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Diffstat (limited to 'datapath/linux-2.6/compat-2.6/random32.c')
-rw-r--r-- | datapath/linux-2.6/compat-2.6/random32.c | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/datapath/linux-2.6/compat-2.6/random32.c b/datapath/linux-2.6/compat-2.6/random32.c new file mode 100644 index 000000000..b0dd2a32b --- /dev/null +++ b/datapath/linux-2.6/compat-2.6/random32.c @@ -0,0 +1,144 @@ +#include <linux/version.h> +#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,19) + +/* + This is a maximally equidistributed combined Tausworthe generator + based on code from GNU Scientific Library 1.5 (30 Jun 2004) + + x_n = (s1_n ^ s2_n ^ s3_n) + + s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19)) + s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25)) + s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11)) + + The period of this generator is about 2^88. + + From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe + Generators", Mathematics of Computation, 65, 213 (1996), 203--213. + + This is available on the net from L'Ecuyer's home page, + + http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps + ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps + + There is an erratum in the paper "Tables of Maximally + Equidistributed Combined LFSR Generators", Mathematics of + Computation, 68, 225 (1999), 261--269: + http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps + + ... the k_j most significant bits of z_j must be non- + zero, for each j. (Note: this restriction also applies to the + computer code given in [4], but was mistakenly not mentioned in + that paper.) + + This affects the seeding procedure by imposing the requirement + s1 > 1, s2 > 7, s3 > 15. + +*/ + +#include <linux/types.h> +#include <linux/module.h> +#include <linux/jiffies.h> +#include <linux/random.h> +#include <linux/smp.h> + +#include "compat26.h" + +struct rnd_state { + u32 s1, s2, s3; +}; + +static struct rnd_state net_rand_state[NR_CPUS]; + +static u32 __random32(struct rnd_state *state) +{ +#define TAUSWORTHE(s,a,b,c,d) ((s&c)<<d) ^ (((s <<a) ^ s)>>b) + + state->s1 = TAUSWORTHE(state->s1, 13, 19, 4294967294UL, 12); + state->s2 = TAUSWORTHE(state->s2, 2, 25, 4294967288UL, 4); + state->s3 = TAUSWORTHE(state->s3, 3, 11, 4294967280UL, 17); + + return (state->s1 ^ state->s2 ^ state->s3); +} + +static void __set_random32(struct rnd_state *state, unsigned long s) +{ + if (s == 0) + s = 1; /* default seed is 1 */ + +#define LCG(n) (69069 * n) + state->s1 = LCG(s); + state->s2 = LCG(state->s1); + state->s3 = LCG(state->s2); + + /* "warm it up" */ + __random32(state); + __random32(state); + __random32(state); + __random32(state); + __random32(state); + __random32(state); +} + +/** + * random32 - pseudo random number generator + * + * A 32 bit pseudo-random number is generated using a fast + * algorithm suitable for simulation. This algorithm is NOT + * considered safe for cryptographic use. + */ +u32 random32(void) +{ + return __random32(&net_rand_state[smp_processor_id()]); +} + +/** + * srandom32 - add entropy to pseudo random number generator + * @seed: seed value + * + * Add some additional seeding to the random32() pool. + * Note: this pool is per cpu so it only affects current CPU. + */ +void srandom32(u32 entropy) +{ + struct rnd_state *state = &net_rand_state[smp_processor_id()]; + __set_random32(state, state->s1 ^ entropy); +} + +static int __init random32_reseed(void); + +/* + * Generate some initially weak seeding values to allow + * to start the random32() engine. + */ +int __init random32_init(void) +{ + int i; + + for (i = 0; i < NR_CPUS; i++) { + struct rnd_state *state = &net_rand_state[i]; + __set_random32(state, i + jiffies); + } + random32_reseed(); + return 0; +} + +/* + * Generate better values after random number generator + * is fully initalized. + */ +static int __init random32_reseed(void) +{ + int i; + unsigned long seed; + + for (i = 0; i < NR_CPUS; i++) { + struct rnd_state *state = &net_rand_state[i]; + + get_random_bytes(&seed, sizeof(seed)); + __set_random32(state, seed); + } + return 0; +} + +#endif /* kernel < 2.6.19 */ |