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064af421 | 1 | /* |
61d71ceb | 2 | * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc. |
064af421 | 3 | * |
a14bc59f BP |
4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
5 | * you may not use this file except in compliance with the License. | |
6 | * You may obtain a copy of the License at: | |
064af421 | 7 | * |
a14bc59f BP |
8 | * http://www.apache.org/licenses/LICENSE-2.0 |
9 | * | |
10 | * Unless required by applicable law or agreed to in writing, software | |
11 | * distributed under the License is distributed on an "AS IS" BASIS, | |
12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
13 | * See the License for the specific language governing permissions and | |
14 | * limitations under the License. | |
064af421 BP |
15 | */ |
16 | ||
17 | #include <config.h> | |
18 | #include "random.h" | |
19 | ||
20 | #include <errno.h> | |
21 | #include <stdlib.h> | |
22 | #include <sys/time.h> | |
23 | ||
10df718e | 24 | #include "entropy.h" |
61d71ceb BP |
25 | #include "hash.h" |
26 | #include "ovs-thread.h" | |
279c9e03 | 27 | #include "timeval.h" |
064af421 BP |
28 | #include "util.h" |
29 | ||
e519ea28 BP |
30 | /* This is the 32-bit PRNG recommended in G. Marsaglia, "Xorshift RNGs", |
31 | * _Journal of Statistical Software_ 8:14 (July 2003). According to the paper, | |
32 | * it has a period of 2**32 - 1 and passes almost all tests of randomness. | |
33 | * | |
34 | * We use this PRNG instead of libc's rand() because rand() varies in quality | |
35 | * and because its maximum value also varies between 32767 and INT_MAX, whereas | |
10df718e BP |
36 | * we often want random numbers in the full range of uint32_t. |
37 | * | |
38 | * This random number generator is intended for purposes that do not require | |
39 | * cryptographic-quality randomness. */ | |
e519ea28 BP |
40 | |
41 | /* Current random state. */ | |
2ba4f163 | 42 | DEFINE_STATIC_PER_THREAD_DATA(uint32_t, seed, 0); |
e519ea28 BP |
43 | |
44 | static uint32_t random_next(void); | |
45 | ||
064af421 BP |
46 | void |
47 | random_init(void) | |
48 | { | |
61d71ceb BP |
49 | uint32_t *seedp = seed_get(); |
50 | while (!*seedp) { | |
064af421 | 51 | struct timeval tv; |
10df718e | 52 | uint32_t entropy; |
61d71ceb | 53 | pthread_t self; |
e519ea28 | 54 | |
279c9e03 | 55 | xgettimeofday(&tv); |
10df718e | 56 | get_entropy_or_die(&entropy, 4); |
61d71ceb | 57 | self = pthread_self(); |
e519ea28 | 58 | |
61d71ceb BP |
59 | *seedp = (tv.tv_sec ^ tv.tv_usec ^ entropy |
60 | ^ hash_bytes(&self, sizeof self, 0)); | |
064af421 BP |
61 | } |
62 | } | |
63 | ||
78f3f316 BP |
64 | void |
65 | random_set_seed(uint32_t seed_) | |
66 | { | |
cb22974d | 67 | ovs_assert(seed_); |
61d71ceb | 68 | *seed_get() = seed_; |
78f3f316 BP |
69 | } |
70 | ||
064af421 BP |
71 | void |
72 | random_bytes(void *p_, size_t n) | |
73 | { | |
74 | uint8_t *p = p_; | |
e519ea28 | 75 | |
064af421 | 76 | random_init(); |
e519ea28 BP |
77 | |
78 | for (; n > 4; p += 4, n -= 4) { | |
79 | uint32_t x = random_next(); | |
80 | memcpy(p, &x, 4); | |
81 | } | |
82 | ||
83 | if (n) { | |
84 | uint32_t x = random_next(); | |
85 | memcpy(p, &x, n); | |
064af421 BP |
86 | } |
87 | } | |
88 | ||
064af421 BP |
89 | |
90 | uint32_t | |
91 | random_uint32(void) | |
92 | { | |
e519ea28 BP |
93 | random_init(); |
94 | return random_next(); | |
064af421 BP |
95 | } |
96 | ||
ddc4f8e2 BP |
97 | uint64_t |
98 | random_uint64(void) | |
99 | { | |
100 | uint64_t x; | |
101 | ||
102 | random_init(); | |
103 | ||
104 | x = random_next(); | |
105 | x |= (uint64_t) random_next() << 32; | |
106 | return x; | |
107 | } | |
108 | ||
e519ea28 BP |
109 | static uint32_t |
110 | random_next(void) | |
111 | { | |
61d71ceb | 112 | uint32_t *seedp = seed_get_unsafe(); |
e519ea28 | 113 | |
61d71ceb BP |
114 | *seedp ^= *seedp << 13; |
115 | *seedp ^= *seedp >> 17; | |
116 | *seedp ^= *seedp << 5; | |
117 | ||
118 | return *seedp; | |
e519ea28 | 119 | } |