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/* $OpenBSD: toeplitz.c,v 1.8 2020/07/17 13:13:36 tb Exp $ */
/*
* Copyright (c) 2009 The DragonFly Project. All rights reserved.
*
* This code is derived from software contributed to The DragonFly Project
* by Sepherosa Ziehau <sepherosa@gmail.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name of The DragonFly Project nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific, prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* Copyright (c) 2019 David Gwynne <dlg@openbsd.org>
* Copyright (c) 2020 Theo Buehler <tb@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <netinet/in.h>
#include <net/toeplitz.h>
/*
* symmetric toeplitz
*/
static stoeplitz_key stoeplitz_keyseed = STOEPLITZ_KEYSEED;
static struct stoeplitz_cache stoeplitz_syskey_cache;
const struct stoeplitz_cache *const
stoeplitz_cache = &stoeplitz_syskey_cache;
/* parity of n16: count (mod 2) of ones in the binary representation. */
int
parity(uint16_t n16)
{
n16 = ((n16 & 0xaaaa) >> 1) ^ (n16 & 0x5555);
n16 = ((n16 & 0xcccc) >> 2) ^ (n16 & 0x3333);
n16 = ((n16 & 0xf0f0) >> 4) ^ (n16 & 0x0f0f);
n16 = ((n16 & 0xff00) >> 8) ^ (n16 & 0x00ff);
return (n16);
}
/*
* The Toeplitz matrix obtained from a seed is invertible if and only if the
* parity of the seed is 1. Generate such a seed uniformly at random.
*/
stoeplitz_key
stoeplitz_random_seed(void)
{
stoeplitz_key seed;
seed = arc4random() & UINT16_MAX;
if (parity(seed) == 0)
seed ^= 1;
return (seed);
}
void
stoeplitz_init(void)
{
stoeplitz_keyseed = stoeplitz_random_seed();
stoeplitz_cache_init(&stoeplitz_syskey_cache, stoeplitz_keyseed);
}
#define NBSK (NBBY * sizeof(stoeplitz_key))
/*
* The Toeplitz hash of a 16-bit number considered as a column vector over
* the field with two elements is calculated as a matrix multiplication with
* a 16x16 circulant Toeplitz matrix T generated by skey.
*
* The first eight columns H of T generate the remaining eight columns using
* the byteswap operation J = swap16: T = [H JH]. Thus, the Toeplitz hash of
* n = [hi lo] is computed via the formula T * n = (H * hi) ^ swap16(H * lo).
*
* Therefore the results H * val for all values of a byte are cached in scache.
*/
void
stoeplitz_cache_init(struct stoeplitz_cache *scache, stoeplitz_key skey)
{
uint16_t column[NBBY];
unsigned int b, shift, val;
bzero(column, sizeof(column));
/* Calculate the first eight columns H of the Toeplitz matrix T. */
for (b = 0; b < NBBY; ++b)
column[b] = skey << b | skey >> (NBSK - b);
/* Cache the results of H * val for all possible values of a byte. */
for (val = 0; val < 256; ++val) {
uint16_t res = 0;
for (b = 0; b < NBBY; ++b) {
shift = NBBY - b - 1;
if (val & (1 << shift))
res ^= column[b];
}
scache->bytes[val] = res;
}
}
uint16_t
stoeplitz_hash_ip4(const struct stoeplitz_cache *scache,
in_addr_t faddr, in_addr_t laddr)
{
return (stoeplitz_hash_n32(scache, faddr ^ laddr));
}
uint16_t
stoeplitz_hash_ip4port(const struct stoeplitz_cache *scache,
in_addr_t faddr, in_addr_t laddr, in_port_t fport, in_port_t lport)
{
return (stoeplitz_hash_n32(scache, faddr ^ laddr ^ fport ^ lport));
}
#ifdef INET6
uint16_t
stoeplitz_hash_ip6(const struct stoeplitz_cache *scache,
const struct in6_addr *faddr6, const struct in6_addr *laddr6)
{
uint32_t n32 = 0;
size_t i;
for (i = 0; i < nitems(faddr6->s6_addr32); i++)
n32 ^= faddr6->s6_addr32[i] ^ laddr6->s6_addr32[i];
return (stoeplitz_hash_n32(scache, n32));
}
uint16_t
stoeplitz_hash_ip6port(const struct stoeplitz_cache *scache,
const struct in6_addr *faddr6, const struct in6_addr *laddr6,
in_port_t fport, in_port_t lport)
{
uint32_t n32 = 0;
size_t i;
for (i = 0; i < nitems(faddr6->s6_addr32); i++)
n32 ^= faddr6->s6_addr32[i] ^ laddr6->s6_addr32[i];
n32 ^= fport ^ lport;
return (stoeplitz_hash_n32(scache, n32));
}
#endif /* INET6 */
void
stoeplitz_to_key(void *key, size_t klen)
{
uint8_t *k = key;
uint16_t skey = htons(stoeplitz_keyseed);
size_t i;
KASSERT((klen % 2) == 0);
for (i = 0; i < klen; i += sizeof(skey)) {
k[i + 0] = skey >> 8;
k[i + 1] = skey;
}
}
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