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NetworkManager/shared/nm-glib-aux/nm-hash-utils.h
Thomas Haller b6fdc30a88 shared: cleanup _get_hash_key_init() and better explain the reasoning 
- add more code comments

- refactor the code flow in _get_hash_key_init() to follow a simpler
  code path.

- use c_siphash_hash() instead of 3 separate steps.

- Drop "?: static_seed" from nm_hash_static(). It's not useful, because
  the only _get_hash_key() for which _get_hash_key()^static_seed is zero
  is ~static_seed. That means, only one value of all the static seeds
  can result in zero here. At that point, we can just coerce that value
  to 3679500967u directly.
2020-04-03 11:26:49 +02:00

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// SPDX-License-Identifier: LGPL-2.1+
/*
* Copyright (C) 2017 Red Hat, Inc.
*/
#ifndef __NM_HASH_UTILS_H__
#define __NM_HASH_UTILS_H__
#include "c-siphash/src/c-siphash.h"
#include "nm-macros-internal.h"
/*****************************************************************************/
#define NM_HASH_SEED_16(a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, aa, ab, ac, ad, ae, af) \
((const guint8[16]) { a0, a1, a2, a3, a4, a5, a6, a7, a8, a9, aa, ab, ac, ad, ae, af })
void nm_hash_siphash42_init (CSipHash *h, guint static_seed);
/* Siphash24 of binary buffer @arr and @len, using the randomized seed from
* other NMHash functions.
*
* Note, that this is guaranteed to use siphash42 under the hood (contrary to
* all other NMHash API, which leave this undefined). That matters at the point,
* where the caller needs to be sure that a reasonably strong hashing algorithm
* is used. (Yes, NMHash is all about siphash24, but otherwise that is not promised
* anywhere).
*
* Another difference is, that this returns guint64 (not guint like other NMHash functions).
*
* Another difference is, that this may also return zero (not like nm_hash_complete()).
*
* Then, why not use c_siphash_hash() directly? Because this also uses the randomized,
* per-run hash-seed like nm_hash_init(). So, you get siphash24 with a random
* seed (which is cached for the current run of the program).
*/
static inline guint64
nm_hash_siphash42 (guint static_seed, const void *ptr, gsize n)
{
CSipHash h;
nm_hash_siphash42_init (&h, static_seed);
c_siphash_append (&h, ptr, n);
return c_siphash_finalize (&h);
}
/*****************************************************************************/
struct _NMHashState {
CSipHash _state;
};
typedef struct _NMHashState NMHashState;
guint nm_hash_static (guint static_seed);
static inline void
nm_hash_init (NMHashState *state, guint static_seed)
{
nm_assert (state);
nm_hash_siphash42_init (&state->_state, static_seed);
}
static inline guint64
nm_hash_complete_u64 (NMHashState *state)
{
nm_assert (state);
/* this returns the native u64 hash value. Note that this differs
* from nm_hash_complete() in two ways:
*
* - the type, guint64 vs. guint.
* - nm_hash_complete() never returns zero.
*
* In practice, nm_hash*() API is implemented via siphash24, so this returns
* the siphash24 value. But that is not guaranteed by the API, and if you need
* siphash24 directly, use c_siphash_*() and nm_hash_siphash42*() API. */
return c_siphash_finalize (&state->_state);
}
static inline guint
nm_hash_complete (NMHashState *state)
{
guint64 h;
h = nm_hash_complete_u64 (state);
/* we don't ever want to return a zero hash.
*
* NMPObject requires that in _idx_obj_part(), and it's just a good idea. */
return (((guint) (h >> 32)) ^ ((guint) h))
?: 1396707757u;
}
static inline void
nm_hash_update (NMHashState *state, const void *ptr, gsize n)
{
nm_assert (state);
nm_assert (n == 0 || ptr);
/* Note: the data passed in here might be sensitive data (secrets),
* that we should nm_explicty_zero() afterwards. However, since
* we are using siphash24 with a random key, that is not really
* necessary. Something to keep in mind, if we ever move away from
* this hash implementation. */
c_siphash_append (&state->_state, ptr, n);
}
#define nm_hash_update_val(state, val) \
G_STMT_START { \
typeof (val) _val = (val); \
\
nm_hash_update ((state), &_val, sizeof (_val)); \
} G_STMT_END
#define nm_hash_update_valp(state, val) \
nm_hash_update ((state), (val), sizeof (*(val))) \
static inline void
nm_hash_update_bool (NMHashState *state, bool val)
{
nm_hash_update (state, &val, sizeof (val));
}
#define _NM_HASH_COMBINE_BOOLS_x_1( t, y) ((y) ? ((t) (1ull << 0)) : ((t) 0ull))
#define _NM_HASH_COMBINE_BOOLS_x_2( t, y, ...) ((y) ? ((t) (1ull << 1)) : ((t) 0ull)) | _NM_HASH_COMBINE_BOOLS_x_1 (t, __VA_ARGS__)
#define _NM_HASH_COMBINE_BOOLS_x_3( t, y, ...) ((y) ? ((t) (1ull << 2)) : ((t) 0ull)) | _NM_HASH_COMBINE_BOOLS_x_2 (t, __VA_ARGS__)
#define _NM_HASH_COMBINE_BOOLS_x_4( t, y, ...) ((y) ? ((t) (1ull << 3)) : ((t) 0ull)) | _NM_HASH_COMBINE_BOOLS_x_3 (t, __VA_ARGS__)
#define _NM_HASH_COMBINE_BOOLS_x_5( t, y, ...) ((y) ? ((t) (1ull << 4)) : ((t) 0ull)) | _NM_HASH_COMBINE_BOOLS_x_4 (t, __VA_ARGS__)
#define _NM_HASH_COMBINE_BOOLS_x_6( t, y, ...) ((y) ? ((t) (1ull << 5)) : ((t) 0ull)) | _NM_HASH_COMBINE_BOOLS_x_5 (t, __VA_ARGS__)
#define _NM_HASH_COMBINE_BOOLS_x_7( t, y, ...) ((y) ? ((t) (1ull << 6)) : ((t) 0ull)) | _NM_HASH_COMBINE_BOOLS_x_6 (t, __VA_ARGS__)
#define _NM_HASH_COMBINE_BOOLS_x_8( t, y, ...) ((y) ? ((t) (1ull << 7)) : ((t) 0ull)) | _NM_HASH_COMBINE_BOOLS_x_7 (t, __VA_ARGS__)
#define _NM_HASH_COMBINE_BOOLS_x_9( t, y, ...) ((y) ? ((t) (1ull << 8)) : ((t) 0ull)) | (G_STATIC_ASSERT_EXPR (sizeof (t) >= 2), (_NM_HASH_COMBINE_BOOLS_x_8 (t, __VA_ARGS__)))
#define _NM_HASH_COMBINE_BOOLS_x_10(t, y, ...) ((y) ? ((t) (1ull << 9)) : ((t) 0ull)) | _NM_HASH_COMBINE_BOOLS_x_9 (t, __VA_ARGS__)
#define _NM_HASH_COMBINE_BOOLS_x_11(t, y, ...) ((y) ? ((t) (1ull << 10)) : ((t) 0ull)) | _NM_HASH_COMBINE_BOOLS_x_10 (t, __VA_ARGS__)
#define _NM_HASH_COMBINE_BOOLS_n2(t, n, ...) _NM_HASH_COMBINE_BOOLS_x_##n (t, __VA_ARGS__)
#define _NM_HASH_COMBINE_BOOLS_n(t, n, ...) _NM_HASH_COMBINE_BOOLS_n2(t, n, __VA_ARGS__)
#define NM_HASH_COMBINE_BOOLS(type, ...) ((type) (_NM_HASH_COMBINE_BOOLS_n(type, NM_NARG (__VA_ARGS__), __VA_ARGS__)))
#define nm_hash_update_bools(state, ...) \
nm_hash_update_val (state, NM_HASH_COMBINE_BOOLS (guint8, __VA_ARGS__))
#define _NM_HASH_COMBINE_VALS_typ_x_1( y) typeof (y) _v1;
#define _NM_HASH_COMBINE_VALS_typ_x_2( y, ...) typeof (y) _v2; _NM_HASH_COMBINE_VALS_typ_x_1 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_3( y, ...) typeof (y) _v3; _NM_HASH_COMBINE_VALS_typ_x_2 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_4( y, ...) typeof (y) _v4; _NM_HASH_COMBINE_VALS_typ_x_3 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_5( y, ...) typeof (y) _v5; _NM_HASH_COMBINE_VALS_typ_x_4 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_6( y, ...) typeof (y) _v6; _NM_HASH_COMBINE_VALS_typ_x_5 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_7( y, ...) typeof (y) _v7; _NM_HASH_COMBINE_VALS_typ_x_6 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_8( y, ...) typeof (y) _v8; _NM_HASH_COMBINE_VALS_typ_x_7 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_9( y, ...) typeof (y) _v9; _NM_HASH_COMBINE_VALS_typ_x_8 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_10(y, ...) typeof (y) _v10; _NM_HASH_COMBINE_VALS_typ_x_9 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_11(y, ...) typeof (y) _v11; _NM_HASH_COMBINE_VALS_typ_x_10 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_12(y, ...) typeof (y) _v12; _NM_HASH_COMBINE_VALS_typ_x_11 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_13(y, ...) typeof (y) _v13; _NM_HASH_COMBINE_VALS_typ_x_12 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_14(y, ...) typeof (y) _v14; _NM_HASH_COMBINE_VALS_typ_x_13 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_15(y, ...) typeof (y) _v15; _NM_HASH_COMBINE_VALS_typ_x_14 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_16(y, ...) typeof (y) _v16; _NM_HASH_COMBINE_VALS_typ_x_15 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_17(y, ...) typeof (y) _v17; _NM_HASH_COMBINE_VALS_typ_x_16 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_18(y, ...) typeof (y) _v18; _NM_HASH_COMBINE_VALS_typ_x_17 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_19(y, ...) typeof (y) _v19; _NM_HASH_COMBINE_VALS_typ_x_18 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_x_20(y, ...) typeof (y) _v20; _NM_HASH_COMBINE_VALS_typ_x_19 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_n2(n, ...) _NM_HASH_COMBINE_VALS_typ_x_##n (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_typ_n(n, ...) _NM_HASH_COMBINE_VALS_typ_n2(n, __VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_1( y) ._v1 = (y),
#define _NM_HASH_COMBINE_VALS_val_x_2( y, ...) ._v2 = (y), _NM_HASH_COMBINE_VALS_val_x_1 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_3( y, ...) ._v3 = (y), _NM_HASH_COMBINE_VALS_val_x_2 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_4( y, ...) ._v4 = (y), _NM_HASH_COMBINE_VALS_val_x_3 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_5( y, ...) ._v5 = (y), _NM_HASH_COMBINE_VALS_val_x_4 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_6( y, ...) ._v6 = (y), _NM_HASH_COMBINE_VALS_val_x_5 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_7( y, ...) ._v7 = (y), _NM_HASH_COMBINE_VALS_val_x_6 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_8( y, ...) ._v8 = (y), _NM_HASH_COMBINE_VALS_val_x_7 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_9( y, ...) ._v9 = (y), _NM_HASH_COMBINE_VALS_val_x_8 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_10(y, ...) ._v10 = (y), _NM_HASH_COMBINE_VALS_val_x_9 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_11(y, ...) ._v11 = (y), _NM_HASH_COMBINE_VALS_val_x_10 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_12(y, ...) ._v12 = (y), _NM_HASH_COMBINE_VALS_val_x_11 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_13(y, ...) ._v13 = (y), _NM_HASH_COMBINE_VALS_val_x_12 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_14(y, ...) ._v14 = (y), _NM_HASH_COMBINE_VALS_val_x_13 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_15(y, ...) ._v15 = (y), _NM_HASH_COMBINE_VALS_val_x_14 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_16(y, ...) ._v16 = (y), _NM_HASH_COMBINE_VALS_val_x_15 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_17(y, ...) ._v17 = (y), _NM_HASH_COMBINE_VALS_val_x_16 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_18(y, ...) ._v18 = (y), _NM_HASH_COMBINE_VALS_val_x_17 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_19(y, ...) ._v19 = (y), _NM_HASH_COMBINE_VALS_val_x_18 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_x_20(y, ...) ._v20 = (y), _NM_HASH_COMBINE_VALS_val_x_19 (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_n2(n, ...) _NM_HASH_COMBINE_VALS_val_x_##n (__VA_ARGS__)
#define _NM_HASH_COMBINE_VALS_val_n(n, ...) _NM_HASH_COMBINE_VALS_val_n2(n, __VA_ARGS__)
/* NM_HASH_COMBINE_VALS() is faster then nm_hash_update_val() as it combines multiple
* calls to nm_hash_update() using a packed structure. */
#define NM_HASH_COMBINE_VALS(var, ...) \
const struct _nm_packed { \
_NM_HASH_COMBINE_VALS_typ_n (NM_NARG (__VA_ARGS__), __VA_ARGS__) \
} var _nm_alignas (guint64) = { \
_NM_HASH_COMBINE_VALS_val_n (NM_NARG (__VA_ARGS__), __VA_ARGS__) \
}
/* nm_hash_update_vals() is faster then nm_hash_update_val() as it combines multiple
* calls to nm_hash_update() using a packed structure. */
#define nm_hash_update_vals(state, ...) \
G_STMT_START { \
NM_HASH_COMBINE_VALS (_val, __VA_ARGS__); \
\
nm_hash_update ((state), &_val, sizeof (_val)); \
} G_STMT_END
static inline void
nm_hash_update_mem (NMHashState *state, const void *ptr, gsize n)
{
/* This also hashes the length of the data. That means,
* hashing two consecutive binary fields (of arbitrary
* length), will hash differently. That is,
* [[1,1], []] differs from [[1],[1]].
*
* If you have a constant length (sizeof), use nm_hash_update()
* instead. */
nm_hash_update (state, &n, sizeof (n));
if (n > 0)
nm_hash_update (state, ptr, n);
}
static inline void
nm_hash_update_str0 (NMHashState *state, const char *str)
{
if (str)
nm_hash_update_mem (state, str, strlen (str));
else {
gsize n = G_MAXSIZE;
nm_hash_update (state, &n, sizeof (n));
}
}
static inline void
nm_hash_update_str (NMHashState *state, const char *str)
{
nm_assert (str);
nm_hash_update (state, str, strlen (str) + 1);
}
#if _NM_CC_SUPPORT_GENERIC
/* Like nm_hash_update_str(), but restricted to arrays only. nm_hash_update_str() only works
* with a @str argument that cannot be NULL. If you have a string pointer, that is never NULL, use
* nm_hash_update() instead. */
#define nm_hash_update_strarr(state, str) \
(_Generic (&(str), \
const char (*) [sizeof (str)]: nm_hash_update_str ((state), (str)), \
char (*) [sizeof (str)]: nm_hash_update_str ((state), (str))) \
)
#else
#define nm_hash_update_strarr(state, str) nm_hash_update_str ((state), (str))
#endif
guint nm_hash_ptr (gconstpointer ptr);
guint nm_direct_hash (gconstpointer str);
guint nm_hash_str (const char *str);
guint nm_str_hash (gconstpointer str);
#define nm_hash_val(static_seed, val) \
({ \
NMHashState _h; \
\
nm_hash_init (&_h, (static_seed)); \
nm_hash_update_val (&_h, (val)); \
nm_hash_complete (&_h); \
})
static inline guint
nm_hash_mem (guint static_seed, const void *ptr, gsize n)
{
NMHashState h;
if (n == 0)
return nm_hash_static (static_seed);
nm_hash_init (&h, static_seed);
nm_hash_update (&h, ptr, n);
return nm_hash_complete (&h);
}
/*****************************************************************************/
/* nm_pstr_*() are for hashing keys that are pointers to strings,
* that is, "const char *const*" types, using strcmp(). */
guint nm_pstr_hash (gconstpointer p);
gboolean nm_pstr_equal (gconstpointer a, gconstpointer b);
/*****************************************************************************/
/* nm_pint_*() are for hashing keys that are pointers to int values,
* that is, "const int *" types. */
guint nm_pint_hash (gconstpointer p);
gboolean nm_pint_equals (gconstpointer a, gconstpointer b);
/*****************************************************************************/
/* this hashes/compares the pointer value that we point to. Basically,
* (*((const void *const*) a) == *((const void *const*) b)). */
guint nm_pdirect_hash (gconstpointer p);
gboolean nm_pdirect_equal (gconstpointer a, gconstpointer b);
/* this hashes/compares the direct pointer value by following pointers to
* pointers 2 times.
* (**((const void *const*const*) a) == **((const void *const*const*) b)). */
guint nm_ppdirect_hash (gconstpointer p);
gboolean nm_ppdirect_equal (gconstpointer a, gconstpointer b);
/*****************************************************************************/
guint nm_pgbytes_hash (gconstpointer p);
gboolean nm_pgbytes_equal (gconstpointer a, gconstpointer b);
/*****************************************************************************/
#define NM_HASH_OBFUSCATE_PTR_FMT "%016" G_GINT64_MODIFIER "x"
/* sometimes we want to log a pointer directly, for providing context/information about
* the message that get logged. Logging pointer values directly defeats ASLR, so we should
* not do that. This returns a "unsigned long long" value that can be used
* instead.
*
* Note that there is a chance that two different pointer values hash to the same obfuscated
* value. So beware of that when reviewing logs. However, such a collision is very unlikely. */
static inline guint64
nm_hash_obfuscate_ptr (guint static_seed, gconstpointer val)
{
NMHashState h;
nm_hash_init (&h, static_seed);
nm_hash_update_val (&h, val);
return nm_hash_complete_u64 (&h);
}
/* if you want to log obfuscated pointer for a certain context (like, NMPRuleManager
* logging user-tags), then you are advised to use nm_hash_obfuscate_ptr() with your
* own, unique static-seed.
*
* However, for example the singleton constructors log the obfuscated pointer values
* for all singletons, so they must all be obfuscated with the same seed. So, this
* macro uses a particular static seed that should be used by when comparing pointer
* values in a global context. */
#define NM_HASH_OBFUSCATE_PTR(ptr) (nm_hash_obfuscate_ptr (1678382159u, ptr))
/*****************************************************************************/
#endif /* __NM_HASH_UTILS_H__ */
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