kernel: Remove some unneeded NULL checks after kmalloc() with M_WAITOK.
[dragonfly.git] / sys / net / pf / pf_subr.c
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1/*
2 * Copyright (c) 2004 The DragonFly Project. All rights reserved.
3 *
4 * Copyright (c) 1982, 1986, 1991, 1993
5 * The Regents of the University of California. All rights reserved.
6 * (c) UNIX System Laboratories, Inc.
7 * All or some portions of this file are derived from material licensed
8 * to the University of California by American Telephone and Telegraph
9 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
10 * the permission of UNIX System Laboratories, Inc.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 * notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 * notice, this list of conditions and the following disclaimer in the
19 * documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 * may be used to endorse or promote products derived from this software
22 * without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 *
36 * @(#)kern_subr.c 8.3 (Berkeley) 1/21/94
37 */
38
39#include <sys/param.h>
40#include <sys/systm.h>
41#include <sys/socket.h>
42#include <sys/socketvar.h>
43#include <sys/proc.h>
44#include <sys/malloc.h>
45#include <sys/queue.h>
46#include <sys/kernel.h>
47#include <sys/resourcevar.h>
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48
49#include <net/if.h>
50
51#include <netinet/in.h>
52#include <netinet/in_var.h>
70224baa 53#include <netinet/tcp.h>
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54
55#include <net/pf/pfvar.h>
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56#include <sys/md5.h>
57#include <sys/random.h>
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58
59/*
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
62 * implementation.
63 *
64 * BEWARE: this is not locked! Required locking is done by the caller.
65 */
66
67void *
68hook_establish(struct hook_desc_head *head, int tail, void (*fn)(void *),
69 void *arg)
70{
71 struct hook_desc *hdp;
72
70224baa 73 hdp = kmalloc(sizeof (*hdp), M_DEVBUF, M_WAITOK);
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74 hdp->hd_fn = fn;
75 hdp->hd_arg = arg;
76 if (tail)
77 TAILQ_INSERT_TAIL(head, hdp, hd_list);
78 else
79 TAILQ_INSERT_HEAD(head, hdp, hd_list);
80
81 return (hdp);
82}
83
84void
85hook_disestablish(struct hook_desc_head *head, void *vhook)
86{
87 struct hook_desc *hdp;
88
89#ifdef DIAGNOSTIC
90 for (hdp = TAILQ_FIRST(head); hdp != NULL;
91 hdp = TAILQ_NEXT(hdp, hd_list))
92 if (hdp == vhook)
93 break;
94 if (hdp == NULL)
95 panic("hook_disestablish: hook not established");
96#endif
97 hdp = vhook;
98 TAILQ_REMOVE(head, hdp, hd_list);
efda3bd0 99 kfree(hdp, M_DEVBUF);
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100}
101
102/*
103 * Run hooks. Startup hooks are invoked right after scheduler_start but
104 * before root is mounted. Shutdown hooks are invoked immediately before the
105 * system is halted or rebooted, i.e. after file systems unmounted,
106 * after crash dump done, etc.
107 */
108void
109dohooks(struct hook_desc_head *head, int flags)
110{
111 struct hook_desc *hdp;
112
113 if ((flags & HOOK_REMOVE) == 0) {
114 TAILQ_FOREACH(hdp, head, hd_list) {
115 (*hdp->hd_fn)(hdp->hd_arg);
116 }
117 } else {
118 while ((hdp = TAILQ_FIRST(head)) != NULL) {
119 TAILQ_REMOVE(head, hdp, hd_list);
120 (*hdp->hd_fn)(hdp->hd_arg);
121 if ((flags & HOOK_FREE) != 0)
efda3bd0 122 kfree(hdp, M_DEVBUF);
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123 }
124 }
125}
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126
127
128/*
129 * Following is where TCP initial sequence number generation occurs.
130 *
131 * There are two places where we must use initial sequence numbers:
132 * 1. In SYN-ACK packets.
133 * 2. In SYN packets.
134 *
135 * All ISNs for SYN-ACK packets are generated by the syncache. See
136 * tcp_syncache.c for details.
137 *
138 * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
139 * depends on this property. In addition, these ISNs should be
140 * unguessable so as to prevent connection hijacking. To satisfy
141 * the requirements of this situation, the algorithm outlined in
142 * RFC 1948 is used, with only small modifications.
143 *
144 * Implementation details:
145 *
146 * Time is based off the system timer, and is corrected so that it
147 * increases by one megabyte per second. This allows for proper
148 * recycling on high speed LANs while still leaving over an hour
149 * before rollover.
150 *
151 * As reading the *exact* system time is too expensive to be done
152 * whenever setting up a TCP connection, we increment the time
153 * offset in two ways. First, a small random positive increment
154 * is added to isn_offset for each connection that is set up.
155 * Second, the function tcp_isn_tick fires once per clock tick
156 * and increments isn_offset as necessary so that sequence numbers
157 * are incremented at approximately ISN_BYTES_PER_SECOND. The
158 * random positive increments serve only to ensure that the same
159 * exact sequence number is never sent out twice (as could otherwise
160 * happen when a port is recycled in less than the system tick
161 * interval.)
162 *
163 * net.inet.tcp.isn_reseed_interval controls the number of seconds
164 * between seeding of isn_secret. This is normally set to zero,
165 * as reseeding should not be necessary.
166 *
167 * Locking of the global variables isn_secret, isn_last_reseed, isn_offset,
168 * isn_offset_old, and isn_ctx is performed using the TCP pcbinfo lock. In
169 * general, this means holding an exclusive (write) lock.
170 */
171
172#define ISN_BYTES_PER_SECOND 1048576
173#define ISN_STATIC_INCREMENT 4096
174#define ISN_RANDOM_INCREMENT (4096 - 1)