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Minor white space and style cleanups.

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This commit is contained in:
Robert Watson 2007-05-11 11:05:30 +00:00
parent c59b9aa51b
commit b34aab2337
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=169467
1 changed files with 27 additions and 36 deletions
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63
sys/netinet/ip_id.c
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@ -37,7 +37,7 @@
* $FreeBSD$
*/
/*
/*-
* seed = random 15bit
* n = prime, g0 = generator to n,
* j = random so that gcd(j,n-1) == 1
@ -52,9 +52,9 @@
* The transaction id is determined by:
* id[n] = seed xor (g^X[n] mod n)
*
* Effectivly the id is restricted to the lower 15 bits, thus
* yielding two different cycles by toggling the msb on and off.
* This avoids reuse issues caused by reseeding.
* Effectivly the id is restricted to the lower 15 bits, thus yielding two
* different cycles by toggling the msb on and off. This avoids reuse issues
* caused by reseeding.
*/
#include "opt_pf.h"
@ -63,14 +63,14 @@
#include <sys/kernel.h>
#include <sys/random.h>
#define RU_OUT 180 /* Time after wich will be reseeded */
#define RU_MAX 30000 /* Uniq cycle, avoid blackjack prediction */
#define RU_GEN 2 /* Starting generator */
#define RU_N 32749 /* RU_N-1 = 2*2*3*2729 */
#define RU_AGEN 7 /* determine ru_a as RU_AGEN^(2*rand) */
#define RU_M 31104 /* RU_M = 2^7*3^5 - don't change */
#define RU_OUT 180 /* Time after wich will be reseeded */
#define RU_MAX 30000 /* Uniq cycle, avoid blackjack prediction */
#define RU_GEN 2 /* Starting generator */
#define RU_N 32749 /* RU_N-1 = 2*2*3*2729 */
#define RU_AGEN 7 /* determine ru_a as RU_AGEN^(2*rand) */
#define RU_M 31104 /* RU_M = 2^7*3^5 - don't change */
#define PFAC_N 3
#define PFAC_N 3
const static u_int16_t pfacts[PFAC_N] = {
2,
3,
@ -86,23 +86,17 @@ static u_int16_t ru_msb = 0;
static long ru_reseed;
static u_int32_t tmp; /* Storage for unused random */
static u_int16_t pmod(u_int16_t, u_int16_t, u_int16_t);
static void ip_initid(void);
u_int16_t ip_randomid(void);
static u_int16_t pmod(u_int16_t, u_int16_t, u_int16_t);
static void ip_initid(void);
u_int16_t ip_randomid(void);
/*
* Do a fast modular exponation, returned value will be in the range
* of 0 - (mod-1)
* Do a fast modular exponation, returned value will be in the range of 0 -
* (mod-1).
*/
#ifdef __STDC__
static u_int16_t
pmod(u_int16_t gen, u_int16_t exp, u_int16_t mod)
#else
static u_int16_t
pmod(gen, exp, mod)
u_int16_t gen, exp, mod;
#endif
{
u_int16_t s, t, u;
@ -120,12 +114,12 @@ pmod(gen, exp, mod)
}
/*
* Initalizes the seed and chooses a suitable generator. Also toggles
* the msb flag. The msb flag is used to generate two distinct
* cycles of random numbers and thus avoiding reuse of ids.
* Initalizes the seed and chooses a suitable generator. Also toggles the
* msb flag. The msb flag is used to generate two distinct cycles of random
* numbers and thus avoiding reuse of ids.
*
* This function is called from id_randomid() when needed, an
* application does not have to worry about it.
* This function is called from id_randomid() when needed, an application
* does not have to worry about it.
*/
static void
ip_initid(void)
@ -138,14 +132,14 @@ ip_initid(void)
read_random((void *) &tmp, sizeof(tmp));
ru_x = (tmp & 0xFFFF) % RU_M;
/* 15 bits of random seed */
/* 15 bits of random seed. */
ru_seed = (tmp >> 16) & 0x7FFF;
read_random((void *) &tmp, sizeof(tmp));
ru_seed2 = tmp & 0x7FFF;
read_random((void *) &tmp, sizeof(tmp));
/* Determine the LCG we use */
/* Determine the LCG we use. */
ru_b = (tmp & 0xfffe) | 1;
ru_a = pmod(RU_AGEN, (tmp >> 16) & 0xfffe, RU_M);
while (ru_b % 3 == 0)
@ -156,11 +150,9 @@ ip_initid(void)
tmp = tmp >> 16;
/*
* Do a fast gcd(j,RU_N-1), so we can find a j with
* gcd(j, RU_N-1) == 1, giving a new generator for
* RU_GEN^j mod RU_N
* Do a fast gcd(j,RU_N-1), so we can find a j with gcd(j, RU_N-1) ==
* 1, giving a new generator for RU_GEN^j mod RU_N.
*/
while (noprime) {
for (i=0; i<PFAC_N; i++)
if (j%pfacts[i] == 0)
@ -193,17 +185,16 @@ ip_randomid(void)
if (!tmp)
read_random((void *) &tmp, sizeof(tmp));
/* Skip a random number of ids */
/* Skip a random number of ids. */
n = tmp & 0x3; tmp = tmp >> 2;
if (ru_counter + n >= RU_MAX)
ip_initid();
for (i = 0; i <= n; i++)
/* Linear Congruential Generator */
/* Linear Congruential Generator. */
ru_x = (ru_a*ru_x + ru_b) % RU_M;
ru_counter += i;
return (ru_seed ^ pmod(ru_g,ru_seed2 ^ ru_x,RU_N)) | ru_msb;
}