7cd4dbe9ca
Lets look at an example where we add arg0="/foo/bar/waldo" to a bloom-filter. The following strings are added: "arg0:/foo/bar/waldo" "arg0-slash-prefix:/foo/bar" "arg0-slash-prefix:/foo" Two problems arise: 1) If we match on "arg0path=/foo/bar/waldo", the dbus-spec explicitly states that equal strings are also considered prefixes. However, in the bloom-match, we can only provide a single match-filter. Therefore, we have to add "arg0-slash-prefix:/foo/bar/waldo" there, but this never occured in the bloom-mask of the message. Hence, this patch makes sure bloom_add_prefixes() adds the full path as prefix, too. 2) If we match on "arg0path=/foo/", the dbus-spec states that arg0path does prefix-matching with the trailing slash _included_, unlike path_namespace= matches, which does *not* include them. This is inconsistent, but we have to support the specs. Therefore, we must add prefixes with _and_ without trailing separators. Hence, this patch makes sure bloom_add_prefixes() adds all prefixes with the trailing slash included. The final set of strings added therefore is: "arg0:/foo/bar/waldo" "arg0-slash-prefix:/foo/bar/waldo" "arg0-slash-prefix:/foo/bar/" "arg0-slash-prefix:/foo/bar" "arg0-slash-prefix:/foo/" "arg0-slash-prefix:/foo" "arg0-slash-prefix:/"
159 lines
4.6 KiB
C
159 lines
4.6 KiB
C
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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/***
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This file is part of systemd.
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Copyright 2013 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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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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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include "util.h"
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#include "siphash24.h"
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#include "bus-bloom.h"
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static inline void set_bit(uint64_t filter[], unsigned long b) {
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filter[b >> 6] |= 1ULL << (b & 63);
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}
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static const sd_id128_t hash_keys[] = {
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SD_ID128_ARRAY(b9,66,0b,f0,46,70,47,c1,88,75,c4,9c,54,b9,bd,15),
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SD_ID128_ARRAY(aa,a1,54,a2,e0,71,4b,39,bf,e1,dd,2e,9f,c5,4a,3b),
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SD_ID128_ARRAY(63,fd,ae,be,cd,82,48,12,a1,6e,41,26,cb,fa,a0,c8),
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SD_ID128_ARRAY(23,be,45,29,32,d2,46,2d,82,03,52,28,fe,37,17,f5),
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SD_ID128_ARRAY(56,3b,bf,ee,5a,4f,43,39,af,aa,94,08,df,f0,fc,10),
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SD_ID128_ARRAY(31,80,c8,73,c7,ea,46,d3,aa,25,75,0f,9e,4c,09,29),
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SD_ID128_ARRAY(7d,f7,18,4b,7b,a4,44,d5,85,3c,06,e0,65,53,96,6d),
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SD_ID128_ARRAY(f2,77,e9,6f,93,b5,4e,71,9a,0c,34,88,39,25,bf,35),
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};
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static void bloom_add_data(
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uint64_t filter[], /* The filter bits */
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size_t size, /* Size of the filter in bytes */
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unsigned k, /* Number of hash functions */
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const void *data, /* Data to hash */
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size_t n) { /* Size of data to hash in bytes */
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uint8_t h[8];
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uint64_t m;
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unsigned w, i, c = 0;
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unsigned hash_index;
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assert(size > 0);
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assert(k > 0);
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/* Determine bits in filter */
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m = size * 8;
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/* Determine how many bytes we need to generate a bit index 0..m for this filter */
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w = (u64log2(m) + 7) / 8;
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assert(w <= sizeof(uint64_t));
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/* Make sure we have enough hash keys to generate m * k bits
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* of hash value. Note that SipHash24 generates 64 bits of
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* hash value for each 128 bits of hash key. */
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assert(k * w <= ELEMENTSOF(hash_keys) * 8);
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for (i = 0, hash_index = 0; i < k; i++) {
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uint64_t p = 0;
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unsigned d;
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for (d = 0; d < w; d++) {
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if (c <= 0) {
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siphash24(h, data, n, hash_keys[hash_index++].bytes);
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c += 8;
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}
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p = (p << 8ULL) | (uint64_t) h[8 - c];
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c--;
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}
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p &= m - 1;
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set_bit(filter, p);
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}
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/* log_debug("bloom: adding <%.*s>", (int) n, (char*) data); */
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}
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void bloom_add_pair(uint64_t filter[], size_t size, unsigned k, const char *a, const char *b) {
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size_t n;
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char *c;
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assert(filter);
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assert(a);
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assert(b);
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n = strlen(a) + 1 + strlen(b);
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c = alloca(n + 1);
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strcpy(stpcpy(stpcpy(c, a), ":"), b);
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bloom_add_data(filter, size, k, c, n);
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}
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void bloom_add_prefixes(uint64_t filter[], size_t size, unsigned k, const char *a, const char *b, char sep) {
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size_t n;
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char *c, *p;
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assert(filter);
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assert(a);
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assert(b);
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n = strlen(a) + 1 + strlen(b);
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c = alloca(n + 1);
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p = stpcpy(stpcpy(c, a), ":");
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strcpy(p, b);
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bloom_add_data(filter, size, k, c, n);
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for (;;) {
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char *e;
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e = strrchr(p, sep);
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if (!e)
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break;
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*(e + 1) = 0;
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bloom_add_data(filter, size, k, c, e - c + 1);
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if (e == p)
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break;
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*e = 0;
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bloom_add_data(filter, size, k, c, e - c);
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}
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}
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bool bloom_validate_parameters(size_t size, unsigned k) {
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uint64_t m;
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unsigned w;
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if (size <= 0)
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return false;
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if (k <= 0)
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return false;
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m = size * 8;
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w = (u64log2(m) + 7) / 8;
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if (w > sizeof(uint64_t))
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return false;
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if (k * w > ELEMENTSOF(hash_keys) * 8)
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return false;
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return true;
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}
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