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Systemd/src/resolve/resolved-dns-query.c
ott 4cbfd62b46 resolve: Adjust and unify D-Bus call timeout (#7847) 
DNS queries have a timeout of DNS_TRANSACTION_ATTEMPTS_MAX *
DNS_TIMEOUT_MAX_USEC = 120 s. Calls to the ResolveHostname method of
the org.freedesktop.resolve1.Manager interface have various call
timeouts that are smaller than 120 s. So it seems correct to adjust
the call timeout to the maximum query timeout and to unify the call
timeout among all callers.

A timeout of 120 s might seem large, in particular since BIND does seem
to have a query timeout of 10 s. However, it seems match the timeout
value of 120 s of Unbound. Moreover, the query and timeout handling of
resolve have problems and might be improved in the future, so this
change is at best an interim solution.
2018-01-23 09:53:31 +09:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
/***
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 "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) {
r = dns_scope_name_needs_search_domain(s, dns_question_first_name(q->question_idna));
if (r < 0)
goto fail;
if (r > 0) {
/* 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 = answer;
answer = NULL;
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 = answer;
answer = NULL;
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)
return match;
if (match == DNS_SCOPE_NO)
continue;
found = match;
if (match == DNS_SCOPE_YES) {
first = s;
break;
} else {
assert(match == DNS_SCOPE_MAYBE);
if (!first)
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)
goto fail;
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 = nq_idna;
nq_idna = NULL;
dns_question_unref(q->question_utf8);
q->question_utf8 = nq_utf8;
nq_utf8 = NULL;
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;
}
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