1 /*
2 * Copyright (c) 2007 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 *
34 * $DragonFly: src/sys/netinet/ip_id.c,v 1.8 2007/11/23 22:29:51 dillon Exp $
35 */
36
37 /*
38 * Random ip sequence number generator. Use the system PRNG to shuffle the
39 * 65536 entry ID space. We reshuffle the front-side of the array as we
40 * index through it, guarenteeing an id will not be reused for at least
41 * 32768 calls.
42 */
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/kernel.h>
46 #include <sys/random.h>
47 #include <sys/globaldata.h>
48
49 #include <net/netmsg2.h>
50 #include <net/netisr2.h>
51
52 #include <netinet/ip_var.h>
53
54 #define IPRANDCOUNT 32
55
56 typedef struct iprandinfo {
57 short randdata[IPRANDCOUNT];
58 int randidx;
59 int isidx;
60 } *iprandinfo_t __cachealign;
61
62 struct iprandinfo iprandcpu[MAXCPU];
63
64 static u_int16_t ip_shuffle[65536];
65
66 static void
ip_idinit_handler(netmsg_t msg)67 ip_idinit_handler(netmsg_t msg)
68 {
69 int i;
70
71 for (i = 0; i < 65536; ++i)
72 ip_randomid();
73
74 /* Done! */
75 netisr_replymsg(&msg->base, 0);
76 }
77
78 /*
79 * Initialize the shuffle. We assume that the system PRNG won't be all that
80 * good this early in the boot sequence but use it anyway. The ids will be
81 * reshuffled as they are popped and the PRNG should be better then.
82 */
83 static void
ip_idinit_shuffle(void * dummy __unused)84 ip_idinit_shuffle(void *dummy __unused)
85 {
86 struct netmsg_base msg;
87 int i;
88
89 for (i = 0; i < 65536; ++i)
90 ip_shuffle[i] = i;
91 for (i = 0; i < ncpus; ++i) {
92 netmsg_init(&msg, NULL, &curthread->td_msgport, 0,
93 ip_idinit_handler);
94 netisr_domsg(&msg, i);
95 iprandcpu[i].isidx = i * (65536 / ncpus_fit);
96 }
97 }
98
99 SYSINIT(ipshuffle, SI_SUB_PSEUDO, SI_ORDER_ANY, ip_idinit_shuffle, NULL);
100
101 /*
102 * Return a random IP id. Use a forward shuffle over half the index
103 * space to avoid duplicates occuring too quickly. Since the initial
104 * shuffle may not have had a good random basis we returned the element
105 * at the shuffle target instead of the current element.
106 */
107 u_int16_t
ip_randomid(void)108 ip_randomid(void)
109 {
110 globaldata_t gd = mycpu;
111 iprandinfo_t info;
112 u_int16_t si, r;
113 int i1, i2;
114
115 info = &iprandcpu[gd->gd_cpuid];
116
117 /*
118 * Reload random array efficiently
119 */
120 if (info->randidx == 0) {
121 info->randidx = IPRANDCOUNT;
122 read_random(info->randdata, sizeof(info->randdata), 1);
123 }
124
125 /*
126 * Get random number (si) and calculate shuffle. The shuffle
127 * is calculated such that the cpus do not interfere with each
128 * other.
129 */
130 si = info->randdata[--info->randidx];
131 i1 = (info->isidx & 0xFFFF & ~ncpus_fit_mask) | gd->gd_cpuid;
132 i2 = ((i1 + (si & 0x7FFF)) & 0xFFFF & ~ncpus_fit_mask) | gd->gd_cpuid;
133
134 /*
135 * Do the shuffle, bump isidx taking into account the cpu
136 * partitioning.
137 */
138 r = ip_shuffle[i2];
139 ip_shuffle[i2] = ip_shuffle[i1];
140 ip_shuffle[i1] = r;
141 info->isidx += ncpus_fit;
142
143 return (r);
144 }
145