resolve: fix misuse of accuracy parameter in sd_event_add_time()

Also, this makes mDNS regular queries sent without delay (except for
one caused by the default accuracy of sd-event).

Note, RFC 6762 Section 5.2 is about continuous mDNS query, which is not
implemented yet.

3 files changed, 13 insertions, 18 deletions

diff --git a/src/resolve/resolved-dns-scope.c b/src/resolve/resolved-dns-scope.c
index a872e9d255..4fbcd3d449 100644
--- a/src/resolve/resolved-dns-scope.c
+++ b/src/resolve/resolved-dns-scope.c
@@ -1204,7 +1204,6 @@ static int on_conflict_dispatch(sd_event_source *es, usec_t usec, void *userdata
 }
 
 int dns_scope_notify_conflict(DnsScope *scope, DnsResourceRecord *rr) {
-        usec_t jitter;
         int r;
 
         assert(scope);
@@ -1233,15 +1232,12 @@ int dns_scope_notify_conflict(DnsScope *scope, DnsResourceRecord *rr) {
         if (scope->conflict_event_source)
                 return 0;
 
-        random_bytes(&jitter, sizeof(jitter));
-        jitter %= LLMNR_JITTER_INTERVAL_USEC;
-
         r = sd_event_add_time_relative(
                         scope->manager->event,
                         &scope->conflict_event_source,
                         CLOCK_BOOTTIME,
-                        jitter,
-                        LLMNR_JITTER_INTERVAL_USEC,
+                        random_u64_range(LLMNR_JITTER_INTERVAL_USEC),
+                        0,
                         on_conflict_dispatch, scope);
         if (r < 0)
                 return log_debug_errno(r, "Failed to add conflict dispatch event: %m");
@@ -1511,7 +1507,7 @@ int dns_scope_announce(DnsScope *scope, bool goodbye) {
                                 &scope->announce_event_source,
                                 CLOCK_BOOTTIME,
                                 MDNS_ANNOUNCE_DELAY,
-                                MDNS_JITTER_RANGE_USEC,
+                                0,
                                 on_announcement_timeout, scope);
                 if (r < 0)
                         return log_debug_errno(r, "Failed to schedule second announcement: %m");
diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index 8dfad1dc7d..b6e94322a0 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -1951,10 +1951,12 @@ int dns_transaction_go(DnsTransaction *t) {
 
         if (!t->initial_jitter_scheduled &&
             IN_SET(t->scope->protocol, DNS_PROTOCOL_LLMNR, DNS_PROTOCOL_MDNS)) {
-                usec_t jitter, accuracy;
+                usec_t jitter;
 
-                /* RFC 4795 Section 2.7 suggests all queries should be delayed by a random time from 0 to
-                 * JITTER_INTERVAL. */
+                /* RFC 4795 Section 2.7 suggests all LLMNR queries should be delayed by a random time from 0 to
+                 * JITTER_INTERVAL.
+                 * RFC 6762 Section 8.1 suggests initial probe queries should be delayed by a random time from
+                 * 0 to 250ms. */
 
                 t->initial_jitter_scheduled = true;
 
@@ -1962,12 +1964,13 @@ int dns_transaction_go(DnsTransaction *t) {
 
                 case DNS_PROTOCOL_LLMNR:
                         jitter = random_u64_range(LLMNR_JITTER_INTERVAL_USEC);
-                        accuracy = LLMNR_JITTER_INTERVAL_USEC;
                         break;
 
                 case DNS_PROTOCOL_MDNS:
-                        jitter = usec_add(random_u64_range(MDNS_JITTER_RANGE_USEC), MDNS_JITTER_MIN_USEC);
-                        accuracy = MDNS_JITTER_RANGE_USEC;
+                        if (t->probing)
+                                jitter = random_u64_range(MDNS_PROBING_INTERVAL_USEC);
+                        else
+                                jitter = 0;
                         break;
                 default:
                         assert_not_reached();
@@ -1979,7 +1982,7 @@ int dns_transaction_go(DnsTransaction *t) {
                                 t->scope->manager->event,
                                 &t->timeout_event_source,
                                 CLOCK_BOOTTIME,
-                                jitter, accuracy,
+                                jitter, 0,
                                 on_transaction_timeout, t);
                 if (r < 0)
                         return r;
diff --git a/src/resolve/resolved-dns-transaction.h b/src/resolve/resolved-dns-transaction.h
index 498cabb7e5..ab86f0f01f 100644
--- a/src/resolve/resolved-dns-transaction.h
+++ b/src/resolve/resolved-dns-transaction.h
@@ -201,10 +201,6 @@ 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)
-
 /* mDNS probing interval, see RFC 6762 Section 8.1 */
 #define MDNS_PROBING_INTERVAL_USEC (250 * USEC_PER_MSEC)