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Systemd/src/resolve/resolved-dns-query.c

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#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 = new(DnsQueryCandidate, 1);
if (!c)
return -ENOMEM;
*c = (DnsQueryCandidate) {
.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);
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) {
_cleanup_(dns_transaction_gcp) DnsTransaction *t = NULL;
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(&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;
}
t->clamp_ttl = c->query->clamp_ttl;
TAKE_PTR(t);
return 1;
}
static int dns_query_candidate_go(DnsQueryCandidate *c) {
DnsTransaction *t;
int r;
unsigned n = 0;
assert(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);
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 (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->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);
}
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. */
(void) set_remove(q->request_dns_stream->queries, q);
q->request_dns_stream = 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 = new(DnsQuery, 1);
if (!q)
return -ENOMEM;
*q = (DnsQuery) {
.question_utf8 = dns_question_ref(question_utf8),
.question_idna = dns_question_ref(question_idna),
.ifindex = ifindex,
.flags = flags,
.answer_dnssec_result = _DNSSEC_RESULT_INVALID,
.answer_protocol = _DNS_PROTOCOL_INVALID,
.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;
}
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) {
_cleanup_(dns_query_candidate_freep) 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;
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_relative(
q->manager->event,
&q->timeout_event_source,
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;
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) {
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 */
}
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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