/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/ /*** This file is part of systemd. Copyright 2014 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. ***/ #include "af-list.h" #include "alloc-util.h" #include "dns-domain.h" #include "fd-util.h" #include "random-util.h" #include "resolved-dns-cache.h" #include "resolved-dns-transaction.h" #include "resolved-llmnr.h" #include "string-table.h" DnsTransaction* dns_transaction_free(DnsTransaction *t) { DnsQueryCandidate *c; DnsZoneItem *i; if (!t) return NULL; sd_event_source_unref(t->timeout_event_source); dns_packet_unref(t->sent); dns_packet_unref(t->received); dns_answer_unref(t->answer); sd_event_source_unref(t->dns_udp_event_source); safe_close(t->dns_udp_fd); dns_server_unref(t->server); dns_stream_free(t->stream); if (t->scope) { hashmap_remove_value(t->scope->transactions_by_key, t->key, t); LIST_REMOVE(transactions_by_scope, t->scope->transactions, t); if (t->id != 0) hashmap_remove(t->scope->manager->dns_transactions, UINT_TO_PTR(t->id)); } dns_resource_key_unref(t->key); while ((c = set_steal_first(t->query_candidates))) set_remove(c->transactions, t); set_free(t->query_candidates); while ((i = set_steal_first(t->zone_items))) i->probe_transaction = NULL; set_free(t->zone_items); free(t); return NULL; } DEFINE_TRIVIAL_CLEANUP_FUNC(DnsTransaction*, dns_transaction_free); void dns_transaction_gc(DnsTransaction *t) { assert(t); if (t->block_gc > 0) return; if (set_isempty(t->query_candidates) && set_isempty(t->zone_items)) dns_transaction_free(t); } int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsResourceKey *key) { _cleanup_(dns_transaction_freep) DnsTransaction *t = NULL; int r; assert(ret); assert(s); assert(key); r = hashmap_ensure_allocated(&s->manager->dns_transactions, NULL); if (r < 0) return r; r = hashmap_ensure_allocated(&s->transactions_by_key, &dns_resource_key_hash_ops); if (r < 0) return r; t = new0(DnsTransaction, 1); if (!t) return -ENOMEM; t->dns_udp_fd = -1; t->answer_source = _DNS_TRANSACTION_SOURCE_INVALID; t->key = dns_resource_key_ref(key); /* Find a fresh, unused transaction id */ do random_bytes(&t->id, sizeof(t->id)); while (t->id == 0 || hashmap_get(s->manager->dns_transactions, UINT_TO_PTR(t->id))); r = hashmap_put(s->manager->dns_transactions, UINT_TO_PTR(t->id), t); if (r < 0) { t->id = 0; return r; } r = hashmap_replace(s->transactions_by_key, t->key, t); if (r < 0) { hashmap_remove(s->manager->dns_transactions, UINT_TO_PTR(t->id)); return r; } LIST_PREPEND(transactions_by_scope, s->transactions, t); t->scope = s; if (ret) *ret = t; t = NULL; return 0; } static void dns_transaction_stop(DnsTransaction *t) { assert(t); t->timeout_event_source = sd_event_source_unref(t->timeout_event_source); t->stream = dns_stream_free(t->stream); /* Note that we do not drop the UDP socket here, as we want to * reuse it to repeat the interaction. */ } static void dns_transaction_tentative(DnsTransaction *t, DnsPacket *p) { _cleanup_free_ char *pretty = NULL; DnsZoneItem *z; assert(t); assert(p); if (manager_our_packet(t->scope->manager, p) != 0) return; in_addr_to_string(p->family, &p->sender, &pretty); log_debug("Transaction on scope %s on %s/%s got tentative packet from %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), pretty); /* RFC 4795, Section 4.1 says that the peer with the * lexicographically smaller IP address loses */ if (memcmp(&p->sender, &p->destination, FAMILY_ADDRESS_SIZE(p->family)) >= 0) { log_debug("Peer has lexicographically larger IP address and thus lost in the conflict."); return; } log_debug("We have the lexicographically larger IP address and thus lost in the conflict."); t->block_gc++; while ((z = set_first(t->zone_items))) { /* First, make sure the zone item drops the reference * to us */ dns_zone_item_probe_stop(z); /* Secondly, report this as conflict, so that we might * look for a different hostname */ dns_zone_item_conflict(z); } t->block_gc--; dns_transaction_gc(t); } void dns_transaction_complete(DnsTransaction *t, DnsTransactionState state) { DnsQueryCandidate *c; DnsZoneItem *z; Iterator i; assert(t); assert(!IN_SET(state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING)); /* Note that this call might invalidate the query. Callers * should hence not attempt to access the query or transaction * after calling this function. */ log_debug("Transaction on scope %s on %s/%s now complete with <%s> from %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), dns_transaction_state_to_string(state), t->answer_source < 0 ? "none" : dns_transaction_source_to_string(t->answer_source)); t->state = state; dns_transaction_stop(t); /* Notify all queries that are interested, but make sure the * transaction isn't freed while we are still looking at it */ t->block_gc++; SET_FOREACH(c, t->query_candidates, i) dns_query_candidate_ready(c); SET_FOREACH(z, t->zone_items, i) dns_zone_item_ready(z); t->block_gc--; dns_transaction_gc(t); } static int on_stream_complete(DnsStream *s, int error) { _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; DnsTransaction *t; assert(s); assert(s->transaction); /* Copy the data we care about out of the stream before we * destroy it. */ t = s->transaction; p = dns_packet_ref(s->read_packet); t->stream = dns_stream_free(t->stream); if (error != 0) { dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES); return 0; } if (dns_packet_validate_reply(p) <= 0) { log_debug("Invalid TCP reply packet."); dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); return 0; } dns_scope_check_conflicts(t->scope, p); t->block_gc++; dns_transaction_process_reply(t, p); t->block_gc--; /* If the response wasn't useful, then complete the transition now */ if (t->state == DNS_TRANSACTION_PENDING) dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); return 0; } static int dns_transaction_open_tcp(DnsTransaction *t) { DnsServer *server = NULL; _cleanup_close_ int fd = -1; int r; assert(t); if (t->stream) return 0; switch (t->scope->protocol) { case DNS_PROTOCOL_DNS: fd = dns_scope_tcp_socket(t->scope, AF_UNSPEC, NULL, 53, &server); break; case DNS_PROTOCOL_LLMNR: /* When we already received a reply to this (but it was truncated), send to its sender address */ if (t->received) fd = dns_scope_tcp_socket(t->scope, t->received->family, &t->received->sender, t->received->sender_port, NULL); else { union in_addr_union address; int family = AF_UNSPEC; /* Otherwise, try to talk to the owner of a * the IP address, in case this is a reverse * PTR lookup */ r = dns_name_address(DNS_RESOURCE_KEY_NAME(t->key), &family, &address); if (r < 0) return r; if (r == 0) return -EINVAL; if (family != t->scope->family) return -ESRCH; fd = dns_scope_tcp_socket(t->scope, family, &address, LLMNR_PORT, NULL); } break; default: return -EAFNOSUPPORT; } if (fd < 0) return fd; 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; } dns_server_unref(t->server); t->server = dns_server_ref(server); t->received = dns_packet_unref(t->received); t->answer = dns_answer_unref(t->answer); t->answer_rcode = 0; 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; } static void dns_transaction_next_dns_server(DnsTransaction *t) { assert(t); t->server = dns_server_unref(t->server); t->dns_udp_event_source = sd_event_source_unref(t->dns_udp_event_source); t->dns_udp_fd = safe_close(t->dns_udp_fd); dns_scope_next_dns_server(t->scope); } void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) { usec_t ts; int r; assert(t); assert(p); assert(t->state == DNS_TRANSACTION_PENDING); assert(t->scope); assert(t->scope->manager); /* Note that this call might invalidate the query. Callers * should hence not attempt to access the query or transaction * after calling this function. */ switch (t->scope->protocol) { case DNS_PROTOCOL_LLMNR: 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. */ if (DNS_PACKET_LLMNR_T(p)) { dns_transaction_tentative(t, p); return; } break; case DNS_PROTOCOL_MDNS: assert(t->scope->link); /* For mDNS we will not accept any packets from other interfaces */ if (p->ifindex != t->scope->link->ifindex) return; if (p->family != t->scope->family) return; break; case DNS_PROTOCOL_DNS: break; default: assert_not_reached("Invalid DNS protocol."); } if (t->received != p) { dns_packet_unref(t->received); t->received = dns_packet_ref(p); } t->answer_source = DNS_TRANSACTION_NETWORK; 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; } } assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); switch (t->scope->protocol) { case DNS_PROTOCOL_DNS: assert(t->server); 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 dns_server_packet_received(t->server, t->current_features, ts - t->start_usec, p->size); break; case DNS_PROTOCOL_LLMNR: case DNS_PROTOCOL_MDNS: dns_scope_packet_received(t->scope, ts - t->start_usec); break; default: break; } if (DNS_PACKET_TC(p)) { /* Truncated packets for mDNS are not allowed. Give up immediately. */ if (t->scope->protocol == DNS_PROTOCOL_MDNS) { dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); return; } /* 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 and mDNS, 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 */ dns_transaction_next_dns_server(t); 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; } if (t->scope->protocol == DNS_PROTOCOL_DNS) { /* Only consider responses with equivalent query section to the request */ if (p->question->n_keys != 1 || dns_resource_key_equal(p->question->keys[0], t->key) <= 0) { dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY); return; } /* 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); /* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */ if (DNS_PACKET_SHALL_CACHE(p)) 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); } if (DNS_PACKET_RCODE(p) == DNS_RCODE_SUCCESS) dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS); else dns_transaction_complete(t, DNS_TRANSACTION_FAILURE); } 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 && DNS_PACKET_ID(p) == t->id) dns_transaction_process_reply(t, p); else log_debug("Invalid DNS packet."); return 0; } static int dns_transaction_emit(DnsTransaction *t) { int r; assert(t); if (t->scope->protocol == DNS_PROTOCOL_DNS && !t->server) { DnsServer *server = NULL; _cleanup_close_ int fd = -1; fd = dns_scope_udp_dns_socket(t->scope, &server); if (fd < 0) return fd; r = sd_event_add_io(t->scope->manager->event, &t->dns_udp_event_source, fd, EPOLLIN, on_dns_packet, t); if (r < 0) return r; t->dns_udp_fd = fd; fd = -1; t->server = dns_server_ref(server); } r = dns_scope_emit(t->scope, t->dns_udp_fd, t->server, t->sent); if (r < 0) return r; if (t->server) t->current_features = t->server->possible_features; return 0; } static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdata) { DnsTransaction *t = userdata; int r; assert(s); assert(t); if (!t->initial_jitter_scheduled || t->initial_jitter_elapsed) { /* Timeout reached? Increase the timeout for the server used */ switch (t->scope->protocol) { case DNS_PROTOCOL_DNS: assert(t->server); dns_server_packet_lost(t->server, t->current_features, usec - t->start_usec); break; case DNS_PROTOCOL_LLMNR: case DNS_PROTOCOL_MDNS: dns_scope_packet_lost(t->scope, usec - t->start_usec); break; default: assert_not_reached("Invalid DNS protocol."); } if (t->initial_jitter_scheduled) t->initial_jitter_elapsed = true; } /* ...and try again with a new server */ dns_transaction_next_dns_server(t); r = dns_transaction_go(t); if (r < 0) dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES); 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_MDNS: assert(t->n_attempts > 0); return (1 << (t->n_attempts - 1)) * USEC_PER_SEC; case DNS_PROTOCOL_LLMNR: return t->scope->resend_timeout; default: assert_not_reached("Invalid DNS protocol."); } } static int dns_transaction_prepare_next_attempt(DnsTransaction *t, usec_t ts) { bool had_stream; int r; assert(t); had_stream = !!t->stream; dns_transaction_stop(t); 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; } t->n_attempts++; t->start_usec = ts; t->received = dns_packet_unref(t->received); t->answer = dns_answer_unref(t->answer); t->answer_rcode = 0; t->answer_source = _DNS_TRANSACTION_SOURCE_INVALID; /* 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; t->answer_authenticated = true; dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS); return 0; } } /* Check the zone, but only if this transaction is not used * for probing or verifying a zone item. */ if (set_isempty(t->zone_items)) { r = dns_zone_lookup(&t->scope->zone, t->key, &t->answer, NULL, NULL); if (r < 0) return r; if (r > 0) { t->answer_rcode = DNS_RCODE_SUCCESS; t->answer_source = DNS_TRANSACTION_ZONE; t->answer_authenticated = true; dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS); return 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->answer_rcode, &t->answer, &t->answer_authenticated); if (r < 0) return r; if (r > 0) { t->answer_source = DNS_TRANSACTION_CACHE; if (t->answer_rcode == DNS_RCODE_SUCCESS) dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS); else dns_transaction_complete(t, DNS_TRANSACTION_FAILURE); return 0; } } return 1; } static int dns_transaction_make_packet_mdns(DnsTransaction *t) { _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; bool add_known_answers = false; DnsTransaction *other; unsigned qdcount; usec_t ts; int r; assert(t); assert(t->scope->protocol == DNS_PROTOCOL_MDNS); /* Discard any previously prepared packet, so we can start over and coaleasce again */ t->sent = dns_packet_unref(t->sent); r = dns_packet_new_query(&p, t->scope->protocol, 0, false); if (r < 0) return r; r = dns_packet_append_key(p, t->key, NULL); if (r < 0) return r; qdcount = 1; if (dns_key_is_shared(t->key)) add_known_answers = true; /* * For mDNS, we want to coalesce as many open queries in pending transactions into one single * query packet on the wire as possible. To achieve that, we iterate through all pending transactions * in our current scope, and see whether their timing contraints allow them to be sent. */ assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); LIST_FOREACH(transactions_by_scope, other, t->scope->transactions) { /* Skip ourselves */ if (other == t) continue; if (other->state != DNS_TRANSACTION_PENDING) continue; if (other->next_attempt_after > ts) continue; if (qdcount >= UINT16_MAX) break; r = dns_packet_append_key(p, other->key, NULL); /* * If we can't stuff more questions into the packet, just give up. * One of the 'other' transactions will fire later and take care of the rest. */ if (r == -EMSGSIZE) break; if (r < 0) return r; r = dns_transaction_prepare_next_attempt(other, ts); if (r <= 0) continue; ts += transaction_get_resend_timeout(other); r = sd_event_add_time( other->scope->manager->event, &other->timeout_event_source, clock_boottime_or_monotonic(), ts, 0, on_transaction_timeout, other); if (r < 0) return r; other->state = DNS_TRANSACTION_PENDING; other->next_attempt_after = ts; qdcount ++; if (dns_key_is_shared(other->key)) add_known_answers = true; } DNS_PACKET_HEADER(p)->qdcount = htobe16(qdcount); DNS_PACKET_HEADER(p)->id = t->id; /* Append known answer section if we're asking for any shared record */ if (add_known_answers) { r = dns_cache_export_shared_to_packet(&t->scope->cache, p); if (r < 0) return r; } t->sent = p; p = NULL; return 0; } static int dns_transaction_make_packet(DnsTransaction *t) { _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; int r; assert(t); if (t->scope->protocol == DNS_PROTOCOL_MDNS) return dns_transaction_make_packet_mdns(t); if (t->sent) return 0; r = dns_packet_new_query(&p, t->scope->protocol, 0, t->scope->dnssec_mode == DNSSEC_YES); 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; } int dns_transaction_go(DnsTransaction *t) { usec_t ts; int r; assert(t); assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0); r = dns_transaction_prepare_next_attempt(t, ts); if (r <= 0) return r; 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->initial_jitter_scheduled && (t->scope->protocol == DNS_PROTOCOL_LLMNR || t->scope->protocol == DNS_PROTOCOL_MDNS)) { usec_t jitter, accuracy; /* RFC 4795 Section 2.7 suggests all queries should be * delayed by a random time from 0 to JITTER_INTERVAL. */ t->initial_jitter_scheduled = true; random_bytes(&jitter, sizeof(jitter)); switch (t->scope->protocol) { case DNS_PROTOCOL_LLMNR: jitter %= LLMNR_JITTER_INTERVAL_USEC; accuracy = LLMNR_JITTER_INTERVAL_USEC; break; case DNS_PROTOCOL_MDNS: jitter %= MDNS_JITTER_RANGE_USEC; jitter += MDNS_JITTER_MIN_USEC; accuracy = MDNS_JITTER_RANGE_USEC; break; default: assert_not_reached("bad protocol"); } r = sd_event_add_time( t->scope->manager->event, &t->timeout_event_source, clock_boottime_or_monotonic(), ts + jitter, accuracy, on_transaction_timeout, t); if (r < 0) return r; t->n_attempts = 0; t->next_attempt_after = ts; t->state = DNS_TRANSACTION_PENDING; log_debug("Delaying %s transaction for " USEC_FMT "us.", dns_protocol_to_string(t->scope->protocol), 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 or lack of * support try via TCP */ r = dns_transaction_emit(t); if (r == -EMSGSIZE || r == -EAGAIN) 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); } ts += transaction_get_resend_timeout(t); r = sd_event_add_time( t->scope->manager->event, &t->timeout_event_source, clock_boottime_or_monotonic(), ts, 0, on_transaction_timeout, t); if (r < 0) return r; t->state = DNS_TRANSACTION_PENDING; t->next_attempt_after = ts; 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); static const char* const dns_transaction_source_table[_DNS_TRANSACTION_SOURCE_MAX] = { [DNS_TRANSACTION_NETWORK] = "network", [DNS_TRANSACTION_CACHE] = "cache", [DNS_TRANSACTION_ZONE] = "zone", [DNS_TRANSACTION_TRUST_ANCHOR] = "trust-anchor", }; DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source, DnsTransactionSource);