FreeBSD/Linux Kernel Cross Reference
sys/netinet/tcp_seq.h

     /*
      * Copyright (c) 1982, 1986, 1993, 1995
      *      The Regents of the University of California.  All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by the University of
     *      California, Berkeley and its contributors.
     * 4. Neither the name of the University nor the names of its contributors
     *    may be used to endorse or promote products derived from this software
     *    without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     *      @(#)tcp_seq.h   8.3 (Berkeley) 6/21/95
     * $FreeBSD: src/sys/netinet/tcp_seq.h,v 1.6.4.2 2000/10/06 20:45:13 alfred Exp $
     */
    
    #ifndef _NETINET_TCP_SEQ_H_
    #define _NETINET_TCP_SEQ_H_
    /*
     * TCP sequence numbers are 32 bit integers operated
     * on with modular arithmetic.  These macros can be
     * used to compare such integers.
     */
    #define SEQ_LT(a,b)     ((int)((a)-(b)) < 0)
    #define SEQ_LEQ(a,b)    ((int)((a)-(b)) <= 0)
    #define SEQ_GT(a,b)     ((int)((a)-(b)) > 0)
    #define SEQ_GEQ(a,b)    ((int)((a)-(b)) >= 0)
    
    /* for modulo comparisons of timestamps */
    #define TSTMP_LT(a,b)   ((int)((a)-(b)) < 0)
    #define TSTMP_GEQ(a,b)  ((int)((a)-(b)) >= 0)
    
    /*
     * TCP connection counts are 32 bit integers operated
     * on with modular arithmetic.  These macros can be
     * used to compare such integers.
     */
    #define CC_LT(a,b)      ((int)((a)-(b)) < 0)
    #define CC_LEQ(a,b)     ((int)((a)-(b)) <= 0)
    #define CC_GT(a,b)      ((int)((a)-(b)) > 0)
    #define CC_GEQ(a,b)     ((int)((a)-(b)) >= 0)
    
    /* Macro to increment a CC: skip 0 which has a special meaning */
    #define CC_INC(c)       (++(c) == 0 ? ++(c) : (c))
    
    /*
     * Macros to initialize tcp sequence numbers for
     * send and receive from initial send and receive
     * sequence numbers.
     */
    #define tcp_rcvseqinit(tp) \
            (tp)->rcv_adv = (tp)->rcv_nxt = (tp)->irs + 1
    
    #define tcp_sendseqinit(tp) \
            (tp)->snd_una = (tp)->snd_nxt = (tp)->snd_max = (tp)->snd_up = \
                (tp)->iss
    
    #define TCP_PAWS_IDLE   (24 * 24 * 60 * 60 * PR_SLOWHZ)
                                            /* timestamp wrap-around time */
    
    #ifdef KERNEL
    extern tcp_cc   tcp_ccgen;              /* global connection count */
    
    /*
     * Increment for tcp_iss each second.
     * This is designed to increment at the standard 250 KB/s,
     * but with a random component averaging 128 KB.
     * We also increment tcp_iss by a quarter of this amount
     * each time we use the value for a new connection.
     * If defined, the tcp_random18() macro should produce a
     * number in the range [0-0x3ffff] that is hard to predict.
     */
    #ifndef tcp_random18
    #define tcp_random18()  (arc4random() & 0x3ffff)
    #endif
    #define TCP_ISSINCR     (122*1024 + tcp_random18())
    
    extern tcp_seq  tcp_iss;                /* tcp initial send seq # */
    #else
   #define TCP_ISSINCR     (250*1024)      /* increment for tcp_iss each second */
   #endif /* KERNEL */
   #endif /* _NETINET_TCP_SEQ_H_ */

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