandwidthShaper, PokeHandlers, DriverManager, Grid elements, Counter.
• Configuration parsing
  • Configuration arguments that represent time can take suffixes like "h" for hours and "m" for minutes, as well as "s" for seconds, "ms" for milliseconds, and so forth.
  • Bug fixes in cp_real unparsing.
  • Add cp_double() and cpDouble, available only at user level.
  • Fix static binding errors in configuration language. Also, configuration language supports `${VAR-DEFAULT}' variable reference syntax, which uses the text `DEFAULT' if `$VAR' is not set.
• General
  • General configuration cleanup: Split config.h into multiple files to reduce needless recompilation; regularize symbols.
  • Task improvements should make everything a bit more robust. For example, Task::unschedule() always unschedules the task right away; it grabs a lock.
• Grid
  • New startup scripts for generating Grid configurations.
  • New elements implement Grid-level route tracing and statistics: GridProbeSender, GridProbeHandler, and GridProbeReplyReceiver.
  • Extended logging code in old Grid elements.
• Acknowledgements
  • Thanks to the usual suspects (AUTHORS), and to Geir kp13@gmx.co.uk, Luigi Rizzo rizzo@aciri.org, and Atanu Ghosh atanu@aciri.org.

• General
  • Added `etc/diagrams' directory, containing source code we use to generate Click diagrams.
  • Added `etc/samplellrpc' directory, a simple program demonstrating how to poke a Linux kernel Click's LLRPC handlers with ioctl() calls.
  • Added `etc/libclick' directory, which contains a self-sufficient distribution for building the Click user-level library.
  • Add `--enable-warp9' configuration option, which loosens element specifications to enable high-speed tests. For example, with `--enable-warp9' on, PollDevice does not set timestamps on packets it receives.
  • Add `--enable-greedy' configuration option, which prevents the Linux kernel driver from giving up the CPU. Use only if you have multiple CPUs. (Benjie Chen)
  • Many bug fixes.
• Drivers
  • Add preliminary support for a polling FreeBSD kernel driver!! (Nickolai B. Zeldovich)
  • Add polling support for EEpro 100 devices (Nickolai B. Zeldovich), and improve polling support for Tulip and Acenic (Benjie Chen, Nickolai).
  • Significantly more stable support for Linux 2.4, and update the kernel patch to Linux 2.4.9.
• Parsing
  • Time arguments understand suffixes like "ms", for milliseconds, and "us", for microseconds. So you can say `1ms' or `2sec' or `5000usec'.
  • Support IP prefix syntax like `192.111/16'. Requested by Vern Paxson vern@aciri.org.
• Elements
  • FromDump is significantly faster, supports new keyword arguments, and can read Linux tcpdump files. Also, FromDump supports FDDI encapsulation.
  • ToDump can write to standard output.
  • Removed deprecated elements HashDemux, PullToPush, FromBPF, and ToBPF.
  • Fix bugs in Linux kernel module device elements: avoid dereferencing null devices, and be careful about device reference counts for Linux 2.4.
  • Bug fixes to IPRewriter, TCPRewriter, Switch, PullSwitch, ....
  • Added functionality to ControlSocket, RED, FromLinux, FromDump, ....
  • Added SetPacketType, IPLookupRadix, ....
  • Renamed LookupIPRoute to StaticIPLookup, LookupIPRoute2 to RadixIPLookup, and LookupIPRouteLinux to LinuxIPLookup. The old names are still available.
• Internal
  • The format of `elements.conf' files has changed.
  • The header files for ScheduleInfo, AddressInfo, AlignmentInfo, Error, and DriverManager are stored in `<include/click/standard>'. This makes it simpler to distribute a self-contained Click library.
  • Bug fix: Elements are uninitialized and destroyed in the reverse order from which they were initialized. Reported by Kyle Jamieson jamieson@mit.edu.
  • Made most Click configuration tests into Autoconf macros in `acclick.m4'. This file may be shared among "Click-like" packages.
  • Check for byte order, and provide CLICK_BYTE_ORDER configuration constant.
  • Add Packet::tcp_header() and Packet::udp_header() convenience functions.

• General
  • Added preliminary support for Linux 2.4! The patch is in etc/linux-2.4.4-patch; it also applies to Linux 2.4.5. Click can receive and send packets, and there is preliminary support for polling, as well. We will be improving Linux 2.4's stability with time. Thanks to Nickolai B. Zeldovich.
  • Many bug fixes, particularly to ARPResponder, ToLinux, LookupIPRoute, cp_unparse_real2, cpArguments.
  • Updated etc/samplepackage to bring it up to date. It is a good starting point for building your own package.
• Elements
  • In the kernel, FromDevice, PollDevice, and ToDevice watch for notifications when devices go up or down. Now you can remove a device that the Click configuration refers to; the relevant element will simply stop pushing or pulling packets. If you add the device back again, the relevant element will seamlessly attach to it. Also added the `ALLOW_NONEXISTENT' keyword argument to these elements.
  • In the kernel, AddressInfo supports device names as Ethernet address shorthand. So you can say `EtherEncap(..., eth0, ...)' and it will use eth0's Ethernet address.
  • Added KernelHandlerProxy element, and added the `PROXY' keyword argument to ControlSocket. Now you can use a ControlSocket to talk to a kernel configuration -- for example, with ClickController. Element donated by Mazu Networks, Inc.
  • FromDump can read modified tcpdump files generated by Linux tcpdump.
  • ICMPSendPings has more keyword arguments. ICMPPingResponder now sets the destination IP address annotation. ICMPRewriter can rewrite ping responses as well as TCP and UDP responses.
  • Added DelayUnqueue, DelayShaper, and IP6Print elements.
• Tools
  • Added click-flatten tool.
• C++ API changes
  • Renamed `u_intXX_t' types to `uintXX_t'.
  • Elements no longer need to `#include <click/package.hh>'.
  • Added cpFilename confparse type at user level, which includes tilde expansion.
  • `hashcode()', the function used by BigHashMap and HashMap to calculate hash values, is now an overloaded function, not a member function. See include/click/ipflowid.hh for an example.

• General
  • Added support for Click multithreading: multiple processors processing packets through the Click configuration simultaneously. This required extensive source code changes and adding optional locks to several elements. Turn multithreading on at configure time with `--enable-multithread=[NTHREADS]'. Most elements in ip, standard, and linuxmodule are synchronized. SMP safe elements are marked with ELEMENT_MT_SAFE(elementname) at the end of the .cc file. See http://www.pdos.lcs.mit.edu/papers/click:usenix01/ for a paper on SMP Click.
  • Multithreading: User can use StaticThreadSched or SortedTaskSched elements to assign schedulable elements such as PollDevice and ToDevice to different threads.
  • Multithreading: Queue is not synchronized, but MSQueue and CPUQueue elements are SMP safe queue implementations. LookupIPRoute is not synchronized. Should use LookupIPRouteMP instead.
  • Multithreading: ARPQuerier and IPRewriter have been synchronzied using spinlocks and readwrite locks.
  • Added FastTCPFlows, FastUDPSrc, and FastUDPFlows elements. These elements can be used to generate test traffic.
  • Added preliminary support for cross-compilation. Everyone loves Doug!!
  • Many bug fixes, and being careful about out-of-memory situations.
  • Added support for special Intel-only assembly instructions, which make things faster. Turn it on at configure time with `--enable-intel-cpu'.
• Kernel driver
  • Changed device polling interface: sk_buff recycling moved out of individual device drivers and into Click (linuxmodule/skbmgr.cc). This requires a different 2.2.18 patch. You will need to apply the patch in this distribution and recompile.
  • Added a polling Intel EEPro 1000 gigabit driver, which can receive or send up to 1.3 million 64 byte packets per second.
  • Added `accessible' and `priority' module parameters (see click-install(1)'s `--private' and `--priority' options).
• Elements
  • Kernel module device elements changed to use the new polling interface. See above.
  • Added MarkIPCE element for ECN support.
  • Added ECN syntax (`ip ect' and `ip ce') and `ip ttl' to IPFilter and IPClassifier.
  • Added DriverManager element that says how to handle please_stop_driver() events.
  • Added keyword arguments to Print, IPPrint, InfiniteSource, RatedSource, RED, TimedSource, ....
  • Added ChatterSocket, DRRSched, PrintOld, PushNull, PullNull, and SetTimestamp elements.
  • Real number parsing functions handle overflow and rounding better.
  • IPRewriter garbage collection optimizations from Benjie.
  • Added AddressTranslator, ProtocolTranslator46, ProtocolTranslator64 elements that can translate between IPv6 networks and IPv4 networks.
• Tools
  • Added click-mkmindriver(1).
  • click-align(1) and click-devirtualize(1) bug fixes.
  • Add `-C CLICKPATH' argument to all relevant tools.
• C++ API changes
  • Added preliminary programmer documentation in Texinfo format (doc/click.texi). Removed old Element and Connection man pages, which were obsolete.
  • The Element class no longer inherents from `ElementLink'. Elements that wish to be scheduled must include and initialize a `Task' object.
  • Changed TimerHook type to `void (*)(Timer *, void *)'.
  • Added Element methods `flow_code' and `configuration'.
  • Renamed `Element::Connection' class to `Element::Port'.
  • Other changes.

• Element packages
  • Added support for element packages. An element package is a group of elements that can be dynamically loaded into a driver. Required several changes described below.
  • Rearranged include files. All include files formerly in `lib/' are now stored in `include/click/' instead. Do not say `#include "element.hh"' any more; say `#include <click/element.hh>' instead. Similar statements hold for `<click/packet.hh>', `<click/confparse.hh>', and many others. Check under include/click for a full list. Required for element package support.
  • Every element should say `MOD_INC_USE_COUNT;' in its constructor and `MOD_DEC_USE_COUNT;' in its destructor. Required for element package support.
  • Added a new directory, `etc/samplepackage', that demonstrates a simple element package. In particular, this shows how to write a Makefile for an element package.
• General
  • Compound element semantics: Connecting to a compound element port whose corresponding `input' or `output' was not mentioned inside the compound element is now an error. Leaving a compound element input or output port unused is also an error.
  • Compound element semantics: Added overloaded compound elements. A single compound element can have multiple definitions; Click uses the definition with matching numbers of arguments, input ports, and output ports. See click(5) for details.
  • Restructured build tools: created `click-buildtool' and `click-mkelemmap'.
  • Changed element documentation format: list of keywords follows `=s'. See elementdoc(7) for details.
  • The `cp_va_parse' family of functions supports keyword arguments. Use cpKeywords, and see `elements/ip/ipprint.cc' for an example. Also supported: adding and removing argument types dynamically.
  • Added support for generic annotations, such as "a one-byte annotation stored in generic annotation byte 13". Transitioned many existing packet annotations to macro wrappers for generic annotations; see `include/click/packet_anno.hh'. New structure is more easily extensible.
  • Many other bug fixes and configuration fixes.
• Elements
  • Added ICMPRewriter and ICMPPingRewriter for rewriting ICMP errors and ICMP pings, respectively.
  • Reorganized ICMP elements into `elements/icmp' directory, and TCP/UDP elements into `elements/tcpudp' directory.
  • IPRewriter and TCPRewriter quickly release completed TCP connections.
  • Improved IPFilter parsing functions and added some new protocols.
  • CheckIPHeader, CheckIPHeader2, CheckICMPHeader, CheckTCPHeader, and CheckUDPHeader can print more detailed information about why they are dropping packets.
  • Fixed bugs in many elements, including ToDump and FromLinux.
  • Classifier optimization is now iterative, not recursive, which gets around problems with small kernel stacks.
  • Removed 'PACKETS' or 'BYTES' argument to Counter. Now it always keeps track of both number of packets and number of bytes. Also added several LLRPCs.
• Kernel driver
  • Added patch for 2.2.18 kernel.
  • Changed /proc/click file handling: Now closing a write handler file may report an error back to the user through the return value of close(). Also, can remove Click kernel module even while someone has a file in /proc/click open.
  • Added TulipStats element for collecting information about Tulip performance.
  • Replaced old cycle-counting elements with SetCycleCount and CycleCountAccum, and similarly for performance counter elements (new elements are SetPerfCount and PerfCountAccum).
  • Fixed crash when Linux and Click both sent packets out the same interface on an SMP machine.

• Incompatible element changes
  • Added support for parsing CIDR-style [Classless Inter-Domain Routing] netmasks in element configuration strings. Old-style netmasks are still supported, but you must use a slash, not a space. So for the 18.26.7 IP prefix, you can write either `18.26.7.0/255.255.255.0' or `18.26.7.0/24'. You will need to change the arguments to any ARPResponder, FromLinux, LookupIPRoute, LookupIPRoute2, and RIPSend elements in your configuration files.
  • Deprecated FromBPF and ToBPF in favor of FromDevice and ToDevice. (But the arguments to FromDevice and ToDevice are the same as FromBPF and ToBPF.)
  • The KernelTap element (formerly Tun) no longer takes a device name as the first argument; it chooses between /dev/tun and /dev/tap automatically. KernelTap also expects and produces ethernet-encapsulated packets (rather than IP), as the Ethernet type field lets it handle IPv6 packets as well as IPv4.
  • Changed the third argument to RatedSource. Used to be a duration to send packets; now it is the number of packets to send.
  • The following elements have been renamed.

OLD			NEW
------------------	------------------
CheckPaint*		PaintTee
FromBPF			FromDevice
HashDemux*		HashSwitch
Meter			BandwidthMeter
PacketMeter		Meter
PacketShaper		Shaper
PullToPush*		Unqueue
SetIPAddress+		StoreIPAddress
Shaper			BandwidthShaper
ToBPF			ToDevice
Tun			KernelTap
  
  Footnotes: * Old element name may still be used for this release, but is
               deprecated.
             + A new element has taken the name SetIPAddress.

Our apologies. We don't expect this kind of renaming will be a common event.

• To reiterate, the elements that measure bytes per second are now named BandwidthMeter and BandwidthShaper. The elements that measure packets per second have taken the names Meter and Shaper.
• Removed the SaveIPFields and IPsec elements (they were rotting).
• Incompatible C++ API changes
• Reorganized Linux kernel polling patches. If you have a previous version of Click, you must unapply the old kernel patch and apply the new kernel patch before compiling.
• Improved Packet copy-on-write behavior by reflecting it in the C++ class structure. Now there is a class for possibly-shared packets (named Packet), and a class for definitely-not-shared packets (named WritablePacket). WritablePacket is a subclass of Packet. Packet's data is always read-only (that is, the `data()' method returns a `const unsigned char *', and so forth). WritablePacket's data is read/write (the `data()' method returns an `unsigned char *'). `Packet::uniqueify()' and similar methods return a WritablePacket.
• Made configuration argument parsing more uniform among elements. For example, every configuration argument is always a comma-separated string. This is enforced by passing a vector of strings to the `configure' method: `cp_argvec' is called before the `configure' method is called. Changed Element method `int configure(const String &, ErrorHandler *)' to `int configure(const Vector<String> &, ErrorHandler *)', and updated elements.
• The `cp_DATATYPE' functions take pointers instead of references. This makes their use easier to read. * The `cp_DATATYPE' functions no longer take an optional `String *rest' argument. They always parse their argument string entirely.
• Changed Element method `bool configure_first() const' to `int configure_phase() const'. Now element classes can specify their relative configuration and initialization order; for example, ToDevice specifies that it should be configured and initialized after any FromDevices.
• Removed user-level Element method `select_fd()'. Replaced with `add_select(fd, mask)' and `remove_select(fd, mask)', so elements can listen to any number of file descriptors for reading, writing, or both. (`mask' is either `SELECT_READ', `SELECT_WRITE', or `SELECT_READ|SELECT_WRITE'.)
• Other small changes and method renamings should have limited impact. For instance, renamed `Element::number()' to `Element::eindex()'; removed `Element::use()' and `Element::unuse()'; renamed `Element::change_configuration()' to `Element::set_configuration()' and `Element::set_configuration_argument()'.
• Renamed Ethernet and ARP structures; what was `struct ether_header' is now `struct click_ether', and so forth, to avoid conflicts.
• Removed `IPVERSION' constant from `click_ip.h' to support IPv6.
• General
• Added new `tickets' and `handlers' handlers, available by default on every element. Removed default `inputs' and `outputs' handlers, replacing them with `ports'.
• Improved support for large numbers of handlers by reducing memory usage.
• Click configurations can contain cpp(1)-style `#line LINENUMBER' or `# LINENUMBER' directives. The tools generate them, too, so you will get better error messages than before.
• Improved element documentation by adding summaries. The generated elements(n) manual page now groups the elements by function. Also updated and documented the format for doc comments (see `doc/elementdoc.7').
• Added low-level RPC capability. LLRPCs are low-level handlers designed for speed rather than ease of use or human-readable results. In the Linux kernel module, LLRPCs are called in response to ioctl(2) commands on handler files. (The user-level program doesn't support LLRPCs yet.) Unlike handlers, LLRPCs can both take arguments and return results. IPRateMonitor(n), for example, uses LLRPCs to report rate information.
• Lexer changes: Now single and double quotes are interpreted in configuration arguments vaguely as in Perl. Configuration argument parsing is generally more regular.
• Fixed bugs in real-number parsing and unparsing functions.
• User-level driver
• User-level Click will no longer stop by default when an InfiniteSource (or RatedSource or FromDump) runs out of packets to send. Supply the `-s' option to get the old behavior.
• You can give shell globbing syntax to the user-level driver's `-h HANDLER' option; for example, `-h "*.config"'.
• Fixed FromBPF and ToBPF, finally. The fixed versions are called FromDevice and ToDevice.
• Added ControlSocket element so you can call handlers from other programs.
• Kernel driver
• Added patch for Linux kernel 2.2.16. This patch contains the latest changes to Linux. While Click will continue to work under 2.2.14 for the time being, it may not work in the future. If you have a previous version of Click, you must unapply the old kernel patch and apply the new kernel patch before compiling.
• Improved /proc handling. It is now safe to keep open file descriptors to handler files even while uninstalling the kernel module or installing a new configuration. These files will become unusable after the (un)installation -- every operation will return EINVAL -- but the kernel will not crash and the Click module's reference count will not get screwed up.
• Cleaned up polling interface in Linux.
• Elements
• Added QuitWatcher, FrontDropQueue, StripIPHeader, IPClassifier, IPFilter, IPPrint, FTPPortMapper, IPRewriterPatterns, Switch, PullSwitch, StaticSwitch, StaticPullSwitch, RoundRobinSwitch, StrideSwitch, RatedSplitter, BandwidthRatedSplitter, RatedUnqueue, and BandwidthRatedUnqueue, among others. Also mentioned above: user-level FromDevice, ToDevice, and ControlSocket; kernel module ToLinuxSniffers; generic SetIPAddress, StoreIPAddress.
• Added AddressInfo element, which supports network address mnemonics. For example, you can now say `AddressInfo(butt 18.26.4.44); IPEncap(6, butt, 18.26.4.15)'. The `butt' in IPEncap's configuration string then means `18.26.4.44'.
• Added experimental IPv6 elements; `./configure --enable-ip6' to compile them.
• Fixed kernel alignment bug in IP header checking elements: can't use Linux's `fast_ip_csum' on unaligned data.
• Fixed user-level FromDevice and ToDevice bugs. Now FromDevice will not starve other router processing, and ToDevice works on Linux.
• Fixed FromLinux bug: now supports multiple instances of FromLinux for same device (this happens while installing a new configuration: initialize is called on the new FromLinux before the last FromLinux instance is uninitialized).
• Fixed ToLinux: now calls ptype_dispatch inside start_bh_atomic() and end_bh_atomic().
• Modified kernel ToDevice: ToDevice now sends Linux's packets when the device is idle. This prevents Click from starving out packets sent by other processes or Linux.
• Shaper and BandwidthShaper work significantly better. They are less bursty and can correctly shape traffic to low rates.
• Improved Classifier optimizations.
• Radio elements are not compiled by default.
• Added new `elements/local' directory for your own elements. They are not compiled by default.
• Tools
• Added new click-undead(1) tool.
• Fixed click-uncombine(1) bugs and changed its order of arguments.
• Added PollDevice and EtherEncap specifications to click-align(1).
• click-fastclassifier(1) works on IPClassifier and IPFilter.
• Added `--verbose' option to click-install(1).

• Kernel driver
  • Fixed kernel Packet::expensive_push. Patch by Richard Mortier rmm1002@cam.ac.uk.
  • Added /proc/click/version.
• Elements
  • Replace UDPEncap with UDPIPEncap. New element adds both IP and UDP headers, and fixes several bugs in UDPEncap. Thanks to Richard Mortier Richard.Mortier@cl.cam.ac.uk.
• Miscellaneous
  • Fixed findelements.sh: Ethernet switch elements were not being included.

• Kernel and user-level drivers
  • You can hot-swap install Click configurations in the Linux kernel module. In a hot-swap install, packets stored in the old configuration will not be lost. (The new configuration's Queues must have the same names as the old configuration's Queues.) See the click.o(8) man page (under /proc/click/hotconfig) and the click-install(1) man page for more information.
  • Bug fixes: User-level Click correctly handles timed elements like TimedSource and TimedSink and scheduled elements like RatedSource; and the kernel module correctly handles timed elements. Reported by Saurabh Sandhir sandhir@purdue.edu.
  • More changes to ToDevice to enable Linux and Click to send packets independently and not cause race conditions. This includes a new linux kernel patch (etc/linux-2.2.14-patch) and changes to ToDevice. Click runs in a separate kernel thread, so we synchronize ToDevice send operations in kernel with a bit lock (dev->tbusy).
  • Every Linux kernel module now runs as a separate kernel thread, even if HAVE_POLLING is not defined.
  • The click user-level driver can now automatically compile any required package sources. (Click-install has been able to do this for a while.)
  • Every router has its own list of Timers, so Timer has no global state. Originally requested by Leigh Stoller stoller@fast.cs.utah.edu. This changed the Timer abstraction; you now need to call Timer::attach() on a Timer before using it. See timedsource.cc for an example.
  • Fixed bugs and memory leaks.
• Tools
  • click-xform: Bug fixes and performance improvements. Also, click-xform tries to preserve element names from the original configuration. If a pattern element and a replacement element share a name, then when the pattern is applied, the replacing element will use the name of the original element that corresponded to the pattern element. (Phew!)
  • click-devirtualize: Bug fixes. It also uses standards-compliant C++.
  • click-fastclassifier can combine adjacent Classifiers.
  • Added click-combine and click-uncombine.
• Elements
  • Removed UnlimitedElement in favor of `notify_n{in,out}puts()'.
  • Removed TimedElement.
  • Removed Broadcast in favor of Tee.
  • Added select_fd() and selected() to ToBPF.
  • Various other fixes.
• Configurations
  • Added conf/make-udpgen.pl, a Perl script that generates a udpgen-like Click configuration.
  • Added conf/make-udpcount.pl, a Perl script that generates a udpcount-like Click configuration.

• Changed how FromDevice, ToDevice, and PollDevice interact with each other. Before, if you specify just PollDevice w/o ToDevice, the tx queue does not get cleaned because in polling mode tx queue cleaning must be scheduled explicitly. Now, PollDevice looks for a ToDevice on the same device. If no such element exists, it remembers to clean the tx queue itself. Also ToDevice looks for a PollDevice to decide if it should use polling extensions. Some of this code was in the 1.0.3 release, but there was a bug.
• New linux kernel patch (etc/linux-2.2.14-patch): locks are added to protect recycling of sk_buff objects and device polling functions - not extensively tested.
• New elements: UDPEncap (put an UDP header on a packet), RatedSource (like infinite source, but send packets at a given rate).
• udpgen click configuration (conf/udpgen.click): This is better than udpgen.o in that you can utilize device driver polling extensions. Also, on some machines we observe a delay (on order of ms) between when transmission complete and tx interrupt. This causes the transmission queue to not get cleaned fast enough for udpgen to send its packets. Using Click, we can control when the tx queue is cleaned.

• Added `--with-linux[=DIR]' option to `./configure'. Suggested by Richard Mortier Richard.Mortier@cl.cam.ac.uk.
• Removed `default_processing()' method of Element and replaced it with `processing()'. Where you once wrote `Processing default_processing() const { return PUSH; }', now write `const char *processing() const { return PUSH; }'. The new way is more flexible and lets us abstract the element's processing code. See Element(3) for details.
• Added `click-check' tool, a static checker for Click configurations. Currently it only checks push and pull processing for correctness.
• Added `--reverse' option to click-xform. Suggested by Mike Burrows (Compaq SRC).
• Added `--reverse' options to click-fastclassifier and click-devirtualize.
• Renamed click-specialize tool to click-devirtualize. It's clearer. Also fixed several bugs.
• Click-devirtualize now determines automatically whether two specialized elements can share code. As a result, the `--like' option has been removed.
• Fixed bugs: RFC2507Decomp didn't compile. Rewriter updates. Several bugs caught by recent GCCs; patches supplied by Richard Mortier Richard.Mortier@cl.cam.ac.uk.

• Fixed reentrancy bug: in this release, when running in polling mode in kernel, timers are maintained by click, in the same fashion userlevel timers are maintained. Previously, we use linux timers, and so callbacks may get called by linux when click is running, creating possible race conditions. Note: in polling mode, if the click thread yields to other processes, timers will not get called until the click thread runs again.
• Added Rewriter, MappingCreator, and IPMirror elements for rewriting TCP/IP and UDP/IP streams.
• Added MarkIPHeader, CheckTCPHeader, and CheckUDPHeader elements.
• Fixed FromDump and ToDump.
• Added optional queue names to RED.
• Removed `is_a()' and `is_a_cast()' methods of Element. The new way, `cast()', allows arbitrary interfaces.
• Use Linux's fast checksum routines in CheckIPHeader and IPInputCombo.
• Fixed bug in userlevel Click: elements weren't being scheduled, so nothing seemed to happen.

• Fixed Makefile bugs; Linux module installs properly now. Problem reported by Joe Elliott joe@inetd.com.

==== Version 1.0 25.Feb.2000

• Added polling support. Result: 4-5 times better peak performance. The optimization tools can get it up to 6 times better (435,000 64-byte packets per second).
• Replaced work list with stride scheduler.
• In the Linux kernel, Click now runs in a kernel thread.
• Removed packet-upstream events and the associated processing in Queue, Shaper, and so forth. The stride scheduler solves the same problem more elegantly.
• Added `click-specialize' tool.
• Added `click-uninstall' tool.
• Added dynamic IP routing table element (LookupIPRoute2).
• Added stride scheduling packet scheduler element (StrideSched).
• Added PeekHandlers and PokeHandlers elements so you can test read and write handlers at user level.
• Fixed lexer bug: compound elements with `{' are accepted everywhere.
• Added arguments to compound elements.
• Rearranged directory structure. (Include files placed in PREFIX/include/click, not directly in PREFIX/include.)
• Improved several elements, including ARPQuerier.
• Changed interface for registering handlers. See `elements/standard/red.cc' or the Element(3) manual page for examples.
• Many other changes, bug fixes and improvements.

• Added dynamic linking support. Click configuration files can now be ar(1) archives, possibly containing "packages"---dynamically linked object files that are loaded into the kernel module or the user-level program. This means you can make your own element classes and link them dynamically.
• Added `click-fastclassifier' and `click-install' tools.
• Added `--help', `--version', etc. options to tools.
• Added man pages for `click', `click-align', and `click-install'.
• More options for user-level Click, including support for hander invocations on the command line.
• Added `udpgen' and `udpcount' in the `tools' directory.
• Fixed dynamic reconfiguration bug: no more doubled characters.
• Fixed compound element bug: input and output ports bigger than 0 were ignored.

• Support for required-alignment machines via `click-align' tool. Added click-align tool, Align and AlignmentInfo elements.
• More documentation.

• First public release.