summaryrefslogtreecommitdiffstats
path: root/src/resolve/resolved-dns-query.c
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 15:35:18 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 15:35:18 +0000
commitb750101eb236130cf056c675997decbac904cc49 (patch)
treea5df1a06754bdd014cb975c051c83b01c9a97532 /src/resolve/resolved-dns-query.c
parentInitial commit. (diff)
downloadsystemd-b750101eb236130cf056c675997decbac904cc49.tar.xz
systemd-b750101eb236130cf056c675997decbac904cc49.zip
Adding upstream version 252.22.upstream/252.22
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/resolve/resolved-dns-query.c')
-rw-r--r--src/resolve/resolved-dns-query.c1299
1 files changed, 1299 insertions, 0 deletions
diff --git a/src/resolve/resolved-dns-query.c b/src/resolve/resolved-dns-query.c
new file mode 100644
index 0000000..7eb6b97
--- /dev/null
+++ b/src/resolve/resolved-dns-query.c
@@ -0,0 +1,1299 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "alloc-util.h"
+#include "dns-domain.h"
+#include "dns-type.h"
+#include "event-util.h"
+#include "glyph-util.h"
+#include "hostname-util.h"
+#include "local-addresses.h"
+#include "resolved-dns-query.h"
+#include "resolved-dns-synthesize.h"
+#include "resolved-etc-hosts.h"
+#include "string-util.h"
+
+#define QUERIES_MAX 2048
+#define AUXILIARY_QUERIES_MAX 64
+#define CNAME_REDIRECTS_MAX 16
+
+assert_cc(AUXILIARY_QUERIES_MAX < UINT8_MAX);
+assert_cc(CNAME_REDIRECTS_MAX < UINT8_MAX);
+
+static int dns_query_candidate_new(DnsQueryCandidate **ret, DnsQuery *q, DnsScope *s) {
+ DnsQueryCandidate *c;
+
+ assert(ret);
+ assert(q);
+ assert(s);
+
+ c = new(DnsQueryCandidate, 1);
+ if (!c)
+ return -ENOMEM;
+
+ *c = (DnsQueryCandidate) {
+ .n_ref = 1,
+ .query = q,
+ .scope = s,
+ };
+
+ LIST_PREPEND(candidates_by_query, q->candidates, c);
+ LIST_PREPEND(candidates_by_scope, s->query_candidates, c);
+
+ *ret = c;
+ return 0;
+}
+
+static void dns_query_candidate_stop(DnsQueryCandidate *c) {
+ DnsTransaction *t;
+
+ assert(c);
+
+ /* Detach all the DnsTransactions attached to this query */
+
+ while ((t = set_steal_first(c->transactions))) {
+ set_remove(t->notify_query_candidates, c);
+ set_remove(t->notify_query_candidates_done, c);
+ dns_transaction_gc(t);
+ }
+}
+
+static DnsQueryCandidate* dns_query_candidate_unlink(DnsQueryCandidate *c) {
+ assert(c);
+
+ /* Detach this DnsQueryCandidate from the Query and Scope objects */
+
+ if (c->query) {
+ LIST_REMOVE(candidates_by_query, c->query->candidates, c);
+ c->query = NULL;
+ }
+
+ if (c->scope) {
+ LIST_REMOVE(candidates_by_scope, c->scope->query_candidates, c);
+ c->scope = NULL;
+ }
+
+ return c;
+}
+
+static DnsQueryCandidate* dns_query_candidate_free(DnsQueryCandidate *c) {
+ if (!c)
+ return NULL;
+
+ dns_query_candidate_stop(c);
+ dns_query_candidate_unlink(c);
+
+ set_free(c->transactions);
+ dns_search_domain_unref(c->search_domain);
+
+ return mfree(c);
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(DnsQueryCandidate, dns_query_candidate, dns_query_candidate_free);
+
+static int dns_query_candidate_next_search_domain(DnsQueryCandidate *c) {
+ DnsSearchDomain *next;
+
+ assert(c);
+
+ if (c->search_domain && c->search_domain->linked)
+ next = c->search_domain->domains_next;
+ else
+ next = dns_scope_get_search_domains(c->scope);
+
+ for (;;) {
+ if (!next) /* We hit the end of the list */
+ return 0;
+
+ if (!next->route_only)
+ break;
+
+ /* Skip over route-only domains */
+ next = next->domains_next;
+ }
+
+ dns_search_domain_unref(c->search_domain);
+ c->search_domain = dns_search_domain_ref(next);
+
+ return 1;
+}
+
+static int dns_query_candidate_add_transaction(
+ DnsQueryCandidate *c,
+ DnsResourceKey *key,
+ DnsPacket *bypass) {
+
+ _cleanup_(dns_transaction_gcp) DnsTransaction *t = NULL;
+ int r;
+
+ assert(c);
+ assert(c->query); /* We shan't add transactions to a candidate that has been detached already */
+
+ if (key) {
+ /* Regular lookup with a resource key */
+ assert(!bypass);
+
+ t = dns_scope_find_transaction(c->scope, key, c->query->flags);
+ if (!t) {
+ r = dns_transaction_new(&t, c->scope, key, NULL, c->query->flags);
+ if (r < 0)
+ return r;
+ } else if (set_contains(c->transactions, t))
+ return 0;
+ } else {
+ /* "Bypass" lookup with a query packet */
+ assert(bypass);
+
+ r = dns_transaction_new(&t, c->scope, NULL, bypass, c->query->flags);
+ if (r < 0)
+ return r;
+ }
+
+ r = set_ensure_allocated(&t->notify_query_candidates_done, NULL);
+ if (r < 0)
+ return r;
+
+ r = set_ensure_put(&t->notify_query_candidates, NULL, c);
+ if (r < 0)
+ return r;
+
+ r = set_ensure_put(&c->transactions, NULL, t);
+ if (r < 0) {
+ (void) set_remove(t->notify_query_candidates, c);
+ return r;
+ }
+
+ TAKE_PTR(t);
+ return 1;
+}
+
+static int dns_query_candidate_go(DnsQueryCandidate *c) {
+ _unused_ _cleanup_(dns_query_candidate_unrefp) DnsQueryCandidate *keep_c = NULL;
+ DnsTransaction *t;
+ int r;
+ unsigned n = 0;
+
+ assert(c);
+
+ /* Let's keep a reference to the query while we're operating */
+ keep_c = dns_query_candidate_ref(c);
+
+ /* Start the transactions that are not started yet */
+ SET_FOREACH(t, c->transactions) {
+ if (t->state != DNS_TRANSACTION_NULL)
+ continue;
+
+ r = dns_transaction_go(t);
+ if (r < 0)
+ return r;
+
+ n++;
+ }
+
+ /* If there was nothing to start, then let's proceed immediately */
+ if (n == 0)
+ dns_query_candidate_notify(c);
+
+ return 0;
+}
+
+static DnsTransactionState dns_query_candidate_state(DnsQueryCandidate *c) {
+ DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS;
+ DnsTransaction *t;
+
+ assert(c);
+
+ if (c->error_code != 0)
+ return DNS_TRANSACTION_ERRNO;
+
+ SET_FOREACH(t, c->transactions)
+
+ switch (t->state) {
+
+ case DNS_TRANSACTION_NULL:
+ /* If there's a NULL transaction pending, then
+ * this means not all transactions where
+ * started yet, and we were called from within
+ * the stackframe that is supposed to start
+ * remaining transactions. In this case,
+ * simply claim the candidate is pending. */
+
+ case DNS_TRANSACTION_PENDING:
+ case DNS_TRANSACTION_VALIDATING:
+ /* If there's one transaction currently in
+ * VALIDATING state, then this means there's
+ * also one in PENDING state, hence we can
+ * return PENDING immediately. */
+ return DNS_TRANSACTION_PENDING;
+
+ case DNS_TRANSACTION_SUCCESS:
+ state = t->state;
+ break;
+
+ default:
+ if (state != DNS_TRANSACTION_SUCCESS)
+ state = t->state;
+
+ break;
+ }
+
+ return state;
+}
+
+static int dns_query_candidate_setup_transactions(DnsQueryCandidate *c) {
+ DnsQuestion *question;
+ DnsResourceKey *key;
+ int n = 0, r;
+
+ assert(c);
+ assert(c->query); /* We shan't add transactions to a candidate that has been detached already */
+
+ dns_query_candidate_stop(c);
+
+ if (c->query->question_bypass) {
+ /* If this is a bypass query, then pass the original query packet along to the transaction */
+
+ assert(dns_question_size(c->query->question_bypass->question) == 1);
+
+ if (!dns_scope_good_key(c->scope, dns_question_first_key(c->query->question_bypass->question)))
+ return 0;
+
+ r = dns_query_candidate_add_transaction(c, NULL, c->query->question_bypass);
+ if (r < 0)
+ goto fail;
+
+ return 1;
+ }
+
+ question = dns_query_question_for_protocol(c->query, c->scope->protocol);
+
+ /* Create one transaction per question key */
+ DNS_QUESTION_FOREACH(key, question) {
+ _cleanup_(dns_resource_key_unrefp) DnsResourceKey *new_key = NULL;
+ DnsResourceKey *qkey;
+
+ if (c->search_domain) {
+ r = dns_resource_key_new_append_suffix(&new_key, key, c->search_domain->name);
+ if (r < 0)
+ goto fail;
+
+ qkey = new_key;
+ } else
+ qkey = key;
+
+ if (!dns_scope_good_key(c->scope, qkey))
+ continue;
+
+ r = dns_query_candidate_add_transaction(c, qkey, NULL);
+ if (r < 0)
+ goto fail;
+
+ n++;
+ }
+
+ return n;
+
+fail:
+ dns_query_candidate_stop(c);
+ return r;
+}
+
+void dns_query_candidate_notify(DnsQueryCandidate *c) {
+ DnsTransactionState state;
+ int r;
+
+ assert(c);
+
+ if (!c->query) /* This candidate has been abandoned, do nothing. */
+ return;
+
+ state = dns_query_candidate_state(c);
+
+ if (DNS_TRANSACTION_IS_LIVE(state))
+ return;
+
+ if (state != DNS_TRANSACTION_SUCCESS && c->search_domain) {
+
+ r = dns_query_candidate_next_search_domain(c);
+ if (r < 0)
+ goto fail;
+
+ if (r > 0) {
+ /* OK, there's another search domain to try, let's do so. */
+
+ r = dns_query_candidate_setup_transactions(c);
+ if (r < 0)
+ goto fail;
+
+ if (r > 0) {
+ /* New transactions where queued. Start them and wait */
+
+ r = dns_query_candidate_go(c);
+ if (r < 0)
+ goto fail;
+
+ return;
+ }
+ }
+
+ }
+
+ dns_query_ready(c->query);
+ return;
+
+fail:
+ c->error_code = log_warning_errno(r, "Failed to follow search domains: %m");
+ dns_query_ready(c->query);
+}
+
+static void dns_query_stop(DnsQuery *q) {
+ assert(q);
+
+ event_source_disable(q->timeout_event_source);
+
+ LIST_FOREACH(candidates_by_query, c, q->candidates)
+ dns_query_candidate_stop(c);
+}
+
+static void dns_query_unlink_candidates(DnsQuery *q) {
+ assert(q);
+
+ while (q->candidates)
+ /* Here we drop *our* references to each of the candidates. If we had the only reference, the
+ * DnsQueryCandidate object will be freed. */
+ dns_query_candidate_unref(dns_query_candidate_unlink(q->candidates));
+}
+
+static void dns_query_reset_answer(DnsQuery *q) {
+ assert(q);
+
+ q->answer = dns_answer_unref(q->answer);
+ q->answer_rcode = 0;
+ q->answer_dnssec_result = _DNSSEC_RESULT_INVALID;
+ q->answer_errno = 0;
+ q->answer_query_flags = 0;
+ q->answer_protocol = _DNS_PROTOCOL_INVALID;
+ q->answer_family = AF_UNSPEC;
+ q->answer_search_domain = dns_search_domain_unref(q->answer_search_domain);
+ q->answer_full_packet = dns_packet_unref(q->answer_full_packet);
+}
+
+DnsQuery *dns_query_free(DnsQuery *q) {
+ if (!q)
+ return NULL;
+
+ q->timeout_event_source = sd_event_source_disable_unref(q->timeout_event_source);
+
+ while (q->auxiliary_queries)
+ dns_query_free(q->auxiliary_queries);
+
+ if (q->auxiliary_for) {
+ assert(q->auxiliary_for->n_auxiliary_queries > 0);
+ q->auxiliary_for->n_auxiliary_queries--;
+ LIST_REMOVE(auxiliary_queries, q->auxiliary_for->auxiliary_queries, q);
+ }
+
+ dns_query_unlink_candidates(q);
+
+ dns_question_unref(q->question_idna);
+ dns_question_unref(q->question_utf8);
+ dns_packet_unref(q->question_bypass);
+ dns_question_unref(q->collected_questions);
+
+ dns_query_reset_answer(q);
+
+ sd_bus_message_unref(q->bus_request);
+ sd_bus_track_unref(q->bus_track);
+
+ if (q->varlink_request) {
+ varlink_set_userdata(q->varlink_request, NULL);
+ varlink_unref(q->varlink_request);
+ }
+
+ if (q->request_packet)
+ hashmap_remove_value(q->stub_listener_extra ?
+ q->stub_listener_extra->queries_by_packet :
+ q->manager->stub_queries_by_packet,
+ q->request_packet,
+ q);
+
+ dns_packet_unref(q->request_packet);
+ dns_answer_unref(q->reply_answer);
+ dns_answer_unref(q->reply_authoritative);
+ dns_answer_unref(q->reply_additional);
+
+ if (q->request_stream) {
+ /* Detach the stream from our query, in case something else keeps a reference to it. */
+ (void) set_remove(q->request_stream->queries, q);
+ q->request_stream = dns_stream_unref(q->request_stream);
+ }
+
+ free(q->request_address_string);
+
+ if (q->manager) {
+ LIST_REMOVE(queries, q->manager->dns_queries, q);
+ q->manager->n_dns_queries--;
+ }
+
+ return mfree(q);
+}
+
+int dns_query_new(
+ Manager *m,
+ DnsQuery **ret,
+ DnsQuestion *question_utf8,
+ DnsQuestion *question_idna,
+ DnsPacket *question_bypass,
+ int ifindex,
+ uint64_t flags) {
+
+ _cleanup_(dns_query_freep) DnsQuery *q = NULL;
+ char key_str[DNS_RESOURCE_KEY_STRING_MAX];
+ DnsResourceKey *key;
+ int r;
+
+ assert(m);
+
+ if (question_bypass) {
+ /* It's either a "bypass" query, or a regular one, but can't be both. */
+ if (question_utf8 || question_idna)
+ return -EINVAL;
+
+ } else {
+ bool good = false;
+
+ /* This (primarily) checks two things:
+ *
+ * 1. That the question is not empty
+ * 2. That all RR keys in the question objects are for the same domain
+ *
+ * Or in other words, a single DnsQuery object may be used to look up A+AAAA combination for
+ * the same domain name, or SRV+TXT (for DNS-SD services), but not for unrelated lookups. */
+
+ if (dns_question_size(question_utf8) > 0) {
+ r = dns_question_is_valid_for_query(question_utf8);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ return -EINVAL;
+
+ good = true;
+ }
+
+ /* If the IDNA and UTF8 questions are the same, merge their references */
+ r = dns_question_is_equal(question_idna, question_utf8);
+ if (r < 0)
+ return r;
+ if (r > 0)
+ question_idna = question_utf8;
+ else {
+ if (dns_question_size(question_idna) > 0) {
+ r = dns_question_is_valid_for_query(question_idna);
+ if (r < 0)
+ return r;
+ if (r == 0)
+ return -EINVAL;
+
+ good = true;
+ }
+ }
+
+ if (!good) /* don't allow empty queries */
+ return -EINVAL;
+ }
+
+ if (m->n_dns_queries >= QUERIES_MAX)
+ return -EBUSY;
+
+ q = new(DnsQuery, 1);
+ if (!q)
+ return -ENOMEM;
+
+ *q = (DnsQuery) {
+ .question_utf8 = dns_question_ref(question_utf8),
+ .question_idna = dns_question_ref(question_idna),
+ .question_bypass = dns_packet_ref(question_bypass),
+ .ifindex = ifindex,
+ .flags = flags,
+ .answer_dnssec_result = _DNSSEC_RESULT_INVALID,
+ .answer_protocol = _DNS_PROTOCOL_INVALID,
+ .answer_family = AF_UNSPEC,
+ };
+
+ if (question_bypass) {
+ DNS_QUESTION_FOREACH(key, question_bypass->question)
+ log_debug("Looking up bypass packet for %s.",
+ dns_resource_key_to_string(key, key_str, sizeof key_str));
+ } else {
+ /* First dump UTF8 question */
+ DNS_QUESTION_FOREACH(key, question_utf8)
+ log_debug("Looking up RR for %s.",
+ dns_resource_key_to_string(key, key_str, sizeof key_str));
+
+ /* And then dump the IDNA question, but only what hasn't been dumped already through the UTF8 question. */
+ DNS_QUESTION_FOREACH(key, question_idna) {
+ r = dns_question_contains_key(question_utf8, key);
+ if (r < 0)
+ return r;
+ if (r > 0)
+ continue;
+
+ log_debug("Looking up IDNA RR for %s.",
+ dns_resource_key_to_string(key, key_str, sizeof key_str));
+ }
+ }
+
+ LIST_PREPEND(queries, m->dns_queries, q);
+ m->n_dns_queries++;
+ q->manager = m;
+
+ if (ret)
+ *ret = q;
+
+ TAKE_PTR(q);
+ return 0;
+}
+
+int dns_query_make_auxiliary(DnsQuery *q, DnsQuery *auxiliary_for) {
+ assert(q);
+ assert(auxiliary_for);
+
+ /* Ensure that the query is not auxiliary yet, and
+ * nothing else is auxiliary to it either */
+ assert(!q->auxiliary_for);
+ assert(!q->auxiliary_queries);
+
+ /* Ensure that the unit we shall be made auxiliary for isn't
+ * auxiliary itself */
+ assert(!auxiliary_for->auxiliary_for);
+
+ if (auxiliary_for->n_auxiliary_queries >= AUXILIARY_QUERIES_MAX)
+ return -EAGAIN;
+
+ LIST_PREPEND(auxiliary_queries, auxiliary_for->auxiliary_queries, q);
+ q->auxiliary_for = auxiliary_for;
+
+ auxiliary_for->n_auxiliary_queries++;
+ return 0;
+}
+
+void dns_query_complete(DnsQuery *q, DnsTransactionState state) {
+ assert(q);
+ assert(!DNS_TRANSACTION_IS_LIVE(state));
+ assert(DNS_TRANSACTION_IS_LIVE(q->state));
+
+ /* Note that this call might invalidate the query. Callers should hence not attempt to access the
+ * query or transaction after calling this function. */
+
+ q->state = state;
+
+ (void) manager_monitor_send(q->manager, q->state, q->answer_rcode, q->answer_errno, q->question_idna, q->question_utf8, q->question_bypass, q->collected_questions, q->answer);
+
+ dns_query_stop(q);
+ if (q->complete)
+ q->complete(q);
+}
+
+static int on_query_timeout(sd_event_source *s, usec_t usec, void *userdata) {
+ DnsQuery *q = ASSERT_PTR(userdata);
+
+ assert(s);
+
+ dns_query_complete(q, DNS_TRANSACTION_TIMEOUT);
+ return 0;
+}
+
+static int dns_query_add_candidate(DnsQuery *q, DnsScope *s) {
+ _cleanup_(dns_query_candidate_unrefp) DnsQueryCandidate *c = NULL;
+ int r;
+
+ assert(q);
+ assert(s);
+
+ r = dns_query_candidate_new(&c, q, s);
+ if (r < 0)
+ return r;
+
+ /* If this a single-label domain on DNS, we might append a suitable search domain first. */
+ if (!FLAGS_SET(q->flags, SD_RESOLVED_NO_SEARCH) &&
+ dns_scope_name_wants_search_domain(s, dns_question_first_name(q->question_idna))) {
+ /* OK, we want a search domain now. Let's find one for this scope */
+
+ r = dns_query_candidate_next_search_domain(c);
+ if (r < 0)
+ return r;
+ }
+
+ r = dns_query_candidate_setup_transactions(c);
+ if (r < 0)
+ return r;
+
+ TAKE_PTR(c);
+ return 0;
+}
+
+static int dns_query_synthesize_reply(DnsQuery *q, DnsTransactionState *state) {
+ _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
+ int r;
+
+ assert(q);
+ assert(state);
+
+ /* Tries to synthesize localhost RR replies (and others) where appropriate. Note that this is done *after* the
+ * the normal lookup finished. The data from the network hence takes precedence over the data we
+ * synthesize. (But note that many scopes refuse to resolve certain domain names) */
+
+ if (!IN_SET(*state,
+ DNS_TRANSACTION_RCODE_FAILURE,
+ DNS_TRANSACTION_NO_SERVERS,
+ DNS_TRANSACTION_TIMEOUT,
+ DNS_TRANSACTION_ATTEMPTS_MAX_REACHED,
+ DNS_TRANSACTION_NETWORK_DOWN,
+ DNS_TRANSACTION_NOT_FOUND))
+ return 0;
+
+ if (FLAGS_SET(q->flags, SD_RESOLVED_NO_SYNTHESIZE))
+ return 0;
+
+ r = dns_synthesize_answer(
+ q->manager,
+ q->question_bypass ? q->question_bypass->question : q->question_utf8,
+ q->ifindex,
+ &answer);
+ if (r == -ENXIO) {
+ /* If we get ENXIO this tells us to generate NXDOMAIN unconditionally. */
+
+ dns_query_reset_answer(q);
+ q->answer_rcode = DNS_RCODE_NXDOMAIN;
+ q->answer_protocol = dns_synthesize_protocol(q->flags);
+ q->answer_family = dns_synthesize_family(q->flags);
+ q->answer_query_flags = SD_RESOLVED_AUTHENTICATED|SD_RESOLVED_CONFIDENTIAL|SD_RESOLVED_SYNTHETIC;
+ *state = DNS_TRANSACTION_RCODE_FAILURE;
+
+ return 0;
+ }
+ if (r <= 0)
+ return r;
+
+ dns_query_reset_answer(q);
+
+ q->answer = TAKE_PTR(answer);
+ q->answer_rcode = DNS_RCODE_SUCCESS;
+ q->answer_protocol = dns_synthesize_protocol(q->flags);
+ q->answer_family = dns_synthesize_family(q->flags);
+ q->answer_query_flags = SD_RESOLVED_AUTHENTICATED|SD_RESOLVED_CONFIDENTIAL|SD_RESOLVED_SYNTHETIC;
+
+ *state = DNS_TRANSACTION_SUCCESS;
+
+ return 1;
+}
+
+static int dns_query_try_etc_hosts(DnsQuery *q) {
+ _cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
+ int r;
+
+ assert(q);
+
+ /* Looks in /etc/hosts for matching entries. Note that this is done *before* the normal lookup is
+ * done. The data from /etc/hosts hence takes precedence over the network. */
+
+ if (FLAGS_SET(q->flags, SD_RESOLVED_NO_SYNTHESIZE))
+ return 0;
+
+ r = manager_etc_hosts_lookup(
+ q->manager,
+ q->question_bypass ? q->question_bypass->question : q->question_utf8,
+ &answer);
+ if (r <= 0)
+ return r;
+
+ dns_query_reset_answer(q);
+
+ q->answer = TAKE_PTR(answer);
+ q->answer_rcode = DNS_RCODE_SUCCESS;
+ q->answer_protocol = dns_synthesize_protocol(q->flags);
+ q->answer_family = dns_synthesize_family(q->flags);
+ q->answer_query_flags = SD_RESOLVED_AUTHENTICATED|SD_RESOLVED_CONFIDENTIAL|SD_RESOLVED_SYNTHETIC;
+
+ return 1;
+}
+
+int dns_query_go(DnsQuery *q) {
+ DnsScopeMatch found = DNS_SCOPE_NO;
+ DnsScope *first = NULL;
+ int r;
+
+ assert(q);
+
+ if (q->state != DNS_TRANSACTION_NULL)
+ return 0;
+
+ r = dns_query_try_etc_hosts(q);
+ if (r < 0)
+ return r;
+ if (r > 0) {
+ dns_query_complete(q, DNS_TRANSACTION_SUCCESS);
+ return 1;
+ }
+
+ LIST_FOREACH(scopes, s, q->manager->dns_scopes) {
+ DnsScopeMatch match;
+
+ match = dns_scope_good_domain(s, q);
+ assert(match >= 0);
+ if (match > found) { /* Does this match better? If so, remember how well it matched, and the first one
+ * that matches this well */
+ found = match;
+ first = s;
+ }
+ }
+
+ if (found == DNS_SCOPE_NO) {
+ DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS;
+
+ r = dns_query_synthesize_reply(q, &state);
+ if (r < 0)
+ return r;
+
+ dns_query_complete(q, state);
+ return 1;
+ }
+
+ r = dns_query_add_candidate(q, first);
+ if (r < 0)
+ goto fail;
+
+ LIST_FOREACH(scopes, s, first->scopes_next) {
+ DnsScopeMatch match;
+
+ match = dns_scope_good_domain(s, q);
+ assert(match >= 0);
+ if (match < found)
+ continue;
+
+ r = dns_query_add_candidate(q, s);
+ if (r < 0)
+ goto fail;
+ }
+
+ dns_query_reset_answer(q);
+
+ r = event_reset_time_relative(
+ q->manager->event,
+ &q->timeout_event_source,
+ CLOCK_BOOTTIME,
+ SD_RESOLVED_QUERY_TIMEOUT_USEC,
+ 0, on_query_timeout, q,
+ 0, "query-timeout", true);
+ if (r < 0)
+ goto fail;
+
+ q->state = DNS_TRANSACTION_PENDING;
+ q->block_ready++;
+
+ /* Start the transactions */
+ LIST_FOREACH(candidates_by_query, c, q->candidates) {
+ r = dns_query_candidate_go(c);
+ if (r < 0) {
+ q->block_ready--;
+ goto fail;
+ }
+ }
+
+ q->block_ready--;
+ dns_query_ready(q);
+
+ return 1;
+
+fail:
+ dns_query_stop(q);
+ return r;
+}
+
+static void dns_query_accept(DnsQuery *q, DnsQueryCandidate *c) {
+ DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS;
+ bool has_authenticated = false, has_non_authenticated = false, has_confidential = false, has_non_confidential = false;
+ DnssecResult dnssec_result_authenticated = _DNSSEC_RESULT_INVALID, dnssec_result_non_authenticated = _DNSSEC_RESULT_INVALID;
+ DnsTransaction *t;
+ int r;
+
+ assert(q);
+
+ if (!c) {
+ r = dns_query_synthesize_reply(q, &state);
+ if (r < 0)
+ goto fail;
+
+ dns_query_complete(q, state);
+ return;
+ }
+
+ if (c->error_code != 0) {
+ /* If the candidate had an error condition of its own, start with that. */
+ state = DNS_TRANSACTION_ERRNO;
+ q->answer = dns_answer_unref(q->answer);
+ q->answer_rcode = 0;
+ q->answer_dnssec_result = _DNSSEC_RESULT_INVALID;
+ q->answer_query_flags = 0;
+ q->answer_errno = c->error_code;
+ q->answer_full_packet = dns_packet_unref(q->answer_full_packet);
+ }
+
+ SET_FOREACH(t, c->transactions) {
+
+ switch (t->state) {
+
+ case DNS_TRANSACTION_SUCCESS: {
+ /* We found a successful reply, merge it into the answer */
+
+ if (state == DNS_TRANSACTION_SUCCESS) {
+ r = dns_answer_extend(&q->answer, t->answer);
+ if (r < 0)
+ goto fail;
+
+ q->answer_query_flags |= dns_transaction_source_to_query_flags(t->answer_source);
+ } else {
+ /* Override non-successful previous answers */
+ DNS_ANSWER_REPLACE(q->answer, dns_answer_ref(t->answer));
+ q->answer_query_flags = dns_transaction_source_to_query_flags(t->answer_source);
+ }
+
+ q->answer_rcode = t->answer_rcode;
+ q->answer_errno = 0;
+
+ DNS_PACKET_REPLACE(q->answer_full_packet, dns_packet_ref(t->received));
+
+ if (FLAGS_SET(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED)) {
+ has_authenticated = true;
+ dnssec_result_authenticated = t->answer_dnssec_result;
+ } else {
+ has_non_authenticated = true;
+ dnssec_result_non_authenticated = t->answer_dnssec_result;
+ }
+
+ if (FLAGS_SET(t->answer_query_flags, SD_RESOLVED_CONFIDENTIAL))
+ has_confidential = true;
+ else
+ has_non_confidential = true;
+
+ state = DNS_TRANSACTION_SUCCESS;
+ break;
+ }
+
+ case DNS_TRANSACTION_NULL:
+ case DNS_TRANSACTION_PENDING:
+ case DNS_TRANSACTION_VALIDATING:
+ case DNS_TRANSACTION_ABORTED:
+ /* Ignore transactions that didn't complete */
+ continue;
+
+ default:
+ /* Any kind of failure? Store the data away, if there's nothing stored yet. */
+ if (state == DNS_TRANSACTION_SUCCESS)
+ continue;
+
+ /* If there's already an authenticated negative reply stored, then prefer that over any unauthenticated one */
+ if (FLAGS_SET(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED) &&
+ !FLAGS_SET(t->answer_query_flags, SD_RESOLVED_AUTHENTICATED))
+ continue;
+
+ DNS_ANSWER_REPLACE(q->answer, dns_answer_ref(t->answer));
+ q->answer_rcode = t->answer_rcode;
+ q->answer_dnssec_result = t->answer_dnssec_result;
+ q->answer_query_flags = t->answer_query_flags | dns_transaction_source_to_query_flags(t->answer_source);
+ q->answer_errno = t->answer_errno;
+ DNS_PACKET_REPLACE(q->answer_full_packet, dns_packet_ref(t->received));
+
+ state = t->state;
+ break;
+ }
+ }
+
+ if (state == DNS_TRANSACTION_SUCCESS) {
+ SET_FLAG(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED, has_authenticated && !has_non_authenticated);
+ SET_FLAG(q->answer_query_flags, SD_RESOLVED_CONFIDENTIAL, has_confidential && !has_non_confidential);
+ q->answer_dnssec_result = FLAGS_SET(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED) ? dnssec_result_authenticated : dnssec_result_non_authenticated;
+ }
+
+ q->answer_protocol = c->scope->protocol;
+ q->answer_family = c->scope->family;
+
+ dns_search_domain_unref(q->answer_search_domain);
+ q->answer_search_domain = dns_search_domain_ref(c->search_domain);
+
+ r = dns_query_synthesize_reply(q, &state);
+ if (r < 0)
+ goto fail;
+
+ dns_query_complete(q, state);
+ return;
+
+fail:
+ q->answer_errno = -r;
+ dns_query_complete(q, DNS_TRANSACTION_ERRNO);
+}
+
+void dns_query_ready(DnsQuery *q) {
+ DnsQueryCandidate *bad = NULL;
+ bool pending = false;
+
+ assert(q);
+ assert(DNS_TRANSACTION_IS_LIVE(q->state));
+
+ /* Note that this call might invalidate the query. Callers
+ * should hence not attempt to access the query or transaction
+ * after calling this function, unless the block_ready
+ * counter was explicitly bumped before doing so. */
+
+ if (q->block_ready > 0)
+ return;
+
+ LIST_FOREACH(candidates_by_query, c, q->candidates) {
+ DnsTransactionState state;
+
+ state = dns_query_candidate_state(c);
+ switch (state) {
+
+ case DNS_TRANSACTION_SUCCESS:
+ /* One of the candidates is successful,
+ * let's use it, and copy its data out */
+ dns_query_accept(q, c);
+ return;
+
+ case DNS_TRANSACTION_NULL:
+ case DNS_TRANSACTION_PENDING:
+ case DNS_TRANSACTION_VALIDATING:
+ /* One of the candidates is still going on,
+ * let's maybe wait for it */
+ pending = true;
+ break;
+
+ default:
+ /* Any kind of failure */
+ bad = c;
+ break;
+ }
+ }
+
+ if (pending)
+ return;
+
+ dns_query_accept(q, bad);
+}
+
+static int dns_query_collect_question(DnsQuery *q, DnsQuestion *question) {
+ _cleanup_(dns_question_unrefp) DnsQuestion *merged = NULL;
+ int r;
+
+ assert(q);
+
+ if (dns_question_size(question) == 0)
+ return 0;
+
+ /* When redirecting, save the first element in the chain, for informational purposes when monitoring */
+ r = dns_question_merge(q->collected_questions, question, &merged);
+ if (r < 0)
+ return r;
+
+ dns_question_unref(q->collected_questions);
+ q->collected_questions = TAKE_PTR(merged);
+
+ return 0;
+}
+
+static int dns_query_cname_redirect(DnsQuery *q, const DnsResourceRecord *cname) {
+ _cleanup_(dns_question_unrefp) DnsQuestion *nq_idna = NULL, *nq_utf8 = NULL;
+ int r, k;
+
+ assert(q);
+
+ if (q->n_cname_redirects >= CNAME_REDIRECTS_MAX)
+ return -ELOOP;
+ q->n_cname_redirects++;
+
+ r = dns_question_cname_redirect(q->question_idna, cname, &nq_idna);
+ if (r < 0)
+ return r;
+ if (r > 0)
+ log_debug("Following CNAME/DNAME %s %s %s.",
+ dns_question_first_name(q->question_idna),
+ special_glyph(SPECIAL_GLYPH_ARROW_RIGHT),
+ dns_question_first_name(nq_idna));
+
+ k = dns_question_is_equal(q->question_idna, q->question_utf8);
+ if (k < 0)
+ return k;
+ if (k > 0) {
+ /* Same question? Shortcut new question generation */
+ nq_utf8 = dns_question_ref(nq_idna);
+ k = r;
+ } else {
+ k = dns_question_cname_redirect(q->question_utf8, cname, &nq_utf8);
+ if (k < 0)
+ return k;
+ if (k > 0)
+ log_debug("Following UTF8 CNAME/DNAME %s %s %s.",
+ dns_question_first_name(q->question_utf8),
+ special_glyph(SPECIAL_GLYPH_ARROW_RIGHT),
+ dns_question_first_name(nq_utf8));
+ }
+
+ if (r == 0 && k == 0) /* No actual cname happened? */
+ return -ELOOP;
+
+ if (q->answer_protocol == DNS_PROTOCOL_DNS)
+ /* Don't permit CNAME redirects from unicast DNS to LLMNR or MulticastDNS, so that global resources
+ * cannot invade the local namespace. The opposite way we permit: local names may redirect to global
+ * ones. */
+ q->flags &= ~(SD_RESOLVED_LLMNR|SD_RESOLVED_MDNS); /* mask away the local protocols */
+
+ /* Turn off searching for the new name */
+ q->flags |= SD_RESOLVED_NO_SEARCH;
+
+ r = dns_query_collect_question(q, q->question_idna);
+ if (r < 0)
+ return r;
+ r = dns_query_collect_question(q, q->question_utf8);
+ if (r < 0)
+ return r;
+
+ /* Install the redirected question */
+ dns_question_unref(q->question_idna);
+ q->question_idna = TAKE_PTR(nq_idna);
+
+ dns_question_unref(q->question_utf8);
+ q->question_utf8 = TAKE_PTR(nq_utf8);
+
+ dns_query_unlink_candidates(q);
+
+ /* Note that we do *not* reset the answer here, because the answer we previously got might already
+ * include everything we need, let's check that first */
+
+ q->state = DNS_TRANSACTION_NULL;
+
+ return 0;
+}
+
+int dns_query_process_cname_one(DnsQuery *q) {
+ _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *cname = NULL;
+ DnsQuestion *question;
+ DnsResourceRecord *rr;
+ bool full_match = true;
+ DnsResourceKey *k;
+ int r;
+
+ assert(q);
+
+ /* Processes a CNAME redirect if there's one. Returns one of three values:
+ *
+ * CNAME_QUERY_MATCH → direct RR match, caller should just use the RRs in this answer (and not
+ * bother with any CNAME/DNAME stuff)
+ *
+ * CNAME_QUERY_NOMATCH → no match at all, neither direct nor CNAME/DNAME, caller might decide to
+ * restart query or take things as NODATA reply.
+ *
+ * CNAME_QUERY_CNAME → no direct RR match, but a CNAME/DNAME match that we now followed for one step.
+ *
+ * The function might also return a failure, in particular -ELOOP if we encountered too many
+ * CNAMEs/DNAMEs in a chain or if following CNAMEs/DNAMEs was turned off.
+ *
+ * Note that this function doesn't actually restart the query. The caller can decide to do that in
+ * case of CNAME_QUERY_CNAME, though. */
+
+ if (!IN_SET(q->state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_NULL))
+ return DNS_QUERY_NOMATCH;
+
+ question = dns_query_question_for_protocol(q, q->answer_protocol);
+
+ /* Small reminder: our question will consist of one or more RR keys that match in name, but not in
+ * record type. Specifically, when we do an address lookup the question will typically consist of one
+ * A and one AAAA key lookup for the same domain name. When we get a response from a server we need
+ * to check if the answer answers all our questions to use it. Note that a response of CNAME/DNAME
+ * can answer both an A and the AAAA question for us, but an A/AAAA response only the relevant
+ * type.
+ *
+ * Hence we first check of the answers we collected are sufficient to answer all our questions
+ * directly. If one question wasn't answered we go on, waiting for more replies. However, if there's
+ * a CNAME/DNAME response we use it, and redirect to it, regardless if it was a response to the A or
+ * the AAAA query. */
+
+ DNS_QUESTION_FOREACH(k, question) {
+ bool match = false;
+
+ DNS_ANSWER_FOREACH(rr, q->answer) {
+ r = dns_resource_key_match_rr(k, rr, DNS_SEARCH_DOMAIN_NAME(q->answer_search_domain));
+ if (r < 0)
+ return r;
+ if (r > 0) {
+ match = true; /* Yay, we found an RR that matches the key we are looking for */
+ break;
+ }
+ }
+
+ if (!match) {
+ /* Hmm. :-( there's no response for this key. This doesn't match. */
+ full_match = false;
+ break;
+ }
+ }
+
+ if (full_match)
+ return DNS_QUERY_MATCH; /* The answer can answer our question in full, no need to follow CNAMEs/DNAMEs */
+
+ /* Let's see if there is a CNAME/DNAME to match. This case is simpler: we accept the CNAME/DNAME that
+ * matches any of our questions. */
+ DNS_ANSWER_FOREACH(rr, q->answer) {
+ r = dns_question_matches_cname_or_dname(question, rr, DNS_SEARCH_DOMAIN_NAME(q->answer_search_domain));
+ if (r < 0)
+ return r;
+ if (r > 0 && !cname)
+ cname = dns_resource_record_ref(rr);
+ }
+
+ if (!cname)
+ return DNS_QUERY_NOMATCH; /* No match and no CNAME/DNAME to follow */
+
+ if (q->flags & SD_RESOLVED_NO_CNAME)
+ return -ELOOP;
+
+ if (!FLAGS_SET(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED))
+ q->previous_redirect_unauthenticated = true;
+ if (!FLAGS_SET(q->answer_query_flags, SD_RESOLVED_CONFIDENTIAL))
+ q->previous_redirect_non_confidential = true;
+ if (!FLAGS_SET(q->answer_query_flags, SD_RESOLVED_SYNTHETIC))
+ q->previous_redirect_non_synthetic = true;
+
+ /* OK, let's actually follow the CNAME */
+ r = dns_query_cname_redirect(q, cname);
+ if (r < 0)
+ return r;
+
+ return DNS_QUERY_CNAME; /* Tell caller that we did a single CNAME/DNAME redirection step */
+}
+
+int dns_query_process_cname_many(DnsQuery *q) {
+ int r;
+
+ assert(q);
+
+ /* Follows CNAMEs through the current packet: as long as the current packet can fulfill our
+ * redirected CNAME queries we keep going, and restart the query once the current packet isn't good
+ * enough anymore. It's a wrapper around dns_query_process_cname_one() and returns the same values,
+ * but with extended semantics. Specifically:
+ *
+ * DNS_QUERY_MATCH → as above
+ *
+ * DNS_QUERY_CNAME → we ran into a CNAME/DNAME redirect that we could not answer from the current
+ * message, and thus restarted the query to resolve it.
+ *
+ * DNS_QUERY_NOMATCH → we reached the end of CNAME/DNAME chain, and there are no direct matches nor a
+ * CNAME/DNAME match. i.e. this is a NODATA case.
+ *
+ * Note that this function will restart the query for the caller if needed, and that's the case
+ * DNS_QUERY_CNAME is returned.
+ */
+
+ r = dns_query_process_cname_one(q);
+ if (r != DNS_QUERY_CNAME)
+ return r; /* The first redirect is special: if it doesn't answer the question that's no
+ * reason to restart the query, we just accept this as a NODATA answer. */
+
+ for (;;) {
+ r = dns_query_process_cname_one(q);
+ if (r < 0 || r == DNS_QUERY_MATCH)
+ return r;
+ if (r == DNS_QUERY_NOMATCH) {
+ /* OK, so we followed one or more CNAME/DNAME RR but the existing packet can't answer
+ * this. Let's restart the query hence, with the new question. Why the different
+ * handling than the first chain element? Because if the server answers a direct
+ * question with an empty answer then this is a NODATA response. But if it responds
+ * with a CNAME chain that ultimately is incomplete (i.e. a non-empty but truncated
+ * CNAME chain) then we better follow up ourselves and ask for the rest of the
+ * chain. This is particular relevant since our cache will store CNAME/DNAME
+ * redirects that we learnt about for lookups of certain DNS types, but later on we
+ * can reuse this data even for other DNS types, but in that case need to follow up
+ * with the final lookup of the chain ourselves with the RR type we ourselves are
+ * interested in. */
+ r = dns_query_go(q);
+ if (r < 0)
+ return r;
+
+ return DNS_QUERY_CNAME;
+ }
+
+ /* So we found a CNAME that the existing packet already answers, again via a CNAME, let's
+ * continue going then. */
+ assert(r == DNS_QUERY_CNAME);
+ }
+}
+
+DnsQuestion* dns_query_question_for_protocol(DnsQuery *q, DnsProtocol protocol) {
+ assert(q);
+
+ if (q->question_bypass)
+ return q->question_bypass->question;
+
+ switch (protocol) {
+
+ case DNS_PROTOCOL_DNS:
+ return q->question_idna;
+
+ case DNS_PROTOCOL_MDNS:
+ case DNS_PROTOCOL_LLMNR:
+ return q->question_utf8;
+
+ default:
+ return NULL;
+ }
+}
+
+const char *dns_query_string(DnsQuery *q) {
+ const char *name;
+ int r;
+
+ /* Returns a somewhat useful human-readable lookup key string for this query */
+
+ if (q->question_bypass)
+ return dns_question_first_name(q->question_bypass->question);
+
+ if (q->request_address_string)
+ return q->request_address_string;
+
+ if (q->request_address_valid) {
+ r = in_addr_to_string(q->request_family, &q->request_address, &q->request_address_string);
+ if (r >= 0)
+ return q->request_address_string;
+ }
+
+ name = dns_question_first_name(q->question_utf8);
+ if (name)
+ return name;
+
+ return dns_question_first_name(q->question_idna);
+}
+
+bool dns_query_fully_authenticated(DnsQuery *q) {
+ assert(q);
+
+ return FLAGS_SET(q->answer_query_flags, SD_RESOLVED_AUTHENTICATED) && !q->previous_redirect_unauthenticated;
+}
+
+bool dns_query_fully_confidential(DnsQuery *q) {
+ assert(q);
+
+ return FLAGS_SET(q->answer_query_flags, SD_RESOLVED_CONFIDENTIAL) && !q->previous_redirect_non_confidential;
+}
+
+bool dns_query_fully_authoritative(DnsQuery *q) {
+ assert(q);
+
+ /* We are authoritative for everything synthetic (except if a previous CNAME/DNAME) wasn't
+ * synthetic. (Note: SD_RESOLVED_SYNTHETIC is reset on each CNAME/DNAME, hence the explicit check for
+ * previous synthetic DNAME/CNAME redirections.) */
+ if ((q->answer_query_flags & SD_RESOLVED_SYNTHETIC) && !q->previous_redirect_non_synthetic)
+ return true;
+
+ /* We are also authoritative for everything coming only from the trust anchor and the local
+ * zones. (Note: the SD_RESOLVED_FROM_xyz flags we merge on each redirect, hence no need to
+ * explicitly check previous redirects here.) */
+ return (q->answer_query_flags & SD_RESOLVED_FROM_MASK & ~(SD_RESOLVED_FROM_TRUST_ANCHOR | SD_RESOLVED_FROM_ZONE)) == 0;
+}