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tcp_seq.h revision 1.1.1.3 
      1 /*
      2  * Copyright (c) 1982, 1986, 1993, 1995
      3  *	The Regents of the University of California.  All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  * 3. All advertising materials mentioning features or use of this software
     14  *    must display the following acknowledgement:
     15  *	This product includes software developed by the University of
     16  *	California, Berkeley and its contributors.
     17  * 4. Neither the name of the University nor the names of its contributors
     18  *    may be used to endorse or promote products derived from this software
     19  *    without specific prior written permission.
     20  *
     21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     31  * SUCH DAMAGE.
     32  *
     33  *	@(#)tcp_seq.h	8.3 (Berkeley) 6/21/95
     34  */
     35 
     36 /*
     37  * TCP sequence numbers are 32 bit integers operated
     38  * on with modular arithmetic.  These macros can be
     39  * used to compare such integers.
     40  */
     41 #define	SEQ_LT(a,b)	((int)((a)-(b)) < 0)
     42 #define	SEQ_LEQ(a,b)	((int)((a)-(b)) <= 0)
     43 #define	SEQ_GT(a,b)	((int)((a)-(b)) > 0)
     44 #define	SEQ_GEQ(a,b)	((int)((a)-(b)) >= 0)
     45 
     46 /*
     47  * Macros to initialize tcp sequence numbers for
     48  * send and receive from initial send and receive
     49  * sequence numbers.
     50  */
     51 #define	tcp_rcvseqinit(tp) \
     52 	(tp)->rcv_adv = (tp)->rcv_nxt = (tp)->irs + 1
     53 
     54 #define	tcp_sendseqinit(tp) \
     55 	(tp)->snd_una = (tp)->snd_nxt = (tp)->snd_max = (tp)->snd_up = \
     56 	    (tp)->iss
     57 
     58 #ifdef KERNEL
     59 /*
     60  * Increment for tcp_iss each second.
     61  * This is designed to increment at the standard 250 KB/s,
     62  * but with a random component averaging 128 KB.
     63  * We also increment tcp_iss by a quarter of this amount
     64  * each time we use the value for a new connection.
     65  * If defined, the tcp_random18() macro should produce a
     66  * number in the range [0-0x3ffff] that is hard to predict.
     67  */
     68 #ifndef tcp_random18
     69 #define	tcp_random18()	((random() >> 14) & 0x3ffff)
     70 #endif
     71 #define	TCP_ISSINCR	(122*1024 + tcp_random18())
     72 
     73 tcp_seq	tcp_iss;		/* tcp initial send seq # */
     74 #else
     75 #define	TCP_ISSINCR	(250*1024)	/* increment for tcp_iss each second */
     76 #endif
     77