diff options
Diffstat (limited to 'src/resolve/resolved-dns-query.c')
| -rw-r--r-- | src/resolve/resolved-dns-query.c | 1109 |
1 files changed, 1109 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..535ef4e --- /dev/null +++ b/src/resolve/resolved-dns-query.c @@ -0,0 +1,1109 @@ +/* SPDX-License-Identifier: LGPL-2.1+ */ + +#include "alloc-util.h" +#include "dns-domain.h" +#include "dns-type.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 CNAME_MAX 8 +#define QUERIES_MAX 2048 +#define AUXILIARY_QUERIES_MAX 64 + +static int dns_query_candidate_new(DnsQueryCandidate **ret, DnsQuery *q, DnsScope *s) { + DnsQueryCandidate *c; + + assert(ret); + assert(q); + assert(s); + + c = new0(DnsQueryCandidate, 1); + if (!c) + return -ENOMEM; + + c->query = q; + c->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); + + 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); + } +} + +DnsQueryCandidate* dns_query_candidate_free(DnsQueryCandidate *c) { + + if (!c) + return NULL; + + dns_query_candidate_stop(c); + + set_free(c->transactions); + dns_search_domain_unref(c->search_domain); + + if (c->query) + LIST_REMOVE(candidates_by_query, c->query->candidates, c); + + if (c->scope) + LIST_REMOVE(candidates_by_scope, c->scope->query_candidates, c); + + return mfree(c); +} + +static int dns_query_candidate_next_search_domain(DnsQueryCandidate *c) { + DnsSearchDomain *next = NULL; + + 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) { + DnsTransaction *t; + int r; + + assert(c); + assert(key); + + t = dns_scope_find_transaction(c->scope, key, true); + if (!t) { + r = dns_transaction_new(&t, c->scope, key); + if (r < 0) + return r; + } else { + if (set_contains(c->transactions, t)) + return 0; + } + + r = set_ensure_allocated(&c->transactions, NULL); + if (r < 0) + goto gc; + + r = set_ensure_allocated(&t->notify_query_candidates, NULL); + if (r < 0) + goto gc; + + r = set_ensure_allocated(&t->notify_query_candidates_done, NULL); + if (r < 0) + goto gc; + + r = set_put(t->notify_query_candidates, c); + if (r < 0) + goto gc; + + r = set_put(c->transactions, t); + if (r < 0) { + (void) set_remove(t->notify_query_candidates, c); + goto gc; + } + + t->clamp_ttl = c->query->clamp_ttl; + return 1; + +gc: + dns_transaction_gc(t); + return r; +} + +static int dns_query_candidate_go(DnsQueryCandidate *c) { + DnsTransaction *t; + Iterator i; + int r; + unsigned n = 0; + + assert(c); + + /* Start the transactions that are not started yet */ + SET_FOREACH(t, c->transactions, i) { + 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; + Iterator i; + + assert(c); + + if (c->error_code != 0) + return DNS_TRANSACTION_ERRNO; + + SET_FOREACH(t, c->transactions, i) { + + 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 bool dns_query_candidate_is_routable(DnsQueryCandidate *c, uint16_t type) { + int family; + + assert(c); + + /* Checks whether the specified RR type matches an address family that is routable on the link(s) the scope of + * this candidate belongs to. Specifically, whether there's a routable IPv4 address on it if we query an A RR, + * or a routable IPv6 address if we query an AAAA RR. */ + + if (!c->query->suppress_unroutable_family) + return true; + + if (c->scope->protocol != DNS_PROTOCOL_DNS) + return true; + + family = dns_type_to_af(type); + if (family < 0) + return true; + + if (c->scope->link) + return link_relevant(c->scope->link, family, false); + else + return manager_routable(c->scope->manager, family); +} + +static int dns_query_candidate_setup_transactions(DnsQueryCandidate *c) { + DnsQuestion *question; + DnsResourceKey *key; + int n = 0, r; + + assert(c); + + dns_query_candidate_stop(c); + + 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 (!dns_query_candidate_is_routable(c, key->type)) + continue; + + 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); + 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); + + 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: + log_warning_errno(r, "Failed to follow search domains: %m"); + c->error_code = r; + dns_query_ready(c->query); +} + +static void dns_query_stop(DnsQuery *q) { + DnsQueryCandidate *c; + + assert(q); + + q->timeout_event_source = sd_event_source_unref(q->timeout_event_source); + + LIST_FOREACH(candidates_by_query, c, q->candidates) + dns_query_candidate_stop(c); +} + +static void dns_query_free_candidates(DnsQuery *q) { + assert(q); + + while (q->candidates) + dns_query_candidate_free(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_authenticated = false; + q->answer_protocol = _DNS_PROTOCOL_INVALID; + q->answer_family = AF_UNSPEC; + q->answer_search_domain = dns_search_domain_unref(q->answer_search_domain); +} + +DnsQuery *dns_query_free(DnsQuery *q) { + if (!q) + return NULL; + + 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_free_candidates(q); + + dns_question_unref(q->question_idna); + dns_question_unref(q->question_utf8); + + dns_query_reset_answer(q); + + sd_bus_message_unref(q->request); + sd_bus_track_unref(q->bus_track); + + dns_packet_unref(q->request_dns_packet); + dns_packet_unref(q->reply_dns_packet); + + if (q->request_dns_stream) { + /* Detach the stream from our query, in case something else keeps a reference to it. */ + q->request_dns_stream->complete = NULL; + q->request_dns_stream->on_packet = NULL; + q->request_dns_stream->query = NULL; + dns_stream_unref(q->request_dns_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, + int ifindex, + uint64_t flags) { + + _cleanup_(dns_query_freep) DnsQuery *q = NULL; + DnsResourceKey *key; + bool good = false; + int r; + char key_str[DNS_RESOURCE_KEY_STRING_MAX]; + + assert(m); + + 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 = new0(DnsQuery, 1); + if (!q) + return -ENOMEM; + + q->question_utf8 = dns_question_ref(question_utf8); + q->question_idna = dns_question_ref(question_idna); + q->ifindex = ifindex; + q->flags = flags; + q->answer_dnssec_result = _DNSSEC_RESULT_INVALID; + q->answer_protocol = _DNS_PROTOCOL_INVALID; + q->answer_family = AF_UNSPEC; + + /* 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(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; + q = NULL; + + 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; +} + +static 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; + + 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 = userdata; + + assert(s); + assert(q); + + dns_query_complete(q, DNS_TRANSACTION_TIMEOUT); + return 0; +} + +static int dns_query_add_candidate(DnsQuery *q, DnsScope *s) { + DnsQueryCandidate *c; + 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 ((q->flags & SD_RESOLVED_NO_SEARCH) == 0 && + dns_scope_name_needs_search_domain(s, dns_question_first_name(q->question_idna))) { + /* OK, we need a search domain now. Let's find one for this scope */ + + r = dns_query_candidate_next_search_domain(c); + if (r <= 0) /* if there's no search domain, then we won't add any transaction. */ + goto fail; + } + + r = dns_query_candidate_setup_transactions(c); + if (r < 0) + goto fail; + + return 0; + +fail: + dns_query_candidate_free(c); + return r; +} + +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; + + r = dns_synthesize_answer( + q->manager, + 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_authenticated = true; + *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_authenticated = true; + + *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. */ + + r = manager_etc_hosts_lookup( + q->manager, + 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_authenticated = true; + + return 1; +} + +int dns_query_go(DnsQuery *q) { + DnsScopeMatch found = DNS_SCOPE_NO; + DnsScope *s, *first = NULL; + DnsQueryCandidate *c; + 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; + const char *name; + + name = dns_question_first_name(dns_query_question_for_protocol(q, s->protocol)); + if (!name) + continue; + + match = dns_scope_good_domain(s, q->ifindex, q->flags, name); + if (match < 0) { + log_debug("Couldn't check if '%s' matches against scope, ignoring.", name); + continue; + } + + 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; + const char *name; + + name = dns_question_first_name(dns_query_question_for_protocol(q, s->protocol)); + if (!name) + continue; + + match = dns_scope_good_domain(s, q->ifindex, q->flags, name); + if (match < 0) { + log_debug("Couldn't check if '%s' matches against scope, ignoring.", name); + continue; + } + + if (match < found) + continue; + + r = dns_query_add_candidate(q, s); + if (r < 0) + goto fail; + } + + dns_query_reset_answer(q); + + r = sd_event_add_time( + q->manager->event, + &q->timeout_event_source, + clock_boottime_or_monotonic(), + now(clock_boottime_or_monotonic()) + SD_RESOLVED_QUERY_TIMEOUT_USEC, + 0, on_query_timeout, q); + if (r < 0) + goto fail; + + (void) sd_event_source_set_description(q->timeout_event_source, "query-timeout"); + + 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; + DnssecResult dnssec_result_authenticated = _DNSSEC_RESULT_INVALID, dnssec_result_non_authenticated = _DNSSEC_RESULT_INVALID; + DnsTransaction *t; + Iterator i; + 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_authenticated = false; + q->answer_errno = c->error_code; + } + + SET_FOREACH(t, c->transactions, i) { + + switch (t->state) { + + case DNS_TRANSACTION_SUCCESS: { + /* We found a successfully reply, merge it into the answer */ + r = dns_answer_extend(&q->answer, t->answer); + if (r < 0) + goto fail; + + q->answer_rcode = t->answer_rcode; + q->answer_errno = 0; + + if (t->answer_authenticated) { + has_authenticated = true; + dnssec_result_authenticated = t->answer_dnssec_result; + } else { + has_non_authenticated = true; + dnssec_result_non_authenticated = t->answer_dnssec_result; + } + + 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 (q->answer_authenticated && !t->answer_authenticated) + continue; + + q->answer = dns_answer_unref(q->answer); + q->answer_rcode = t->answer_rcode; + q->answer_dnssec_result = t->answer_dnssec_result; + q->answer_authenticated = t->answer_authenticated; + q->answer_errno = t->answer_errno; + + state = t->state; + break; + } + } + + if (state == DNS_TRANSACTION_SUCCESS) { + q->answer_authenticated = has_authenticated && !has_non_authenticated; + q->answer_dnssec_result = q->answer_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, *c; + 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_cname_redirect(DnsQuery *q, const DnsResourceRecord *cname) { + _cleanup_(dns_question_unrefp) DnsQuestion *nq_idna = NULL, *nq_utf8 = NULL; + int r, k; + + assert(q); + + q->n_cname_redirects++; + if (q->n_cname_redirects > CNAME_MAX) + return -ELOOP; + + r = dns_question_cname_redirect(q->question_idna, cname, &nq_idna); + if (r < 0) + return r; + else if (r > 0) + log_debug("Following CNAME/DNAME %s → %s.", dns_question_first_name(q->question_idna), dns_question_first_name(nq_idna)); + + k = dns_question_is_equal(q->question_idna, q->question_utf8); + if (k < 0) + return r; + 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; + else if (k > 0) + log_debug("Following UTF8 CNAME/DNAME %s → %s.", dns_question_first_name(q->question_utf8), 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; + + 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_free_candidates(q); + dns_query_reset_answer(q); + + q->state = DNS_TRANSACTION_NULL; + + return 0; +} + +int dns_query_process_cname(DnsQuery *q) { + _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *cname = NULL; + DnsQuestion *question; + DnsResourceRecord *rr; + int r; + + assert(q); + + 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); + + DNS_ANSWER_FOREACH(rr, q->answer) { + r = dns_question_matches_rr(question, rr, DNS_SEARCH_DOMAIN_NAME(q->answer_search_domain)); + if (r < 0) + return r; + if (r > 0) + return DNS_QUERY_MATCH; /* The answer matches directly, no need to follow cnames */ + + 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 to follow */ + + if (q->flags & SD_RESOLVED_NO_CNAME) + return -ELOOP; + + if (!q->answer_authenticated) + q->previous_redirect_unauthenticated = true; + + /* OK, let's actually follow the CNAME */ + r = dns_query_cname_redirect(q, cname); + if (r < 0) + return r; + + /* Let's see if the answer can already answer the new + * redirected question */ + r = dns_query_process_cname(q); + if (r != DNS_QUERY_NOMATCH) + return r; + + /* OK, it cannot, let's begin with the new query */ + r = dns_query_go(q); + if (r < 0) + return r; + + return DNS_QUERY_RESTARTED; /* We restarted the query for a new cname */ +} + +static int on_bus_track(sd_bus_track *t, void *userdata) { + DnsQuery *q = userdata; + + assert(t); + assert(q); + + log_debug("Client of active query vanished, aborting query."); + dns_query_complete(q, DNS_TRANSACTION_ABORTED); + return 0; +} + +int dns_query_bus_track(DnsQuery *q, sd_bus_message *m) { + int r; + + assert(q); + assert(m); + + if (!q->bus_track) { + r = sd_bus_track_new(sd_bus_message_get_bus(m), &q->bus_track, on_bus_track, q); + if (r < 0) + return r; + } + + r = sd_bus_track_add_sender(q->bus_track, m); + if (r < 0) + return r; + + return 0; +} + +DnsQuestion* dns_query_question_for_protocol(DnsQuery *q, DnsProtocol protocol) { + assert(q); + + 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->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 q->answer_authenticated && !q->previous_redirect_unauthenticated; +} |