Nut/OS  4.10.3
API Reference
tcputil.c
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00001 /*
00002  * Copyright (C) 2001-2004 by egnite Software GmbH. All rights reserved.
00003  *
00004  * Redistribution and use in source and binary forms, with or without
00005  * modification, are permitted provided that the following conditions
00006  * are met:
00007  *
00008  * 1. Redistributions of source code must retain the above copyright
00009  *    notice, this list of conditions and the following disclaimer.
00010  * 2. Redistributions in binary form must reproduce the above copyright
00011  *    notice, this list of conditions and the following disclaimer in the
00012  *    documentation and/or other materials provided with the distribution.
00013  * 3. Neither the name of the copyright holders nor the names of
00014  *    contributors may be used to endorse or promote products derived
00015  *    from this software without specific prior written permission.
00016  *
00017  * THIS SOFTWARE IS PROVIDED BY EGNITE SOFTWARE GMBH AND CONTRIBUTORS
00018  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00019  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
00020  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL EGNITE
00021  * SOFTWARE GMBH OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
00022  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
00023  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
00024  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
00025  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
00026  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
00027  * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00028  * SUCH DAMAGE.
00029  *
00030  * For additional information see http://www.ethernut.de/
00031  *
00032  */
00033 
00034 /*
00035  * $Log$
00036  * Revision 1.4  2008/08/11 07:00:32  haraldkipp
00037  * BSD types replaced by stdint types (feature request #1282721).
00038  *
00039  * Revision 1.3  2008/07/27 11:43:22  haraldkipp
00040  * Configurable TCP retransmissions.
00041  *
00042  * Revision 1.2  2004/07/30 19:54:46  drsung
00043  * Some code of TCP stack redesigned. Round trip time calculation is now
00044  * supported. Fixed several bugs in TCP state machine. Now TCP connections
00045  * should be more reliable under heavy traffic or poor physical connections.
00046  *
00047  * Revision 1.1.1.1  2003/05/09 14:41:45  haraldkipp
00048  * Initial using 3.2.1
00049  *
00050  * Revision 1.10  2003/05/06 18:23:15  harald
00051  * Still not done
00052  *
00053  * Revision 1.9  2003/02/04 18:14:57  harald
00054  * Version 3 released
00055  *
00056  * Revision 1.8  2002/06/26 17:29:36  harald
00057  * First pre-release with 2.4 stack
00058  *
00059  */
00060 
00061 #include <cfg/tcp.h>
00062 
00063 #include <netinet/tcputil.h>
00064 #include <sys/timer.h>
00065 #include <stdio.h>
00066 
00071 
00072 /* Limit retransmission timeout to 200ms as lower and 20secs as upper boundary */
00073 #ifndef TCP_RTTO_MIN
00074 #define TCP_RTTO_MIN    200
00075 #endif
00076 #ifndef TCP_RTTO_MAX
00077 #define TCP_RTTO_MAX    20000
00078 #endif
00079 
00080 #define min(a,b) ((a>b)?b:a)
00081 #define max(a,b) ((a>b)?a:b)
00082 
00083 /*
00084  * Calculate round trip time.
00085  */
00086 void NutTcpCalcRtt(TCPSOCKET * sock)
00087 {
00088     uint16_t delta;
00089     
00090     if (sock->so_retran_time == 0)
00091         return;
00092         
00093     delta = (uint16_t) NutGetMillis() - (sock->so_retran_time & ~1);
00094     
00095     /* According to RFC793 (or STD007), page 41, we use 0.8 for ALPHA and 2.0 for BETA. */
00096     sock->so_rtto = min (TCP_RTTO_MAX, max(TCP_RTTO_MIN, (delta * 4 + sock->so_rtto * 8) / 10));
00097     //@@@printf ("[%04X] new retran timeout: %u, delta: %u\n", (u_short) sock, sock->so_rtto, delta);
00098 }
00099