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-rw-r--r--src/resolve/resolved-dns-transaction.c26
-rw-r--r--src/resolve/resolved-dns-transaction.h4
2 files changed, 24 insertions, 6 deletions
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index f77931ed53..2cf9417a4b 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -751,8 +751,10 @@ int dns_transaction_go(DnsTransaction *t) {
}
}
- if (t->scope->protocol == DNS_PROTOCOL_LLMNR && !t->initial_jitter) {
- usec_t jitter;
+ if (!t->initial_jitter &&
+ (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. */
@@ -760,14 +762,26 @@ int dns_transaction_go(DnsTransaction *t) {
t->initial_jitter = 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;
@@ -775,7 +789,7 @@ int dns_transaction_go(DnsTransaction *t) {
t->n_attempts = 0;
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;
}
diff --git a/src/resolve/resolved-dns-transaction.h b/src/resolve/resolved-dns-transaction.h
index a3058ce6e8..1d445ffee7 100644
--- a/src/resolve/resolved-dns-transaction.h
+++ b/src/resolve/resolved-dns-transaction.h
@@ -119,6 +119,10 @@ DnsTransactionSource dns_transaction_source_from_string(const char *s) _pure_;
/* LLMNR Jitter interval, see RFC 4795 Section 7 */
#define LLMNR_JITTER_INTERVAL_USEC (100 * USEC_PER_MSEC)
+/* mDNS Jitter interval, see RFC 6762 Section 5.2 */
+#define MDNS_JITTER_MIN_USEC (20 * USEC_PER_MSEC)
+#define MDNS_JITTER_RANGE_USEC (100 * USEC_PER_MSEC)
+
/* Maximum attempts to send DNS requests, across all DNS servers */
#define DNS_TRANSACTION_ATTEMPTS_MAX 16