From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 24 Mar 2021 16:17:17 +0000 (+0100)
Subject: resolved: use random_u64_range() for randomizing initial transaction jitter
X-Git-Tag: v249-rc1~497^2~3
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9ee18bf473cdaa8128e898da3cf297b596cc9b99;p=thirdparty%2Fsystemd.git

resolved: use random_u64_range() for randomizing initial transaction jitter
---

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
index f084a70e45c..edce586e695 100644
--- a/src/resolve/resolved-dns-transaction.c
+++ b/src/resolve/resolved-dns-transaction.c
@@ -1941,23 +1941,20 @@ int dns_transaction_go(DnsTransaction *t) {
             IN_SET(t->scope->protocol, DNS_PROTOCOL_LLMNR, 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. */
+                /* RFC 4795 Section 2.7 suggests all queries should be delayed by a random time from 0 to
+                 * JITTER_INTERVAL. */
 
                 t->initial_jitter_scheduled = true;
 
-                random_bytes(&jitter, sizeof(jitter));
-
                 switch (t->scope->protocol) {
 
                 case DNS_PROTOCOL_LLMNR:
-                        jitter %= LLMNR_JITTER_INTERVAL_USEC;
+                        jitter = random_u64_range(LLMNR_JITTER_INTERVAL_USEC);
                         accuracy = LLMNR_JITTER_INTERVAL_USEC;
                         break;
 
                 case DNS_PROTOCOL_MDNS:
-                        jitter %= MDNS_JITTER_RANGE_USEC;
-                        jitter += MDNS_JITTER_MIN_USEC;
+                        jitter = usec_add(random_u64_range(MDNS_JITTER_RANGE_USEC), MDNS_JITTER_MIN_USEC);
                         accuracy = MDNS_JITTER_RANGE_USEC;
                         break;
                 default: