2014-07-31 17:46:40 +02:00
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/*-*- 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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2015-10-27 03:01:06 +01:00
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#include "alloc-util.h"
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2015-08-21 22:55:01 +02:00
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#include "dns-domain.h"
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2015-10-25 13:14:12 +01:00
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#include "fd-util.h"
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#include "random-util.h"
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#include "resolved-dns-transaction.h"
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#include "resolved-llmnr.h"
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2015-10-26 22:31:05 +01:00
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#include "string-table.h"
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2014-07-31 17:46:40 +02:00
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DnsTransaction* dns_transaction_free(DnsTransaction *t) {
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2015-11-25 20:47:27 +01:00
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DnsQueryCandidate *c;
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2014-07-31 17:46:40 +02:00
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DnsZoneItem *i;
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if (!t)
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return NULL;
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sd_event_source_unref(t->timeout_event_source);
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dns_packet_unref(t->sent);
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dns_packet_unref(t->received);
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2015-11-26 22:51:35 +01:00
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dns_answer_unref(t->answer);
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2014-07-31 17:46:40 +02:00
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2015-08-25 18:51:21 +02:00
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sd_event_source_unref(t->dns_udp_event_source);
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safe_close(t->dns_udp_fd);
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2015-07-09 14:19:55 +02:00
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2015-06-24 18:54:12 +02:00
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dns_server_unref(t->server);
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2014-07-31 17:46:40 +02:00
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dns_stream_free(t->stream);
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if (t->scope) {
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2015-11-26 23:51:59 +01:00
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hashmap_remove_value(t->scope->transactions_by_key, t->key, t);
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LIST_REMOVE(transactions_by_scope, t->scope->transactions, t);
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2014-07-31 17:46:40 +02:00
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if (t->id != 0)
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hashmap_remove(t->scope->manager->dns_transactions, UINT_TO_PTR(t->id));
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}
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2015-08-24 23:15:51 +02:00
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dns_resource_key_unref(t->key);
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2015-11-25 20:47:27 +01:00
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while ((c = set_steal_first(t->query_candidates)))
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set_remove(c->transactions, t);
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set_free(t->query_candidates);
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2014-07-31 17:46:40 +02:00
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while ((i = set_steal_first(t->zone_items)))
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i->probe_transaction = NULL;
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set_free(t->zone_items);
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free(t);
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return NULL;
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}
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DEFINE_TRIVIAL_CLEANUP_FUNC(DnsTransaction*, dns_transaction_free);
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void dns_transaction_gc(DnsTransaction *t) {
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assert(t);
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if (t->block_gc > 0)
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return;
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2015-11-25 20:47:27 +01:00
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if (set_isempty(t->query_candidates) && set_isempty(t->zone_items))
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2014-07-31 17:46:40 +02:00
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dns_transaction_free(t);
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}
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2015-08-21 22:55:01 +02:00
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int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsResourceKey *key) {
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2014-07-31 17:46:40 +02:00
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_cleanup_(dns_transaction_freep) DnsTransaction *t = NULL;
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int r;
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assert(ret);
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assert(s);
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2015-08-21 22:55:01 +02:00
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assert(key);
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2014-07-31 17:46:40 +02:00
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2014-08-13 01:00:18 +02:00
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r = hashmap_ensure_allocated(&s->manager->dns_transactions, NULL);
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2014-07-31 17:46:40 +02:00
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if (r < 0)
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return r;
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2015-11-26 23:51:59 +01:00
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r = hashmap_ensure_allocated(&s->transactions_by_key, &dns_resource_key_hash_ops);
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2015-08-24 23:15:51 +02:00
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if (r < 0)
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return r;
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2014-07-31 17:46:40 +02:00
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t = new0(DnsTransaction, 1);
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if (!t)
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return -ENOMEM;
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2015-08-25 18:51:21 +02:00
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t->dns_udp_fd = -1;
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2015-11-26 23:33:55 +01:00
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t->answer_source = _DNS_TRANSACTION_SOURCE_INVALID;
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2015-08-21 22:55:01 +02:00
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t->key = dns_resource_key_ref(key);
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2014-07-31 17:46:40 +02:00
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2015-08-24 23:15:51 +02:00
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/* Find a fresh, unused transaction id */
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2014-07-31 17:46:40 +02:00
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do
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random_bytes(&t->id, sizeof(t->id));
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while (t->id == 0 ||
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hashmap_get(s->manager->dns_transactions, UINT_TO_PTR(t->id)));
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r = hashmap_put(s->manager->dns_transactions, UINT_TO_PTR(t->id), t);
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if (r < 0) {
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t->id = 0;
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return r;
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}
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2015-11-26 23:51:59 +01:00
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r = hashmap_replace(s->transactions_by_key, t->key, t);
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2015-08-24 23:15:51 +02:00
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if (r < 0) {
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hashmap_remove(s->manager->dns_transactions, UINT_TO_PTR(t->id));
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return r;
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}
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2015-11-26 23:51:59 +01:00
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LIST_PREPEND(transactions_by_scope, s->transactions, t);
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2014-07-31 17:46:40 +02:00
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t->scope = s;
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if (ret)
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*ret = t;
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t = NULL;
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return 0;
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}
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static void dns_transaction_stop(DnsTransaction *t) {
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assert(t);
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t->timeout_event_source = sd_event_source_unref(t->timeout_event_source);
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t->stream = dns_stream_free(t->stream);
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2015-11-26 22:51:35 +01:00
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/* Note that we do not drop the UDP socket here, as we want to
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* reuse it to repeat the interaction. */
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2014-07-31 17:46:40 +02:00
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}
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static void dns_transaction_tentative(DnsTransaction *t, DnsPacket *p) {
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2014-08-06 17:21:00 +02:00
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_cleanup_free_ char *pretty = NULL;
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2014-07-31 17:46:40 +02:00
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DnsZoneItem *z;
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assert(t);
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assert(p);
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if (manager_our_packet(t->scope->manager, p) != 0)
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return;
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2014-08-06 17:21:00 +02:00
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in_addr_to_string(p->family, &p->sender, &pretty);
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log_debug("Transaction on scope %s on %s/%s got tentative packet from %s",
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2014-07-31 17:46:40 +02:00
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dns_protocol_to_string(t->scope->protocol),
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t->scope->link ? t->scope->link->name : "*",
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2014-08-06 17:21:00 +02:00
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t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family),
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pretty);
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2014-07-31 17:46:40 +02:00
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2014-08-06 16:15:35 +02:00
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/* RFC 4795, Section 4.1 says that the peer with the
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* lexicographically smaller IP address loses */
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2014-08-10 22:48:16 +02:00
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if (memcmp(&p->sender, &p->destination, FAMILY_ADDRESS_SIZE(p->family)) >= 0) {
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log_debug("Peer has lexicographically larger IP address and thus lost in the conflict.");
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2014-08-06 16:15:35 +02:00
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return;
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}
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2014-08-10 22:48:16 +02:00
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log_debug("We have the lexicographically larger IP address and thus lost in the conflict.");
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2014-08-06 16:15:35 +02:00
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2014-07-31 17:46:40 +02:00
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t->block_gc++;
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2014-08-10 22:28:12 +02:00
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while ((z = set_first(t->zone_items))) {
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/* First, make sure the zone item drops the reference
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* to us */
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dns_zone_item_probe_stop(z);
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/* Secondly, report this as conflict, so that we might
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* look for a different hostname */
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2014-07-31 17:46:40 +02:00
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dns_zone_item_conflict(z);
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2014-08-10 22:28:12 +02:00
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}
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2014-07-31 17:46:40 +02:00
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t->block_gc--;
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dns_transaction_gc(t);
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}
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void dns_transaction_complete(DnsTransaction *t, DnsTransactionState state) {
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2015-11-25 20:47:27 +01:00
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DnsQueryCandidate *c;
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2014-07-31 17:46:40 +02:00
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DnsZoneItem *z;
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Iterator i;
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assert(t);
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assert(!IN_SET(state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING));
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2014-08-05 17:02:23 +02:00
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2014-07-31 17:46:40 +02:00
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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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2015-11-26 23:33:55 +01:00
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log_debug("Transaction on scope %s on %s/%s now complete with <%s> from %s",
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2014-07-31 17:46:40 +02:00
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dns_protocol_to_string(t->scope->protocol),
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t->scope->link ? t->scope->link->name : "*",
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t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family),
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2015-11-26 23:33:55 +01:00
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dns_transaction_state_to_string(state),
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t->answer_source < 0 ? "none" : dns_transaction_source_to_string(t->answer_source));
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2014-07-31 17:46:40 +02:00
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t->state = state;
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dns_transaction_stop(t);
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/* Notify all queries that are interested, but make sure the
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* transaction isn't freed while we are still looking at it */
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t->block_gc++;
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2015-11-25 20:47:27 +01:00
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SET_FOREACH(c, t->query_candidates, i)
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dns_query_candidate_ready(c);
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2014-07-31 17:46:40 +02:00
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SET_FOREACH(z, t->zone_items, i)
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dns_zone_item_ready(z);
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t->block_gc--;
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dns_transaction_gc(t);
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}
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static int on_stream_complete(DnsStream *s, int error) {
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_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
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DnsTransaction *t;
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assert(s);
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assert(s->transaction);
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/* Copy the data we care about out of the stream before we
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* destroy it. */
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t = s->transaction;
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p = dns_packet_ref(s->read_packet);
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t->stream = dns_stream_free(t->stream);
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if (error != 0) {
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dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
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return 0;
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}
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2014-08-06 16:15:35 +02:00
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if (dns_packet_validate_reply(p) <= 0) {
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log_debug("Invalid LLMNR TCP packet.");
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dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
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return 0;
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}
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dns_scope_check_conflicts(t->scope, p);
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2014-07-31 17:46:40 +02:00
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t->block_gc++;
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dns_transaction_process_reply(t, p);
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t->block_gc--;
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/* If the response wasn't useful, then complete the transition now */
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if (t->state == DNS_TRANSACTION_PENDING)
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dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
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return 0;
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}
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static int dns_transaction_open_tcp(DnsTransaction *t) {
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2015-07-25 05:12:49 +02:00
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DnsServer *server = NULL;
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2014-07-31 17:46:40 +02:00
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_cleanup_close_ int fd = -1;
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int r;
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assert(t);
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if (t->stream)
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return 0;
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2015-07-11 22:21:26 +02:00
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switch (t->scope->protocol) {
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case DNS_PROTOCOL_DNS:
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2015-06-24 18:54:12 +02:00
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fd = dns_scope_tcp_socket(t->scope, AF_UNSPEC, NULL, 53, &server);
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2015-07-11 22:21:26 +02:00
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break;
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2014-07-31 17:46:40 +02:00
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2015-07-11 22:21:26 +02:00
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case DNS_PROTOCOL_LLMNR:
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2015-08-21 12:26:34 +02:00
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/* When we already received a reply to this (but it was truncated), send to its sender address */
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2014-07-31 17:46:40 +02:00
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if (t->received)
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2015-06-24 18:54:12 +02:00
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fd = dns_scope_tcp_socket(t->scope, t->received->family, &t->received->sender, t->received->sender_port, NULL);
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2014-07-31 17:46:40 +02:00
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else {
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union in_addr_union address;
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2015-03-27 12:02:49 +01:00
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int family = AF_UNSPEC;
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2014-07-31 17:46:40 +02:00
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/* Otherwise, try to talk to the owner of a
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* the IP address, in case this is a reverse
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* PTR lookup */
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2015-08-21 22:55:01 +02:00
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r = dns_name_address(DNS_RESOURCE_KEY_NAME(t->key), &family, &address);
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2014-07-31 17:46:40 +02:00
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if (r < 0)
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return r;
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if (r == 0)
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return -EINVAL;
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2015-08-21 22:51:05 +02:00
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if (family != t->scope->family)
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2015-08-24 23:47:28 +02:00
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return -ESRCH;
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2014-07-31 17:46:40 +02:00
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2015-06-24 18:54:12 +02:00
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fd = dns_scope_tcp_socket(t->scope, family, &address, LLMNR_PORT, NULL);
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2014-07-31 17:46:40 +02:00
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}
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2015-07-11 22:21:26 +02:00
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break;
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default:
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2014-07-31 17:46:40 +02:00
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return -EAFNOSUPPORT;
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2015-07-11 22:21:26 +02:00
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}
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2014-07-31 17:46:40 +02:00
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if (fd < 0)
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return fd;
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|
|
r = dns_stream_new(t->scope->manager, &t->stream, t->scope->protocol, fd);
|
|
|
|
if (r < 0)
|
|
|
|
return r;
|
|
|
|
|
|
|
|
fd = -1;
|
|
|
|
|
|
|
|
r = dns_stream_write_packet(t->stream, t->sent);
|
|
|
|
if (r < 0) {
|
|
|
|
t->stream = dns_stream_free(t->stream);
|
|
|
|
return r;
|
|
|
|
}
|
|
|
|
|
2015-06-24 18:54:12 +02:00
|
|
|
dns_server_unref(t->server);
|
|
|
|
t->server = dns_server_ref(server);
|
2014-07-31 17:46:40 +02:00
|
|
|
t->received = dns_packet_unref(t->received);
|
2015-11-26 22:51:35 +01:00
|
|
|
t->answer = dns_answer_unref(t->answer);
|
|
|
|
t->answer_rcode = 0;
|
2014-07-31 17:46:40 +02:00
|
|
|
t->stream->complete = on_stream_complete;
|
|
|
|
t->stream->transaction = t;
|
|
|
|
|
|
|
|
/* The interface index is difficult to determine if we are
|
|
|
|
* connecting to the local host, hence fill this in right away
|
|
|
|
* instead of determining it from the socket */
|
|
|
|
if (t->scope->link)
|
|
|
|
t->stream->ifindex = t->scope->link->ifindex;
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2015-07-25 04:45:26 +02:00
|
|
|
static void dns_transaction_next_dns_server(DnsTransaction *t) {
|
|
|
|
assert(t);
|
|
|
|
|
|
|
|
t->server = dns_server_unref(t->server);
|
2015-08-25 18:51:21 +02:00
|
|
|
t->dns_udp_event_source = sd_event_source_unref(t->dns_udp_event_source);
|
|
|
|
t->dns_udp_fd = safe_close(t->dns_udp_fd);
|
2015-07-25 04:45:26 +02:00
|
|
|
|
|
|
|
dns_scope_next_dns_server(t->scope);
|
|
|
|
}
|
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
|
2015-07-28 02:32:24 +02:00
|
|
|
usec_t ts;
|
2014-07-31 17:46:40 +02:00
|
|
|
int r;
|
|
|
|
|
|
|
|
assert(t);
|
|
|
|
assert(p);
|
|
|
|
assert(t->state == DNS_TRANSACTION_PENDING);
|
2015-07-28 02:32:24 +02:00
|
|
|
assert(t->scope);
|
|
|
|
assert(t->scope->manager);
|
2014-07-31 17:46:40 +02:00
|
|
|
|
|
|
|
/* Note that this call might invalidate the query. Callers
|
|
|
|
* should hence not attempt to access the query or transaction
|
|
|
|
* after calling this function. */
|
|
|
|
|
2015-07-11 22:21:26 +02:00
|
|
|
switch (t->scope->protocol) {
|
|
|
|
case DNS_PROTOCOL_LLMNR:
|
2014-07-31 17:46:40 +02:00
|
|
|
assert(t->scope->link);
|
|
|
|
|
|
|
|
/* For LLMNR we will not accept any packets from other
|
|
|
|
* interfaces */
|
|
|
|
|
|
|
|
if (p->ifindex != t->scope->link->ifindex)
|
|
|
|
return;
|
|
|
|
|
|
|
|
if (p->family != t->scope->family)
|
|
|
|
return;
|
|
|
|
|
|
|
|
/* Tentative packets are not full responses but still
|
|
|
|
* useful for identifying uniqueness conflicts during
|
|
|
|
* probing. */
|
2015-07-11 02:35:16 +02:00
|
|
|
if (DNS_PACKET_LLMNR_T(p)) {
|
2014-07-31 17:46:40 +02:00
|
|
|
dns_transaction_tentative(t, p);
|
|
|
|
return;
|
|
|
|
}
|
2015-07-11 22:21:26 +02:00
|
|
|
|
|
|
|
break;
|
|
|
|
|
|
|
|
case DNS_PROTOCOL_DNS:
|
|
|
|
break;
|
|
|
|
|
|
|
|
default:
|
2015-08-04 10:37:59 +02:00
|
|
|
assert_not_reached("Invalid DNS protocol.");
|
2014-07-31 17:46:40 +02:00
|
|
|
}
|
|
|
|
|
|
|
|
if (t->received != p) {
|
|
|
|
dns_packet_unref(t->received);
|
|
|
|
t->received = dns_packet_ref(p);
|
|
|
|
}
|
|
|
|
|
2015-11-26 23:33:55 +01:00
|
|
|
t->answer_source = DNS_TRANSACTION_NETWORK;
|
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
if (p->ipproto == IPPROTO_TCP) {
|
|
|
|
if (DNS_PACKET_TC(p)) {
|
|
|
|
/* Truncated via TCP? Somebody must be fucking with us */
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (DNS_PACKET_ID(p) != t->id) {
|
|
|
|
/* Not the reply to our query? Somebody must be fucking with us */
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
sd-event: make sure sd_event_now() cannot fail
Previously, if the event loop never ran before sd_event_now() would
fail. With this change it will instead fall back to invoking now(). This
way, the function cannot fail anymore, except for programming error when
invoking it with wrong parameters.
This takes into account the fact that many callers did not handle the
error condition correctly, and if the callers did, then they kept simply
invoking now() as fall back on their own. Hence let's shorten the code
using this call, and make things more robust, and let's just fall back
to now() internally.
Whether now() is used or the cache timestamp may still be detected via
the return value of sd_event_now(). If > 0 is returned, then the fall
back to now() was used, if == 0 is returned, then the cached value was
returned.
This patch also simplifies many of the invocations of sd_event_now():
the manual fall back to now() can be removed. Also, in cases where the
call is invoked withing void functions we can now protect the invocation
via assert_se(), acknowledging the fact that the call cannot fail
anymore except for programming errors with the parameters.
This change is inspired by #841.
2015-08-03 17:29:09 +02:00
|
|
|
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
|
2015-07-28 02:32:24 +02:00
|
|
|
|
|
|
|
switch (t->scope->protocol) {
|
|
|
|
case DNS_PROTOCOL_DNS:
|
|
|
|
assert(t->server);
|
|
|
|
|
2015-07-16 14:39:55 +02:00
|
|
|
if (IN_SET(DNS_PACKET_RCODE(p), DNS_RCODE_FORMERR, DNS_RCODE_SERVFAIL, DNS_RCODE_NOTIMP)) {
|
|
|
|
|
|
|
|
/* request failed, immediately try again with reduced features */
|
|
|
|
log_debug("Server returned error: %s", dns_rcode_to_string(DNS_PACKET_RCODE(p)));
|
|
|
|
|
|
|
|
dns_server_packet_failed(t->server, t->current_features);
|
|
|
|
|
|
|
|
r = dns_transaction_go(t);
|
|
|
|
if (r < 0) {
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
|
|
|
return;
|
|
|
|
} else
|
resolved: announce support for large UDP packets
This is often needed for proper DNSSEC support, and even to handle AAAA records
without falling back to TCP.
If the path between the client and server is fully compliant, this should always
work, however, that is not the case, and overlarge packets will get mysteriously
lost in some cases.
For that reason, we use a similar fallback mechanism as we do for palin EDNS0,
EDNS0+DO, etc.:
The large UDP size feature is different from the other supported feature, as we
cannot simply verify that it works based on receiving a reply (as the server
will usually send us much smaller packets than what we claim to support, so
simply receiving a reply does not mean much).
For that reason, we keep track of the largest UDP packet we ever received, as this
is the smallest known good size (defaulting to the standard 512 bytes). If
announcing the default large size of 4096 fails (in the same way as the other
features), we fall back to the known good size. The same logic of retrying after a
grace-period applies.
2015-07-06 16:48:24 +02:00
|
|
|
dns_server_packet_received(t->server, t->current_features, ts - t->start_usec, p->size);
|
2015-07-28 02:32:24 +02:00
|
|
|
|
|
|
|
break;
|
|
|
|
case DNS_PROTOCOL_LLMNR:
|
|
|
|
case DNS_PROTOCOL_MDNS:
|
|
|
|
dns_scope_packet_received(t->scope, ts - t->start_usec);
|
|
|
|
|
|
|
|
break;
|
|
|
|
default:
|
2015-08-04 10:37:59 +02:00
|
|
|
break;
|
2015-07-28 02:32:24 +02:00
|
|
|
}
|
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
if (DNS_PACKET_TC(p)) {
|
|
|
|
/* Response was truncated, let's try again with good old TCP */
|
|
|
|
r = dns_transaction_open_tcp(t);
|
|
|
|
if (r == -ESRCH) {
|
|
|
|
/* No servers found? Damn! */
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
if (r < 0) {
|
|
|
|
/* On LLMNR, if we cannot connect to the host,
|
|
|
|
* we immediately give up */
|
|
|
|
if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
|
|
|
/* On DNS, couldn't send? Try immediately again, with a new server */
|
2015-07-25 04:45:26 +02:00
|
|
|
dns_transaction_next_dns_server(t);
|
2014-07-31 17:46:40 +02:00
|
|
|
|
|
|
|
r = dns_transaction_go(t);
|
|
|
|
if (r < 0) {
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Parse and update the cache */
|
|
|
|
r = dns_packet_extract(p);
|
|
|
|
if (r < 0) {
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
2015-07-09 02:58:15 +02:00
|
|
|
/* Only consider responses with equivalent query section to the request */
|
2015-08-21 22:55:01 +02:00
|
|
|
if (p->question->n_keys != 1 || dns_resource_key_equal(p->question->keys[0], t->key) <= 0) {
|
2015-07-09 02:58:15 +02:00
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
|
2015-07-19 21:42:52 +02:00
|
|
|
return;
|
|
|
|
}
|
2015-07-09 02:58:15 +02:00
|
|
|
|
2015-12-03 21:04:52 +01:00
|
|
|
/* Install the answer as answer to the transaction */
|
|
|
|
dns_answer_unref(t->answer);
|
|
|
|
t->answer = dns_answer_ref(p->answer);
|
|
|
|
t->answer_rcode = DNS_PACKET_RCODE(p);
|
|
|
|
t->answer_authenticated = t->scope->dnssec_mode == DNSSEC_TRUST && DNS_PACKET_AD(p);
|
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
/* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */
|
2015-11-27 00:41:32 +01:00
|
|
|
if (DNS_PACKET_SHALL_CACHE(p))
|
2015-12-03 21:04:52 +01:00
|
|
|
dns_cache_put(&t->scope->cache,
|
|
|
|
t->key,
|
|
|
|
DNS_PACKET_RCODE(p),
|
|
|
|
p->answer,
|
|
|
|
DNS_PACKET_ANCOUNT(p),
|
|
|
|
t->answer_authenticated,
|
|
|
|
0,
|
|
|
|
p->family,
|
|
|
|
&p->sender);
|
2014-07-31 17:46:40 +02:00
|
|
|
|
|
|
|
if (DNS_PACKET_RCODE(p) == DNS_RCODE_SUCCESS)
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
|
|
|
|
else
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
|
|
|
|
}
|
|
|
|
|
2015-07-27 20:18:43 +02:00
|
|
|
static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
|
|
|
|
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
|
|
|
|
DnsTransaction *t = userdata;
|
|
|
|
int r;
|
|
|
|
|
|
|
|
assert(t);
|
|
|
|
assert(t->scope);
|
|
|
|
|
|
|
|
r = manager_recv(t->scope->manager, fd, DNS_PROTOCOL_DNS, &p);
|
|
|
|
if (r <= 0)
|
|
|
|
return r;
|
|
|
|
|
|
|
|
if (dns_packet_validate_reply(p) > 0 &&
|
2015-07-28 02:32:24 +02:00
|
|
|
DNS_PACKET_ID(p) == t->id)
|
2015-07-27 20:18:43 +02:00
|
|
|
dns_transaction_process_reply(t, p);
|
2015-07-28 02:32:24 +02:00
|
|
|
else
|
2015-07-27 20:18:43 +02:00
|
|
|
log_debug("Invalid DNS packet.");
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2015-07-15 19:22:29 +02:00
|
|
|
static int dns_transaction_emit(DnsTransaction *t) {
|
2015-07-27 20:18:43 +02:00
|
|
|
int r;
|
|
|
|
|
|
|
|
assert(t);
|
|
|
|
|
2015-07-15 19:22:29 +02:00
|
|
|
if (t->scope->protocol == DNS_PROTOCOL_DNS && !t->server) {
|
|
|
|
DnsServer *server = NULL;
|
|
|
|
_cleanup_close_ int fd = -1;
|
2015-07-27 20:18:43 +02:00
|
|
|
|
2015-07-15 19:22:29 +02:00
|
|
|
fd = dns_scope_udp_dns_socket(t->scope, &server);
|
|
|
|
if (fd < 0)
|
|
|
|
return fd;
|
2015-07-27 20:18:43 +02:00
|
|
|
|
2015-08-25 18:51:21 +02:00
|
|
|
r = sd_event_add_io(t->scope->manager->event, &t->dns_udp_event_source, fd, EPOLLIN, on_dns_packet, t);
|
2015-07-15 19:22:29 +02:00
|
|
|
if (r < 0)
|
|
|
|
return r;
|
2015-07-27 20:18:43 +02:00
|
|
|
|
2015-08-25 18:51:21 +02:00
|
|
|
t->dns_udp_fd = fd;
|
2015-07-15 19:22:29 +02:00
|
|
|
fd = -1;
|
|
|
|
t->server = dns_server_ref(server);
|
|
|
|
}
|
2015-07-27 20:18:43 +02:00
|
|
|
|
2015-06-23 23:06:09 +02:00
|
|
|
r = dns_scope_emit(t->scope, t->dns_udp_fd, t->server, t->sent);
|
2015-07-15 19:22:29 +02:00
|
|
|
if (r < 0)
|
|
|
|
return r;
|
2015-07-27 20:18:43 +02:00
|
|
|
|
resolved: fallback to TCP if UDP fails
This is inspired by the logic in BIND [0], follow-up patches
will implement the reset of that scheme.
If we get a server error back, or if after several attempts we don't
get a reply at all, we switch from UDP to TCP for the given
server for the current and all subsequent requests. However, if
we ever successfully received a reply over UDP, we never fall
back to TCP, and once a grace-period has passed, we try to upgrade
again to using UDP. The grace-period starts off at five minutes
after the current feature level was verified and then grows
exponentially to six hours. This is to mitigate problems due
to temporary lack of network connectivity, but at the same time
avoid flooding the network with retries when the feature attempted
feature level genuinely does not work.
Note that UDP is likely much more commonly supported than TCP,
but depending on the path between the client and the server, we
may have more luck with TCP in case something is wrong. We really
do prefer UDP though, as that is much more lightweight, that is
why TCP is only the last resort.
[0]: <https://kb.isc.org/article/AA-01219/0/Refinements-to-EDNS-fallback-behavior-can-cause-different-outcomes-in-Recursive-Servers.html>
2015-07-06 08:15:25 +02:00
|
|
|
if (t->server)
|
|
|
|
t->current_features = t->server->possible_features;
|
|
|
|
|
2015-07-15 19:22:29 +02:00
|
|
|
return 0;
|
2015-07-27 20:18:43 +02:00
|
|
|
}
|
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdata) {
|
|
|
|
DnsTransaction *t = userdata;
|
|
|
|
int r;
|
|
|
|
|
|
|
|
assert(s);
|
|
|
|
assert(t);
|
|
|
|
|
resolved: fallback to TCP if UDP fails
This is inspired by the logic in BIND [0], follow-up patches
will implement the reset of that scheme.
If we get a server error back, or if after several attempts we don't
get a reply at all, we switch from UDP to TCP for the given
server for the current and all subsequent requests. However, if
we ever successfully received a reply over UDP, we never fall
back to TCP, and once a grace-period has passed, we try to upgrade
again to using UDP. The grace-period starts off at five minutes
after the current feature level was verified and then grows
exponentially to six hours. This is to mitigate problems due
to temporary lack of network connectivity, but at the same time
avoid flooding the network with retries when the feature attempted
feature level genuinely does not work.
Note that UDP is likely much more commonly supported than TCP,
but depending on the path between the client and the server, we
may have more luck with TCP in case something is wrong. We really
do prefer UDP though, as that is much more lightweight, that is
why TCP is only the last resort.
[0]: <https://kb.isc.org/article/AA-01219/0/Refinements-to-EDNS-fallback-behavior-can-cause-different-outcomes-in-Recursive-Servers.html>
2015-07-06 08:15:25 +02:00
|
|
|
/* Timeout reached? Increase the timeout for the server used */
|
|
|
|
switch (t->scope->protocol) {
|
|
|
|
case DNS_PROTOCOL_DNS:
|
|
|
|
assert(t->server);
|
2014-07-31 17:46:40 +02:00
|
|
|
|
resolved: fallback to TCP if UDP fails
This is inspired by the logic in BIND [0], follow-up patches
will implement the reset of that scheme.
If we get a server error back, or if after several attempts we don't
get a reply at all, we switch from UDP to TCP for the given
server for the current and all subsequent requests. However, if
we ever successfully received a reply over UDP, we never fall
back to TCP, and once a grace-period has passed, we try to upgrade
again to using UDP. The grace-period starts off at five minutes
after the current feature level was verified and then grows
exponentially to six hours. This is to mitigate problems due
to temporary lack of network connectivity, but at the same time
avoid flooding the network with retries when the feature attempted
feature level genuinely does not work.
Note that UDP is likely much more commonly supported than TCP,
but depending on the path between the client and the server, we
may have more luck with TCP in case something is wrong. We really
do prefer UDP though, as that is much more lightweight, that is
why TCP is only the last resort.
[0]: <https://kb.isc.org/article/AA-01219/0/Refinements-to-EDNS-fallback-behavior-can-cause-different-outcomes-in-Recursive-Servers.html>
2015-07-06 08:15:25 +02:00
|
|
|
dns_server_packet_lost(t->server, t->current_features, usec - t->start_usec);
|
|
|
|
|
|
|
|
break;
|
|
|
|
case DNS_PROTOCOL_LLMNR:
|
|
|
|
case DNS_PROTOCOL_MDNS:
|
2015-07-28 02:32:24 +02:00
|
|
|
dns_scope_packet_lost(t->scope, usec - t->start_usec);
|
|
|
|
|
resolved: fallback to TCP if UDP fails
This is inspired by the logic in BIND [0], follow-up patches
will implement the reset of that scheme.
If we get a server error back, or if after several attempts we don't
get a reply at all, we switch from UDP to TCP for the given
server for the current and all subsequent requests. However, if
we ever successfully received a reply over UDP, we never fall
back to TCP, and once a grace-period has passed, we try to upgrade
again to using UDP. The grace-period starts off at five minutes
after the current feature level was verified and then grows
exponentially to six hours. This is to mitigate problems due
to temporary lack of network connectivity, but at the same time
avoid flooding the network with retries when the feature attempted
feature level genuinely does not work.
Note that UDP is likely much more commonly supported than TCP,
but depending on the path between the client and the server, we
may have more luck with TCP in case something is wrong. We really
do prefer UDP though, as that is much more lightweight, that is
why TCP is only the last resort.
[0]: <https://kb.isc.org/article/AA-01219/0/Refinements-to-EDNS-fallback-behavior-can-cause-different-outcomes-in-Recursive-Servers.html>
2015-07-06 08:15:25 +02:00
|
|
|
break;
|
|
|
|
default:
|
|
|
|
assert_not_reached("Invalid DNS protocol.");
|
|
|
|
}
|
|
|
|
|
|
|
|
/* ...and try again with a new server */
|
|
|
|
dns_transaction_next_dns_server(t);
|
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
r = dns_transaction_go(t);
|
|
|
|
if (r < 0)
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
static int dns_transaction_make_packet(DnsTransaction *t) {
|
|
|
|
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
|
|
|
|
int r;
|
|
|
|
|
|
|
|
assert(t);
|
|
|
|
|
|
|
|
if (t->sent)
|
|
|
|
return 0;
|
|
|
|
|
2015-12-03 19:51:04 +01:00
|
|
|
r = dns_packet_new_query(&p, t->scope->protocol, 0, t->scope->dnssec_mode == DNSSEC_YES);
|
2014-07-31 17:46:40 +02:00
|
|
|
if (r < 0)
|
|
|
|
return r;
|
|
|
|
|
2015-08-21 22:55:01 +02:00
|
|
|
r = dns_scope_good_key(t->scope, t->key);
|
|
|
|
if (r < 0)
|
|
|
|
return r;
|
|
|
|
if (r == 0)
|
2014-07-31 17:46:40 +02:00
|
|
|
return -EDOM;
|
|
|
|
|
2015-08-21 22:55:01 +02:00
|
|
|
r = dns_packet_append_key(p, t->key, NULL);
|
|
|
|
if (r < 0)
|
|
|
|
return r;
|
|
|
|
|
|
|
|
DNS_PACKET_HEADER(p)->qdcount = htobe16(1);
|
2014-07-31 17:46:40 +02:00
|
|
|
DNS_PACKET_HEADER(p)->id = t->id;
|
|
|
|
|
|
|
|
t->sent = p;
|
|
|
|
p = NULL;
|
|
|
|
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2015-07-28 02:32:24 +02:00
|
|
|
static usec_t transaction_get_resend_timeout(DnsTransaction *t) {
|
|
|
|
assert(t);
|
|
|
|
assert(t->scope);
|
|
|
|
|
|
|
|
switch (t->scope->protocol) {
|
|
|
|
case DNS_PROTOCOL_DNS:
|
|
|
|
assert(t->server);
|
|
|
|
|
|
|
|
return t->server->resend_timeout;
|
|
|
|
case DNS_PROTOCOL_LLMNR:
|
|
|
|
case DNS_PROTOCOL_MDNS:
|
|
|
|
return t->scope->resend_timeout;
|
|
|
|
default:
|
|
|
|
assert_not_reached("Invalid DNS protocol.");
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
int dns_transaction_go(DnsTransaction *t) {
|
|
|
|
bool had_stream;
|
2015-07-28 02:32:24 +02:00
|
|
|
usec_t ts;
|
2014-07-31 17:46:40 +02:00
|
|
|
int r;
|
|
|
|
|
|
|
|
assert(t);
|
|
|
|
|
|
|
|
had_stream = !!t->stream;
|
|
|
|
|
|
|
|
dns_transaction_stop(t);
|
|
|
|
|
2014-08-05 17:02:23 +02:00
|
|
|
log_debug("Excercising transaction on scope %s on %s/%s",
|
2014-07-31 17:46:40 +02:00
|
|
|
dns_protocol_to_string(t->scope->protocol),
|
|
|
|
t->scope->link ? t->scope->link->name : "*",
|
|
|
|
t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family));
|
|
|
|
|
|
|
|
if (t->n_attempts >= TRANSACTION_ATTEMPTS_MAX(t->scope->protocol)) {
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
|
|
|
if (t->scope->protocol == DNS_PROTOCOL_LLMNR && had_stream) {
|
|
|
|
/* If we already tried via a stream, then we don't
|
|
|
|
* retry on LLMNR. See RFC 4795, Section 2.7. */
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
sd-event: make sure sd_event_now() cannot fail
Previously, if the event loop never ran before sd_event_now() would
fail. With this change it will instead fall back to invoking now(). This
way, the function cannot fail anymore, except for programming error when
invoking it with wrong parameters.
This takes into account the fact that many callers did not handle the
error condition correctly, and if the callers did, then they kept simply
invoking now() as fall back on their own. Hence let's shorten the code
using this call, and make things more robust, and let's just fall back
to now() internally.
Whether now() is used or the cache timestamp may still be detected via
the return value of sd_event_now(). If > 0 is returned, then the fall
back to now() was used, if == 0 is returned, then the cached value was
returned.
This patch also simplifies many of the invocations of sd_event_now():
the manual fall back to now() can be removed. Also, in cases where the
call is invoked withing void functions we can now protect the invocation
via assert_se(), acknowledging the fact that the call cannot fail
anymore except for programming errors with the parameters.
This change is inspired by #841.
2015-08-03 17:29:09 +02:00
|
|
|
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
|
2015-07-28 02:32:24 +02:00
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
t->n_attempts++;
|
2015-07-28 02:32:24 +02:00
|
|
|
t->start_usec = ts;
|
2014-07-31 17:46:40 +02:00
|
|
|
t->received = dns_packet_unref(t->received);
|
2015-11-26 22:51:35 +01:00
|
|
|
t->answer = dns_answer_unref(t->answer);
|
|
|
|
t->answer_rcode = 0;
|
2015-11-26 23:33:55 +01:00
|
|
|
t->answer_source = _DNS_TRANSACTION_SOURCE_INVALID;
|
2014-07-31 17:46:40 +02:00
|
|
|
|
2015-12-03 18:31:24 +01:00
|
|
|
/* Check the trust anchor. Do so only on classic DNS, since DNSSEC does not apply otherwise. */
|
|
|
|
if (t->scope->protocol == DNS_PROTOCOL_DNS) {
|
|
|
|
r = dns_trust_anchor_lookup(&t->scope->manager->trust_anchor, t->key, &t->answer);
|
|
|
|
if (r < 0)
|
|
|
|
return r;
|
|
|
|
if (r > 0) {
|
|
|
|
t->answer_rcode = DNS_RCODE_SUCCESS;
|
|
|
|
t->answer_source = DNS_TRANSACTION_TRUST_ANCHOR;
|
2015-12-03 21:04:52 +01:00
|
|
|
t->answer_authenticated = true;
|
2015-12-03 18:31:24 +01:00
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/* Check the zone, but only if this transaction is not used
|
2015-11-18 15:33:37 +01:00
|
|
|
* for probing or verifying a zone item. */
|
|
|
|
if (set_isempty(t->zone_items)) {
|
|
|
|
|
2015-11-26 22:51:35 +01:00
|
|
|
r = dns_zone_lookup(&t->scope->zone, t->key, &t->answer, NULL, NULL);
|
2015-11-18 15:33:37 +01:00
|
|
|
if (r < 0)
|
|
|
|
return r;
|
|
|
|
if (r > 0) {
|
2015-11-26 22:51:35 +01:00
|
|
|
t->answer_rcode = DNS_RCODE_SUCCESS;
|
2015-11-26 23:33:55 +01:00
|
|
|
t->answer_source = DNS_TRANSACTION_ZONE;
|
2015-12-03 21:04:52 +01:00
|
|
|
t->answer_authenticated = true;
|
2015-11-18 15:33:37 +01:00
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2014-08-05 01:42:15 +02:00
|
|
|
/* Check the cache, but only if this transaction is not used
|
|
|
|
* for probing or verifying a zone item. */
|
|
|
|
if (set_isempty(t->zone_items)) {
|
2014-08-01 18:09:07 +02:00
|
|
|
|
2014-08-05 01:42:15 +02:00
|
|
|
/* Before trying the cache, let's make sure we figured out a
|
|
|
|
* server to use. Should this cause a change of server this
|
|
|
|
* might flush the cache. */
|
|
|
|
dns_scope_get_dns_server(t->scope);
|
2014-08-01 18:09:07 +02:00
|
|
|
|
2014-08-05 01:42:15 +02:00
|
|
|
/* Let's then prune all outdated entries */
|
|
|
|
dns_cache_prune(&t->scope->cache);
|
|
|
|
|
2015-12-03 21:04:52 +01:00
|
|
|
r = dns_cache_lookup(&t->scope->cache, t->key, &t->answer_rcode, &t->answer, &t->answer_authenticated);
|
2014-08-05 01:42:15 +02:00
|
|
|
if (r < 0)
|
|
|
|
return r;
|
|
|
|
if (r > 0) {
|
2015-11-26 23:33:55 +01:00
|
|
|
t->answer_source = DNS_TRANSACTION_CACHE;
|
2015-11-26 22:51:35 +01:00
|
|
|
if (t->answer_rcode == DNS_RCODE_SUCCESS)
|
2014-08-05 01:42:15 +02:00
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
|
|
|
|
else
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
|
|
|
|
return 0;
|
|
|
|
}
|
2014-07-31 17:46:40 +02:00
|
|
|
}
|
|
|
|
|
2014-08-05 17:01:33 +02:00
|
|
|
if (t->scope->protocol == DNS_PROTOCOL_LLMNR && !t->initial_jitter) {
|
|
|
|
usec_t jitter;
|
|
|
|
|
|
|
|
/* RFC 4795 Section 2.7 suggests all queries should be
|
|
|
|
* delayed by a random time from 0 to JITTER_INTERVAL. */
|
|
|
|
|
|
|
|
t->initial_jitter = true;
|
|
|
|
|
|
|
|
random_bytes(&jitter, sizeof(jitter));
|
|
|
|
jitter %= LLMNR_JITTER_INTERVAL_USEC;
|
|
|
|
|
|
|
|
r = sd_event_add_time(
|
|
|
|
t->scope->manager->event,
|
|
|
|
&t->timeout_event_source,
|
|
|
|
clock_boottime_or_monotonic(),
|
2015-07-28 02:32:24 +02:00
|
|
|
ts + jitter,
|
2014-08-06 16:15:35 +02:00
|
|
|
LLMNR_JITTER_INTERVAL_USEC,
|
2014-08-05 17:01:33 +02:00
|
|
|
on_transaction_timeout, t);
|
|
|
|
if (r < 0)
|
|
|
|
return r;
|
|
|
|
|
|
|
|
t->n_attempts = 0;
|
|
|
|
t->state = DNS_TRANSACTION_PENDING;
|
|
|
|
|
|
|
|
log_debug("Delaying LLMNR transaction for " USEC_FMT "us.", jitter);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
/* Otherwise, we need to ask the network */
|
|
|
|
r = dns_transaction_make_packet(t);
|
|
|
|
if (r == -EDOM) {
|
|
|
|
/* Not the right request to make on this network?
|
|
|
|
* (i.e. an A request made on IPv6 or an AAAA request
|
|
|
|
* made on IPv4, on LLMNR or mDNS.) */
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
if (r < 0)
|
|
|
|
return r;
|
|
|
|
|
|
|
|
if (t->scope->protocol == DNS_PROTOCOL_LLMNR &&
|
2015-08-21 22:55:01 +02:00
|
|
|
(dns_name_endswith(DNS_RESOURCE_KEY_NAME(t->key), "in-addr.arpa") > 0 ||
|
|
|
|
dns_name_endswith(DNS_RESOURCE_KEY_NAME(t->key), "ip6.arpa") > 0)) {
|
2014-07-31 17:46:40 +02:00
|
|
|
|
|
|
|
/* RFC 4795, Section 2.4. says reverse lookups shall
|
|
|
|
* always be made via TCP on LLMNR */
|
|
|
|
r = dns_transaction_open_tcp(t);
|
|
|
|
} else {
|
resolved: fallback to TCP if UDP fails
This is inspired by the logic in BIND [0], follow-up patches
will implement the reset of that scheme.
If we get a server error back, or if after several attempts we don't
get a reply at all, we switch from UDP to TCP for the given
server for the current and all subsequent requests. However, if
we ever successfully received a reply over UDP, we never fall
back to TCP, and once a grace-period has passed, we try to upgrade
again to using UDP. The grace-period starts off at five minutes
after the current feature level was verified and then grows
exponentially to six hours. This is to mitigate problems due
to temporary lack of network connectivity, but at the same time
avoid flooding the network with retries when the feature attempted
feature level genuinely does not work.
Note that UDP is likely much more commonly supported than TCP,
but depending on the path between the client and the server, we
may have more luck with TCP in case something is wrong. We really
do prefer UDP though, as that is much more lightweight, that is
why TCP is only the last resort.
[0]: <https://kb.isc.org/article/AA-01219/0/Refinements-to-EDNS-fallback-behavior-can-cause-different-outcomes-in-Recursive-Servers.html>
2015-07-06 08:15:25 +02:00
|
|
|
/* Try via UDP, and if that fails due to large size or lack of
|
|
|
|
* support try via TCP */
|
2015-07-15 19:22:29 +02:00
|
|
|
r = dns_transaction_emit(t);
|
resolved: fallback to TCP if UDP fails
This is inspired by the logic in BIND [0], follow-up patches
will implement the reset of that scheme.
If we get a server error back, or if after several attempts we don't
get a reply at all, we switch from UDP to TCP for the given
server for the current and all subsequent requests. However, if
we ever successfully received a reply over UDP, we never fall
back to TCP, and once a grace-period has passed, we try to upgrade
again to using UDP. The grace-period starts off at five minutes
after the current feature level was verified and then grows
exponentially to six hours. This is to mitigate problems due
to temporary lack of network connectivity, but at the same time
avoid flooding the network with retries when the feature attempted
feature level genuinely does not work.
Note that UDP is likely much more commonly supported than TCP,
but depending on the path between the client and the server, we
may have more luck with TCP in case something is wrong. We really
do prefer UDP though, as that is much more lightweight, that is
why TCP is only the last resort.
[0]: <https://kb.isc.org/article/AA-01219/0/Refinements-to-EDNS-fallback-behavior-can-cause-different-outcomes-in-Recursive-Servers.html>
2015-07-06 08:15:25 +02:00
|
|
|
if (r == -EMSGSIZE || r == -EAGAIN)
|
2014-07-31 17:46:40 +02:00
|
|
|
r = dns_transaction_open_tcp(t);
|
|
|
|
}
|
resolved: fallback to TCP if UDP fails
This is inspired by the logic in BIND [0], follow-up patches
will implement the reset of that scheme.
If we get a server error back, or if after several attempts we don't
get a reply at all, we switch from UDP to TCP for the given
server for the current and all subsequent requests. However, if
we ever successfully received a reply over UDP, we never fall
back to TCP, and once a grace-period has passed, we try to upgrade
again to using UDP. The grace-period starts off at five minutes
after the current feature level was verified and then grows
exponentially to six hours. This is to mitigate problems due
to temporary lack of network connectivity, but at the same time
avoid flooding the network with retries when the feature attempted
feature level genuinely does not work.
Note that UDP is likely much more commonly supported than TCP,
but depending on the path between the client and the server, we
may have more luck with TCP in case something is wrong. We really
do prefer UDP though, as that is much more lightweight, that is
why TCP is only the last resort.
[0]: <https://kb.isc.org/article/AA-01219/0/Refinements-to-EDNS-fallback-behavior-can-cause-different-outcomes-in-Recursive-Servers.html>
2015-07-06 08:15:25 +02:00
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
if (r == -ESRCH) {
|
|
|
|
/* No servers to send this to? */
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
|
|
|
|
return 0;
|
2015-06-24 18:54:12 +02:00
|
|
|
} else if (r < 0) {
|
2014-08-05 04:15:45 +02:00
|
|
|
if (t->scope->protocol != DNS_PROTOCOL_DNS) {
|
|
|
|
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
|
2014-07-31 17:46:40 +02:00
|
|
|
/* Couldn't send? Try immediately again, with a new server */
|
2015-07-25 04:45:26 +02:00
|
|
|
dns_transaction_next_dns_server(t);
|
2014-07-31 17:46:40 +02:00
|
|
|
|
|
|
|
return dns_transaction_go(t);
|
|
|
|
}
|
|
|
|
|
2014-08-01 00:55:51 +02:00
|
|
|
r = sd_event_add_time(
|
|
|
|
t->scope->manager->event,
|
|
|
|
&t->timeout_event_source,
|
|
|
|
clock_boottime_or_monotonic(),
|
2015-07-28 02:32:24 +02:00
|
|
|
ts + transaction_get_resend_timeout(t), 0,
|
2014-08-01 00:55:51 +02:00
|
|
|
on_transaction_timeout, t);
|
2014-07-31 17:46:40 +02:00
|
|
|
if (r < 0)
|
|
|
|
return r;
|
|
|
|
|
|
|
|
t->state = DNS_TRANSACTION_PENDING;
|
|
|
|
return 1;
|
|
|
|
}
|
|
|
|
|
|
|
|
static const char* const dns_transaction_state_table[_DNS_TRANSACTION_STATE_MAX] = {
|
|
|
|
[DNS_TRANSACTION_NULL] = "null",
|
|
|
|
[DNS_TRANSACTION_PENDING] = "pending",
|
|
|
|
[DNS_TRANSACTION_FAILURE] = "failure",
|
|
|
|
[DNS_TRANSACTION_SUCCESS] = "success",
|
|
|
|
[DNS_TRANSACTION_NO_SERVERS] = "no-servers",
|
|
|
|
[DNS_TRANSACTION_TIMEOUT] = "timeout",
|
|
|
|
[DNS_TRANSACTION_ATTEMPTS_MAX_REACHED] = "attempts-max-reached",
|
|
|
|
[DNS_TRANSACTION_INVALID_REPLY] = "invalid-reply",
|
|
|
|
[DNS_TRANSACTION_RESOURCES] = "resources",
|
|
|
|
[DNS_TRANSACTION_ABORTED] = "aborted",
|
|
|
|
};
|
|
|
|
DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state, DnsTransactionState);
|
2015-11-26 23:33:55 +01:00
|
|
|
|
|
|
|
static const char* const dns_transaction_source_table[_DNS_TRANSACTION_SOURCE_MAX] = {
|
|
|
|
[DNS_TRANSACTION_NETWORK] = "network",
|
|
|
|
[DNS_TRANSACTION_CACHE] = "cache",
|
|
|
|
[DNS_TRANSACTION_ZONE] = "zone",
|
2015-12-03 18:31:24 +01:00
|
|
|
[DNS_TRANSACTION_TRUST_ANCHOR] = "trust-anchor",
|
2015-11-26 23:33:55 +01:00
|
|
|
};
|
|
|
|
DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source, DnsTransactionSource);
|