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

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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2014 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include "hostname-util.h"
#include "dns-domain.h"
#include "local-addresses.h"
#include "resolved-dns-query.h"
/* How long to wait for the query in total */
#define QUERY_TIMEOUT_USEC (30 * USEC_PER_SEC)
#define CNAME_MAX 8
#define QUERIES_MAX 2048
static void dns_query_stop(DnsQuery *q) {
DnsTransaction *t;
assert(q);
q->timeout_event_source = sd_event_source_unref(q->timeout_event_source);
while ((t = set_steal_first(q->transactions))) {
set_remove(t->queries, q);
dns_transaction_gc(t);
}
}
DnsQuery *dns_query_free(DnsQuery *q) {
if (!q)
return NULL;
dns_query_stop(q);
set_free(q->transactions);
dns_question_unref(q->question);
dns_answer_unref(q->answer);
sd_bus_message_unref(q->request);
sd_bus_track_unref(q->bus_track);
if (q->manager) {
LIST_REMOVE(queries, q->manager->dns_queries, q);
q->manager->n_dns_queries--;
}
free(q);
return NULL;
}
int dns_query_new(Manager *m, DnsQuery **ret, DnsQuestion *question, int ifindex, uint64_t flags) {
_cleanup_(dns_query_freep) DnsQuery *q = NULL;
unsigned i;
int r;
assert(m);
assert(question);
r = dns_question_is_valid(question);
if (r < 0)
return r;
if (m->n_dns_queries >= QUERIES_MAX)
return -EBUSY;
q = new0(DnsQuery, 1);
if (!q)
return -ENOMEM;
q->question = dns_question_ref(question);
q->ifindex = ifindex;
q->flags = flags;
for (i = 0; i < question->n_keys; i++) {
_cleanup_free_ char *p;
r = dns_resource_key_to_string(question->keys[i], &p);
if (r < 0)
return r;
log_debug("Looking up RR for %s", p);
}
LIST_PREPEND(queries, m->dns_queries, q);
m->n_dns_queries++;
q->manager = m;
if (ret)
*ret = q;
q = NULL;
return 0;
}
static void dns_query_complete(DnsQuery *q, DnsTransactionState state) {
assert(q);
assert(!IN_SET(state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING));
assert(IN_SET(q->state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING));
/* Note that this call might invalidate the query. Callers
* should hence not attempt to access the query or transaction
* after calling this function. */
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_transaction(DnsQuery *q, DnsScope *s, DnsResourceKey *key) {
DnsTransaction *t;
int r;
assert(q);
assert(s);
r = set_ensure_allocated(&q->transactions, NULL);
if (r < 0)
return r;
t = dns_scope_find_transaction(s, key, true);
if (!t) {
r = dns_transaction_new(&t, s, key);
if (r < 0)
return r;
}
r = set_ensure_allocated(&t->queries, NULL);
if (r < 0)
goto gc;
r = set_put(t->queries, q);
if (r < 0)
goto gc;
r = set_put(q->transactions, t);
if (r < 0) {
set_remove(t->queries, q);
goto gc;
}
return 0;
gc:
dns_transaction_gc(t);
return r;
}
static int dns_query_add_transaction_split(DnsQuery *q, DnsScope *s) {
int r;
assert(q);
assert(s);
if (s->protocol == DNS_PROTOCOL_MDNS) {
r = dns_query_add_transaction(q, s, NULL);
if (r < 0)
return r;
} else {
unsigned i;
/* On DNS and LLMNR we can only send a single
* question per datagram, hence issue multiple
* transactions. */
for (i = 0; i < q->question->n_keys; i++) {
r = dns_query_add_transaction(q, s, q->question->keys[i]);
if (r < 0)
return r;
}
}
return 0;
}
static int SYNTHESIZE_IFINDEX(int ifindex) {
/* When the caller asked for resolving on a specific
* interface, we synthesize the answer for that
* interface. However, if nothing specific was claimed and we
* only return localhost RRs, we synthesize the answer for
* localhost. */
if (ifindex > 0)
return ifindex;
return LOOPBACK_IFINDEX;
}
static int SYNTHESIZE_FAMILY(uint64_t flags) {
/* Picks an address family depending on set flags. This is
* purely for synthesized answers, where the family we return
* for the reply should match what was requested in the
* question, even though we are synthesizing the answer
* here. */
if (!(flags & SD_RESOLVED_DNS)) {
if (flags & SD_RESOLVED_LLMNR_IPV4)
return AF_INET;
if (flags & SD_RESOLVED_LLMNR_IPV6)
return AF_INET6;
}
return AF_UNSPEC;
}
static DnsProtocol SYNTHESIZE_PROTOCOL(uint64_t flags) {
/* Similar as SYNTHESIZE_FAMILY() but does this for the
* protocol. If resolving via DNS was requested, we claim it
* was DNS. Similar, if nothing specific was
* requested. However, if only resolving via LLMNR was
* requested we return that. */
if (flags & SD_RESOLVED_DNS)
return DNS_PROTOCOL_DNS;
if (flags & SD_RESOLVED_LLMNR)
return DNS_PROTOCOL_LLMNR;
return DNS_PROTOCOL_DNS;
}
static int dns_type_to_af(uint16_t t) {
switch (t) {
case DNS_TYPE_A:
return AF_INET;
case DNS_TYPE_AAAA:
return AF_INET6;
case DNS_TYPE_ANY:
return AF_UNSPEC;
default:
return -EINVAL;
}
}
static int synthesize_localhost_rr(DnsQuery *q, DnsResourceKey *key, DnsAnswer **answer) {
int r;
assert(q);
assert(key);
assert(answer);
r = dns_answer_reserve(answer, 2);
if (r < 0)
return r;
if (IN_SET(key->type, DNS_TYPE_A, DNS_TYPE_ANY)) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_A, DNS_RESOURCE_KEY_NAME(key));
if (!rr)
return -ENOMEM;
rr->a.in_addr.s_addr = htobe32(INADDR_LOOPBACK);
r = dns_answer_add(*answer, rr, SYNTHESIZE_IFINDEX(q->ifindex));
if (r < 0)
return r;
}
if (IN_SET(key->type, DNS_TYPE_AAAA, DNS_TYPE_ANY)) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_AAAA, DNS_RESOURCE_KEY_NAME(key));
if (!rr)
return -ENOMEM;
rr->aaaa.in6_addr = in6addr_loopback;
r = dns_answer_add(*answer, rr, SYNTHESIZE_IFINDEX(q->ifindex));
if (r < 0)
return r;
}
return 0;
}
static int answer_add_ptr(DnsAnswer **answer, const char *from, const char *to, int ifindex) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_PTR, from);
if (!rr)
return -ENOMEM;
rr->ptr.name = strdup(to);
if (!rr->ptr.name)
return -ENOMEM;
return dns_answer_add(*answer, rr, ifindex);
}
static int synthesize_localhost_ptr(DnsQuery *q, DnsResourceKey *key, DnsAnswer **answer) {
int r;
assert(q);
assert(key);
assert(answer);
r = dns_answer_reserve(answer, 1);
if (r < 0)
return r;
if (IN_SET(key->type, DNS_TYPE_PTR, DNS_TYPE_ANY)) {
r = answer_add_ptr(answer, DNS_RESOURCE_KEY_NAME(key), "localhost", SYNTHESIZE_IFINDEX(q->ifindex));
if (r < 0)
return r;
}
return 0;
}
static int answer_add_addresses_rr(
DnsAnswer **answer,
const char *name,
struct local_address *addresses,
unsigned n_addresses) {
unsigned j;
int r;
assert(answer);
assert(name);
r = dns_answer_reserve(answer, n_addresses);
if (r < 0)
return r;
for (j = 0; j < n_addresses; j++) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
r = dns_resource_record_new_address(&rr, addresses[j].family, &addresses[j].address, name);
if (r < 0)
return r;
r = dns_answer_add(*answer, rr, addresses[j].ifindex);
if (r < 0)
return r;
}
return 0;
}
static int answer_add_addresses_ptr(
DnsAnswer **answer,
const char *name,
struct local_address *addresses,
unsigned n_addresses,
int af, const union in_addr_union *match) {
unsigned j;
int r;
assert(answer);
assert(name);
for (j = 0; j < n_addresses; j++) {
_cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
if (af != AF_UNSPEC) {
if (addresses[j].family != af)
continue;
if (match && !in_addr_equal(af, match, &addresses[j].address))
continue;
}
r = dns_answer_reserve(answer, 1);
if (r < 0)
return r;
r = dns_resource_record_new_reverse(&rr, addresses[j].family, &addresses[j].address, name);
if (r < 0)
return r;
r = dns_answer_add(*answer, rr, addresses[j].ifindex);
if (r < 0)
return r;
}
return 0;
}
static int synthesize_system_hostname_rr(DnsQuery *q, DnsResourceKey *key, DnsAnswer **answer) {
_cleanup_free_ struct local_address *addresses = NULL;
int n = 0, af;
assert(q);
assert(key);
assert(answer);
af = dns_type_to_af(key->type);
if (af >= 0) {
n = local_addresses(q->manager->rtnl, q->ifindex, af, &addresses);
if (n < 0)
return n;
if (n == 0) {
struct local_address buffer[2];
/* If we have no local addresses then use ::1
* and 127.0.0.2 as local ones. */
if (af == AF_INET || af == AF_UNSPEC)
buffer[n++] = (struct local_address) {
.family = AF_INET,
.ifindex = SYNTHESIZE_IFINDEX(q->ifindex),
.address.in.s_addr = htobe32(0x7F000002),
};
if (af == AF_INET6 || af == AF_UNSPEC)
buffer[n++] = (struct local_address) {
.family = AF_INET6,
.ifindex = SYNTHESIZE_IFINDEX(q->ifindex),
.address.in6 = in6addr_loopback,
};
return answer_add_addresses_rr(answer, DNS_RESOURCE_KEY_NAME(key), buffer, n);
}
}
return answer_add_addresses_rr(answer, DNS_RESOURCE_KEY_NAME(key), addresses, n);
}
static int synthesize_system_hostname_ptr(DnsQuery *q, int af, const union in_addr_union *address, DnsAnswer **answer) {
_cleanup_free_ struct local_address *addresses = NULL;
int n, r;
assert(q);
assert(address);
assert(answer);
if (af == AF_INET && address->in.s_addr == htobe32(0x7F000002)) {
/* Always map the IPv4 address 127.0.0.2 to the local
* hostname, in addition to "localhost": */
r = dns_answer_reserve(answer, 3);
if (r < 0)
return r;
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", q->manager->llmnr_hostname, SYNTHESIZE_IFINDEX(q->ifindex));
if (r < 0)
return r;
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", q->manager->mdns_hostname, SYNTHESIZE_IFINDEX(q->ifindex));
if (r < 0)
return r;
r = answer_add_ptr(answer, "2.0.0.127.in-addr.arpa", "localhost", SYNTHESIZE_IFINDEX(q->ifindex));
if (r < 0)
return r;
return 0;
}
n = local_addresses(q->manager->rtnl, q->ifindex, af, &addresses);
if (n < 0)
return n;
r = answer_add_addresses_ptr(answer, q->manager->llmnr_hostname, addresses, n, af, address);
if (r < 0)
return r;
return answer_add_addresses_ptr(answer, q->manager->mdns_hostname, addresses, n, af, address);
}
static int synthesize_gateway_rr(DnsQuery *q, DnsResourceKey *key, DnsAnswer **answer) {
_cleanup_free_ struct local_address *addresses = NULL;
int n = 0, af;
assert(q);
assert(key);
assert(answer);
af = dns_type_to_af(key->type);
if (af >= 0) {
n = local_gateways(q->manager->rtnl, q->ifindex, af, &addresses);
if (n < 0)
return n;
}
return answer_add_addresses_rr(answer, DNS_RESOURCE_KEY_NAME(key), addresses, n);
}
static int synthesize_gateway_ptr(DnsQuery *q, int af, const union in_addr_union *address, DnsAnswer **answer) {
_cleanup_free_ struct local_address *addresses = NULL;
int n;
assert(q);
assert(address);
assert(answer);
n = local_gateways(q->manager->rtnl, q->ifindex, af, &addresses);
if (n < 0)
return n;
return answer_add_addresses_ptr(answer, "gateway", addresses, n, af, address);
}
static int dns_query_synthesize_reply(DnsQuery *q, DnsTransactionState *state) {
_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
unsigned i;
int r;
assert(q);
assert(state);
/* Tries to synthesize localhost RR replies where appropriate */
if (!IN_SET(*state,
DNS_TRANSACTION_FAILURE,
DNS_TRANSACTION_NO_SERVERS,
DNS_TRANSACTION_TIMEOUT,
DNS_TRANSACTION_ATTEMPTS_MAX_REACHED))
return 0;
for (i = 0; i < q->question->n_keys; i++) {
union in_addr_union address;
const char *name;
int af;
if (q->question->keys[i]->class != DNS_CLASS_IN &&
q->question->keys[i]->class != DNS_CLASS_ANY)
continue;
name = DNS_RESOURCE_KEY_NAME(q->question->keys[i]);
if (is_localhost(name)) {
r = synthesize_localhost_rr(q, q->question->keys[i], &answer);
if (r < 0)
return log_error_errno(r, "Failed to synthesize localhost RRs: %m");
} else if (manager_is_own_hostname(q->manager, name)) {
r = synthesize_system_hostname_rr(q, q->question->keys[i], &answer);
if (r < 0)
return log_error_errno(r, "Failed to synthesize system hostname RRs: %m");
} else if (is_gateway_hostname(name)) {
r = synthesize_gateway_rr(q, q->question->keys[i], &answer);
if (r < 0)
return log_error_errno(r, "Failed to synthesize gateway RRs: %m");
} else if ((dns_name_endswith(name, "127.in-addr.arpa") > 0 && dns_name_equal(name, "2.0.0.127.in-addr.arpa") == 0) ||
dns_name_equal(name, "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa") > 0) {
r = synthesize_localhost_ptr(q, q->question->keys[i], &answer);
if (r < 0)
return log_error_errno(r, "Failed to synthesize localhost PTR RRs: %m");
} else if (dns_name_address(name, &af, &address) > 0) {
r = synthesize_system_hostname_ptr(q, af, &address, &answer);
if (r < 0)
return log_error_errno(r, "Failed to synthesize system hostname PTR RR: %m");
r = synthesize_gateway_ptr(q, af, &address, &answer);
if (r < 0)
return log_error_errno(r, "Failed to synthesize gateway hostname PTR RR: %m");
}
}
if (!answer)
return 0;
dns_answer_unref(q->answer);
q->answer = answer;
answer = NULL;
q->answer_family = SYNTHESIZE_FAMILY(q->flags);
q->answer_protocol = SYNTHESIZE_PROTOCOL(q->flags);
q->answer_rcode = DNS_RCODE_SUCCESS;
*state = DNS_TRANSACTION_SUCCESS;
return 1;
}
int dns_query_go(DnsQuery *q) {
DnsScopeMatch found = DNS_SCOPE_NO;
DnsScope *s, *first = NULL;
DnsTransaction *t;
const char *name;
Iterator i;
int r;
assert(q);
if (q->state != DNS_TRANSACTION_NULL)
return 0;
assert(q->question);
assert(q->question->n_keys > 0);
name = DNS_RESOURCE_KEY_NAME(q->question->keys[0]);
LIST_FOREACH(scopes, s, q->manager->dns_scopes) {
DnsScopeMatch match;
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;
dns_query_synthesize_reply(q, &state);
if (state != DNS_TRANSACTION_NO_SERVERS) {
dns_query_complete(q, state);
return 1;
}
return -ESRCH;
}
r = dns_query_add_transaction_split(q, first);
if (r < 0)
goto fail;
LIST_FOREACH(scopes, s, first->scopes_next) {
DnsScopeMatch match;
match = dns_scope_good_domain(s, q->ifindex, q->flags, name);
if (match < 0)
goto fail;
if (match != found)
continue;
r = dns_query_add_transaction_split(q, s);
if (r < 0)
goto fail;
}
q->answer = dns_answer_unref(q->answer);
q->answer_rcode = 0;
q->answer_family = AF_UNSPEC;
q->answer_protocol = _DNS_PROTOCOL_INVALID;
r = sd_event_add_time(
q->manager->event,
&q->timeout_event_source,
clock_boottime_or_monotonic(),
now(clock_boottime_or_monotonic()) + QUERY_TIMEOUT_USEC, 0,
on_query_timeout, q);
if (r < 0)
goto fail;
q->state = DNS_TRANSACTION_PENDING;
q->block_ready++;
/* Start the transactions that are not started yet */
SET_FOREACH(t, q->transactions, i) {
if (t->state != DNS_TRANSACTION_NULL)
continue;
r = dns_transaction_go(t);
if (r < 0)
goto fail;
}
q->block_ready--;
dns_query_ready(q);
return 1;
fail:
dns_query_stop(q);
return r;
}
void dns_query_ready(DnsQuery *q) {
DnsTransaction *t;
DnsTransactionState state = DNS_TRANSACTION_NO_SERVERS;
_cleanup_(dns_answer_unrefp) DnsAnswer *answer = NULL;
int rcode = 0;
DnsScope *scope = NULL;
bool pending = false;
Iterator i;
assert(q);
assert(IN_SET(q->state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING));
/* Note that this call might invalidate the query. Callers
* should hence not attempt to access the query or transaction
* after calling this function, unless the block_ready
* counter was explicitly bumped before doing so. */
if (q->block_ready > 0)
return;
SET_FOREACH(t, q->transactions, i) {
/* If we found a successful answer, ignore all answers from other scopes */
if (state == DNS_TRANSACTION_SUCCESS && t->scope != scope)
continue;
/* One of the transactions is still going on, let's maybe wait for it */
if (IN_SET(t->state, DNS_TRANSACTION_PENDING, DNS_TRANSACTION_NULL)) {
pending = true;
continue;
}
/* One of the transactions is successful, let's use
* it, and copy its data out */
if (t->state == DNS_TRANSACTION_SUCCESS) {
DnsAnswer *a;
if (t->received) {
rcode = DNS_PACKET_RCODE(t->received);
a = t->received->answer;
} else {
rcode = t->cached_rcode;
a = t->cached;
}
if (state == DNS_TRANSACTION_SUCCESS) {
DnsAnswer *merged;
merged = dns_answer_merge(answer, a);
if (!merged) {
dns_query_complete(q, DNS_TRANSACTION_RESOURCES);
return;
}
dns_answer_unref(answer);
answer = merged;
} else {
dns_answer_unref(answer);
answer = dns_answer_ref(a);
}
scope = t->scope;
state = DNS_TRANSACTION_SUCCESS;
continue;
}
/* One of the transactions has failed, let's see
* whether we find anything better, but if not, return
* its response data */
if (state != DNS_TRANSACTION_SUCCESS && t->state == DNS_TRANSACTION_FAILURE) {
DnsAnswer *a;
if (t->received) {
rcode = DNS_PACKET_RCODE(t->received);
a = t->received->answer;
} else {
rcode = t->cached_rcode;
a = t->cached;
}
dns_answer_unref(answer);
answer = dns_answer_ref(a);
scope = t->scope;
state = DNS_TRANSACTION_FAILURE;
continue;
}
if (state == DNS_TRANSACTION_NO_SERVERS && t->state != DNS_TRANSACTION_NO_SERVERS)
state = t->state;
}
if (pending) {
/* If so far we weren't successful, and there's
* something still pending, then wait for it */
if (state != DNS_TRANSACTION_SUCCESS)
return;
/* If we already were successful, then only wait for
* other transactions on the same scope to finish. */
SET_FOREACH(t, q->transactions, i) {
if (t->scope == scope && IN_SET(t->state, DNS_TRANSACTION_PENDING, DNS_TRANSACTION_NULL))
return;
}
}
if (IN_SET(state, DNS_TRANSACTION_SUCCESS, DNS_TRANSACTION_FAILURE)) {
q->answer = dns_answer_ref(answer);
q->answer_rcode = rcode;
q->answer_protocol = scope ? scope->protocol : _DNS_PROTOCOL_INVALID;
q->answer_family = scope ? scope->family : AF_UNSPEC;
}
/* Try to synthesize a reply if we couldn't resolve something. */
dns_query_synthesize_reply(q, &state);
dns_query_complete(q, state);
}
int dns_query_cname_redirect(DnsQuery *q, const char *name) {
_cleanup_(dns_question_unrefp) DnsQuestion *nq = NULL;
int r;
assert(q);
if (q->n_cname_redirects > CNAME_MAX)
return -ELOOP;
r = dns_question_cname_redirect(q->question, name, &nq);
if (r < 0)
return r;
dns_question_unref(q->question);
q->question = nq;
nq = NULL;
q->n_cname_redirects++;
dns_query_stop(q);
q->state = DNS_TRANSACTION_NULL;
return 0;
}
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;
}
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