2 * Copyright (c) 2004 The DragonFly Project. All rights reserved.
4 * Copyright (c) 1982, 1986, 1991, 1993
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6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
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10 * the permission of UNIX System Laboratories, Inc.
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13 * modification, are permitted provided that the following conditions
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36 * @(#)kern_subr.c 8.3 (Berkeley) 1/21/94
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/socket.h>
42 #include <sys/socketvar.h>
44 #include <sys/malloc.h>
45 #include <sys/queue.h>
46 #include <sys/kernel.h>
47 #include <sys/resourcevar.h>
51 #include <netinet/in.h>
52 #include <netinet/in_var.h>
53 #include <netinet/tcp.h>
55 #include <net/pf/pfvar.h>
57 #include <sys/random.h>
60 * This implements additional functions used by pf which can not be ported
61 * easyly. At this point it boils down to mostly the Net/OpenBSD hook
64 * BEWARE: this is not locked! Required locking is done by the caller.
68 hook_establish(struct hook_desc_head *head, int tail, void (*fn)(void *),
71 struct hook_desc *hdp;
73 hdp = kmalloc(sizeof (*hdp), M_DEVBUF, M_WAITOK);
80 TAILQ_INSERT_TAIL(head, hdp, hd_list);
82 TAILQ_INSERT_HEAD(head, hdp, hd_list);
88 hook_disestablish(struct hook_desc_head *head, void *vhook)
90 struct hook_desc *hdp;
93 for (hdp = TAILQ_FIRST(head); hdp != NULL;
94 hdp = TAILQ_NEXT(hdp, hd_list))
98 panic("hook_disestablish: hook not established");
101 TAILQ_REMOVE(head, hdp, hd_list);
102 kfree(hdp, M_DEVBUF);
106 * Run hooks. Startup hooks are invoked right after scheduler_start but
107 * before root is mounted. Shutdown hooks are invoked immediately before the
108 * system is halted or rebooted, i.e. after file systems unmounted,
109 * after crash dump done, etc.
112 dohooks(struct hook_desc_head *head, int flags)
114 struct hook_desc *hdp;
116 if ((flags & HOOK_REMOVE) == 0) {
117 TAILQ_FOREACH(hdp, head, hd_list) {
118 (*hdp->hd_fn)(hdp->hd_arg);
121 while ((hdp = TAILQ_FIRST(head)) != NULL) {
122 TAILQ_REMOVE(head, hdp, hd_list);
123 (*hdp->hd_fn)(hdp->hd_arg);
124 if ((flags & HOOK_FREE) != 0)
125 kfree(hdp, M_DEVBUF);
132 * Following is where TCP initial sequence number generation occurs.
134 * There are two places where we must use initial sequence numbers:
135 * 1. In SYN-ACK packets.
138 * All ISNs for SYN-ACK packets are generated by the syncache. See
139 * tcp_syncache.c for details.
141 * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
142 * depends on this property. In addition, these ISNs should be
143 * unguessable so as to prevent connection hijacking. To satisfy
144 * the requirements of this situation, the algorithm outlined in
145 * RFC 1948 is used, with only small modifications.
147 * Implementation details:
149 * Time is based off the system timer, and is corrected so that it
150 * increases by one megabyte per second. This allows for proper
151 * recycling on high speed LANs while still leaving over an hour
154 * As reading the *exact* system time is too expensive to be done
155 * whenever setting up a TCP connection, we increment the time
156 * offset in two ways. First, a small random positive increment
157 * is added to isn_offset for each connection that is set up.
158 * Second, the function tcp_isn_tick fires once per clock tick
159 * and increments isn_offset as necessary so that sequence numbers
160 * are incremented at approximately ISN_BYTES_PER_SECOND. The
161 * random positive increments serve only to ensure that the same
162 * exact sequence number is never sent out twice (as could otherwise
163 * happen when a port is recycled in less than the system tick
166 * net.inet.tcp.isn_reseed_interval controls the number of seconds
167 * between seeding of isn_secret. This is normally set to zero,
168 * as reseeding should not be necessary.
170 * Locking of the global variables isn_secret, isn_last_reseed, isn_offset,
171 * isn_offset_old, and isn_ctx is performed using the TCP pcbinfo lock. In
172 * general, this means holding an exclusive (write) lock.
175 #define ISN_BYTES_PER_SECOND 1048576
176 #define ISN_STATIC_INCREMENT 4096
177 #define ISN_RANDOM_INCREMENT (4096 - 1)