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-rw-r--r--src/resolve/resolved-dns-transaction.c538
1 files changed, 538 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
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+++ b/src/resolve/resolved-dns-transaction.c
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+/*-*- 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, 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) {
+ DnsZoneItem *z;
+ Iterator i;
+
+ assert(t);
+ assert(p);
+
+ if (manager_our_packet(t->scope->manager, p) != 0)
+ return;
+
+ log_debug("Transaction on scope %s on %s/%s got tentative packet",
+ 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));
+
+ t->block_gc++;
+ SET_FOREACH(z, t->zone_items, i)
+ 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));
+ assert(IN_SET(t->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>",
+ 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;
+ }
+
+ 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);
+
+ 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("Beginning 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;
+
+ /* First, let's try the cache */
+ 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) {
+ if (t->cached_rcode == DNS_RCODE_SUCCESS)
+ dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
+ else
+ dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
+ 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_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_send(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) {
+ /* 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_MONOTONIC, now(CLOCK_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);