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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 | ||
24 | #define CACHE_MAX 1024 | |
25 | #define CACHE_TTL_MAX_USEC (10 * USEC_PER_MINUTE) | |
26 | ||
27 | static void dns_cache_item_free(DnsCacheItem *i) { | |
28 | if (!i) | |
29 | return; | |
30 | ||
31 | dns_resource_record_unref(i->rr); | |
32 | free(i); | |
33 | } | |
34 | ||
35 | DEFINE_TRIVIAL_CLEANUP_FUNC(DnsCacheItem*, dns_cache_item_free); | |
36 | ||
37 | static void dns_cache_item_remove_and_free(DnsCache *c, DnsCacheItem *i) { | |
38 | DnsCacheItem *first; | |
39 | ||
40 | assert(c); | |
41 | ||
42 | if (!i) | |
43 | return; | |
44 | ||
45 | first = hashmap_get(c->rrsets, &i->rr->key); | |
46 | LIST_REMOVE(rrsets, first, i); | |
47 | ||
48 | if (first) | |
49 | assert_se(hashmap_replace(c->rrsets, &first->rr->key, first) >= 0); | |
50 | else | |
51 | hashmap_remove(c->rrsets, &i->rr->key); | |
52 | ||
53 | prioq_remove(c->expire, i, &i->expire_prioq_idx); | |
54 | ||
55 | dns_cache_item_free(i); | |
56 | } | |
57 | ||
58 | void dns_cache_flush(DnsCache *c) { | |
59 | DnsCacheItem *i; | |
60 | ||
61 | assert(c); | |
62 | ||
63 | while ((i = hashmap_first(c->rrsets))) | |
64 | dns_cache_item_remove_and_free(c, i); | |
65 | ||
66 | assert(hashmap_size(c->rrsets) == 0); | |
67 | assert(prioq_size(c->expire) == 0); | |
68 | ||
69 | hashmap_free(c->rrsets); | |
70 | c->rrsets = NULL; | |
71 | ||
72 | prioq_free(c->expire); | |
73 | c->expire = NULL; | |
74 | } | |
75 | ||
76 | void dns_cache_remove(DnsCache *c, DnsResourceKey *key) { | |
77 | DnsCacheItem *i; | |
78 | ||
79 | assert(c); | |
80 | assert(key); | |
81 | ||
82 | while ((i = hashmap_get(c->rrsets, &key))) | |
83 | dns_cache_item_remove_and_free(c, i); | |
84 | } | |
85 | ||
86 | static void dns_cache_make_space(DnsCache *c, unsigned add) { | |
87 | assert(c); | |
88 | ||
89 | if (add <= 0) | |
90 | return; | |
91 | ||
92 | /* Makes space for n new entries. Note that we actually allow | |
93 | * the cache to grow beyond CACHE_MAX, but only when we shall | |
94 | * add more RRs to the cache than CACHE_MAX at once. In that | |
95 | * case the cache will be emptied completely otherwise. */ | |
96 | ||
97 | for (;;) { | |
98 | _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; | |
99 | DnsCacheItem *i; | |
100 | ||
101 | if (prioq_size(c->expire) <= 0) | |
102 | break; | |
103 | ||
104 | if (prioq_size(c->expire) + add < CACHE_MAX) | |
105 | break; | |
106 | ||
107 | i = prioq_peek(c->expire); | |
108 | rr = dns_resource_record_ref(i->rr); | |
109 | dns_cache_remove(c, &rr->key); | |
110 | } | |
111 | } | |
112 | ||
113 | void dns_cache_prune(DnsCache *c) { | |
114 | usec_t t = 0; | |
115 | ||
116 | assert(c); | |
117 | ||
118 | /* Remove all entries that are past their TTL */ | |
119 | ||
120 | for (;;) { | |
121 | DnsCacheItem *i; | |
122 | usec_t ttl; | |
123 | ||
124 | i = prioq_peek(c->expire); | |
125 | if (!i) | |
126 | break; | |
127 | ||
128 | ttl = i->rr->ttl * USEC_PER_SEC; | |
129 | if (ttl > CACHE_TTL_MAX_USEC) | |
130 | ttl = CACHE_TTL_MAX_USEC; | |
131 | ||
132 | if (t <= 0) | |
133 | t = now(CLOCK_MONOTONIC); | |
134 | ||
135 | if (i->timestamp + ttl > t) | |
136 | break; | |
137 | ||
138 | dns_cache_remove(c, &i->rr->key); | |
139 | } | |
140 | } | |
141 | ||
142 | static int dns_cache_item_prioq_compare_func(const void *a, const void *b) { | |
143 | usec_t t, z; | |
144 | const DnsCacheItem *x = a, *y = b; | |
145 | ||
146 | t = x->timestamp + x->rr->ttl * USEC_PER_SEC; | |
147 | z = y->timestamp + y->rr->ttl * USEC_PER_SEC; | |
148 | ||
149 | if (t < z) | |
150 | return -1; | |
151 | if (t > z) | |
152 | return 1; | |
153 | return 0; | |
154 | } | |
155 | ||
156 | static void dns_cache_item_update(DnsCache *c, DnsCacheItem *i, DnsResourceRecord *rr, usec_t timestamp) { | |
157 | assert(c); | |
158 | assert(i); | |
159 | assert(rr); | |
160 | ||
161 | if (!i->rrsets_prev) { | |
162 | /* We are the first item in the list, we need to | |
163 | * update the key used in the hashmap */ | |
164 | ||
165 | assert_se(hashmap_replace(c->rrsets, &rr->key, i) >= 0); | |
166 | } | |
167 | ||
168 | dns_resource_record_unref(i->rr); | |
169 | i->rr = dns_resource_record_ref(rr); | |
170 | ||
171 | i->timestamp = timestamp; | |
172 | ||
173 | prioq_reshuffle(c->expire, i, &i->expire_prioq_idx); | |
174 | } | |
175 | ||
176 | int dns_cache_put(DnsCache *c, DnsResourceRecord *rr, usec_t timestamp) { | |
177 | _cleanup_(dns_cache_item_freep) DnsCacheItem *i = NULL; | |
178 | DnsCacheItem *first = NULL, *existing; | |
179 | int r; | |
180 | ||
181 | assert(c); | |
182 | assert(rr); | |
183 | ||
184 | /* New TTL is 0? Delete the entry... */ | |
185 | if (rr->ttl <= 0) { | |
186 | dns_cache_remove(c, &rr->key); | |
187 | return 0; | |
188 | } | |
189 | ||
190 | /* Entry exists already? Update TTL and timestamp */ | |
191 | existing = dns_cache_get(c, rr); | |
192 | if (existing) { | |
193 | dns_cache_item_update(c, existing, rr, timestamp); | |
194 | return 0; | |
195 | } | |
196 | ||
197 | /* Otherwise, add the new RR */ | |
198 | r = prioq_ensure_allocated(&c->expire, dns_cache_item_prioq_compare_func); | |
199 | if (r < 0) | |
200 | return r; | |
201 | ||
202 | r = hashmap_ensure_allocated(&c->rrsets, dns_resource_key_hash_func, dns_resource_key_compare_func); | |
203 | if (r < 0) | |
204 | return r; | |
205 | ||
206 | dns_cache_make_space(c, 1); | |
207 | ||
208 | i = new0(DnsCacheItem, 1); | |
209 | if (!i) | |
210 | return -ENOMEM; | |
211 | ||
212 | i->rr = dns_resource_record_ref(rr); | |
213 | i->timestamp = timestamp; | |
214 | i->expire_prioq_idx = PRIOQ_IDX_NULL; | |
215 | ||
216 | r = prioq_put(c->expire, i, &i->expire_prioq_idx); | |
217 | if (r < 0) | |
218 | return r; | |
219 | ||
220 | first = hashmap_get(c->rrsets, &i->rr->key); | |
221 | if (first) { | |
222 | LIST_PREPEND(rrsets, first, i); | |
223 | assert_se(hashmap_replace(c->rrsets, &first->rr->key, first) >= 0); | |
224 | } else { | |
225 | r = hashmap_put(c->rrsets, &i->rr->key, i); | |
226 | if (r < 0) { | |
227 | prioq_remove(c->expire, i, &i->expire_prioq_idx); | |
228 | return r; | |
229 | } | |
230 | } | |
231 | ||
232 | i = NULL; | |
233 | ||
234 | return 0; | |
235 | } | |
236 | ||
237 | int dns_cache_put_rrs(DnsCache *c, DnsResourceRecord **rrs, unsigned n_rrs, usec_t timestamp) { | |
238 | unsigned i, added = 0; | |
239 | int r; | |
240 | ||
241 | assert(c); | |
242 | ||
243 | if (n_rrs <= 0) | |
244 | return 0; | |
245 | ||
246 | assert(rrs); | |
247 | ||
248 | /* First iteration, delete all matching old RRs, so that we | |
249 | * only keep complete rrsets in place. */ | |
250 | for (i = 0; i < n_rrs; i++) | |
251 | dns_cache_remove(c, &rrs[i]->key); | |
252 | ||
253 | dns_cache_make_space(c, n_rrs); | |
254 | ||
255 | /* Second iteration, add in new RRs */ | |
256 | for (added = 0; added < n_rrs; added++) { | |
257 | if (timestamp <= 0) | |
258 | timestamp = now(CLOCK_MONOTONIC); | |
259 | ||
260 | r = dns_cache_put(c, rrs[added], timestamp); | |
261 | if (r < 0) | |
262 | goto fail; | |
263 | ||
264 | } | |
265 | ||
266 | return 0; | |
267 | ||
268 | fail: | |
269 | /* Adding all RRs failed. Let's clean up what we already | |
270 | * added, just in case */ | |
271 | ||
272 | for (i = 0; i < added; i++) | |
273 | dns_cache_remove(c, &rrs[i]->key); | |
274 | ||
275 | return r; | |
276 | } | |
277 | ||
278 | DnsCacheItem* dns_cache_lookup(DnsCache *c, DnsResourceKey *key) { | |
279 | assert(c); | |
280 | assert(key); | |
281 | ||
282 | return hashmap_get(c->rrsets, key); | |
283 | } | |
284 | ||
285 | DnsCacheItem* dns_cache_get(DnsCache *c, DnsResourceRecord *rr) { | |
286 | DnsCacheItem *i; | |
287 | ||
288 | assert(c); | |
289 | assert(rr); | |
290 | ||
291 | LIST_FOREACH(rrsets, i, hashmap_get(c->rrsets, &rr->key)) | |
292 | if (dns_resource_record_equal(i->rr, rr)) | |
293 | return i; | |
294 | ||
295 | return NULL; | |
296 | } | |
297 | ||
298 | int dns_cache_lookup_many(DnsCache *c, DnsResourceKey *keys, unsigned n_keys, DnsResourceRecord ***rrs) { | |
299 | DnsResourceRecord **p = NULL; | |
300 | size_t allocated = 0, used = 0; | |
301 | unsigned i; | |
302 | int r; | |
303 | ||
304 | assert(c); | |
305 | assert(rrs); | |
306 | ||
307 | if (n_keys <= 0) { | |
308 | *rrs = NULL; | |
309 | return 0; | |
310 | } | |
311 | ||
312 | assert(keys); | |
313 | ||
314 | for (i = 0; i < n_keys; i++) { | |
315 | DnsCacheItem *j; | |
316 | ||
317 | j = dns_cache_lookup(c, &keys[i]); | |
318 | if (!j) { | |
319 | *rrs = NULL; | |
320 | r = 0; | |
321 | goto fail; | |
322 | } | |
323 | ||
324 | LIST_FOREACH(rrsets, j, j) { | |
325 | ||
326 | if (!GREEDY_REALLOC(p, allocated, used+1)) { | |
327 | r = -ENOMEM; | |
328 | goto fail; | |
329 | } | |
330 | ||
331 | p[used++] = dns_resource_record_ref(j->rr); | |
332 | } | |
333 | } | |
334 | ||
335 | *rrs = p; | |
336 | return (int) used; | |
337 | ||
338 | fail: | |
339 | dns_resource_record_freev(p, used); | |
340 | return r; | |
341 | } |