2 * Copyright (c) 2007 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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
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.
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,
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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,
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31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * $DragonFly: src/sys/netinet/ip_id.c,v 1.8 2007/11/23 22:29:51 dillon Exp $
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
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>
49 #include <net/netmsg2.h>
50 #include <net/netisr2.h>
52 #include <netinet/ip_var.h>
54 #define IPRANDCOUNT 32
56 typedef struct iprandinfo
{
57 short randdata
[IPRANDCOUNT
];
60 } *iprandinfo_t __cachealign
;
62 struct iprandinfo iprandcpu
[MAXCPU
];
64 static u_int16_t ip_shuffle
[65536];
67 ip_idinit_handler(netmsg_t msg
)
71 for (i
= 0; i
< 65536; ++i
)
75 netisr_replymsg(&msg
->base
, 0);
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.
84 ip_idinit_shuffle(void *dummy __unused
)
86 struct netmsg_base msg
;
89 for (i
= 0; i
< 65536; ++i
)
91 for (i
= 0; i
< ncpus
; ++i
) {
92 netmsg_init(&msg
, NULL
, &curthread
->td_msgport
, 0,
94 netisr_domsg(&msg
, i
);
95 iprandcpu
[i
].isidx
= i
* (65536 / ncpus_fit
);
99 SYSINIT(ipshuffle
, SI_SUB_PSEUDO
, SI_ORDER_ANY
, ip_idinit_shuffle
, NULL
);
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.
110 globaldata_t gd
= mycpu
;
115 info
= &iprandcpu
[gd
->gd_cpuid
];
118 * Reload random array efficiently
120 if (info
->randidx
== 0) {
121 info
->randidx
= IPRANDCOUNT
;
122 read_random_unlimited(info
->randdata
, sizeof(info
->randdata
));
126 * Get random number (si) and calculate shuffle. The shuffle
127 * is calculated such that the cpus do not interfere with each
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
;
135 * Do the shuffle, bump isidx taking into account the cpu
139 ip_shuffle
[i2
] = ip_shuffle
[i1
];
141 info
->isidx
+= ncpus_fit
;