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Systemd/src/resolve/resolved-dns-transaction.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 "af-list.h"
#include "alloc-util.h"
#include "dns-domain.h"
#include "fd-util.h"
#include "random-util.h"
#include "resolved-dns-cache.h"
#include "resolved-dns-transaction.h"
#include "resolved-llmnr.h"
#include "string-table.h"
DnsTransaction* dns_transaction_free(DnsTransaction *t) {
DnsQueryCandidate *c;
DnsZoneItem *i;
DnsTransaction *z;
if (!t)
return NULL;
sd_event_source_unref(t->timeout_event_source);
dns_packet_unref(t->sent);
dns_packet_unref(t->received);
dns_answer_unref(t->answer);
sd_event_source_unref(t->dns_udp_event_source);
safe_close(t->dns_udp_fd);
dns_server_unref(t->server);
dns_stream_free(t->stream);
if (t->scope) {
hashmap_remove_value(t->scope->transactions_by_key, t->key, t);
LIST_REMOVE(transactions_by_scope, t->scope->transactions, t);
if (t->id != 0)
hashmap_remove(t->scope->manager->dns_transactions, UINT_TO_PTR(t->id));
}
dns_resource_key_unref(t->key);
while ((c = set_steal_first(t->notify_query_candidates)))
set_remove(c->transactions, t);
set_free(t->notify_query_candidates);
while ((i = set_steal_first(t->notify_zone_items)))
i->probe_transaction = NULL;
set_free(t->notify_zone_items);
while ((z = set_steal_first(t->notify_transactions)))
set_remove(z->dnssec_transactions, t);
set_free(t->notify_transactions);
while ((z = set_steal_first(t->dnssec_transactions))) {
set_remove(z->notify_transactions, t);
dns_transaction_gc(z);
}
set_free(t->dnssec_transactions);
dns_answer_unref(t->validated_keys);
free(t);
return NULL;
}
DEFINE_TRIVIAL_CLEANUP_FUNC(DnsTransaction*, dns_transaction_free);
void dns_transaction_gc(DnsTransaction *t) {
assert(t);
if (t->block_gc > 0)
return;
if (set_isempty(t->notify_query_candidates) &&
set_isempty(t->notify_zone_items) &&
set_isempty(t->notify_transactions))
dns_transaction_free(t);
}
int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsResourceKey *key) {
_cleanup_(dns_transaction_freep) DnsTransaction *t = NULL;
int r;
assert(ret);
assert(s);
assert(key);
/* Don't allow looking up invalid or pseudo RRs */
if (IN_SET(key->type, DNS_TYPE_OPT, 0, DNS_TYPE_TSIG, DNS_TYPE_TKEY))
return -EINVAL;
/* We only support the IN class */
if (key->class != DNS_CLASS_IN)
return -EOPNOTSUPP;
r = hashmap_ensure_allocated(&s->manager->dns_transactions, NULL);
if (r < 0)
return r;
r = hashmap_ensure_allocated(&s->transactions_by_key, &dns_resource_key_hash_ops);
if (r < 0)
return r;
t = new0(DnsTransaction, 1);
if (!t)
return -ENOMEM;
t->dns_udp_fd = -1;
t->answer_source = _DNS_TRANSACTION_SOURCE_INVALID;
t->dnssec_result = _DNSSEC_RESULT_INVALID;
t->key = dns_resource_key_ref(key);
/* Find a fresh, unused transaction id */
do
random_bytes(&t->id, sizeof(t->id));
while (t->id == 0 ||
hashmap_get(s->manager->dns_transactions, UINT_TO_PTR(t->id)));
r = hashmap_put(s->manager->dns_transactions, UINT_TO_PTR(t->id), t);
if (r < 0) {
t->id = 0;
return r;
}
r = hashmap_replace(s->transactions_by_key, t->key, t);
if (r < 0) {
hashmap_remove(s->manager->dns_transactions, UINT_TO_PTR(t->id));
return r;
}
LIST_PREPEND(transactions_by_scope, s->transactions, t);
t->scope = s;
if (ret)
*ret = t;
t = NULL;
return 0;
}
static void dns_transaction_stop(DnsTransaction *t) {
assert(t);
t->timeout_event_source = sd_event_source_unref(t->timeout_event_source);
t->stream = dns_stream_free(t->stream);
/* Note that we do not drop the UDP socket here, as we want to
* reuse it to repeat the interaction. */
}
static void dns_transaction_tentative(DnsTransaction *t, DnsPacket *p) {
_cleanup_free_ char *pretty = NULL;
DnsZoneItem *z;
assert(t);
assert(p);
if (manager_our_packet(t->scope->manager, p) != 0)
return;
in_addr_to_string(p->family, &p->sender, &pretty);
log_debug("Transaction on scope %s on %s/%s got tentative packet from %s",
dns_protocol_to_string(t->scope->protocol),
t->scope->link ? t->scope->link->name : "*",
t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family),
pretty);
/* RFC 4795, Section 4.1 says that the peer with the
* lexicographically smaller IP address loses */
if (memcmp(&p->sender, &p->destination, FAMILY_ADDRESS_SIZE(p->family)) >= 0) {
log_debug("Peer has lexicographically larger IP address and thus lost in the conflict.");
return;
}
log_debug("We have the lexicographically larger IP address and thus lost in the conflict.");
t->block_gc++;
while ((z = set_first(t->notify_zone_items))) {
/* First, make sure the zone item drops the reference
* to us */
dns_zone_item_probe_stop(z);
/* Secondly, report this as conflict, so that we might
* look for a different hostname */
dns_zone_item_conflict(z);
}
t->block_gc--;
dns_transaction_gc(t);
}
void dns_transaction_complete(DnsTransaction *t, DnsTransactionState state) {
DnsQueryCandidate *c;
DnsZoneItem *z;
DnsTransaction *d;
Iterator i;
assert(t);
assert(!DNS_TRANSACTION_IS_LIVE(state));
/* Note that this call might invalidate the query. Callers
* should hence not attempt to access the query or transaction
* after calling this function. */
log_debug("Transaction on scope %s on %s/%s now complete with <%s> from %s",
dns_protocol_to_string(t->scope->protocol),
t->scope->link ? t->scope->link->name : "*",
t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family),
dns_transaction_state_to_string(state),
t->answer_source < 0 ? "none" : dns_transaction_source_to_string(t->answer_source));
t->state = state;
dns_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(c, t->notify_query_candidates, i)
dns_query_candidate_notify(c);
SET_FOREACH(z, t->notify_zone_items, i)
dns_zone_item_notify(z);
SET_FOREACH(d, t->notify_transactions, i)
dns_transaction_notify(d, t);
t->block_gc--;
dns_transaction_gc(t);
}
static int on_stream_complete(DnsStream *s, int error) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
DnsTransaction *t;
assert(s);
assert(s->transaction);
/* Copy the data we care about out of the stream before we
* destroy it. */
t = s->transaction;
p = dns_packet_ref(s->read_packet);
t->stream = dns_stream_free(t->stream);
if (error != 0) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return 0;
}
if (dns_packet_validate_reply(p) <= 0) {
log_debug("Invalid TCP reply packet.");
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return 0;
}
dns_scope_check_conflicts(t->scope, p);
t->block_gc++;
dns_transaction_process_reply(t, p);
t->block_gc--;
/* If the response wasn't useful, then complete the transition now */
if (t->state == DNS_TRANSACTION_PENDING)
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return 0;
}
static int dns_transaction_open_tcp(DnsTransaction *t) {
DnsServer *server = NULL;
_cleanup_close_ int fd = -1;
int r;
assert(t);
if (t->stream)
return 0;
switch (t->scope->protocol) {
case DNS_PROTOCOL_DNS:
fd = dns_scope_tcp_socket(t->scope, AF_UNSPEC, NULL, 53, &server);
break;
case DNS_PROTOCOL_LLMNR:
/* When we already received a reply to this (but it was truncated), send to its sender address */
if (t->received)
fd = dns_scope_tcp_socket(t->scope, t->received->family, &t->received->sender, t->received->sender_port, NULL);
else {
union in_addr_union address;
int family = AF_UNSPEC;
/* Otherwise, try to talk to the owner of a
* the IP address, in case this is a reverse
* PTR lookup */
r = dns_name_address(DNS_RESOURCE_KEY_NAME(t->key), &family, &address);
if (r < 0)
return r;
if (r == 0)
return -EINVAL;
if (family != t->scope->family)
return -ESRCH;
fd = dns_scope_tcp_socket(t->scope, family, &address, LLMNR_PORT, NULL);
}
break;
default:
return -EAFNOSUPPORT;
}
if (fd < 0)
return fd;
r = dns_stream_new(t->scope->manager, &t->stream, t->scope->protocol, fd);
if (r < 0)
return r;
fd = -1;
r = dns_stream_write_packet(t->stream, t->sent);
if (r < 0) {
t->stream = dns_stream_free(t->stream);
return r;
}
dns_server_unref(t->server);
t->server = dns_server_ref(server);
t->received = dns_packet_unref(t->received);
t->answer = dns_answer_unref(t->answer);
t->answer_rcode = 0;
t->stream->complete = on_stream_complete;
t->stream->transaction = t;
/* The interface index is difficult to determine if we are
* connecting to the local host, hence fill this in right away
* instead of determining it from the socket */
if (t->scope->link)
t->stream->ifindex = t->scope->link->ifindex;
return 0;
}
static void dns_transaction_next_dns_server(DnsTransaction *t) {
assert(t);
t->server = dns_server_unref(t->server);
t->dns_udp_event_source = sd_event_source_unref(t->dns_udp_event_source);
t->dns_udp_fd = safe_close(t->dns_udp_fd);
dns_scope_next_dns_server(t->scope);
}
static void dns_transaction_cache_answer(DnsTransaction *t) {
unsigned n_cache;
assert(t);
/* For mDNS we cache whenever we get the packet, rather than
* in each transaction. */
if (!IN_SET(t->scope->protocol, DNS_PROTOCOL_DNS, DNS_PROTOCOL_LLMNR))
return;
/* We never cache if this packet is from the local host, under
* the assumption that a locally running DNS server would
* cache this anyway, and probably knows better when to flush
* the cache then we could. */
if (!DNS_PACKET_SHALL_CACHE(t->received))
return;
/* According to RFC 4795, section 2.9. only the RRs from the
* answer section shall be cached. However, if we know the
* message is authenticated, we might as well cache
* everything. */
if (t->answer_authenticated)
n_cache = dns_answer_size(t->answer);
else
n_cache = DNS_PACKET_ANCOUNT(t->received);
dns_cache_put(&t->scope->cache,
t->key,
t->answer_rcode,
t->answer,
n_cache,
t->answer_authenticated,
0,
t->received->family,
&t->received->sender);
}
static void dns_transaction_process_dnssec(DnsTransaction *t) {
int r;
assert(t);
/* Are there ongoing DNSSEC transactions? If so, let's wait for them. */
if (!set_isempty(t->dnssec_transactions))
return;
/* All our auxiliary DNSSEC transactions are complete now. Try
* to validate our RRset now. */
r = dns_transaction_validate_dnssec(t);
if (r < 0) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return;
}
if (!IN_SET(t->dnssec_result, _DNSSEC_RESULT_INVALID, DNSSEC_VALIDATED, DNSSEC_NO_SIGNATURE /* FOR NOW! */)) {
dns_transaction_complete(t, DNS_TRANSACTION_DNSSEC_FAILED);
return;
}
dns_transaction_cache_answer(t);
if (t->answer_rcode == DNS_RCODE_SUCCESS)
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
else
dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
}
void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
usec_t ts;
int r;
assert(t);
assert(p);
assert(t->state == DNS_TRANSACTION_PENDING);
assert(t->scope);
assert(t->scope->manager);
/* Note that this call might invalidate the query. Callers
* should hence not attempt to access the query or transaction
* after calling this function. */
log_debug("Processing incoming packet on transaction %" PRIu16".", t->id);
switch (t->scope->protocol) {
case DNS_PROTOCOL_LLMNR:
assert(t->scope->link);
/* For LLMNR we will not accept any packets from other
* interfaces */
if (p->ifindex != t->scope->link->ifindex)
return;
if (p->family != t->scope->family)
return;
/* Tentative packets are not full responses but still
* useful for identifying uniqueness conflicts during
* probing. */
if (DNS_PACKET_LLMNR_T(p)) {
dns_transaction_tentative(t, p);
return;
}
break;
case DNS_PROTOCOL_MDNS:
assert(t->scope->link);
/* For mDNS we will not accept any packets from other interfaces */
if (p->ifindex != t->scope->link->ifindex)
return;
if (p->family != t->scope->family)
return;
break;
case DNS_PROTOCOL_DNS:
break;
default:
assert_not_reached("Invalid DNS protocol.");
}
if (t->received != p) {
dns_packet_unref(t->received);
t->received = dns_packet_ref(p);
}
t->answer_source = DNS_TRANSACTION_NETWORK;
if (p->ipproto == IPPROTO_TCP) {
if (DNS_PACKET_TC(p)) {
/* Truncated via TCP? Somebody must be fucking with us */
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return;
}
if (DNS_PACKET_ID(p) != t->id) {
/* Not the reply to our query? Somebody must be fucking with us */
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return;
}
}
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
switch (t->scope->protocol) {
case DNS_PROTOCOL_DNS:
assert(t->server);
if (IN_SET(DNS_PACKET_RCODE(p), DNS_RCODE_FORMERR, DNS_RCODE_SERVFAIL, DNS_RCODE_NOTIMP)) {
/* Request failed, immediately try again with reduced features */
log_debug("Server returned error: %s", dns_rcode_to_string(DNS_PACKET_RCODE(p)));
dns_server_packet_failed(t->server, t->current_features);
r = dns_transaction_go(t);
if (r < 0) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return;
}
return;
} else
dns_server_packet_received(t->server, t->current_features, ts - t->start_usec, p->size);
break;
case DNS_PROTOCOL_LLMNR:
case DNS_PROTOCOL_MDNS:
dns_scope_packet_received(t->scope, ts - t->start_usec);
break;
default:
assert_not_reached("Invalid DNS protocol.");
}
if (DNS_PACKET_TC(p)) {
/* Truncated packets for mDNS are not allowed. Give up immediately. */
if (t->scope->protocol == DNS_PROTOCOL_MDNS) {
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return;
}
/* Response was truncated, let's try again with good old TCP */
r = dns_transaction_open_tcp(t);
if (r == -ESRCH) {
/* No servers found? Damn! */
dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
return;
}
if (r < 0) {
/* On LLMNR, if we cannot connect to the host,
* we immediately give up */
if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return;
}
/* On DNS, couldn't send? Try immediately again, with a new server */
dns_transaction_next_dns_server(t);
r = dns_transaction_go(t);
if (r < 0) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return;
}
return;
}
}
/* Parse message, if it isn't parsed yet. */
r = dns_packet_extract(p);
if (r < 0) {
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return;
}
if (IN_SET(t->scope->protocol, DNS_PROTOCOL_DNS, DNS_PROTOCOL_LLMNR)) {
/* Only consider responses with equivalent query section to the request */
r = dns_packet_is_reply_for(p, t->key);
if (r < 0) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return;
}
if (r == 0) {
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return;
}
/* Install the answer as answer to the transaction */
dns_answer_unref(t->answer);
t->answer = dns_answer_ref(p->answer);
t->answer_rcode = DNS_PACKET_RCODE(p);
t->answer_authenticated = t->scope->dnssec_mode == DNSSEC_TRUST && DNS_PACKET_AD(p);
r = dns_transaction_request_dnssec_keys(t);
if (r < 0) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return;
}
if (r > 0) {
/* There are DNSSEC transactions pending now. Update the state accordingly. */
t->state = DNS_TRANSACTION_VALIDATING;
return;
}
}
dns_transaction_process_dnssec(t);
}
static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
DnsTransaction *t = userdata;
int r;
assert(t);
assert(t->scope);
r = manager_recv(t->scope->manager, fd, DNS_PROTOCOL_DNS, &p);
if (r <= 0)
return r;
if (dns_packet_validate_reply(p) > 0 &&
DNS_PACKET_ID(p) == t->id)
dns_transaction_process_reply(t, p);
else
log_debug("Invalid DNS packet, ignoring.");
return 0;
}
static int dns_transaction_emit(DnsTransaction *t) {
int r;
assert(t);
if (t->scope->protocol == DNS_PROTOCOL_DNS && !t->server) {
DnsServer *server = NULL;
_cleanup_close_ int fd = -1;
fd = dns_scope_udp_dns_socket(t->scope, &server);
if (fd < 0)
return fd;
r = sd_event_add_io(t->scope->manager->event, &t->dns_udp_event_source, fd, EPOLLIN, on_dns_packet, t);
if (r < 0)
return r;
t->dns_udp_fd = fd;
fd = -1;
t->server = dns_server_ref(server);
}
r = dns_scope_emit(t->scope, t->dns_udp_fd, t->server, t->sent);
if (r < 0)
return r;
if (t->server)
t->current_features = t->server->possible_features;
return 0;
}
static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdata) {
DnsTransaction *t = userdata;
int r;
assert(s);
assert(t);
if (!t->initial_jitter_scheduled || t->initial_jitter_elapsed) {
/* Timeout reached? Increase the timeout for the server used */
switch (t->scope->protocol) {
case DNS_PROTOCOL_DNS:
assert(t->server);
dns_server_packet_lost(t->server, t->current_features, usec - t->start_usec);
break;
case DNS_PROTOCOL_LLMNR:
case DNS_PROTOCOL_MDNS:
dns_scope_packet_lost(t->scope, usec - t->start_usec);
break;
default:
assert_not_reached("Invalid DNS protocol.");
}
if (t->initial_jitter_scheduled)
t->initial_jitter_elapsed = true;
}
/* ...and try again with a new server */
dns_transaction_next_dns_server(t);
r = dns_transaction_go(t);
if (r < 0)
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return 0;
}
static usec_t transaction_get_resend_timeout(DnsTransaction *t) {
assert(t);
assert(t->scope);
switch (t->scope->protocol) {
case DNS_PROTOCOL_DNS:
assert(t->server);
return t->server->resend_timeout;
case DNS_PROTOCOL_MDNS:
assert(t->n_attempts > 0);
return (1 << (t->n_attempts - 1)) * USEC_PER_SEC;
case DNS_PROTOCOL_LLMNR:
return t->scope->resend_timeout;
default:
assert_not_reached("Invalid DNS protocol.");
}
}
static int dns_transaction_prepare(DnsTransaction *t, usec_t ts) {
bool had_stream;
int r;
assert(t);
had_stream = !!t->stream;
dns_transaction_stop(t);
if (t->n_attempts >= TRANSACTION_ATTEMPTS_MAX(t->scope->protocol)) {
dns_transaction_complete(t, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED);
return 0;
}
if (t->scope->protocol == DNS_PROTOCOL_LLMNR && had_stream) {
/* If we already tried via a stream, then we don't
* retry on LLMNR. See RFC 4795, Section 2.7. */
dns_transaction_complete(t, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED);
return 0;
}
t->n_attempts++;
t->start_usec = ts;
t->received = dns_packet_unref(t->received);
t->answer = dns_answer_unref(t->answer);
t->answer_rcode = 0;
t->answer_source = _DNS_TRANSACTION_SOURCE_INVALID;
/* Check the trust anchor. Do so only on classic DNS, since DNSSEC does not apply otherwise. */
if (t->scope->protocol == DNS_PROTOCOL_DNS) {
r = dns_trust_anchor_lookup(&t->scope->manager->trust_anchor, t->key, &t->answer);
if (r < 0)
return r;
if (r > 0) {
t->answer_rcode = DNS_RCODE_SUCCESS;
t->answer_source = DNS_TRANSACTION_TRUST_ANCHOR;
t->answer_authenticated = true;
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
return 0;
}
}
/* Check the zone, but only if this transaction is not used
* for probing or verifying a zone item. */
if (set_isempty(t->notify_zone_items)) {
r = dns_zone_lookup(&t->scope->zone, t->key, &t->answer, NULL, NULL);
if (r < 0)
return r;
if (r > 0) {
t->answer_rcode = DNS_RCODE_SUCCESS;
t->answer_source = DNS_TRANSACTION_ZONE;
t->answer_authenticated = true;
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
return 0;
}
}
/* Check the cache, but only if this transaction is not used
* for probing or verifying a zone item. */
if (set_isempty(t->notify_zone_items)) {
/* Before trying the cache, let's make sure we figured out a
* server to use. Should this cause a change of server this
* might flush the cache. */
dns_scope_get_dns_server(t->scope);
/* Let's then prune all outdated entries */
dns_cache_prune(&t->scope->cache);
r = dns_cache_lookup(&t->scope->cache, t->key, &t->answer_rcode, &t->answer, &t->answer_authenticated);
if (r < 0)
return r;
if (r > 0) {
t->answer_source = DNS_TRANSACTION_CACHE;
if (t->answer_rcode == DNS_RCODE_SUCCESS)
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
else
dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
return 0;
}
}
return 1;
}
static int dns_transaction_make_packet_mdns(DnsTransaction *t) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
bool add_known_answers = false;
DnsTransaction *other;
unsigned qdcount;
usec_t ts;
int r;
assert(t);
assert(t->scope->protocol == DNS_PROTOCOL_MDNS);
/* Discard any previously prepared packet, so we can start over and coaleasce again */
t->sent = dns_packet_unref(t->sent);
r = dns_packet_new_query(&p, t->scope->protocol, 0, false);
if (r < 0)
return r;
r = dns_packet_append_key(p, t->key, NULL);
if (r < 0)
return r;
qdcount = 1;
if (dns_key_is_shared(t->key))
add_known_answers = true;
/*
* For mDNS, we want to coalesce as many open queries in pending transactions into one single
* query packet on the wire as possible. To achieve that, we iterate through all pending transactions
* in our current scope, and see whether their timing contraints allow them to be sent.
*/
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
LIST_FOREACH(transactions_by_scope, other, t->scope->transactions) {
/* Skip ourselves */
if (other == t)
continue;
if (other->state != DNS_TRANSACTION_PENDING)
continue;
if (other->next_attempt_after > ts)
continue;
if (qdcount >= UINT16_MAX)
break;
r = dns_packet_append_key(p, other->key, NULL);
/*
* If we can't stuff more questions into the packet, just give up.
* One of the 'other' transactions will fire later and take care of the rest.
*/
if (r == -EMSGSIZE)
break;
if (r < 0)
return r;
r = dns_transaction_prepare(other, ts);
if (r <= 0)
continue;
ts += transaction_get_resend_timeout(other);
r = sd_event_add_time(
other->scope->manager->event,
&other->timeout_event_source,
clock_boottime_or_monotonic(),
ts, 0,
on_transaction_timeout, other);
if (r < 0)
return r;
other->state = DNS_TRANSACTION_PENDING;
other->next_attempt_after = ts;
qdcount ++;
if (dns_key_is_shared(other->key))
add_known_answers = true;
}
DNS_PACKET_HEADER(p)->qdcount = htobe16(qdcount);
/* Append known answer section if we're asking for any shared record */
if (add_known_answers) {
r = dns_cache_export_shared_to_packet(&t->scope->cache, p);
if (r < 0)
return r;
}
t->sent = p;
p = NULL;
return 0;
}
static int dns_transaction_make_packet(DnsTransaction *t) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
int r;
assert(t);
if (t->scope->protocol == DNS_PROTOCOL_MDNS)
return dns_transaction_make_packet_mdns(t);
if (t->sent)
return 0;
r = dns_packet_new_query(&p, t->scope->protocol, 0, t->scope->dnssec_mode == DNSSEC_YES);
if (r < 0)
return r;
r = dns_scope_good_key(t->scope, t->key);
if (r < 0)
return r;
if (r == 0)
return -EDOM;
r = dns_packet_append_key(p, t->key, NULL);
if (r < 0)
return r;
DNS_PACKET_HEADER(p)->qdcount = htobe16(1);
DNS_PACKET_HEADER(p)->id = t->id;
t->sent = p;
p = NULL;
return 0;
}
int dns_transaction_go(DnsTransaction *t) {
usec_t ts;
int r;
assert(t);
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
r = dns_transaction_prepare(t, ts);
if (r <= 0)
return r;
if (log_get_max_level() >= LOG_DEBUG) {
_cleanup_free_ char *ks = NULL;
(void) dns_resource_key_to_string(t->key, &ks);
log_debug("Excercising transaction for <%s> on scope %s on %s/%s",
ks ? strstrip(ks) : "???",
dns_protocol_to_string(t->scope->protocol),
t->scope->link ? t->scope->link->name : "*",
t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family));
}
if (!t->initial_jitter_scheduled &&
(t->scope->protocol == DNS_PROTOCOL_LLMNR ||
t->scope->protocol == DNS_PROTOCOL_MDNS)) {
usec_t jitter, accuracy;
/* RFC 4795 Section 2.7 suggests all queries should be
* delayed by a random time from 0 to JITTER_INTERVAL. */
t->initial_jitter_scheduled = true;
random_bytes(&jitter, sizeof(jitter));
switch (t->scope->protocol) {
case DNS_PROTOCOL_LLMNR:
jitter %= LLMNR_JITTER_INTERVAL_USEC;
accuracy = LLMNR_JITTER_INTERVAL_USEC;
break;
case DNS_PROTOCOL_MDNS:
jitter %= MDNS_JITTER_RANGE_USEC;
jitter += MDNS_JITTER_MIN_USEC;
accuracy = MDNS_JITTER_RANGE_USEC;
break;
default:
assert_not_reached("bad protocol");
}
r = sd_event_add_time(
t->scope->manager->event,
&t->timeout_event_source,
clock_boottime_or_monotonic(),
ts + jitter, accuracy,
on_transaction_timeout, t);
if (r < 0)
return r;
t->n_attempts = 0;
t->next_attempt_after = ts;
t->state = DNS_TRANSACTION_PENDING;
log_debug("Delaying %s transaction for " USEC_FMT "us.", dns_protocol_to_string(t->scope->protocol), jitter);
return 0;
}
/* Otherwise, we need to ask the network */
r = dns_transaction_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_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
return 0;
}
if (r < 0)
return r;
if (t->scope->protocol == DNS_PROTOCOL_LLMNR &&
(dns_name_endswith(DNS_RESOURCE_KEY_NAME(t->key), "in-addr.arpa") > 0 ||
dns_name_endswith(DNS_RESOURCE_KEY_NAME(t->key), "ip6.arpa") > 0)) {
/* RFC 4795, Section 2.4. says reverse lookups shall
* always be made via TCP on LLMNR */
r = dns_transaction_open_tcp(t);
} else {
/* Try via UDP, and if that fails due to large size or lack of
* support try via TCP */
r = dns_transaction_emit(t);
if (r == -EMSGSIZE || r == -EAGAIN)
r = dns_transaction_open_tcp(t);
}
if (r == -ESRCH) {
/* No servers to send this to? */
dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
return 0;
} else if (r < 0) {
if (t->scope->protocol != DNS_PROTOCOL_DNS) {
dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
return 0;
}
/* Couldn't send? Try immediately again, with a new server */
dns_transaction_next_dns_server(t);
return dns_transaction_go(t);
}
ts += transaction_get_resend_timeout(t);
r = sd_event_add_time(
t->scope->manager->event,
&t->timeout_event_source,
clock_boottime_or_monotonic(),
ts, 0,
on_transaction_timeout, t);
if (r < 0)
return r;
t->state = DNS_TRANSACTION_PENDING;
t->next_attempt_after = ts;
return 1;
}
static int dns_transaction_add_dnssec_transaction(DnsTransaction *t, DnsResourceKey *key, DnsTransaction **ret) {
DnsTransaction *aux;
int r;
assert(t);
assert(ret);
assert(key);
aux = dns_scope_find_transaction(t->scope, key, true);
if (!aux) {
r = dns_transaction_new(&aux, t->scope, key);
if (r < 0)
return r;
} else {
if (set_contains(t->dnssec_transactions, aux)) {
*ret = aux;
return 0;
}
}
r = set_ensure_allocated(&t->dnssec_transactions, NULL);
if (r < 0)
goto gc;
r = set_ensure_allocated(&aux->notify_transactions, NULL);
if (r < 0)
goto gc;
r = set_put(t->dnssec_transactions, aux);
if (r < 0)
goto gc;
r = set_put(aux->notify_transactions, t);
if (r < 0) {
(void) set_remove(t->dnssec_transactions, aux);
goto gc;
}
*ret = aux;
return 1;
gc:
dns_transaction_gc(aux);
return r;
}
static int dns_transaction_request_dnssec_rr(DnsTransaction *t, DnsResourceKey *key) {
_cleanup_(dns_answer_unrefp) DnsAnswer *a = NULL;
DnsTransaction *aux;
int r;
assert(t);
assert(key);
/* Try to get the data from the trust anchor */
r = dns_trust_anchor_lookup(&t->scope->manager->trust_anchor, key, &a);
if (r < 0)
return r;
if (r > 0) {
r = dns_answer_extend(&t->validated_keys, a);
if (r < 0)
return r;
return 0;
}
/* This didn't work, ask for it via the network/cache then. */
r = dns_transaction_add_dnssec_transaction(t, key, &aux);
if (r < 0)
return r;
if (aux->state == DNS_TRANSACTION_NULL) {
r = dns_transaction_go(aux);
if (r < 0)
return r;
}
return 0;
}
int dns_transaction_request_dnssec_keys(DnsTransaction *t) {
DnsResourceRecord *rr;
int r;
assert(t);
if (t->scope->dnssec_mode != DNSSEC_YES)
return 0;
DNS_ANSWER_FOREACH(rr, t->answer) {
switch (rr->key->type) {
case DNS_TYPE_RRSIG: {
/* For each RRSIG we request the matching DNSKEY */
_cleanup_(dns_resource_key_unrefp) DnsResourceKey *dnskey = NULL;
/* If this RRSIG is about a DNSKEY RR and the
* signer is the same as the owner, then we
* already have the DNSKEY, and we don't have
* to look for more. */
if (rr->rrsig.type_covered == DNS_TYPE_DNSKEY) {
r = dns_name_equal(rr->rrsig.signer, DNS_RESOURCE_KEY_NAME(rr->key));
if (r < 0)
return r;
if (r > 0)
continue;
}
/* If the signer is not a parent of the owner,
* then the signature is bogus, let's ignore
* it. */
r = dns_name_endswith(DNS_RESOURCE_KEY_NAME(rr->key), rr->rrsig.signer);
if (r < 0)
return r;
if (r == 0)
continue;
dnskey = dns_resource_key_new(rr->key->class, DNS_TYPE_DNSKEY, rr->rrsig.signer);
if (!dnskey)
return -ENOMEM;
log_debug("Requesting DNSKEY to validate transaction %" PRIu16" (key tag: %" PRIu16 ").", t->id, rr->rrsig.key_tag);
r = dns_transaction_request_dnssec_rr(t, dnskey);
if (r < 0)
return r;
break;
}
case DNS_TYPE_DNSKEY: {
/* For each DNSKEY we request the matching DS */
_cleanup_(dns_resource_key_unrefp) DnsResourceKey *ds = NULL;
ds = dns_resource_key_new(rr->key->class, DNS_TYPE_DS, DNS_RESOURCE_KEY_NAME(rr->key));
if (!ds)
return -ENOMEM;
log_debug("Requesting DS to validate transaction %" PRIu16" (key tag: %" PRIu16 ").", t->id, dnssec_keytag(rr));
r = dns_transaction_request_dnssec_rr(t, ds);
if (r < 0)
return r;
break;
}}
}
return !set_isempty(t->dnssec_transactions);
}
void dns_transaction_notify(DnsTransaction *t, DnsTransaction *source) {
int r;
assert(t);
assert(IN_SET(t->state, DNS_TRANSACTION_PENDING, DNS_TRANSACTION_VALIDATING));
assert(source);
/* Invoked whenever any of our auxiliary DNSSEC transactions
completed its work. We simply copy the answer from that
transaction over. */
if (source->state != DNS_TRANSACTION_SUCCESS) {
log_debug("Auxiliary DNSSEC RR query failed.");
t->dnssec_result = DNSSEC_FAILED_AUXILIARY;
} else {
r = dns_answer_extend(&t->validated_keys, source->answer);
if (r < 0) {
log_error_errno(r, "Failed to merge validated DNSSEC key data: %m");
t->dnssec_result = DNSSEC_FAILED_AUXILIARY;
}
}
/* Detach us from the DNSSEC transaction. */
(void) set_remove(t->dnssec_transactions, source);
(void) set_remove(source->notify_transactions, t);
/* If the state is still PENDING, we are still in the loop
* that adds further DNSSEC transactions, hence don't check if
* we are ready yet. If the state is VALIDATING however, we
* should check if we are complete now. */
if (t->state == DNS_TRANSACTION_VALIDATING)
dns_transaction_process_dnssec(t);
}
int dns_transaction_validate_dnssec(DnsTransaction *t) {
_cleanup_(dns_answer_unrefp) DnsAnswer *validated = NULL;
DnsResourceRecord *rr;
int ifindex, r;
assert(t);
/* We have now collected all DS and DNSKEY RRs in
* t->validated_keys, let's see which RRs we can now
* authenticate with that. */
if (t->scope->dnssec_mode != DNSSEC_YES)
return 0;
/* Already validated */
if (t->dnssec_result != _DNSSEC_RESULT_INVALID)
return 0;
if (IN_SET(t->answer_source, DNS_TRANSACTION_ZONE, DNS_TRANSACTION_TRUST_ANCHOR)) {
t->dnssec_result = DNSSEC_VALIDATED;
t->answer_authenticated = true;
return 0;
}
if (log_get_max_level() >= LOG_DEBUG) {
_cleanup_free_ char *ks = NULL;
(void) dns_resource_key_to_string(t->key, &ks);
log_debug("Validating response from transaction %" PRIu16 " (%s).", t->id, ks ? strstrip(ks) : "???");
}
/* First see if there are DNSKEYs we already known a validated DS for. */
DNS_ANSWER_FOREACH_IFINDEX(rr, ifindex, t->answer) {
r = dnssec_verify_dnskey_search(rr, t->validated_keys);
if (r < 0)
return r;
if (r == 0)
continue;
/* If so, the DNSKEY is validated too. */
r = dns_answer_add_extend(&t->validated_keys, rr, ifindex);
if (r < 0)
return r;
}
for (;;) {
bool changed = false, missing_key_for_transaction = false;
DNS_ANSWER_FOREACH(rr, t->answer) {
DnssecResult result;
if (rr->key->type == DNS_TYPE_RRSIG)
continue;
r = dnssec_verify_rrset_search(t->answer, rr->key, t->validated_keys, USEC_INFINITY, &result);
if (r < 0)
return r;
if (log_get_max_level() >= LOG_DEBUG) {
_cleanup_free_ char *rrs = NULL;
(void) dns_resource_record_to_string(rr, &rrs);
log_debug("Looking at %s: %s", rrs ? strstrip(rrs) : "???", dnssec_result_to_string(result));
}
switch (result) {
case DNSSEC_VALIDATED:
/* Add the validated RRset to the new list of validated RRsets */
r = dns_answer_copy_by_key(&validated, t->answer, rr->key);
if (r < 0)
return r;
if (rr->key->type == DNS_TYPE_DNSKEY) {
/* If we just validated a
* DNSKEY RRset, then let's
* add these keys to the set
* of validated keys for this
* transaction. */
r = dns_answer_copy_by_key(&t->validated_keys, t->answer, rr->key);
if (r < 0)
return r;
}
/* Now, remove this RRset from the RRs still to process */
r = dns_answer_remove_by_key(&t->answer, rr->key);
if (r < 0)
return r;
changed = true;
break;
case DNSSEC_INVALID:
case DNSSEC_NO_SIGNATURE:
case DNSSEC_SIGNATURE_EXPIRED:
/* Is this the RRset that we were looking for? If so, this is fatal for the whole transaction */
r = dns_resource_key_match_rr(t->key, rr, NULL);
if (r < 0)
return r;
if (r > 0) {
t->dnssec_result = result;
return 0;
}
/* Is this a CNAME for a record we were looking for? If so, it's also fatal for the whole transaction */
r = dns_resource_key_match_cname_or_dname(t->key, rr->key, NULL);
if (r < 0)
return r;
if (r > 0) {
t->dnssec_result = result;
return 0;
}
/* This is just something auxiliary. Just remove the RRset and continue. */
r = dns_answer_remove_by_key(&t->answer, rr->key);
if (r < 0)
return r;
changed = true;
break;
case DNSSEC_MISSING_KEY:
/* They key is missing? Let's continue
* with the next iteration, maybe
* we'll find it in an DNSKEY RRset
* later on. */
r = dns_resource_key_equal(rr->key, t->key);
if (r < 0)
return r;
if (r > 0)
missing_key_for_transaction = true;
break;
default:
assert_not_reached("Unexpected DNSSEC result");
}
if (changed)
break;
}
if (changed)
continue;
/* This didn't work either, there's no point in
* continuing. */
if (missing_key_for_transaction) {
t->dnssec_result = DNSSEC_MISSING_KEY;
return 0;
}
break;
}
dns_answer_unref(t->answer);
t->answer = validated;
validated = NULL;
t->answer_authenticated = true;
t->dnssec_result = DNSSEC_VALIDATED;
return 1;
}
static const char* const dns_transaction_state_table[_DNS_TRANSACTION_STATE_MAX] = {
[DNS_TRANSACTION_NULL] = "null",
[DNS_TRANSACTION_PENDING] = "pending",
[DNS_TRANSACTION_VALIDATING] = "validating",
[DNS_TRANSACTION_FAILURE] = "failure",
[DNS_TRANSACTION_SUCCESS] = "success",
[DNS_TRANSACTION_NO_SERVERS] = "no-servers",
[DNS_TRANSACTION_TIMEOUT] = "timeout",
[DNS_TRANSACTION_ATTEMPTS_MAX_REACHED] = "attempts-max-reached",
[DNS_TRANSACTION_INVALID_REPLY] = "invalid-reply",
[DNS_TRANSACTION_RESOURCES] = "resources",
[DNS_TRANSACTION_ABORTED] = "aborted",
[DNS_TRANSACTION_DNSSEC_FAILED] = "dnssec-failed",
};
DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state, DnsTransactionState);
static const char* const dns_transaction_source_table[_DNS_TRANSACTION_SOURCE_MAX] = {
[DNS_TRANSACTION_NETWORK] = "network",
[DNS_TRANSACTION_CACHE] = "cache",
[DNS_TRANSACTION_ZONE] = "zone",
[DNS_TRANSACTION_TRUST_ANCHOR] = "trust-anchor",
};
DEFINE_STRING_TABLE_LOOKUP(dns_transaction_source, DnsTransactionSource);
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