FUTURE  * TODO: The lwIP source code makes some invalid assumptions on processor    word-length, storage sizes and alignment. See the mailing lists for    problems with exoteric (/DSP) architectures showing these problems.    We still have to fix some of these issues neatly.  * TODO: the ARP layer is not protected against concurrent access. If    you run from a multitasking OS, serialize access to ARP (called from    your network device driver and from a timeout thread.)  * TODO: the PPP code is broken in a few ways. There are namespace    collisions on BSD systems and many assumptions on word-length    (sizeof(int)). In ppp.c an assumption is made on the availability of    a thread subsystem. Either PPP needs to be moved to contrib/ports/???    or rearranged to be more generic.HISTORY(CVS HEAD)  * [New changes go here](STABLE-1_1_1)  2006-03-03  Christiaan Simons  * ipv4/ip_frag.c: Added bound-checking assertions on ip_reassbitmap    access and added pbuf_alloc() return value checks.  2006-01-01  Leon Woestenberg <leon.woestenberg@gmx.net>  * tcp_{in,out}.c, tcp_out.c: Removed 'even sndbuf' fix in TCP, which is    now handled by the checksum routine properly.  2006-02-27  Leon Woestenberg <leon.woestenberg@gmx.net>   * pbuf.c: Fix alignment; pbuf_init() would not work unless     pbuf_pool_memory[] was properly aligned. (Patch by Curt McDowell.)  2005-12-20  Leon Woestenberg <leon.woestenberg@gmx.net>  * tcp.c: Remove PCBs which stay in LAST_ACK state too long. Patch    submitted by Mitrani Hiroshi.      2005-12-15  Christiaan Simons  * inet.c: Disabled the added summing routine to preserve code space.  2005-12-14  Leon Woestenberg <leon.woestenberg@gmx.net>  * tcp_in.c: Duplicate FIN ACK race condition fix by Kelvin Lawson.    Added Curt McDowell's optimized checksumming routine for future    inclusion. Need to create test case for unaliged, aligned, odd,    even length combination of cases on various endianess machines.  2005-12-09  Christiaan Simons  * inet.c: Rewrote standard checksum routine in proper portable C.  2005-11-25  Christiaan Simons  * udp.c tcp.c: Removed SO_REUSE hack. Should reside in socket code only.  * *.c: introduced cc.h LWIP_DEBUG formatters matching the u16_t, s16_t,    u32_t, s32_t typedefs. This solves most debug word-length assumes.    2005-07-17 Leon Woestenberg <leon.woestenberg@gmx.net>  * inet.c: Fixed unaligned 16-bit access in the standard checksum    routine by Peter Jolasson.  * slipif.c: Fixed implementation assumption of single-pbuf datagrams.  2005-02-04 Leon Woestenberg <leon.woestenberg@gmx.net>  * tcp_out.c: Fixed uninitialized 'queue' referenced in memerr branch.  * tcp_{out|in}.c: Applied patch fixing unaligned access.  2005-01-04 Leon Woestenberg <leon.woestenberg@gmx.net>  * pbuf.c: Fixed missing semicolon after LWIP_DEBUG statement.  2005-01-03 Leon Woestenberg <leon.woestenberg@gmx.net>  * udp.c: UDP pcb->recv() was called even when it was NULL.(STABLE-1_1_0)  2004-12-28 Leon Woestenberg <leon.woestenberg@gmx.net>  * etharp.*: Disabled multiple packets on the ARP queue.    This clashes with TCP queueing.  2004-11-28 Leon Woestenberg <leon.woestenberg@gmx.net>  * etharp.*: Fixed race condition from ARP request to ARP timeout.    Halved the ARP period, doubled the period counts.    ETHARP_MAX_PENDING now should be at least 2. This prevents    the counter from reaching 0 right away (which would allow    too little time for ARP responses to be received).      2004-11-25 Leon Woestenberg <leon.woestenberg@gmx.net>  * dhcp.c: Decline messages were not multicast but unicast.  * etharp.c: ETHARP_CREATE is renamed to ETHARP_TRY_HARD.    Do not try hard to insert arbitrary packet's source address,    etharp_ip_input() now calls etharp_update() without ETHARP_TRY_HARD.     etharp_query() now always DOES call ETHARP_TRY_HARD so that users    querying an address will see it appear in the cache (DHCP could    suffer from this when a server invalidly gave an in-use address.)  * ipv4/ip_addr.h: Renamed ip_addr_maskcmp() to _netcmp() as we are    comparing network addresses (identifiers), not the network masks    themselves.  * ipv4/ip_addr.c: ip_addr_isbroadcast() now checks that the given    IP address actually belongs to the network of the given interface.  2004-11-24 Kieran Mansley <kjm25@cam.ac.uk>  * tcp.c: Increment pcb->snd_buf when ACK is received in SYN_SENT state.(STABLE-1_1_0-RC1)  2004-10-16 Kieran Mansley <kjm25@cam.ac.uk>  * tcp.c: Add code to tcp_recved() to send an ACK (window update) immediately,	even if one is already pending, if the rcv_wnd is above a threshold	(currently TCP_WND/2). This avoids waiting for a timer to expire to send a	delayed ACK in order to open the window if the stack is only receiving data.  2004-09-12 Kieran Mansley <kjm25@cam.ac.uk>  * tcp*.*: Retransmit time-out handling improvement by Sam Jansen.  2004-08-20 Tony Mountifield <tony@softins.co.uk>  * etharp.c: Make sure the first pbuf queued on an ARP entry    is properly ref counted.  2004-07-27 Tony Mountifield <tony@softins.co.uk>  * debug.h: Added (int) cast in LWIP_DEBUGF() to avoid compiler    warnings about comparison.  * pbuf.c: Stopped compiler complaining of empty if statement    when LWIP_DEBUGF() empty.  Closed an unclosed comment.  * tcp.c: Stopped compiler complaining of empty if statement    when LWIP_DEBUGF() empty.  * ip.h Corrected IPH_TOS() macro: returns a byte, so doesn't need htons().  * inet.c: Added a couple of casts to quiet the compiler.    No need to test isascii(c) before isdigit(c) or isxdigit(c).  2004-07-22 Tony Mountifield <tony@softins.co.uk>  * inet.c: Made data types consistent in inet_ntoa().    Added casts for return values of checksum routines, to pacify compiler.  * ip_frag.c, tcp_out.c, sockets.c, pbuf.c    Small corrections to some debugging statements, to pacify compiler.  2004-07-21 Tony Mountifield <tony@softins.co.uk>  * etharp.c: Removed spurious semicolon and added missing end-of-comment.  * ethernetif.c Updated low_level_output() to match prototype for    netif->linkoutput and changed low_level_input() similarly for consistency.  * api_msg.c: Changed recv_raw() from int to u8_t, to match prototype    of raw_recv() in raw.h and so avoid compiler error.  * sockets.c: Added trivial (int) cast to keep compiler happier.  * ip.c, netif.c Changed debug statements to use the tidier ip4_addrN() macros.  (STABLE-1_0_0)  ++ Changes:  2004-07-05 Leon Woestenberg <leon.woestenberg@gmx.net>  * sockets.*: Restructured LWIP_PRIVATE_TIMEVAL. Make sure    your cc.h file defines this either 1 or 0. If non-defined,    defaults to 1.  * .c: Added <string.h> and <errno.h> includes where used.  * etharp.c: Made some array indices unsigned.  2004-06-27 Leon Woestenberg <leon.woestenberg@gmx.net>  * netif.*: Added netif_set_up()/down().  * dhcp.c: Changes to restart program flow.  2004-05-07 Leon Woestenberg <leon.woestenberg@gmx.net>  * etharp.c: In find_entry(), instead of a list traversal per candidate, do a    single-pass lookup for different candidates. Should exploit locality.  2004-04-29 Leon Woestenberg <leon.woestenberg@gmx.net>  * tcp*.c: Cleaned up source comment documentation for Doxygen processing.  * opt.h: ETHARP_ALWAYS_INSERT option removed to comply with ARP RFC.  * etharp.c: update_arp_entry() only adds new ARP entries when adviced to by    the caller. This deprecates the ETHARP_ALWAYS_INSERT overrule option.  ++ Bug fixes:  2004-04-27 Leon Woestenberg <leon.woestenberg@gmx.net>  * etharp.c: Applied patch of bug #8708 by Toni Mountifield with a solution    suggested by Timmy Brolin. Fix for 32-bit processors that cannot access    non-aligned 32-bit words, such as soms 32-bit TCP/IP header fields. Fix    is to prefix the 14-bit Ethernet headers with two padding bytes.  2004-04-23 Leon Woestenberg <leon.woestenberg@gmx.net>  * ip_addr.c: Fix in the ip_addr_isbroadcast() check.  * etharp.c: Fixed the case where the packet that initiates the ARP request    is not queued, and gets lost. Fixed the case where the packets destination    address is already known; we now always queue the packet and perform an ARP    request.  (STABLE-0_7_0)  ++ Bug fixes:  * Fixed TCP bug for SYN_SENT to ESTABLISHED state transition.  * Fixed TCP bug in dequeueing of FIN from out of order segment queue.  * Fixed two possible NULL references in rare cases.(STABLE-0_6_6)  ++ Bug fixes:  * Fixed DHCP which did not include the IP address in DECLINE messages.  ++ Changes:  * etharp.c has been hauled over a bit.(STABLE-0_6_5)  ++ Bug fixes:  * Fixed TCP bug induced by bad window resizing with unidirectional TCP traffic.  * Packets sent from ARP queue had invalid source hardware address.  ++ Changes:  * Pass-by ARP requests do now update the cache.  ++ New features:  * No longer dependent on ctype.h.  * New socket options.  * Raw IP pcb support.(STABLE-0_6_4)  ++ Bug fixes:  * Some debug formatters and casts fixed.  * Numereous fixes in PPP.  ++ Changes:  * DEBUGF now is LWIP_DEBUGF  * pbuf_dechain() has been re-enabled.  * Mentioned the changed use of CVS branches in README.(STABLE-0_6_3)  ++ Bug fixes:  * Fixed pool pbuf memory leak in pbuf_alloc().    Occured if not enough PBUF_POOL pbufs for a packet pbuf chain.    Reported by Savin Zlobec.  * PBUF_POOL chains had their tot_len field not set for non-first    pbufs. Fixed in pbuf_alloc().  ++ New features:  * Added PPP stack contributed by Marc Boucher  ++ Changes:  * Now drops short packets for ICMP/UDP/TCP protocols. More robust.  * ARP queueuing now queues the latest packet instead of the first.    This is the RFC recommended behaviour, but can be overridden in    lwipopts.h.(0.6.2)  ++ Bugfixes:  * TCP has been fixed to deal with the new use of the pbuf->ref    counter.  * DHCP dhcp_inform() crash bug fixed.  ++ Changes:  * Removed pbuf_pool_free_cache and pbuf_pool_alloc_cache. Also removed    pbuf_refresh(). This has sped up pbuf pool operations considerably.    Implemented by David Haas.(0.6.1)  ++ New features:  * The packet buffer implementation has been enhanced to support    zero-copy and copy-on-demand for packet buffers which have their    payloads in application-managed memory.    Implemented by David Haas.    Use PBUF_REF to make a pbuf refer to RAM. lwIP will use zero-copy    if an outgoing packet can be directly sent on the link, or perform    a copy-on-demand when necessary.    The application can safely assume the packet is sent, and the RAM    is available to the application directly after calling udp_send()    or similar function.  ++ Bugfixes:  * ARP_QUEUEING should now correctly work for all cases, including    PBUF_REF.    Implemented by Leon Woestenberg.  ++ Changes:  * IP_ADDR_ANY is no longer a NULL pointer. Instead, it is a pointer    to a '0.0.0.0' IP address.  * The packet buffer implementation is changed. The pbuf->ref counter