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322345fd LP |
1 | /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ |
2 | ||
3 | /*** | |
4 | This file is part of systemd. | |
5 | ||
6 | Copyright 2014 Lennart Poettering | |
7 | ||
8 | systemd is free software; you can redistribute it and/or modify it | |
9 | under the terms of the GNU Lesser General Public License as published by | |
10 | the Free Software Foundation; either version 2.1 of the License, or | |
11 | (at your option) any later version. | |
12 | ||
13 | systemd is distributed in the hope that it will be useful, but | |
14 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
16 | Lesser General Public License for more details. | |
17 | ||
18 | You should have received a copy of the GNU Lesser General Public License | |
19 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
20 | ***/ | |
21 | ||
22 | #include "resolved-dns-cache.h" | |
23 | ||
cbd4560e | 24 | /* Never cache more than 1K entries */ |
322345fd | 25 | #define CACHE_MAX 1024 |
cbd4560e LP |
26 | |
27 | /* We never keep any item longer than 10min in our cache */ | |
322345fd LP |
28 | #define CACHE_TTL_MAX_USEC (10 * USEC_PER_MINUTE) |
29 | ||
30 | static void dns_cache_item_free(DnsCacheItem *i) { | |
31 | if (!i) | |
32 | return; | |
33 | ||
34 | dns_resource_record_unref(i->rr); | |
35 | free(i); | |
36 | } | |
37 | ||
38 | DEFINE_TRIVIAL_CLEANUP_FUNC(DnsCacheItem*, dns_cache_item_free); | |
39 | ||
40 | static void dns_cache_item_remove_and_free(DnsCache *c, DnsCacheItem *i) { | |
41 | DnsCacheItem *first; | |
42 | ||
43 | assert(c); | |
44 | ||
45 | if (!i) | |
46 | return; | |
47 | ||
48 | first = hashmap_get(c->rrsets, &i->rr->key); | |
49 | LIST_REMOVE(rrsets, first, i); | |
50 | ||
51 | if (first) | |
52 | assert_se(hashmap_replace(c->rrsets, &first->rr->key, first) >= 0); | |
53 | else | |
54 | hashmap_remove(c->rrsets, &i->rr->key); | |
55 | ||
56 | prioq_remove(c->expire, i, &i->expire_prioq_idx); | |
57 | ||
58 | dns_cache_item_free(i); | |
59 | } | |
60 | ||
61 | void dns_cache_flush(DnsCache *c) { | |
62 | DnsCacheItem *i; | |
63 | ||
64 | assert(c); | |
65 | ||
66 | while ((i = hashmap_first(c->rrsets))) | |
67 | dns_cache_item_remove_and_free(c, i); | |
68 | ||
69 | assert(hashmap_size(c->rrsets) == 0); | |
70 | assert(prioq_size(c->expire) == 0); | |
71 | ||
72 | hashmap_free(c->rrsets); | |
73 | c->rrsets = NULL; | |
74 | ||
75 | prioq_free(c->expire); | |
76 | c->expire = NULL; | |
77 | } | |
78 | ||
79 | void dns_cache_remove(DnsCache *c, DnsResourceKey *key) { | |
80 | DnsCacheItem *i; | |
81 | ||
82 | assert(c); | |
83 | assert(key); | |
84 | ||
cbd4560e | 85 | while ((i = hashmap_get(c->rrsets, key))) |
322345fd LP |
86 | dns_cache_item_remove_and_free(c, i); |
87 | } | |
88 | ||
89 | static void dns_cache_make_space(DnsCache *c, unsigned add) { | |
90 | assert(c); | |
91 | ||
92 | if (add <= 0) | |
93 | return; | |
94 | ||
95 | /* Makes space for n new entries. Note that we actually allow | |
96 | * the cache to grow beyond CACHE_MAX, but only when we shall | |
97 | * add more RRs to the cache than CACHE_MAX at once. In that | |
98 | * case the cache will be emptied completely otherwise. */ | |
99 | ||
100 | for (;;) { | |
101 | _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; | |
102 | DnsCacheItem *i; | |
103 | ||
104 | if (prioq_size(c->expire) <= 0) | |
105 | break; | |
106 | ||
107 | if (prioq_size(c->expire) + add < CACHE_MAX) | |
108 | break; | |
109 | ||
110 | i = prioq_peek(c->expire); | |
cbd4560e LP |
111 | assert(i); |
112 | ||
113 | /* Take an extra reference to the RR so that the key | |
114 | * doesn't go away in the middle of the remove call */ | |
322345fd LP |
115 | rr = dns_resource_record_ref(i->rr); |
116 | dns_cache_remove(c, &rr->key); | |
117 | } | |
118 | } | |
119 | ||
120 | void dns_cache_prune(DnsCache *c) { | |
121 | usec_t t = 0; | |
122 | ||
123 | assert(c); | |
124 | ||
125 | /* Remove all entries that are past their TTL */ | |
126 | ||
127 | for (;;) { | |
cbd4560e | 128 | _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; |
322345fd LP |
129 | DnsCacheItem *i; |
130 | usec_t ttl; | |
131 | ||
132 | i = prioq_peek(c->expire); | |
133 | if (!i) | |
134 | break; | |
135 | ||
136 | ttl = i->rr->ttl * USEC_PER_SEC; | |
137 | if (ttl > CACHE_TTL_MAX_USEC) | |
138 | ttl = CACHE_TTL_MAX_USEC; | |
139 | ||
140 | if (t <= 0) | |
141 | t = now(CLOCK_MONOTONIC); | |
142 | ||
143 | if (i->timestamp + ttl > t) | |
144 | break; | |
145 | ||
cbd4560e LP |
146 | /* Take an extra reference to the RR so that the key |
147 | * doesn't go away in the middle of the remove call */ | |
148 | rr = dns_resource_record_ref(i->rr); | |
149 | dns_cache_remove(c, &rr->key); | |
322345fd LP |
150 | } |
151 | } | |
152 | ||
153 | static int dns_cache_item_prioq_compare_func(const void *a, const void *b) { | |
154 | usec_t t, z; | |
155 | const DnsCacheItem *x = a, *y = b; | |
156 | ||
157 | t = x->timestamp + x->rr->ttl * USEC_PER_SEC; | |
158 | z = y->timestamp + y->rr->ttl * USEC_PER_SEC; | |
159 | ||
160 | if (t < z) | |
161 | return -1; | |
162 | if (t > z) | |
163 | return 1; | |
164 | return 0; | |
165 | } | |
166 | ||
167 | static void dns_cache_item_update(DnsCache *c, DnsCacheItem *i, DnsResourceRecord *rr, usec_t timestamp) { | |
168 | assert(c); | |
169 | assert(i); | |
170 | assert(rr); | |
171 | ||
172 | if (!i->rrsets_prev) { | |
173 | /* We are the first item in the list, we need to | |
174 | * update the key used in the hashmap */ | |
175 | ||
176 | assert_se(hashmap_replace(c->rrsets, &rr->key, i) >= 0); | |
177 | } | |
178 | ||
cbd4560e | 179 | dns_resource_record_ref(rr); |
322345fd | 180 | dns_resource_record_unref(i->rr); |
cbd4560e | 181 | i->rr = rr; |
322345fd LP |
182 | |
183 | i->timestamp = timestamp; | |
322345fd LP |
184 | prioq_reshuffle(c->expire, i, &i->expire_prioq_idx); |
185 | } | |
186 | ||
187 | int dns_cache_put(DnsCache *c, DnsResourceRecord *rr, usec_t timestamp) { | |
188 | _cleanup_(dns_cache_item_freep) DnsCacheItem *i = NULL; | |
189 | DnsCacheItem *first = NULL, *existing; | |
190 | int r; | |
191 | ||
192 | assert(c); | |
193 | assert(rr); | |
194 | ||
195 | /* New TTL is 0? Delete the entry... */ | |
196 | if (rr->ttl <= 0) { | |
197 | dns_cache_remove(c, &rr->key); | |
198 | return 0; | |
199 | } | |
200 | ||
201 | /* Entry exists already? Update TTL and timestamp */ | |
202 | existing = dns_cache_get(c, rr); | |
203 | if (existing) { | |
204 | dns_cache_item_update(c, existing, rr, timestamp); | |
205 | return 0; | |
206 | } | |
207 | ||
208 | /* Otherwise, add the new RR */ | |
209 | r = prioq_ensure_allocated(&c->expire, dns_cache_item_prioq_compare_func); | |
210 | if (r < 0) | |
211 | return r; | |
212 | ||
213 | r = hashmap_ensure_allocated(&c->rrsets, dns_resource_key_hash_func, dns_resource_key_compare_func); | |
214 | if (r < 0) | |
215 | return r; | |
216 | ||
217 | dns_cache_make_space(c, 1); | |
218 | ||
219 | i = new0(DnsCacheItem, 1); | |
220 | if (!i) | |
221 | return -ENOMEM; | |
222 | ||
223 | i->rr = dns_resource_record_ref(rr); | |
224 | i->timestamp = timestamp; | |
225 | i->expire_prioq_idx = PRIOQ_IDX_NULL; | |
226 | ||
227 | r = prioq_put(c->expire, i, &i->expire_prioq_idx); | |
228 | if (r < 0) | |
229 | return r; | |
230 | ||
231 | first = hashmap_get(c->rrsets, &i->rr->key); | |
232 | if (first) { | |
233 | LIST_PREPEND(rrsets, first, i); | |
234 | assert_se(hashmap_replace(c->rrsets, &first->rr->key, first) >= 0); | |
235 | } else { | |
236 | r = hashmap_put(c->rrsets, &i->rr->key, i); | |
237 | if (r < 0) { | |
238 | prioq_remove(c->expire, i, &i->expire_prioq_idx); | |
239 | return r; | |
240 | } | |
241 | } | |
242 | ||
243 | i = NULL; | |
244 | ||
245 | return 0; | |
246 | } | |
247 | ||
248 | int dns_cache_put_rrs(DnsCache *c, DnsResourceRecord **rrs, unsigned n_rrs, usec_t timestamp) { | |
249 | unsigned i, added = 0; | |
250 | int r; | |
251 | ||
252 | assert(c); | |
253 | ||
254 | if (n_rrs <= 0) | |
255 | return 0; | |
256 | ||
257 | assert(rrs); | |
258 | ||
259 | /* First iteration, delete all matching old RRs, so that we | |
260 | * only keep complete rrsets in place. */ | |
261 | for (i = 0; i < n_rrs; i++) | |
262 | dns_cache_remove(c, &rrs[i]->key); | |
263 | ||
264 | dns_cache_make_space(c, n_rrs); | |
265 | ||
266 | /* Second iteration, add in new RRs */ | |
267 | for (added = 0; added < n_rrs; added++) { | |
268 | if (timestamp <= 0) | |
269 | timestamp = now(CLOCK_MONOTONIC); | |
270 | ||
271 | r = dns_cache_put(c, rrs[added], timestamp); | |
272 | if (r < 0) | |
273 | goto fail; | |
274 | ||
275 | } | |
276 | ||
277 | return 0; | |
278 | ||
279 | fail: | |
280 | /* Adding all RRs failed. Let's clean up what we already | |
281 | * added, just in case */ | |
282 | ||
283 | for (i = 0; i < added; i++) | |
284 | dns_cache_remove(c, &rrs[i]->key); | |
285 | ||
286 | return r; | |
287 | } | |
288 | ||
289 | DnsCacheItem* dns_cache_lookup(DnsCache *c, DnsResourceKey *key) { | |
290 | assert(c); | |
291 | assert(key); | |
292 | ||
293 | return hashmap_get(c->rrsets, key); | |
294 | } | |
295 | ||
296 | DnsCacheItem* dns_cache_get(DnsCache *c, DnsResourceRecord *rr) { | |
297 | DnsCacheItem *i; | |
298 | ||
299 | assert(c); | |
300 | assert(rr); | |
301 | ||
302 | LIST_FOREACH(rrsets, i, hashmap_get(c->rrsets, &rr->key)) | |
303 | if (dns_resource_record_equal(i->rr, rr)) | |
304 | return i; | |
305 | ||
306 | return NULL; | |
307 | } | |
308 | ||
309 | int dns_cache_lookup_many(DnsCache *c, DnsResourceKey *keys, unsigned n_keys, DnsResourceRecord ***rrs) { | |
310 | DnsResourceRecord **p = NULL; | |
311 | size_t allocated = 0, used = 0; | |
312 | unsigned i; | |
313 | int r; | |
314 | ||
315 | assert(c); | |
316 | assert(rrs); | |
317 | ||
318 | if (n_keys <= 0) { | |
319 | *rrs = NULL; | |
320 | return 0; | |
321 | } | |
322 | ||
323 | assert(keys); | |
324 | ||
325 | for (i = 0; i < n_keys; i++) { | |
326 | DnsCacheItem *j; | |
327 | ||
328 | j = dns_cache_lookup(c, &keys[i]); | |
329 | if (!j) { | |
330 | *rrs = NULL; | |
331 | r = 0; | |
332 | goto fail; | |
333 | } | |
334 | ||
335 | LIST_FOREACH(rrsets, j, j) { | |
336 | ||
337 | if (!GREEDY_REALLOC(p, allocated, used+1)) { | |
338 | r = -ENOMEM; | |
339 | goto fail; | |
340 | } | |
341 | ||
342 | p[used++] = dns_resource_record_ref(j->rr); | |
343 | } | |
344 | } | |
345 | ||
346 | *rrs = p; | |
347 | return (int) used; | |
348 | ||
349 | fail: | |
350 | dns_resource_record_freev(p, used); | |
351 | return r; | |
352 | } |