565 lines
16 KiB
C
565 lines
16 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 2014 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 "resolved-dns-cache.h"
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#include "resolved-dns-packet.h"
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/* Never cache more than 1K entries */
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#define CACHE_MAX 1024
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/* We never keep any item longer than 10min in our cache */
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#define CACHE_TTL_MAX_USEC (10 * USEC_PER_MINUTE)
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typedef enum DnsCacheItemType DnsCacheItemType;
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typedef struct DnsCacheItem DnsCacheItem;
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enum DnsCacheItemType {
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DNS_CACHE_POSITIVE,
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DNS_CACHE_NODATA,
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DNS_CACHE_NXDOMAIN,
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};
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struct DnsCacheItem {
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DnsResourceKey *key;
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DnsResourceRecord *rr;
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usec_t until;
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DnsCacheItemType type;
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unsigned prioq_idx;
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int owner_family;
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union in_addr_union owner_address;
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LIST_FIELDS(DnsCacheItem, by_key);
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};
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static void dns_cache_item_free(DnsCacheItem *i) {
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if (!i)
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return;
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dns_resource_record_unref(i->rr);
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dns_resource_key_unref(i->key);
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free(i);
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}
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DEFINE_TRIVIAL_CLEANUP_FUNC(DnsCacheItem*, dns_cache_item_free);
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static void dns_cache_item_remove_and_free(DnsCache *c, DnsCacheItem *i) {
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DnsCacheItem *first;
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assert(c);
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if (!i)
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return;
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first = hashmap_get(c->by_key, i->key);
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LIST_REMOVE(by_key, first, i);
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if (first)
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assert_se(hashmap_replace(c->by_key, first->key, first) >= 0);
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else
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hashmap_remove(c->by_key, i->key);
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prioq_remove(c->by_expiry, i, &i->prioq_idx);
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dns_cache_item_free(i);
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}
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void dns_cache_flush(DnsCache *c) {
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DnsCacheItem *i;
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assert(c);
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while ((i = hashmap_first(c->by_key)))
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dns_cache_item_remove_and_free(c, i);
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assert(hashmap_size(c->by_key) == 0);
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assert(prioq_size(c->by_expiry) == 0);
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hashmap_free(c->by_key);
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c->by_key = NULL;
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prioq_free(c->by_expiry);
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c->by_expiry = NULL;
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}
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static void dns_cache_remove(DnsCache *c, DnsResourceKey *key) {
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DnsCacheItem *i;
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assert(c);
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assert(key);
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while ((i = hashmap_get(c->by_key, key)))
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dns_cache_item_remove_and_free(c, i);
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}
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static void dns_cache_make_space(DnsCache *c, unsigned add) {
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assert(c);
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if (add <= 0)
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return;
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/* Makes space for n new entries. Note that we actually allow
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* the cache to grow beyond CACHE_MAX, but only when we shall
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* add more RRs to the cache than CACHE_MAX at once. In that
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* case the cache will be emptied completely otherwise. */
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for (;;) {
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_cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
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DnsCacheItem *i;
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if (prioq_size(c->by_expiry) <= 0)
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break;
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if (prioq_size(c->by_expiry) + add < CACHE_MAX)
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break;
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i = prioq_peek(c->by_expiry);
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assert(i);
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/* Take an extra reference to the key so that it
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* doesn't go away in the middle of the remove call */
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key = dns_resource_key_ref(i->key);
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dns_cache_remove(c, key);
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}
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}
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void dns_cache_prune(DnsCache *c) {
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usec_t t = 0;
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assert(c);
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/* Remove all entries that are past their TTL */
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for (;;) {
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_cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
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DnsCacheItem *i;
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i = prioq_peek(c->by_expiry);
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if (!i)
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break;
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if (t <= 0)
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t = now(CLOCK_BOOTTIME);
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if (i->until > t)
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break;
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/* Take an extra reference to the key so that it
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* doesn't go away in the middle of the remove call */
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key = dns_resource_key_ref(i->key);
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dns_cache_remove(c, key);
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}
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}
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static int dns_cache_item_prioq_compare_func(const void *a, const void *b) {
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const DnsCacheItem *x = a, *y = b;
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if (x->until < y->until)
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return -1;
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if (x->until > y->until)
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return 1;
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return 0;
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}
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static int dns_cache_init(DnsCache *c) {
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int r;
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assert(c);
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r = prioq_ensure_allocated(&c->by_expiry, dns_cache_item_prioq_compare_func);
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if (r < 0)
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return r;
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r = hashmap_ensure_allocated(&c->by_key, &dns_resource_key_hash_ops);
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if (r < 0)
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return r;
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return r;
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}
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static int dns_cache_link_item(DnsCache *c, DnsCacheItem *i) {
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DnsCacheItem *first;
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int r;
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assert(c);
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assert(i);
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r = prioq_put(c->by_expiry, i, &i->prioq_idx);
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if (r < 0)
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return r;
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first = hashmap_get(c->by_key, i->key);
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if (first) {
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LIST_PREPEND(by_key, first, i);
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assert_se(hashmap_replace(c->by_key, first->key, first) >= 0);
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} else {
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r = hashmap_put(c->by_key, i->key, i);
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if (r < 0) {
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prioq_remove(c->by_expiry, i, &i->prioq_idx);
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return r;
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}
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}
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return 0;
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}
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static DnsCacheItem* dns_cache_get(DnsCache *c, DnsResourceRecord *rr) {
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DnsCacheItem *i;
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assert(c);
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assert(rr);
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LIST_FOREACH(by_key, i, hashmap_get(c->by_key, rr->key))
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if (i->rr && dns_resource_record_equal(i->rr, rr) > 0)
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return i;
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return NULL;
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}
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static void dns_cache_item_update_positive(DnsCache *c, DnsCacheItem *i, DnsResourceRecord *rr, usec_t timestamp) {
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assert(c);
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assert(i);
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assert(rr);
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i->type = DNS_CACHE_POSITIVE;
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if (!i->by_key_prev) {
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/* We are the first item in the list, we need to
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* update the key used in the hashmap */
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assert_se(hashmap_replace(c->by_key, rr->key, i) >= 0);
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}
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dns_resource_record_ref(rr);
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dns_resource_record_unref(i->rr);
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i->rr = rr;
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dns_resource_key_unref(i->key);
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i->key = dns_resource_key_ref(rr->key);
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i->until = timestamp + MIN(rr->ttl * USEC_PER_SEC, CACHE_TTL_MAX_USEC);
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prioq_reshuffle(c->by_expiry, i, &i->prioq_idx);
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}
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static int dns_cache_put_positive(
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DnsCache *c,
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DnsResourceRecord *rr,
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usec_t timestamp,
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int owner_family,
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const union in_addr_union *owner_address) {
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_cleanup_(dns_cache_item_freep) DnsCacheItem *i = NULL;
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DnsCacheItem *existing;
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int r;
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assert(c);
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assert(rr);
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assert(owner_address);
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/* New TTL is 0? Delete the entry... */
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if (rr->ttl <= 0) {
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dns_cache_remove(c, rr->key);
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return 0;
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}
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if (rr->key->class == DNS_CLASS_ANY)
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return 0;
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if (rr->key->type == DNS_TYPE_ANY)
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return 0;
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/* Entry exists already? Update TTL and timestamp */
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existing = dns_cache_get(c, rr);
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if (existing) {
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dns_cache_item_update_positive(c, existing, rr, timestamp);
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return 0;
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}
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/* Otherwise, add the new RR */
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r = dns_cache_init(c);
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if (r < 0)
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return r;
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dns_cache_make_space(c, 1);
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i = new0(DnsCacheItem, 1);
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if (!i)
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return -ENOMEM;
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i->type = DNS_CACHE_POSITIVE;
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i->key = dns_resource_key_ref(rr->key);
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i->rr = dns_resource_record_ref(rr);
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i->until = timestamp + MIN(i->rr->ttl * USEC_PER_SEC, CACHE_TTL_MAX_USEC);
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i->prioq_idx = PRIOQ_IDX_NULL;
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i->owner_family = owner_family;
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i->owner_address = *owner_address;
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r = dns_cache_link_item(c, i);
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if (r < 0)
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return r;
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i = NULL;
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return 0;
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}
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static int dns_cache_put_negative(
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DnsCache *c,
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DnsResourceKey *key,
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int rcode,
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usec_t timestamp,
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uint32_t soa_ttl,
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int owner_family,
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const union in_addr_union *owner_address) {
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_cleanup_(dns_cache_item_freep) DnsCacheItem *i = NULL;
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int r;
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assert(c);
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assert(key);
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assert(owner_address);
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dns_cache_remove(c, key);
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if (key->class == DNS_CLASS_ANY)
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return 0;
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if (key->type == DNS_TYPE_ANY)
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return 0;
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if (soa_ttl <= 0)
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return 0;
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if (!IN_SET(rcode, DNS_RCODE_SUCCESS, DNS_RCODE_NXDOMAIN))
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return 0;
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r = dns_cache_init(c);
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if (r < 0)
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return r;
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dns_cache_make_space(c, 1);
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i = new0(DnsCacheItem, 1);
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if (!i)
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return -ENOMEM;
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i->type = rcode == DNS_RCODE_SUCCESS ? DNS_CACHE_NODATA : DNS_CACHE_NXDOMAIN;
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i->key = dns_resource_key_ref(key);
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i->until = timestamp + MIN(soa_ttl * USEC_PER_SEC, CACHE_TTL_MAX_USEC);
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i->prioq_idx = PRIOQ_IDX_NULL;
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i->owner_family = owner_family;
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i->owner_address = *owner_address;
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r = dns_cache_link_item(c, i);
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if (r < 0)
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return r;
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i = NULL;
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return 0;
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}
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int dns_cache_put(
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DnsCache *c,
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DnsQuestion *q,
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int rcode,
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DnsAnswer *answer,
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unsigned max_rrs,
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usec_t timestamp,
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int owner_family,
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const union in_addr_union *owner_address) {
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unsigned i;
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int r;
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assert(c);
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assert(q);
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/* First, delete all matching old RRs, so that we only keep
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* complete by_key in place. */
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for (i = 0; i < q->n_keys; i++)
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dns_cache_remove(c, q->keys[i]);
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if (!answer)
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return 0;
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for (i = 0; i < answer->n_rrs; i++)
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dns_cache_remove(c, answer->rrs[i]->key);
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/* We only care for positive replies and NXDOMAINs, on all
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* other replies we will simply flush the respective entries,
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* and that's it */
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if (!IN_SET(rcode, DNS_RCODE_SUCCESS, DNS_RCODE_NXDOMAIN))
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return 0;
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/* Make some space for our new entries */
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dns_cache_make_space(c, answer->n_rrs + q->n_keys);
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if (timestamp <= 0)
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timestamp = now(CLOCK_BOOTTIME);
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/* Second, add in positive entries for all contained RRs */
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for (i = 0; i < MIN(max_rrs, answer->n_rrs); i++) {
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r = dns_cache_put_positive(c, answer->rrs[i], timestamp, owner_family, owner_address);
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if (r < 0)
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goto fail;
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}
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/* Third, add in negative entries for all keys with no RR */
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for (i = 0; i < q->n_keys; i++) {
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DnsResourceRecord *soa = NULL;
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r = dns_answer_contains(answer, q->keys[i]);
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if (r < 0)
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goto fail;
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if (r > 0)
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continue;
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r = dns_answer_find_soa(answer, q->keys[i], &soa);
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if (r < 0)
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goto fail;
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if (r == 0)
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continue;
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r = dns_cache_put_negative(c, q->keys[i], rcode, timestamp, MIN(soa->soa.minimum, soa->ttl), owner_family, owner_address);
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if (r < 0)
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goto fail;
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}
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return 0;
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fail:
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/* Adding all RRs failed. Let's clean up what we already
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* added, just in case */
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for (i = 0; i < q->n_keys; i++)
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dns_cache_remove(c, q->keys[i]);
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for (i = 0; i < answer->n_rrs; i++)
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dns_cache_remove(c, answer->rrs[i]->key);
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return r;
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}
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int dns_cache_lookup(DnsCache *c, DnsQuestion *q, int *rcode, DnsAnswer **ret) {
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_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
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unsigned i, n = 0;
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int r;
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bool nxdomain = false;
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assert(c);
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assert(q);
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assert(rcode);
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assert(ret);
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if (q->n_keys <= 0) {
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*ret = NULL;
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*rcode = 0;
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return 0;
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}
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for (i = 0; i < q->n_keys; i++) {
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DnsCacheItem *j;
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if (q->keys[i]->type == DNS_TYPE_ANY ||
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q->keys[i]->class == DNS_CLASS_ANY) {
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/* If we have ANY lookups we simply refresh */
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*ret = NULL;
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*rcode = 0;
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return 0;
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}
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j = hashmap_get(c->by_key, q->keys[i]);
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if (!j) {
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/* If one question cannot be answered we need to refresh */
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*ret = NULL;
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*rcode = 0;
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return 0;
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}
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LIST_FOREACH(by_key, j, j) {
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if (j->rr)
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n++;
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else if (j->type == DNS_CACHE_NXDOMAIN)
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nxdomain = true;
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}
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}
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if (n <= 0) {
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*ret = NULL;
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*rcode = nxdomain ? DNS_RCODE_NXDOMAIN : DNS_RCODE_SUCCESS;
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return 1;
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}
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answer = dns_answer_new(n);
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if (!answer)
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return -ENOMEM;
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for (i = 0; i < q->n_keys; i++) {
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DnsCacheItem *j;
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j = hashmap_get(c->by_key, q->keys[i]);
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LIST_FOREACH(by_key, j, j) {
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if (j->rr) {
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r = dns_answer_add(answer, j->rr);
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if (r < 0)
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return r;
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}
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}
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}
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*ret = answer;
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*rcode = DNS_RCODE_SUCCESS;
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answer = NULL;
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return n;
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}
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int dns_cache_check_conflicts(DnsCache *cache, DnsResourceRecord *rr, int owner_family, const union in_addr_union *owner_address) {
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DnsCacheItem *i, *first;
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bool same_owner = true;
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assert(cache);
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assert(rr);
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dns_cache_prune(cache);
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/* See if there's a cache entry for the same key. If there
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* isn't there's no conflict */
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first = hashmap_get(cache->by_key, rr->key);
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if (!first)
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return 0;
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/* See if the RR key is owned by the same owner, if so, there
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* isn't a conflict either */
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LIST_FOREACH(by_key, i, first) {
|
|
if (i->owner_family != owner_family ||
|
|
!in_addr_equal(owner_family, &i->owner_address, owner_address)) {
|
|
same_owner = false;
|
|
break;
|
|
}
|
|
}
|
|
if (same_owner)
|
|
return 0;
|
|
|
|
/* See if there's the exact same RR in the cache. If yes, then
|
|
* there's no conflict. */
|
|
if (dns_cache_get(cache, rr))
|
|
return 0;
|
|
|
|
/* There's a conflict */
|
|
return 1;
|
|
}
|