5947c05768
If kern.random.initial_seeding.bypass_before_seeding is disabled, random(4) and arc4random(9) will block indefinitely until enough entropy is available to initially seed Fortuna. It seems that zero flowids are perfectly valid, so avoid blocking on random until initial seeding takes place. Discussed with: bz (earlier revision) Reviewed by: thj Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D20011
274 lines
8.3 KiB
C
274 lines
8.3 KiB
C
/*-
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* SPDX-License-Identifier: (BSD-3-Clause AND BSD-2-Clause)
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*
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* Copyright (C) 2003 WIDE Project.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the project nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $KAME: ip6_id.c,v 1.13 2003/09/16 09:11:19 itojun Exp $
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*/
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/*-
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* Copyright 1998 Niels Provos <provos@citi.umich.edu>
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* All rights reserved.
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*
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* Theo de Raadt <deraadt@openbsd.org> came up with the idea of using
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* such a mathematical system to generate more random (yet non-repeating)
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* ids to solve the resolver/named problem. But Niels designed the
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* actual system based on the constraints.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $OpenBSD: ip6_id.c,v 1.3 2003/12/12 06:57:12 itojun Exp $
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*/
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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/*
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* seed = random (bits - 1) bit
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* n = prime, g0 = generator to n,
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* j = random so that gcd(j,n-1) == 1
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* g = g0^j mod n will be a generator again.
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*
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* X[0] = random seed.
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* X[n] = a*X[n-1]+b mod m is a Linear Congruential Generator
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* with a = 7^(even random) mod m,
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* b = random with gcd(b,m) == 1
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* m = constant and a maximal period of m-1.
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*
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* The transaction id is determined by:
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* id[n] = seed xor (g^X[n] mod n)
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*
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* Effectively the id is restricted to the lower (bits - 1) bits, thus
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* yielding two different cycles by toggling the msb on and off.
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* This avoids reuse issues caused by reseeding.
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*/
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#include <sys/types.h>
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#include <sys/param.h>
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#include <sys/kernel.h>
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#include <sys/random.h>
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#include <sys/socket.h>
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#include <sys/libkern.h>
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#include <net/if.h>
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#include <net/route.h>
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#include <net/vnet.h>
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#include <netinet/in.h>
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#include <netinet/ip6.h>
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#include <netinet6/ip6_var.h>
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#ifndef INT32_MAX
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#define INT32_MAX 0x7fffffffU
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#endif
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struct randomtab {
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const int ru_bits; /* resulting bits */
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const long ru_out; /* Time after which will be reseeded */
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const u_int32_t ru_max; /* Uniq cycle, avoid blackjack prediction */
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const u_int32_t ru_gen; /* Starting generator */
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const u_int32_t ru_n; /* ru_n: prime, ru_n - 1: product of pfacts[] */
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const u_int32_t ru_agen; /* determine ru_a as ru_agen^(2*rand) */
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const u_int32_t ru_m; /* ru_m = 2^x*3^y */
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const u_int32_t pfacts[4]; /* factors of ru_n */
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u_int32_t ru_counter;
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u_int32_t ru_msb;
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u_int32_t ru_x;
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u_int32_t ru_seed, ru_seed2;
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u_int32_t ru_a, ru_b;
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u_int32_t ru_g;
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long ru_reseed;
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};
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static struct randomtab randomtab_32 = {
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32, /* resulting bits */
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180, /* Time after which will be reseeded */
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1000000000, /* Uniq cycle, avoid blackjack prediction */
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2, /* Starting generator */
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2147483629, /* RU_N-1 = 2^2*3^2*59652323 */
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7, /* determine ru_a as RU_AGEN^(2*rand) */
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1836660096, /* RU_M = 2^7*3^15 - don't change */
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{ 2, 3, 59652323, 0 }, /* factors of ru_n */
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};
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static struct randomtab randomtab_20 = {
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20, /* resulting bits */
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180, /* Time after which will be reseeded */
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200000, /* Uniq cycle, avoid blackjack prediction */
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2, /* Starting generator */
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524269, /* RU_N-1 = 2^2*3^2*14563 */
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7, /* determine ru_a as RU_AGEN^(2*rand) */
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279936, /* RU_M = 2^7*3^7 - don't change */
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{ 2, 3, 14563, 0 }, /* factors of ru_n */
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};
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static u_int32_t pmod(u_int32_t, u_int32_t, u_int32_t);
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static void initid(struct randomtab *);
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static u_int32_t randomid(struct randomtab *);
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/*
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* Do a fast modular exponation, returned value will be in the range
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* of 0 - (mod-1)
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*/
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static u_int32_t
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pmod(u_int32_t gen, u_int32_t expo, u_int32_t mod)
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{
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u_int64_t s, t, u;
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s = 1;
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t = gen;
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u = expo;
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while (u) {
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if (u & 1)
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s = (s * t) % mod;
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u >>= 1;
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t = (t * t) % mod;
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}
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return (s);
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}
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/*
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* Initializes the seed and chooses a suitable generator. Also toggles
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* the msb flag. The msb flag is used to generate two distinct
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* cycles of random numbers and thus avoiding reuse of ids.
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*
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* This function is called from id_randomid() when needed, an
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* application does not have to worry about it.
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*/
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static void
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initid(struct randomtab *p)
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{
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u_int32_t j, i;
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int noprime = 1;
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p->ru_x = arc4random() % p->ru_m;
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/* (bits - 1) bits of random seed */
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p->ru_seed = arc4random() & (~0U >> (32 - p->ru_bits + 1));
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p->ru_seed2 = arc4random() & (~0U >> (32 - p->ru_bits + 1));
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/* Determine the LCG we use */
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p->ru_b = (arc4random() & (~0U >> (32 - p->ru_bits))) | 1;
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p->ru_a = pmod(p->ru_agen,
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(arc4random() & (~0U >> (32 - p->ru_bits))) & (~1U), p->ru_m);
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while (p->ru_b % 3 == 0)
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p->ru_b += 2;
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j = arc4random() % p->ru_n;
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/*
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* Do a fast gcd(j, RU_N - 1), so we can find a j with
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* gcd(j, RU_N - 1) == 1, giving a new generator for
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* RU_GEN^j mod RU_N
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*/
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while (noprime) {
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for (i = 0; p->pfacts[i] > 0; i++)
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if (j % p->pfacts[i] == 0)
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break;
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if (p->pfacts[i] == 0)
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noprime = 0;
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else
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j = (j + 1) % p->ru_n;
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}
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p->ru_g = pmod(p->ru_gen, j, p->ru_n);
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p->ru_counter = 0;
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p->ru_reseed = time_uptime + p->ru_out;
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p->ru_msb = p->ru_msb ? 0 : (1U << (p->ru_bits - 1));
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}
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static u_int32_t
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randomid(struct randomtab *p)
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{
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int i, n;
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if (p->ru_counter >= p->ru_max || time_uptime > p->ru_reseed)
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initid(p);
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/* Skip a random number of ids */
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n = arc4random() & 0x3;
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if (p->ru_counter + n >= p->ru_max)
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initid(p);
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for (i = 0; i <= n; i++) {
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/* Linear Congruential Generator */
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p->ru_x = (u_int32_t)((u_int64_t)p->ru_a * p->ru_x + p->ru_b) % p->ru_m;
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}
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p->ru_counter += i;
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return (p->ru_seed ^ pmod(p->ru_g, p->ru_seed2 + p->ru_x, p->ru_n)) |
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p->ru_msb;
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}
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u_int32_t
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ip6_randomid(void)
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{
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return randomid(&randomtab_32);
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}
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u_int32_t
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ip6_randomflowlabel(void)
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{
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/*
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* It's ok to emit zero flow labels early, before random is available
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* (seeded). RFC 6437:
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*
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* "A Flow Label of zero is used to indicate packets that have not been
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* labeled."
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*/
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if (__predict_false(!is_random_seeded()))
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return (0);
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return randomid(&randomtab_20) & 0xfffff;
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}
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