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 "resolved-dns-query.h"
#include "resolved-dns-domain.h"
#define TRANSACTION_TIMEOUT_USEC (5 * USEC_PER_SEC)
#define QUERY_TIMEOUT_USEC (30 * USEC_PER_SEC)
#define ATTEMPTS_MAX 8
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#define CNAME_MAX 8
#define QUERIES_MAX 2048
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static int dns_query_transaction_go(DnsQueryTransaction *t);
DnsQueryTransaction* dns_query_transaction_free(DnsQueryTransaction *t) {
DnsQuery *q;
if (!t)
return NULL;
sd_event_source_unref(t->timeout_event_source);
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dns_question_unref(t->question);
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dns_packet_unref(t->sent);
dns_packet_unref(t->received);
dns_answer_unref(t->cached);
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sd_event_source_unref(t->tcp_event_source);
safe_close(t->tcp_fd);
if (t->scope) {
LIST_REMOVE(transactions_by_scope, t->scope->transactions, t);
if (t->id != 0)
hashmap_remove(t->scope->manager->dns_query_transactions, UINT_TO_PTR(t->id));
}
while ((q = set_steal_first(t->queries)))
set_remove(q->transactions, t);
set_free(t->queries);
free(t);
return NULL;
}
DEFINE_TRIVIAL_CLEANUP_FUNC(DnsQueryTransaction*, dns_query_transaction_free);
static void dns_query_transaction_gc(DnsQueryTransaction *t) {
assert(t);
if (t->block_gc > 0)
return;
if (set_isempty(t->queries))
dns_query_transaction_free(t);
}
static int dns_query_transaction_new(DnsQueryTransaction **ret, DnsScope *s, DnsQuestion *q) {
_cleanup_(dns_query_transaction_freep) DnsQueryTransaction *t = NULL;
int r;
assert(ret);
assert(s);
assert(q);
r = hashmap_ensure_allocated(&s->manager->dns_query_transactions, NULL, NULL);
if (r < 0)
return r;
t = new0(DnsQueryTransaction, 1);
if (!t)
return -ENOMEM;
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t->tcp_fd = -1;
t->question = dns_question_ref(q);
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do
random_bytes(&t->id, sizeof(t->id));
while (t->id == 0 ||
hashmap_get(s->manager->dns_query_transactions, UINT_TO_PTR(t->id)));
r = hashmap_put(s->manager->dns_query_transactions, UINT_TO_PTR(t->id), t);
if (r < 0) {
t->id = 0;
return r;
}
LIST_PREPEND(transactions_by_scope, s->transactions, t);
t->scope = s;
if (ret)
*ret = t;
t = NULL;
return 0;
}
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static void dns_query_transaction_stop(DnsQueryTransaction *t) {
assert(t);
t->timeout_event_source = sd_event_source_unref(t->timeout_event_source);
t->tcp_event_source = sd_event_source_unref(t->tcp_event_source);
t->tcp_fd = safe_close(t->tcp_fd);
}
void dns_query_transaction_complete(DnsQueryTransaction *t, DnsQueryState state) {
DnsQuery *q;
Iterator i;
assert(t);
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assert(!IN_SET(state, DNS_QUERY_NULL, DNS_QUERY_PENDING));
assert(IN_SET(t->state, DNS_QUERY_NULL, DNS_QUERY_PENDING));
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/* Note that this call might invalidate the query. Callers
* should hence not attempt to access the query or transaction
* after calling this function. */
t->state = state;
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dns_query_transaction_stop(t);
/* Notify all queries that are interested, but make sure the
* transaction isn't freed while we are still looking at it */
t->block_gc++;
SET_FOREACH(q, t->queries, i)
dns_query_ready(q);
t->block_gc--;
dns_query_transaction_gc(t);
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}
static int on_tcp_ready(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
DnsQueryTransaction *t = userdata;
int r;
assert(t);
if (revents & EPOLLOUT) {
struct iovec iov[2];
be16_t sz;
ssize_t ss;
sz = htobe16(t->sent->size);
iov[0].iov_base = &sz;
iov[0].iov_len = sizeof(sz);
iov[1].iov_base = DNS_PACKET_DATA(t->sent);
iov[1].iov_len = t->sent->size;
IOVEC_INCREMENT(iov, 2, t->tcp_written);
ss = writev(fd, iov, 2);
if (ss < 0) {
if (errno != EINTR && errno != EAGAIN) {
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dns_query_transaction_complete(t, DNS_QUERY_RESOURCES);
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return -errno;
}
} else
t->tcp_written += ss;
/* Are we done? If so, disable the event source for EPOLLOUT */
if (t->tcp_written >= sizeof(sz) + t->sent->size) {
r = sd_event_source_set_io_events(s, EPOLLIN);
if (r < 0) {
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dns_query_transaction_complete(t, DNS_QUERY_RESOURCES);
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return r;
}
}
}
if (revents & (EPOLLIN|EPOLLHUP|EPOLLRDHUP)) {
if (t->tcp_read < sizeof(t->tcp_read_size)) {
ssize_t ss;
ss = read(fd, (uint8_t*) &t->tcp_read_size + t->tcp_read, sizeof(t->tcp_read_size) - t->tcp_read);
if (ss < 0) {
if (errno != EINTR && errno != EAGAIN) {
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dns_query_transaction_complete(t, DNS_QUERY_RESOURCES);
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return -errno;
}
} else if (ss == 0) {
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dns_query_transaction_complete(t, DNS_QUERY_RESOURCES);
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return -EIO;
} else
t->tcp_read += ss;
}
if (t->tcp_read >= sizeof(t->tcp_read_size)) {
if (be16toh(t->tcp_read_size) < DNS_PACKET_HEADER_SIZE) {
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dns_query_transaction_complete(t, DNS_QUERY_INVALID_REPLY);
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return -EBADMSG;
}
if (t->tcp_read < sizeof(t->tcp_read_size) + be16toh(t->tcp_read_size)) {
ssize_t ss;
if (!t->received) {
r = dns_packet_new(&t->received, t->scope->protocol, be16toh(t->tcp_read_size));
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if (r < 0) {
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dns_query_transaction_complete(t, DNS_QUERY_RESOURCES);
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return r;
}
}
ss = read(fd,
(uint8_t*) DNS_PACKET_DATA(t->received) + t->tcp_read - sizeof(t->tcp_read_size),
sizeof(t->tcp_read_size) + be16toh(t->tcp_read_size) - t->tcp_read);
if (ss < 0) {
if (errno != EINTR && errno != EAGAIN) {
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dns_query_transaction_complete(t, DNS_QUERY_RESOURCES);
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return -errno;
}
} else if (ss == 0) {
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dns_query_transaction_complete(t, DNS_QUERY_RESOURCES);
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return -EIO;
} else
t->tcp_read += ss;
}
if (t->tcp_read >= sizeof(t->tcp_read_size) + be16toh(t->tcp_read_size)) {
t->received->size = be16toh(t->tcp_read_size);
dns_query_transaction_process_reply(t, t->received);
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return 0;
}
}
}
return 0;
}
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static int dns_query_transaction_open_tcp(DnsQueryTransaction *t) {
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int r;
assert(t);
if (t->scope->protocol == DNS_PROTOCOL_DNS)
return -ENOTSUP;
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if (t->tcp_fd >= 0)
return 0;
t->tcp_written = 0;
t->tcp_read = 0;
t->received = dns_packet_unref(t->received);
t->tcp_fd = dns_scope_tcp_socket(t->scope);
if (t->tcp_fd < 0)
return t->tcp_fd;
r = sd_event_add_io(t->scope->manager->event, &t->tcp_event_source, t->tcp_fd, EPOLLIN|EPOLLOUT, on_tcp_ready, t);
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if (r < 0) {
t->tcp_fd = safe_close(t->tcp_fd);
return r;
}
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return 0;
}
void dns_query_transaction_process_reply(DnsQueryTransaction *t, DnsPacket *p) {
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int r;
assert(t);
assert(p);
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assert(t->state == DNS_QUERY_PENDING);
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/* Note that this call might invalidate the query. Callers
* should hence not attempt to access the query or transaction
* after calling this function. */
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if (t->received != p) {
dns_packet_unref(t->received);
t->received = dns_packet_ref(p);
}
if (t->tcp_fd >= 0) {
if (DNS_PACKET_TC(p)) {
/* Truncated via TCP? Somebody must be fucking with us */
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dns_query_transaction_complete(t, DNS_QUERY_INVALID_REPLY);
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return;
}
if (DNS_PACKET_ID(p) != t->id) {
/* Not the reply to our query? Somebody must be fucking with us */
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dns_query_transaction_complete(t, DNS_QUERY_INVALID_REPLY);
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return;
}
}
if (DNS_PACKET_TC(p)) {
/* Response was truncated, let's try again with good old TCP */
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r = dns_query_transaction_open_tcp(t);
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if (r == -ESRCH) {
/* No servers found? Damn! */
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dns_query_transaction_complete(t, DNS_QUERY_NO_SERVERS);
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return;
}
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if (r < 0) {
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/* Couldn't send? Try immediately again, with a new server */
dns_scope_next_dns_server(t->scope);
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r = dns_query_transaction_go(t);
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if (r < 0) {
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dns_query_transaction_complete(t, DNS_QUERY_RESOURCES);
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return;
}
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return;
}
}
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/* Parse and update the cache */
r = dns_packet_extract(p);
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if (r < 0) {
dns_query_transaction_complete(t, DNS_QUERY_INVALID_REPLY);
return;
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} else
dns_cache_put(&t->scope->cache, p->question, DNS_PACKET_RCODE(p), p->answer, 0);
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if (DNS_PACKET_RCODE(p) == DNS_RCODE_SUCCESS)
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dns_query_transaction_complete(t, DNS_QUERY_SUCCESS);
else
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dns_query_transaction_complete(t, DNS_QUERY_FAILURE);
}
static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdata) {
DnsQueryTransaction *t = userdata;
int r;
assert(s);
assert(t);
/* Timeout reached? Try again, with a new server */
dns_scope_next_dns_server(t->scope);
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r = dns_query_transaction_go(t);
if (r < 0)
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dns_query_transaction_complete(t, DNS_QUERY_RESOURCES);
return 0;
}
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static int dns_query_make_packet(DnsQueryTransaction *t) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
unsigned n, added = 0;
int r;
assert(t);
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if (t->sent)
return 0;
r = dns_packet_new_query(&p, t->scope->protocol, 0);
if (r < 0)
return r;
for (n = 0; n < t->question->n_keys; n++) {
r = dns_scope_good_key(t->scope, t->question->keys[n]);
if (r < 0)
return r;
if (r == 0)
continue;
r = dns_packet_append_key(p, t->question->keys[n], NULL);
if (r < 0)
return r;
added++;
}
if (added <= 0)
return -EDOM;
DNS_PACKET_HEADER(p)->qdcount = htobe16(added);
DNS_PACKET_HEADER(p)->id = t->id;
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t->sent = p;
p = NULL;
return 0;
}
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static int dns_query_transaction_go(DnsQueryTransaction *t) {
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int r;
assert(t);
dns_query_transaction_stop(t);
if (t->n_attempts >= ATTEMPTS_MAX) {
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dns_query_transaction_complete(t, DNS_QUERY_ATTEMPTS_MAX);
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return 0;
}
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t->n_attempts++;
t->received = dns_packet_unref(t->received);
t->cached = dns_answer_unref(t->cached);
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t->cached_rcode = 0;
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/* First, let's try the cache */
dns_cache_prune(&t->scope->cache);
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r = dns_cache_lookup(&t->scope->cache, t->question, &t->cached_rcode, &t->cached);
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if (r < 0)
return r;
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if (r > 0) {
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if (t->cached_rcode == DNS_RCODE_SUCCESS)
dns_query_transaction_complete(t, DNS_QUERY_SUCCESS);
else
dns_query_transaction_complete(t, DNS_QUERY_FAILURE);
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return 0;
}
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/* Otherwise, we need to ask the network */
r = dns_query_make_packet(t);
if (r == -EDOM) {
/* Not the right request to make on this network?
* (i.e. an A request made on IPv6 or an AAAA request
* made on IPv4, on LLMNR or mDNS.) */
dns_query_transaction_complete(t, DNS_QUERY_NO_SERVERS);
return 0;
}
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if (r < 0)
return r;
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/* Try via UDP, and if that fails due to large size try via TCP */
r = dns_scope_send(t->scope, t->sent);
if (r == -EMSGSIZE)
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r = dns_query_transaction_open_tcp(t);
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if (r == -ESRCH) {
/* No servers to send this to? */
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dns_query_transaction_complete(t, DNS_QUERY_NO_SERVERS);
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return 0;
}
if (r < 0) {
/* Couldn't send? Try immediately again, with a new server */
dns_scope_next_dns_server(t->scope);
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return dns_query_transaction_go(t);
}
r = sd_event_add_time(t->scope->manager->event, &t->timeout_event_source, CLOCK_MONOTONIC, now(CLOCK_MONOTONIC) + TRANSACTION_TIMEOUT_USEC, 0, on_transaction_timeout, t);
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if (r < 0)
return r;
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t->state = DNS_QUERY_PENDING;
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return 1;
}
DnsQuery *dns_query_free(DnsQuery *q) {
DnsQueryTransaction *t;
if (!q)
return NULL;
sd_bus_message_unref(q->request);
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dns_question_unref(q->question);
dns_answer_unref(q->answer);
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sd_event_source_unref(q->timeout_event_source);
while ((t = set_steal_first(q->transactions))) {
set_remove(t->queries, q);
dns_query_transaction_gc(t);
}
set_free(q->transactions);
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) {
_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);
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for (i = 0; i < question->n_keys; i++) {
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log_debug("Looking up RR for %s %s %s",
strna(dns_class_to_string(question->keys[i]->class)),
strna(dns_type_to_string(question->keys[i]->type)),
DNS_RESOURCE_KEY_NAME(question->keys[i]));
}
LIST_PREPEND(queries, m->dns_queries, q);
m->n_dns_queries++;
q->manager = m;
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if (ret)
*ret = q;
q = NULL;
return 0;
}
static void dns_query_stop(DnsQuery *q) {
DnsQueryTransaction *t;
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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_query_transaction_gc(t);
}
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}
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static void dns_query_complete(DnsQuery *q, DnsQueryState state) {
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assert(q);
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assert(!IN_SET(state, DNS_QUERY_NULL, DNS_QUERY_PENDING));
assert(IN_SET(q->state, DNS_QUERY_NULL, DNS_QUERY_PENDING));
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/* Note that this call might invalidate the query. Callers
* should hence not attempt to access the query or transaction
* after calling this function. */
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q->state = state;
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dns_query_stop(q);
if (q->complete)
q->complete(q);
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}
static int on_query_timeout(sd_event_source *s, usec_t usec, void *userdata) {
DnsQuery *q = userdata;
assert(s);
assert(q);
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dns_query_complete(q, DNS_QUERY_TIMEOUT);
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return 0;
}
static int dns_query_add_transaction(DnsQuery *q, DnsScope *s) {
DnsQueryTransaction *t;
int r;
assert(q);
r = set_ensure_allocated(&q->transactions, NULL, NULL);
if (r < 0)
return r;
LIST_FOREACH(transactions_by_scope, t, s->transactions)
if (dns_question_is_superset(t->question, q->question))
break;
if (!t) {
r = dns_query_transaction_new(&t, s, q->question);
if (r < 0)
return r;
}
r = set_ensure_allocated(&t->queries, NULL, NULL);
if (r < 0)
goto fail;
r = set_put(t->queries, q);
if (r < 0)
goto fail;
r = set_put(q->transactions, t);
if (r < 0) {
set_remove(t->queries, q);
goto fail;
}
return 0;
fail:
dns_query_transaction_gc(t);
return r;
}
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int dns_query_go(DnsQuery *q) {
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DnsScopeMatch found = DNS_SCOPE_NO;
DnsScope *s, *first = NULL;
DnsQueryTransaction *t;
const char *name;
Iterator i;
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int r;
assert(q);
if (q->state != DNS_QUERY_NULL)
return 0;
assert(q->question);
assert(q->question->n_keys > 0);
name = DNS_RESOURCE_KEY_NAME(q->question->keys[0]);
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LIST_FOREACH(scopes, s, q->manager->dns_scopes) {
DnsScopeMatch match;
match = dns_scope_good_domain(s, 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)
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return -ESRCH;
r = dns_query_add_transaction(q, first);
if (r < 0)
return r;
LIST_FOREACH(scopes, s, first->scopes_next) {
DnsScopeMatch match;
match = dns_scope_good_domain(s, name);
if (match < 0)
return match;
if (match != found)
continue;
r = dns_query_add_transaction(q, s);
if (r < 0)
return r;
}
q->answer = dns_answer_unref(q->answer);
q->answer_ifindex = 0;
q->answer_rcode = 0;
r = sd_event_add_time(q->manager->event, &q->timeout_event_source, CLOCK_MONOTONIC, now(CLOCK_MONOTONIC) + QUERY_TIMEOUT_USEC, 0, on_query_timeout, q);
if (r < 0)
goto fail;
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q->state = DNS_QUERY_PENDING;
q->block_ready++;
SET_FOREACH(t, q->transactions, i) {
if (t->state == DNS_QUERY_NULL) {
r = dns_query_transaction_go(t);
if (r < 0)
goto fail;
}
}
q->block_ready--;
dns_query_ready(q);
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return 1;
fail:
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dns_query_stop(q);
return r;
}
void dns_query_ready(DnsQuery *q) {
DnsQueryTransaction *t;
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DnsQueryState state = DNS_QUERY_NO_SERVERS;
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DnsAnswer *failure_answer = NULL;
int failure_rcode = 0, failure_ifindex = 0;
Iterator i;
assert(q);
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assert(IN_SET(q->state, DNS_QUERY_NULL, DNS_QUERY_PENDING));
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/* 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
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* counter was explicitly bumped before doing so. */
if (q->block_ready > 0)
return;
SET_FOREACH(t, q->transactions, i) {
/* One of the transactions is still going on, let's wait for it */
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if (t->state == DNS_QUERY_PENDING || t->state == DNS_QUERY_NULL)
return;
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/* One of the transactions is successful, let's use
* it, and copy its data out */
if (t->state == DNS_QUERY_SUCCESS) {
if (t->received) {
q->answer = dns_answer_ref(t->received->answer);
q->answer_ifindex = t->received->ifindex;
q->answer_rcode = DNS_PACKET_RCODE(t->received);
} else {
q->answer = dns_answer_ref(t->cached);
q->answer_ifindex = t->scope->link ? t->scope->link->ifindex : 0;
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q->answer_rcode = t->cached_rcode;
}
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dns_query_complete(q, DNS_QUERY_SUCCESS);
return;
}
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/* One of the transactions has failed, let's see
* whether we find anything better, but if not, return
* its response packet */
if (t->state == DNS_QUERY_FAILURE) {
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if (t->received) {
failure_answer = t->received->answer;
failure_ifindex = t->received->ifindex;
failure_rcode = DNS_PACKET_RCODE(t->received);
} else {
failure_answer = t->cached;
failure_ifindex = t->scope->link ? t->scope->link->ifindex : 0;
failure_rcode = t->cached_rcode;
}
state = DNS_QUERY_FAILURE;
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continue;
}
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if (state == DNS_QUERY_NO_SERVERS && t->state != DNS_QUERY_NO_SERVERS)
state = t->state;
}
if (state == DNS_QUERY_FAILURE) {
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q->answer = dns_answer_ref(failure_answer);
q->answer_ifindex = failure_ifindex;
q->answer_rcode = failure_rcode;
}
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dns_query_complete(q, state);
}
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int dns_query_cname_redirect(DnsQuery *q, const char *name) {
_cleanup_(dns_question_unrefp) DnsQuestion *nq = NULL;
int r;
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assert(q);
if (q->n_cname_redirects > CNAME_MAX)
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return -ELOOP;
r = dns_question_cname_redirect(q->question, name, &nq);
if (r < 0)
return r;
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dns_question_unref(q->question);
q->question = nq;
nq = NULL;
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q->n_cname_redirects++;
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dns_query_stop(q);
q->state = DNS_QUERY_NULL;
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return 0;
}