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-rw-r--r--src/resolve/resolved-dns-transaction.c337
1 files changed, 251 insertions, 86 deletions
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 1103a34c6f..90f07e6c4b 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -24,6 +24,7 @@
#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"
@@ -243,7 +244,7 @@ static int on_stream_complete(DnsStream *s, int error) {
}
if (dns_packet_validate_reply(p) <= 0) {
- log_debug("Invalid LLMNR TCP packet.");
+ log_debug("Invalid TCP reply packet.");
dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
return 0;
}
@@ -384,6 +385,18 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
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;
@@ -446,6 +459,13 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
}
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) {
@@ -454,7 +474,7 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
return;
}
if (r < 0) {
- /* On LLMNR, if we cannot connect to the host,
+ /* On LLMNR and mDNS, 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);
@@ -481,29 +501,31 @@ void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
return;
}
- /* Only consider responses with equivalent query section to the request */
- if (p->question->n_keys != 1 || dns_resource_key_equal(p->question->keys[0], t->key) <= 0) {
- dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
- return;
- }
+ if (t->scope->protocol == DNS_PROTOCOL_DNS) {
+ /* Only consider responses with equivalent query section to the request */
+ if (p->question->n_keys != 1 || dns_resource_key_equal(p->question->keys[0], t->key) <= 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);
-
- /* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */
- if (DNS_PACKET_SHALL_CACHE(p))
- dns_cache_put(&t->scope->cache,
- t->key,
- DNS_PACKET_RCODE(p),
- p->answer,
- DNS_PACKET_ANCOUNT(p),
- t->answer_authenticated,
- 0,
- p->family,
- &p->sender);
+ /* 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);
+
+ /* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */
+ if (DNS_PACKET_SHALL_CACHE(p))
+ dns_cache_put(&t->scope->cache,
+ t->key,
+ DNS_PACKET_RCODE(p),
+ p->answer,
+ DNS_PACKET_ANCOUNT(p),
+ t->answer_authenticated,
+ 0,
+ p->family,
+ &p->sender);
+ }
if (DNS_PACKET_RCODE(p) == DNS_RCODE_SUCCESS)
dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
@@ -571,21 +593,26 @@ static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdat
assert(s);
assert(t);
- /* Timeout reached? Increase the timeout for the server used */
- switch (t->scope->protocol) {
- case DNS_PROTOCOL_DNS:
- assert(t->server);
+ 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);
+ 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;
+ 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.");
+ 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 */
@@ -598,38 +625,6 @@ static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdat
return 0;
}
-static int dns_transaction_make_packet(DnsTransaction *t) {
- _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
- int r;
-
- assert(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;
-}
-
static usec_t transaction_get_resend_timeout(DnsTransaction *t) {
assert(t);
assert(t->scope);
@@ -639,17 +634,18 @@ static usec_t transaction_get_resend_timeout(DnsTransaction *t) {
assert(t->server);
return t->server->resend_timeout;
- case DNS_PROTOCOL_LLMNR:
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.");
}
}
-int dns_transaction_go(DnsTransaction *t) {
+static int dns_transaction_prepare_next_attempt(DnsTransaction *t, usec_t ts) {
bool had_stream;
- usec_t ts;
int r;
assert(t);
@@ -658,11 +654,6 @@ int dns_transaction_go(DnsTransaction *t) {
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;
@@ -675,8 +666,6 @@ int dns_transaction_go(DnsTransaction *t) {
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);
@@ -739,31 +728,203 @@ int dns_transaction_go(DnsTransaction *t) {
}
}
- if (t->scope->protocol == DNS_PROTOCOL_LLMNR && !t->initial_jitter) {
- usec_t jitter;
+ 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_next_attempt(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);
+ DNS_PACKET_HEADER(p)->id = t->id;
+
+ /* 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_next_attempt(t, ts);
+ if (r <= 0)
+ return r;
+
+ 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->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 = true;
+ t->initial_jitter_scheduled = true;
random_bytes(&jitter, sizeof(jitter));
- jitter %= LLMNR_JITTER_INTERVAL_USEC;
+
+ 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,
- LLMNR_JITTER_INTERVAL_USEC,
+ 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 LLMNR transaction for " USEC_FMT "us.", jitter);
+ log_debug("Delaying %s transaction for " USEC_FMT "us.", dns_protocol_to_string(t->scope->protocol), jitter);
return 0;
}
@@ -810,16 +971,20 @@ int dns_transaction_go(DnsTransaction *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 + transaction_get_resend_timeout(t), 0,
+ ts, 0,
on_transaction_timeout, t);
if (r < 0)
return r;
t->state = DNS_TRANSACTION_PENDING;
+ t->next_attempt_after = ts;
+
return 1;
}
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-16 11:00:59 +0000