meaning has changed, and several pbuf functions have been
    adapted accordingly.

  * netif drivers have to be changed to set the hardware address length field
    that must be initialized correctly by the driver (hint: 6 for Ethernet MAC).
    See the contrib/ports/c16x cs8900 driver as a driver example.

  * netif's have a dhcp field that must be initialized to NULL by the driver.
    See the contrib/ports/c16x cs8900 driver as a driver example.

(0.5.x) This file has been unmaintained up to 0.6.1. All changes are
  logged in CVS but have not been explained here.

(0.5.3) Changes since version 0.5.2

  ++ Bugfixes:

  * memp_malloc(MEMP_API_MSG) could fail with multiple application
    threads because it wasn't protected by semaphores.

  ++ Other changes:

  * struct ip_addr now packed.

  * The name of the time variable in arp.c has been changed to ctime
    to avoid conflicts with the time() function.

(0.5.2) Changes since version 0.5.1

  ++ New features:

  * A new TCP function, tcp_tmr(), now handles both TCP timers.

  ++ Bugfixes:

  * A bug in tcp_parseopt() could cause the stack to hang because of a
    malformed TCP option.

  * The address of new connections in the accept() function in the BSD
    socket library was not handled correctly.

  * pbuf_dechain() did not update the ->tot_len field of the tail.

  * Aborted TCP connections were not handled correctly in all
    situations.

  ++ Other changes:

  * All protocol header structs are now packed.

  * The ->len field in the tcp_seg structure now counts the actual
    amount of data, and does not add one for SYN and FIN segments.

(0.5.1) Changes since version 0.5.0

  ++ New features:

  * Possible to run as a user process under Linux.

  * Preliminary support for cross platform packed structs.

  * ARP timer now implemented.

  ++ Bugfixes:

  * TCP output queue length was badly initialized when opening
    connections.

  * TCP delayed ACKs were not sent correctly.

  * Explicit initialization of BSS segment variables.

  * read() in BSD socket library could drop data.

  * Problems with memory alignment.

  * Situations when all TCP buffers were used could lead to
    starvation.

  * TCP MSS option wasn't parsed correctly.

  * Problems with UDP checksum calculation.

  * IP multicast address tests had endianess problems.

  * ARP requests had wrong destination hardware address.

  ++ Other changes:

  * struct eth_addr changed from u16_t[3] array to u8_t[6].

  * A ->linkoutput() member was added to struct netif.

  * TCP and UDP ->dest_* struct members where changed to ->remote_*.

  * ntoh* macros are now null definitions for big endian CPUs.

(0.5.0) Changes since version 0.4.2

  ++ New features:

  * Redesigned operating system emulation layer to make porting easier.

  * Better control over TCP output buffers.

  * Documenation added.

  ++ Bugfixes:

  * Locking issues in buffer management.

  * Bugfixes in the sequential API.

  * IP forwarding could cause memory leakage. This has been fixed.

  ++ Other changes:

  * Directory structure somewhat changed; the core/ tree has been
    collapsed.

(0.4.2) Changes since version 0.4.1

  ++ New features:

  * Experimental ARP implementation added.

  * Skeleton Ethernet driver added.

  * Experimental BSD socket API library added.

  ++ Bugfixes:

  * In very intense situations, memory leakage could occur. This has
    been fixed.

  ++ Other changes:

  * Variables named "data" and "code" have been renamed in order to
    avoid name conflicts in certain compilers.

  * Variable++ have in appliciable cases been translated to ++variable
    since some compilers generate better code in the latter case.

(0.4.1) Changes since version 0.4

  ++ New features:

  * TCP: Connection attempts time out earlier than data
    transmissions. Nagle algorithm implemented. Push flag set on the
    last segment in a burst.

  * UDP: experimental support for UDP-Lite extensions.

  ++ Bugfixes:

  * TCP: out of order segments were in some cases handled incorrectly,
    and this has now been fixed. Delayed acknowledgements was broken
    in 0.4, has now been fixed. Binding to an address that is in use
    now results in an error. Reset connections sometimes hung an
    application; this has been fixed.

  * Checksum calculation sometimes failed for chained pbufs with odd
    lengths. This has been fixed.

  * API: a lot of bug fixes in the API. The UDP API has been improved
    and tested. Error reporting and handling has been
    improved. Logical flaws and race conditions for incoming TCP
    connections has been found and removed.

  * Memory manager: alignment issues. Reallocating memory sometimes
    failed, this has been fixed.

  * Generic library: bcopy was flawed and has been fixed.

  ++ Other changes:

  * API: all datatypes has been changed from generic ones such as
    ints, to specified ones such as u16_t. Functions that return
    errors now have the correct type (err_t).

  * General: A lot of code cleaned up and debugging code removed. Many
    portability issues have been fixed.

  * The license was changed; the advertising clause was removed.

  * C64 port added.

  * Thanks: Huge thanks go to Dagan Galarneau, Horst Garnetzke, Petri
    Kosunen, Mikael Caleres, and Frits Wilmink for reporting and
    fixing bugs!

(0.4) Changes since version 0.3.1

  * Memory management has been radically changed; instead of
    allocating memory from a shared heap, memory for objects that are
    rapidly allocated and deallocated is now kept in pools. Allocation
    and deallocation from those memory pools is very fast. The shared
    heap is still present but is used less frequently.

  * The memory, memory pool, and packet buffer subsystems now support
    4-, 2-, or 1-byte alignment.

  * "Out of memory" situations are handled in a more robust way.

  * Stack usage has been reduced.

  * Easier configuration of lwIP parameters such as memory usage,
    TTLs, statistics gathering, etc. All configuration parameters are
    now kept in a single header file "lwipopts.h".

  * The directory structure has been changed slightly so that all
    architecture specific files are kept under the src/arch
    hierarchy.

  * Error propagation has been improved, both in the protocol modules
    and in the API.

  * The code for the RTXC architecture has been implemented, tested
    and put to use.

  * Bugs have been found and corrected in the TCP, UDP, IP, API, and
    the Internet checksum modules.

  * Bugs related to porting between a 32-bit and a 16-bit architecture
    have been found and corrected.

  * The license has been changed slightly to conform more with the
    original BSD license, including the advertisement clause.

(0.3.1) Changes since version 0.3

  * Fix of a fatal bug in the buffer management. Pbufs with allocated
    RAM never returned the RAM when the pbuf was deallocated.

  * TCP congestion control, window updates and retransmissions did not
    work correctly. This has now been fixed.

  * Bugfixes in the API.

(0.3) Changes since version 0.2

  * New and improved directory structure. All include files are now
    kept in a dedicated include/ directory.

  * The API now has proper error handling. A new function,
    netconn_err(), now returns an error code for the connection in
    case of errors.

  * Improvements in the memory management subsystem. The system now
    keeps a pointer to the lowest free memory block. A new function,
    mem_malloc2() tries to allocate memory once, and if it fails tries
    to free some memory and retry the allocation.

  * Much testing has been done with limited memory
    configurations. lwIP now does a better job when overloaded.

  * Some bugfixes and improvements to the buffer (pbuf) subsystem.

  * Many bugfixes in the TCP code:

    - Fixed a bug in tcp_close().

    - The TCP receive window was incorrectly closed when out of
      sequence segments was received. This has been fixed.

    - Connections are now timed-out of the FIN-WAIT-2 state.

    - The initial congestion window could in some cases be too
      large. This has been fixed.

    - The retransmission queue could in some cases be screwed up. This
      has been fixed.

    - TCP RST flag now handled correctly.

    - Out of sequence data was in some cases never delivered to the
      application. This has been fixed.

    - Retransmitted segments now contain the correct acknowledgment
      number and advertised window.

    - TCP retransmission timeout backoffs are not correctly computed
      (ala BSD). After a number of retransmissions, TCP now gives up
      the connection.

  * TCP connections now are kept on three lists, one for active
    connections, one for listening connections, and one for
    connections that are in TIME-WAIT. This greatly speeds up the fast
    timeout processing for sending delayed ACKs.

  * TCP now provides proper feedback to the application when a
    connection has been successfully set up.

  * More comments have been added to the code. The code has also been
    somewhat cleaned up.

(0.2) Initial public release.