724 lines
24 KiB
C
724 lines
24 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-llmnr.h"
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#include "resolved-dns-transaction.h"
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#include "random-util.h"
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#include "dns-domain.h"
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DnsTransaction* dns_transaction_free(DnsTransaction *t) {
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DnsQuery *q;
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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_resource_key_unref(t->key);
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dns_packet_unref(t->sent);
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dns_packet_unref(t->received);
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dns_answer_unref(t->cached);
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sd_event_source_unref(t->dns_event_source);
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safe_close(t->dns_fd);
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dns_server_unref(t->server);
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dns_stream_free(t->stream);
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if (t->scope) {
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LIST_REMOVE(transactions_by_scope, t->scope->transactions, t);
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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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while ((q = set_steal_first(t->queries)))
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set_remove(q->transactions, t);
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set_free(t->queries);
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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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if (set_isempty(t->queries) && set_isempty(t->zone_items))
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dns_transaction_free(t);
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}
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int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsResourceKey *key) {
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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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assert(key);
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r = hashmap_ensure_allocated(&s->manager->dns_transactions, NULL);
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if (r < 0)
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return r;
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t = new0(DnsTransaction, 1);
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if (!t)
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return -ENOMEM;
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t->dns_fd = -1;
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t->key = dns_resource_key_ref(key);
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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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LIST_PREPEND(transactions_by_scope, s->transactions, t);
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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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}
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static void dns_transaction_tentative(DnsTransaction *t, DnsPacket *p) {
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_cleanup_free_ char *pretty = NULL;
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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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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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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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pretty);
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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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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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return;
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}
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log_debug("We have the lexicographically larger IP address and thus lost in the conflict.");
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t->block_gc++;
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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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dns_zone_item_conflict(z);
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}
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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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DnsQuery *q;
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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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if (!IN_SET(t->state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING))
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return;
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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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log_debug("Transaction on scope %s on %s/%s now complete with <%s>",
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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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dns_transaction_state_to_string(state));
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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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SET_FOREACH(q, t->queries, i)
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dns_query_ready(q);
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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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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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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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DnsServer *server = NULL;
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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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if (t->scope->protocol == DNS_PROTOCOL_DNS)
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fd = dns_scope_tcp_socket(t->scope, AF_UNSPEC, NULL, 53, &server);
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else if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
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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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if (t->received)
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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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else {
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union in_addr_union address;
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int family = AF_UNSPEC;
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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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r = dns_name_address(DNS_RESOURCE_KEY_NAME(t->key), &family, &address);
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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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if (family != t->scope->family)
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return -EAFNOSUPPORT;
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fd = dns_scope_tcp_socket(t->scope, family, &address, LLMNR_PORT, NULL);
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}
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} else
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return -EAFNOSUPPORT;
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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);
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if (r < 0)
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return r;
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fd = -1;
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r = dns_stream_write_packet(t->stream, t->sent);
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if (r < 0) {
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t->stream = dns_stream_free(t->stream);
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return r;
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}
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dns_server_unref(t->server);
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t->server = dns_server_ref(server);
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t->received = dns_packet_unref(t->received);
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t->stream->complete = on_stream_complete;
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t->stream->transaction = t;
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/* The interface index is difficult to determine if we are
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* connecting to the local host, hence fill this in right away
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* instead of determining it from the socket */
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if (t->scope->link)
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t->stream->ifindex = t->scope->link->ifindex;
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return 0;
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}
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static void dns_transaction_next_dns_server(DnsTransaction *t) {
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assert(t);
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t->server = dns_server_unref(t->server);
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t->dns_event_source = sd_event_source_unref(t->dns_event_source);
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t->dns_fd = safe_close(t->dns_fd);
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dns_scope_next_dns_server(t->scope);
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}
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void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
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usec_t ts;
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int r;
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assert(t);
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assert(p);
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assert(t->state == DNS_TRANSACTION_PENDING);
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assert(t->scope);
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assert(t->scope->manager);
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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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if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
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assert(t->scope->link);
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/* For LLMNR we will not accept any packets from other
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* interfaces */
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if (p->ifindex != t->scope->link->ifindex)
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return;
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if (p->family != t->scope->family)
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return;
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/* Tentative packets are not full responses but still
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* useful for identifying uniqueness conflicts during
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* probing. */
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if (DNS_PACKET_LLMNR_T(p)) {
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dns_transaction_tentative(t, p);
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return;
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}
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}
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if (t->received != p) {
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dns_packet_unref(t->received);
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t->received = dns_packet_ref(p);
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}
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if (p->ipproto == IPPROTO_TCP) {
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if (DNS_PACKET_TC(p)) {
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/* Truncated via TCP? Somebody must be fucking with us */
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dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
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return;
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}
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if (DNS_PACKET_ID(p) != t->id) {
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/* Not the reply to our query? Somebody must be fucking with us */
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dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
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return;
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}
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}
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assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
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switch (t->scope->protocol) {
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case DNS_PROTOCOL_DNS:
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assert(t->server);
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dns_server_packet_received(t->server, ts - t->start_usec);
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break;
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case DNS_PROTOCOL_LLMNR:
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case DNS_PROTOCOL_MDNS:
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dns_scope_packet_received(t->scope, ts - t->start_usec);
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break;
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default:
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assert_not_reached("Invalid DNS protocol.");
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}
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if (DNS_PACKET_TC(p)) {
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/* Response was truncated, let's try again with good old TCP */
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r = dns_transaction_open_tcp(t);
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if (r == -ESRCH) {
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/* No servers found? Damn! */
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dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
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return;
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}
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if (r < 0) {
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/* On LLMNR, if we cannot connect to the host,
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* we immediately give up */
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if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
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dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
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return;
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}
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/* On DNS, couldn't send? Try immediately again, with a new server */
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dns_transaction_next_dns_server(t);
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r = dns_transaction_go(t);
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if (r < 0) {
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dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
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return;
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}
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return;
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}
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}
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/* Parse and update the cache */
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r = dns_packet_extract(p);
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if (r < 0) {
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dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
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return;
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}
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/* Only consider responses with equivalent query section to the request */
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if (p->question->n_keys != 1 || dns_resource_key_equal(p->question->keys[0], t->key) <= 0) {
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dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
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return;
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}
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/* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */
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dns_cache_put(&t->scope->cache, p->question, DNS_PACKET_RCODE(p), p->answer, DNS_PACKET_ANCOUNT(p), 0, p->family, &p->sender);
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if (DNS_PACKET_RCODE(p) == DNS_RCODE_SUCCESS)
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dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
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else
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dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
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}
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static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
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_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
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DnsTransaction *t = userdata;
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int r;
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assert(t);
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assert(t->scope);
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r = manager_recv(t->scope->manager, fd, DNS_PROTOCOL_DNS, &p);
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if (r <= 0)
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return r;
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if (dns_packet_validate_reply(p) > 0 &&
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DNS_PACKET_ID(p) == t->id)
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dns_transaction_process_reply(t, p);
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else
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log_debug("Invalid DNS packet.");
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return 0;
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}
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static int dns_transaction_emit(DnsTransaction *t) {
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int r;
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assert(t);
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if (t->scope->protocol == DNS_PROTOCOL_DNS && !t->server) {
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DnsServer *server = NULL;
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_cleanup_close_ int fd = -1;
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fd = dns_scope_udp_dns_socket(t->scope, &server);
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if (fd < 0)
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return fd;
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r = sd_event_add_io(t->scope->manager->event, &t->dns_event_source, fd, EPOLLIN, on_dns_packet, t);
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if (r < 0)
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return r;
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t->dns_fd = fd;
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fd = -1;
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t->server = dns_server_ref(server);
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}
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r = dns_scope_emit(t->scope, t->dns_fd, t->sent);
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if (r < 0)
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return r;
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return 0;
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}
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static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdata) {
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DnsTransaction *t = userdata;
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int r;
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assert(s);
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assert(t);
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/* Timeout reached? Try again, with a new server */
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dns_transaction_next_dns_server(t);
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/* ... and possibly increased timeout */
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if (t->server)
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dns_server_packet_lost(t->server, usec - t->start_usec);
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else
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dns_scope_packet_lost(t->scope, usec - t->start_usec);
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r = dns_transaction_go(t);
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if (r < 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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static int dns_transaction_make_packet(DnsTransaction *t) {
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_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
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int r;
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assert(t);
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if (t->sent)
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return 0;
|
|
|
|
r = dns_packet_new_query(&p, t->scope->protocol, 0);
|
|
if (r < 0)
|
|
return r;
|
|
|
|
r = dns_scope_good_key(t->scope, t->key);
|
|
if (r < 0)
|
|
return r;
|
|
if (r == 0)
|
|
return -EDOM;
|
|
|
|
r = dns_packet_append_key(p, t->key, NULL);
|
|
if (r < 0)
|
|
return r;
|
|
|
|
DNS_PACKET_HEADER(p)->qdcount = htobe16(1);
|
|
DNS_PACKET_HEADER(p)->id = t->id;
|
|
|
|
t->sent = p;
|
|
p = NULL;
|
|
|
|
return 0;
|
|
}
|
|
|
|
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.");
|
|
}
|
|
}
|
|
|
|
int dns_transaction_go(DnsTransaction *t) {
|
|
bool had_stream;
|
|
usec_t ts;
|
|
int r;
|
|
|
|
assert(t);
|
|
|
|
had_stream = !!t->stream;
|
|
|
|
dns_transaction_stop(t);
|
|
|
|
log_debug("Excercising transaction on scope %s on %s/%s",
|
|
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;
|
|
}
|
|
|
|
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
|
|
|
|
t->n_attempts++;
|
|
t->start_usec = ts;
|
|
t->received = dns_packet_unref(t->received);
|
|
t->cached = dns_answer_unref(t->cached);
|
|
t->cached_rcode = 0;
|
|
|
|
/* Check the cache, but only if this transaction is not used
|
|
* for probing or verifying a zone item. */
|
|
if (set_isempty(t->zone_items)) {
|
|
|
|
/* 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);
|
|
|
|
/* Let's then prune all outdated entries */
|
|
dns_cache_prune(&t->scope->cache);
|
|
|
|
r = dns_cache_lookup(&t->scope->cache, t->key, &t->cached_rcode, &t->cached);
|
|
if (r < 0)
|
|
return r;
|
|
if (r > 0) {
|
|
if (t->cached_rcode == DNS_RCODE_SUCCESS)
|
|
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
|
|
else
|
|
dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
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(),
|
|
ts + jitter,
|
|
LLMNR_JITTER_INTERVAL_USEC,
|
|
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;
|
|
}
|
|
|
|
/* 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 &&
|
|
(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)) {
|
|
|
|
/* RFC 4795, Section 2.4. says reverse lookups shall
|
|
* always be made via TCP on LLMNR */
|
|
r = dns_transaction_open_tcp(t);
|
|
} else {
|
|
/* Try via UDP, and if that fails due to large size try via TCP */
|
|
r = dns_transaction_emit(t);
|
|
if (r == -EMSGSIZE)
|
|
r = dns_transaction_open_tcp(t);
|
|
}
|
|
if (r == -ESRCH) {
|
|
/* No servers to send this to? */
|
|
dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
|
|
return 0;
|
|
} else if (r < 0) {
|
|
if (t->scope->protocol != DNS_PROTOCOL_DNS) {
|
|
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
|
|
return 0;
|
|
}
|
|
|
|
/* Couldn't send? Try immediately again, with a new server */
|
|
dns_transaction_next_dns_server(t);
|
|
|
|
return dns_transaction_go(t);
|
|
}
|
|
|
|
r = sd_event_add_time(
|
|
t->scope->manager->event,
|
|
&t->timeout_event_source,
|
|
clock_boottime_or_monotonic(),
|
|
ts + transaction_get_resend_timeout(t), 0,
|
|
on_transaction_timeout, t);
|
|
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);
|