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281d2d9fad
"nm-utils/nm-shared-utils.h" shall contain utility function without other dependencies. It is intended to be used by other projects as-is. nm_utils_random_bytes() requires getrandom() and a HAVE_GETRANDOM configure check. That makes it more cumbersome to re-use "nm-shared-utils.h", in cases where you don't care about nm_utils_random_bytes(). Split nm_utils_random_bytes() out to a separate file. Same for hash utils, which depend on nm_utils_random_bytes(). Also, hash utils will eventually be extended to use siphash24.
50 lines
1.5 KiB
C
50 lines
1.5 KiB
C
/* -*- Mode: C; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4 -*- */
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/* NetworkManager -- Network link manager
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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* Boston, MA 02110-1301 USA.
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*
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* (C) Copyright 2017 Red Hat, Inc.
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*/
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#include "nm-default.h"
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#include "nm-hash-utils.h"
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#include "nm-shared-utils.h"
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#include "nm-random-utils.h"
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/*****************************************************************************/
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guint
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NM_HASH_INIT (guint seed)
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{
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static volatile guint global_seed = 0;
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guint g, s;
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/* we xor @seed with a random @global_seed. This is to make the hashing behavior
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* less predictable and harder to exploit collisions. */
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g = global_seed;
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if (G_UNLIKELY (g == 0)) {
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nm_utils_random_bytes (&s, sizeof (s));
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if (s == 0)
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s = 42;
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g_atomic_int_compare_and_exchange ((int *) &global_seed, 0, s);
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g = global_seed;
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nm_assert (g);
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}
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return g ^ seed;
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}
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