a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster#include "af-list.h"

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster#include "resolved-llmnr.h"

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster#include "resolved-dns-transaction.h"

f948ca04a28ccfeed9633bf4b0fb0d2c59c37478David Luna#include "random-util.h"

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan FosterDnsTransaction* dns_transaction_free(DnsTransaction *t) {

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster DnsQuery *q;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster DnsZoneItem *i;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster if (!t)

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster return NULL;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster sd_event_source_unref(t->timeout_event_source);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster dns_question_unref(t->question);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster dns_packet_unref(t->sent);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster dns_packet_unref(t->received);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster dns_answer_unref(t->cached);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster sd_event_source_unref(t->dns_event_source);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster safe_close(t->dns_fd);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster dns_server_unref(t->server);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster dns_stream_free(t->stream);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

f948ca04a28ccfeed9633bf4b0fb0d2c59c37478David Luna if (t->scope) {

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster LIST_REMOVE(transactions_by_scope, t->scope->transactions, t);

f948ca04a28ccfeed9633bf4b0fb0d2c59c37478David Luna

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster if (t->id != 0)

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster hashmap_remove(t->scope->manager->dns_transactions, UINT_TO_PTR(t->id));

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster }

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster while ((q = set_steal_first(t->queries)))

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster set_remove(q->transactions, t);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster set_free(t->queries);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster while ((i = set_steal_first(t->zone_items)))

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster i->probe_transaction = NULL;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster set_free(t->zone_items);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster free(t);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster return NULL;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster}

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan FosterDEFINE_TRIVIAL_CLEANUP_FUNC(DnsTransaction*, dns_transaction_free);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Fostervoid dns_transaction_gc(DnsTransaction *t) {

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster assert(t);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster if (t->block_gc > 0)

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster return;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster if (set_isempty(t->queries) && set_isempty(t->zone_items))

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster dns_transaction_free(t);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster}

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Fosterint dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsQuestion *q) {

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster _cleanup_(dns_transaction_freep) DnsTransaction *t = NULL;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster int r;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster assert(ret);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster assert(s);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster assert(q);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster r = hashmap_ensure_allocated(&s->manager->dns_transactions, NULL);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster if (r < 0)

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster return r;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster t = new0(DnsTransaction, 1);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster if (!t)

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster return -ENOMEM;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster t->dns_fd = -1;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster t->question = dns_question_ref(q);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster do

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster random_bytes(&t->id, sizeof(t->id));

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster while (t->id == 0 ||

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster hashmap_get(s->manager->dns_transactions, UINT_TO_PTR(t->id)));

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster r = hashmap_put(s->manager->dns_transactions, UINT_TO_PTR(t->id), t);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster if (r < 0) {

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster t->id = 0;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster return r;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster }

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster LIST_PREPEND(transactions_by_scope, s->transactions, t);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster t->scope = s;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster if (ret)

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster *ret = t;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster t = NULL;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster return 0;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster}

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Fosterstatic void dns_transaction_stop(DnsTransaction *t) {

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster assert(t);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster t->timeout_event_source = sd_event_source_unref(t->timeout_event_source);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster t->stream = dns_stream_free(t->stream);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster}

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Fosterstatic void dns_transaction_tentative(DnsTransaction *t, DnsPacket *p) {

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster _cleanup_free_ char *pretty = NULL;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster DnsZoneItem *z;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster assert(t);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster assert(p);

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster if (manager_our_packet(t->scope->manager, p) != 0)

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster return;

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster

a688bcbb4bcff5398fdd29b86f83450257dc0df4Allan Foster 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

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->zone_items))) {

/* First, make sure the zone item drops the reference

dns_zone_item_probe_stop(z);

/* Secondly, report this as conflict, so that we might

dns_zone_item_conflict(z);

}

t->block_gc--;

dns_transaction_gc(t);

}

void dns_transaction_complete(DnsTransaction *t, DnsTransactionState state) {

DnsQuery *q;

DnsZoneItem *z;

Iterator i;

assert(t);

assert(!IN_SET(state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING));

if (!IN_SET(t->state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING))

return;

/* Note that this call might invalidate the query. Callers

log_debug("Transaction on scope %s on %s/%s now complete with <%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->state = state;

dns_transaction_stop(t);

/* Notify all queries that are interested, but make sure the

t->block_gc++;

SET_FOREACH(q, t->queries, i)

dns_query_ready(q);

SET_FOREACH(z, t->zone_items, i)

dns_zone_item_ready(z);

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

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 LLMNR TCP 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) {

_cleanup_(dns_server_unrefp) DnsServer *server = NULL;

_cleanup_close_ int fd = -1;

int r;

assert(t);

if (t->stream)

return 0;

if (t->scope->protocol == DNS_PROTOCOL_DNS)

fd = dns_scope_tcp_socket(t->scope, AF_UNSPEC, NULL, 53, &server);

else if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {

/* When we already received a query 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

r = dns_question_extract_reverse_address(t->question, &family, &address);

if (r < 0)

return r;

if (r == 0)

return -EINVAL;

fd = dns_scope_tcp_socket(t->scope, family, &address, LLMNR_PORT, NULL);

}

} else

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->stream->complete = on_stream_complete;

t->stream->transaction = t;

/* The interface index is difficult to determine if we are

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_event_source = sd_event_source_unref(t->dns_event_source);

t->dns_fd = safe_close(t->dns_fd);

dns_scope_next_dns_server(t->scope);

}

void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {

int r;

assert(t);

assert(p);

assert(t->state == DNS_TRANSACTION_PENDING);

/* Note that this call might invalidate the query. Callers

if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {

assert(t->scope->link);

/* For LLMNR we will not accept any packets from other

if (p->ifindex != t->scope->link->ifindex)

return;

if (p->family != t->scope->family)

return;

/* Tentative packets are not full responses but still

if (DNS_PACKET_LLMNR_T(p)) {

dns_transaction_tentative(t, p);

return;

}

}

if (t->scope->protocol == DNS_PROTOCOL_DNS) {

/* For DNS we are fine with accepting packets on any

assert(t->server);

if (t->server->family != p->family)

return;

if (!in_addr_equal(p->family, &p->sender, &t->server->address))

return;

if (p->sender_port != 53)

return;

}

if (t->received != p) {

dns_packet_unref(t->received);

t->received = dns_packet_ref(p);

}

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;

}

}

if (DNS_PACKET_TC(p)) {

/* 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,

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 and update the cache */

r = dns_packet_extract(p);

if (r < 0) {

dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);

return;

}

/* Only consider responses with equivalent query section to the request */

if (!dns_question_is_superset(p->question, t->question) ||

!dns_question_is_superset(t->question, p->question)) {

dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);

return;

}

/* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */

dns_cache_put(&t->scope->cache, p->question, DNS_PACKET_RCODE(p), p->answer, DNS_PACKET_ANCOUNT(p), 0, p->family, &p->sender);

if (DNS_PACKET_RCODE(p) == DNS_RCODE_SUCCESS)

dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);

else

dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);

}

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.");

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_event_source, fd, EPOLLIN, on_dns_packet, t);

if (r < 0)

return r;

t->dns_fd = fd;

fd = -1;

t->server = dns_server_ref(server);

}

r = dns_scope_emit(t->scope, t->dns_fd, t->sent);

if (r < 0)

return r;

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);

/* Timeout reached? 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 int dns_transaction_make_packet(DnsTransaction *t) {

_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;

unsigned n, added = 0;

int r;

assert(t);

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;

t->sent = p;

p = NULL;

return 0;

}

int dns_transaction_go(DnsTransaction *t) {

bool had_stream;

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

dns_transaction_complete(t, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED);

return 0;

}

t->n_attempts++;

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

if (set_isempty(t->zone_items)) {

/* Before trying the cache, let's make sure we figured out a

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->question, &t->cached_rcode, &t->cached);

if (r < 0)

return r;

if (r > 0) {

log_debug("Cache hit!");

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

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(),

now(clock_boottime_or_monotonic()) + 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;

}

log_debug("Cache miss!");

/* 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?

dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);

return 0;

}

if (r < 0)

return r;

if (t->scope->protocol == DNS_PROTOCOL_LLMNR &&

(dns_question_endswith(t->question, "in-addr.arpa") > 0 ||

dns_question_endswith(t->question, "ip6.arpa") > 0)) {

/* RFC 4795, Section 2.4. says reverse lookups shall

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(),

now(clock_boottime_or_monotonic()) + TRANSACTION_TIMEOUT_USEC(t->scope->protocol), 0,

on_transaction_timeout, t);

if (r < 0)

return r;

t->state = DNS_TRANSACTION_PENDING;

return 1;

}

static const char* const dns_transaction_state_table[_DNS_TRANSACTION_STATE_MAX] = {

[DNS_TRANSACTION_NULL] = "null",

[DNS_TRANSACTION_PENDING] = "pending",

[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",

};

DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state, DnsTransactionState);