453 lines
13 KiB
C
453 lines
13 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 "af-list.h"
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#include "resolved-dns-query.h"
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#include "resolved-dns-domain.h"
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/* How long to wait for the query in total */
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#define QUERY_TIMEOUT_USEC (30 * USEC_PER_SEC)
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#define CNAME_MAX 8
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#define QUERIES_MAX 2048
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static void dns_query_stop(DnsQuery *q) {
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DnsTransaction *t;
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assert(q);
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q->timeout_event_source = sd_event_source_unref(q->timeout_event_source);
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while ((t = set_steal_first(q->transactions))) {
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set_remove(t->queries, q);
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dns_transaction_gc(t);
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}
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}
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DnsQuery *dns_query_free(DnsQuery *q) {
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if (!q)
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return NULL;
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dns_query_stop(q);
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set_free(q->transactions);
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dns_question_unref(q->question);
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dns_answer_unref(q->answer);
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sd_bus_message_unref(q->request);
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if (q->manager) {
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LIST_REMOVE(queries, q->manager->dns_queries, q);
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q->manager->n_dns_queries--;
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}
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free(q);
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return NULL;
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}
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int dns_query_new(Manager *m, DnsQuery **ret, DnsQuestion *question) {
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_cleanup_(dns_query_freep) DnsQuery *q = NULL;
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unsigned i;
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int r;
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assert(m);
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assert(question);
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r = dns_question_is_valid(question);
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if (r < 0)
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return r;
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if (m->n_dns_queries >= QUERIES_MAX)
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return -EBUSY;
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q = new0(DnsQuery, 1);
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if (!q)
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return -ENOMEM;
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q->question = dns_question_ref(question);
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for (i = 0; i < question->n_keys; i++) {
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_cleanup_free_ char *p;
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r = dns_resource_key_to_string(question->keys[i], &p);
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if (r < 0)
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return r;
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log_debug("Looking up RR for %s", p);
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}
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LIST_PREPEND(queries, m->dns_queries, q);
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m->n_dns_queries++;
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q->manager = m;
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if (ret)
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*ret = q;
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q = NULL;
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return 0;
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}
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static void dns_query_complete(DnsQuery *q, DnsTransactionState state) {
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assert(q);
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assert(!IN_SET(state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING));
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assert(IN_SET(q->state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING));
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/* Note that this call might invalidate the query. Callers
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* should hence not attempt to access the query or transaction
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* after calling this function. */
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q->state = state;
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dns_query_stop(q);
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if (q->complete)
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q->complete(q);
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}
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static int on_query_timeout(sd_event_source *s, usec_t usec, void *userdata) {
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DnsQuery *q = userdata;
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assert(s);
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assert(q);
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dns_query_complete(q, DNS_TRANSACTION_TIMEOUT);
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return 0;
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}
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static int dns_query_add_transaction(DnsQuery *q, DnsScope *s, DnsResourceKey *key) {
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_cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
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DnsTransaction *t;
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int r;
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assert(q);
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assert(s);
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r = set_ensure_allocated(&q->transactions, NULL, NULL);
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if (r < 0)
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return r;
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if (key) {
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question = dns_question_new(1);
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if (!question)
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return -ENOMEM;
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r = dns_question_add(question, key);
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if (r < 0)
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return r;
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} else
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question = dns_question_ref(q->question);
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t = dns_scope_find_transaction(s, question);
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if (!t) {
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r = dns_transaction_new(&t, s, question);
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if (r < 0)
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return r;
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}
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r = set_ensure_allocated(&t->queries, NULL, NULL);
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if (r < 0)
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goto gc;
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r = set_put(t->queries, q);
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if (r < 0)
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goto gc;
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r = set_put(q->transactions, t);
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if (r < 0) {
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set_remove(t->queries, q);
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goto gc;
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}
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return 0;
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gc:
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dns_transaction_gc(t);
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return r;
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}
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static int dns_query_add_transaction_split(DnsQuery *q, DnsScope *s) {
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int r;
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assert(q);
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assert(s);
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if (s->protocol == DNS_PROTOCOL_MDNS) {
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r = dns_query_add_transaction(q, s, NULL);
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if (r < 0)
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return r;
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} else {
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unsigned i;
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/* On DNS and LLMNR we can only send a single
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* question per datagram, hence issue multiple
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* transactions. */
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for (i = 0; i < q->question->n_keys; i++) {
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r = dns_query_add_transaction(q, s, q->question->keys[i]);
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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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return 0;
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}
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int dns_query_go(DnsQuery *q) {
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DnsScopeMatch found = DNS_SCOPE_NO;
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DnsScope *s, *first = NULL;
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DnsTransaction *t;
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const char *name;
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Iterator i;
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int r;
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assert(q);
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if (q->state != DNS_TRANSACTION_NULL)
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return 0;
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assert(q->question);
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assert(q->question->n_keys > 0);
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name = DNS_RESOURCE_KEY_NAME(q->question->keys[0]);
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LIST_FOREACH(scopes, s, q->manager->dns_scopes) {
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DnsScopeMatch match;
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match = dns_scope_good_domain(s, name);
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if (match < 0)
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return match;
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if (match == DNS_SCOPE_NO)
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continue;
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found = match;
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if (match == DNS_SCOPE_YES) {
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first = s;
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break;
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} else {
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assert(match == DNS_SCOPE_MAYBE);
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if (!first)
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first = s;
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}
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}
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if (found == DNS_SCOPE_NO)
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return -ESRCH;
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r = dns_query_add_transaction_split(q, first);
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if (r < 0)
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goto fail;
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LIST_FOREACH(scopes, s, first->scopes_next) {
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DnsScopeMatch match;
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match = dns_scope_good_domain(s, name);
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if (match < 0)
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goto fail;
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if (match != found)
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continue;
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r = dns_query_add_transaction_split(q, s);
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if (r < 0)
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goto fail;
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}
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q->answer = dns_answer_unref(q->answer);
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q->answer_ifindex = 0;
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q->answer_rcode = 0;
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r = sd_event_add_time(
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q->manager->event,
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&q->timeout_event_source,
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clock_boottime_or_monotonic(),
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now(clock_boottime_or_monotonic()) + QUERY_TIMEOUT_USEC, 0,
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on_query_timeout, q);
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if (r < 0)
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goto fail;
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q->state = DNS_TRANSACTION_PENDING;
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q->block_ready++;
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/* Start the transactions that are not started yet */
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SET_FOREACH(t, q->transactions, i) {
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if (t->state != DNS_TRANSACTION_NULL)
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continue;
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r = dns_transaction_go(t);
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if (r < 0)
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goto fail;
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}
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q->block_ready--;
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dns_query_ready(q);
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return 1;
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fail:
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dns_query_stop(q);
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return r;
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}
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void dns_query_ready(DnsQuery *q) {
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DnsTransaction *t;
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DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS;
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_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
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int rcode = 0;
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DnsScope *scope = NULL;
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bool pending = false;
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Iterator i;
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assert(q);
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assert(IN_SET(q->state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING));
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/* Note that this call might invalidate the query. Callers
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* should hence not attempt to access the query or transaction
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* after calling this function, unless the block_ready
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* counter was explicitly bumped before doing so. */
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if (q->block_ready > 0)
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return;
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SET_FOREACH(t, q->transactions, i) {
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/* If we found a successful answer, ignore all answers from other scopes */
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if (state == DNS_TRANSACTION_SUCCESS && t->scope != scope)
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continue;
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/* One of the transactions is still going on, let's maybe wait for it */
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if (IN_SET(t->state, DNS_TRANSACTION_PENDING, DNS_TRANSACTION_NULL)) {
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pending = true;
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continue;
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}
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/* One of the transactions is successful, let's use
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* it, and copy its data out */
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if (t->state == DNS_TRANSACTION_SUCCESS) {
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DnsAnswer *a;
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if (t->received) {
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rcode = DNS_PACKET_RCODE(t->received);
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a = t->received->answer;
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} else {
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rcode = t->cached_rcode;
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a = t->cached;
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}
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if (state == DNS_TRANSACTION_SUCCESS) {
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DnsAnswer *merged;
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merged = dns_answer_merge(answer, a);
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if (!merged) {
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dns_query_complete(q, DNS_TRANSACTION_RESOURCES);
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return;
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}
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dns_answer_unref(answer);
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answer = merged;
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} else {
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dns_answer_unref(answer);
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answer = dns_answer_ref(a);
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}
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scope = t->scope;
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state = DNS_TRANSACTION_SUCCESS;
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continue;
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}
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/* One of the transactions has failed, let's see
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* whether we find anything better, but if not, return
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* its response data */
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if (state != DNS_TRANSACTION_SUCCESS && t->state == DNS_TRANSACTION_FAILURE) {
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DnsAnswer *a;
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if (t->received) {
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rcode = DNS_PACKET_RCODE(t->received);
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a = t->received->answer;
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} else {
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rcode = t->cached_rcode;
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a = t->cached;
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}
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dns_answer_unref(answer);
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answer = dns_answer_ref(a);
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scope = t->scope;
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state = DNS_TRANSACTION_FAILURE;
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continue;
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}
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if (state == DNS_TRANSACTION_NO_SERVERS && t->state != DNS_TRANSACTION_NO_SERVERS)
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state = t->state;
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}
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if (pending) {
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/* If so far we weren't successful, and there's
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* something still pending, then wait for it */
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if (state != DNS_TRANSACTION_SUCCESS)
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return;
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/* If we already were successful, then only wait for
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* other transactions on the same scope to finish. */
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SET_FOREACH(t, q->transactions, i) {
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if (t->scope == scope && IN_SET(t->state, DNS_TRANSACTION_PENDING, DNS_TRANSACTION_NULL))
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return;
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}
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}
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if (IN_SET(state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_FAILURE)) {
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q->answer = dns_answer_ref(answer);
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q->answer_rcode = rcode;
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q->answer_ifindex = (scope && scope->link) ? scope->link->ifindex : 0;
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}
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dns_query_complete(q, state);
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}
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int dns_query_cname_redirect(DnsQuery *q, const char *name) {
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_cleanup_(dns_question_unrefp) DnsQuestion *nq = NULL;
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int r;
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assert(q);
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if (q->n_cname_redirects > CNAME_MAX)
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return -ELOOP;
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r = dns_question_cname_redirect(q->question, name, &nq);
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if (r < 0)
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return r;
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dns_question_unref(q->question);
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q->question = nq;
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nq = NULL;
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q->n_cname_redirects++;
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dns_query_stop(q);
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q->state = DNS_TRANSACTION_NULL;
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return 0;
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}
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