1 /* 2 * Copyright (c) 1982, 1986, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 * 7 * @(#)tcp_seq.h 8.2 (Berkeley) 05/24/95 8 */ 9 10 /* 11 * TCP sequence numbers are 32 bit integers operated 12 * on with modular arithmetic. These macros can be 13 * used to compare such integers. 14 */ 15 #define SEQ_LT(a,b) ((int)((a)-(b)) < 0) 16 #define SEQ_LEQ(a,b) ((int)((a)-(b)) <= 0) 17 #define SEQ_GT(a,b) ((int)((a)-(b)) > 0) 18 #define SEQ_GEQ(a,b) ((int)((a)-(b)) >= 0) 19 20 /* 21 * Macros to initialize tcp sequence numbers for 22 * send and receive from initial send and receive 23 * sequence numbers. 24 */ 25 #define tcp_rcvseqinit(tp) \ 26 (tp)->rcv_adv = (tp)->rcv_nxt = (tp)->irs + 1 27 28 #define tcp_sendseqinit(tp) \ 29 (tp)->snd_una = (tp)->snd_nxt = (tp)->snd_max = (tp)->snd_up = \ 30 (tp)->iss 31 32 #ifdef KERNEL 33 /* 34 * Increment for tcp_iss each second. 35 * This is designed to increment at the standard 250 KB/s, 36 * but with a random component averaging 128 KB. 37 * We also increment tcp_iss by a quarter of this amount 38 * each time we use the value for a new connection. 39 * If defined, the tcp_random18() macro should produce a 40 * number in the range [0-0x3ffff] that is hard to predict. 41 */ 42 #ifndef tcp_tandom18 43 #define tcp_random18() ((random() >> 14) & 0x3ffff) 44 #endif 45 #define TCP_ISSINCR (122*1024 + tcp_random18()) 46 47 tcp_seq tcp_iss; /* tcp initial send seq # */ 48 #else 49 #define TCP_ISSINCR (250*1024) /* increment for tcp_iss each second */ 50 #endif 51