/*-*- 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 "resolved-dns-transaction.h" DnsTransaction* dns_transaction_free(DnsTransaction *t) { DnsQuery *q; DnsZoneItem *i; if (!t) return NULL; sd_event_source_unref(t->timeout_event_source); dns_question_unref(t->question); dns_packet_unref(t->sent); dns_packet_unref(t->received); dns_answer_unref(t->cached); dns_stream_free(t->stream); if (t->scope) { 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)); } while ((q = set_steal_first(t->queries))) set_remove(q->transactions, t); set_free(t->queries); 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->queries) && set_isempty(t->zone_items)) dns_transaction_free(t); } int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsQuestion *q) { _cleanup_(dns_transaction_freep) DnsTransaction *t = NULL; int r; assert(ret); assert(s); assert(q); r = hashmap_ensure_allocated(&s->manager->dns_transactions, NULL); if (r < 0) return r; t = new0(DnsTransaction, 1); if (!t) return -ENOMEM; t->question = dns_question_ref(q); 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; } 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); } 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) { DnsQuery *q; DnsZoneItem *z; Iterator i; assert(t); assert(!IN_SET(state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING)); if (!IN_SET(t->state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING)) return; /* 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>", 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->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(q, t->queries, i) dns_query_ready(q); 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 LLMNR TCP 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) { _cleanup_close_ int fd = -1; int r; assert(t); if (t->stream) return 0; if (t->scope->protocol == DNS_PROTOCOL_DNS) fd = dns_scope_tcp_socket(t->scope, AF_UNSPEC, NULL, 53); else if (t->scope->protocol == DNS_PROTOCOL_LLMNR) { /* When we already received a query 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); else { union in_addr_union address; int family; /* Otherwise, try to talk to the owner of a * the IP address, in case this is a reverse * PTR lookup */ r = dns_question_extract_reverse_address(t->question, &family, &address); if (r < 0) return r; if (r == 0) return -EINVAL; fd = dns_scope_tcp_socket(t->scope, family, &address, 5355); } } else 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; } t->received = dns_packet_unref(t->received); 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; } void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) { int r; assert(t); assert(p); assert(t->state == 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. */ if (t->scope->protocol == 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_T(p)) { dns_transaction_tentative(t, p); return; } } if (t->scope->protocol == DNS_PROTOCOL_DNS) { /* For DNS we are fine with accepting packets on any * interface, but the source IP address must be one of * a valid DNS server */ if (!dns_scope_good_dns_server(t->scope, p->family, &p->sender)) return; if (p->sender_port != 53) return; } if (t->received != p) { dns_packet_unref(t->received); t->received = dns_packet_ref(p); } 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; } } 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 */ dns_scope_next_dns_server(t->scope); 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; } /* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */ dns_cache_put(&t->scope->cache, p->question, DNS_PACKET_RCODE(p), p->answer, DNS_PACKET_ANCOUNT(p), 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_transaction_timeout(sd_event_source *s, usec_t usec, void *userdata) { DnsTransaction *t = userdata; int r; assert(s); assert(t); /* Timeout reached? Try again, with a new server */ dns_scope_next_dns_server(t->scope); 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; unsigned n, added = 0; int r; assert(t); if (t->sent) return 0; r = dns_packet_new_query(&p, t->scope->protocol, 0); if (r < 0) return r; for (n = 0; n < t->question->n_keys; n++) { r = dns_scope_good_key(t->scope, t->question->keys[n]); if (r < 0) return r; if (r == 0) continue; r = dns_packet_append_key(p, t->question->keys[n], NULL); if (r < 0) return r; added++; } if (added <= 0) return -EDOM; DNS_PACKET_HEADER(p)->qdcount = htobe16(added); DNS_PACKET_HEADER(p)->id = t->id; t->sent = p; p = NULL; return 0; } int dns_transaction_go(DnsTransaction *t) { bool had_stream; 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; } t->n_attempts++; 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->question, &t->cached_rcode, &t->cached); if (r < 0) return r; if (r > 0) { log_debug("Cache hit!"); 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(), now(clock_boottime_or_monotonic()) + 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; } log_debug("Cache miss!"); /* 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_question_endswith(t->question, "in-addr.arpa") > 0 || dns_question_endswith(t->question, "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_scope_emit(t->scope, t->sent); 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; } 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_scope_next_dns_server(t->scope); return dns_transaction_go(t); } r = sd_event_add_time( t->scope->manager->event, &t->timeout_event_source, clock_boottime_or_monotonic(), now(clock_boottime_or_monotonic()) + TRANSACTION_TIMEOUT_USEC(t->scope->protocol), 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);