static void test_dns_name_endswith_one(const char *a, const char *b, int ret) {
assert_se(dns_name_endswith(a, b) == ret);
}
int dns_transaction_go(DnsTransaction *t) {
bool had_stream;
usec_t ts;
int r;
assert(t);
had_stream = !!t->stream;
dns_transaction_stop(t);
log_debug("Excercising transaction on scope %s on %s/%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));
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;
}
assert_se(sd_event_now(t->scope->manager->event, clock_boottime_or_monotonic(), &ts) >= 0);
t->n_attempts++;
t->start_usec = ts;
t->received = dns_packet_unref(t->received);
t->cached = dns_answer_unref(t->cached);
t->cached_rcode = 0;
/* Check the cache, but only if this transaction is not used
* for probing or verifying a zone item. */
if (set_isempty(t->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/* Let's then prune all outdated entries */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->cached_rcode, &t->cached);
if (r < 0)
return r;
if (r > 0) {
if (t->cached_rcode == DNS_RCODE_SUCCESS)
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
else
dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
return 0;
}
}
if (t->scope->protocol == DNS_PROTOCOL_LLMNR && !t->initial_jitter) {
usec_t jitter;
/* RFC 4795 Section 2.7 suggests all queries should be
* delayed by a random time from 0 to JITTER_INTERVAL. */
t->initial_jitter = true;
random_bytes(&jitter, sizeof(jitter));
jitter %= LLMNR_JITTER_INTERVAL_USEC;
r = sd_event_add_time(
t->scope->manager->event,
&t->timeout_event_source,
clock_boottime_or_monotonic(),
ts + jitter,
LLMNR_JITTER_INTERVAL_USEC,
on_transaction_timeout, t);
if (r < 0)
return r;
t->n_attempts = 0;
t->state = DNS_TRANSACTION_PENDING;
log_debug("Delaying LLMNR transaction for " USEC_FMT "us.", 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 try via TCP */
r = dns_transaction_emit(t);
if (r == -EMSGSIZE)
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);
}
r = sd_event_add_time(
t->scope->manager->event,
&t->timeout_event_source,
clock_boottime_or_monotonic(),
ts + transaction_get_resend_timeout(t), 0,
on_transaction_timeout, t);
if (r < 0)
return r;
t->state = DNS_TRANSACTION_PENDING;
return 1;
}