From: Vladimír Čunát <vladimir.cunat@nic.cz>
Date: Fri, 5 Feb 2021 15:42:34 +0000 (+0100)
Subject: daemon/udp_queue: rate-limit also other errors
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fheads%2Fsendmmsg-logs-limit;p=thirdparty%2Fknot-resolver.git

daemon/udp_queue: rate-limit also other errors

than EWOULDBLOCK, as long as the error remains the same.
Apparently we may print lots of these on Turris OS:
https://forum.turris.cz/t/5-1-8-kresd-throwing-many-errors-in-var-log-messages/14775
---

diff --git a/daemon/udp_queue.c b/daemon/udp_queue.c
index 9cf39401a..33c4cc3d5 100644
--- a/daemon/udp_queue.c
+++ b/daemon/udp_queue.c
@@ -75,18 +75,23 @@ static void udp_queue_send(int fd)
 	if (!q->len) return;
 	int sent_len = sendmmsg(fd, q->msgvec, q->len, 0);
 	/* ATM we don't really do anything about failures. */
-	int err = sent_len < 0 ? errno : EAGAIN /* unknown error, really */;
+	const int err = sent_len < 0 ? errno : EAGAIN /* unknown error, really */;
 	if (unlikely(sent_len != q->len)) {
-		if (err != EWOULDBLOCK) {
-			kr_log_error("ERROR: udp sendmmsg() sent %d / %d; %s\n",
-					sent_len, q->len, strerror(err));
-		} else {
-			const uint64_t stamp_now = kr_now();
-			static uint64_t stamp_last = 0;
-			if (stamp_now > stamp_last + 60*1000) {
+		/* Rate-limit the logs to at most once per minute,
+		 * in case the error code remains the same. */
+		const uint64_t stamp_now = kr_now();
+		static uint64_t stamp_last = 0;
+		static int err_last = 0;
+		if (err != err_last || stamp_now > stamp_last + 60*1000) {
+			if (err != EWOULDBLOCK) {
+				kr_log_error("ERROR: udp sendmmsg() sent %d / %d; %s"
+						"(reported at most once per minute)\n",
+						sent_len, q->len, strerror(err));
+			} else {
 				kr_log_info("WARNING: dropped UDP reply packet(s) due to network overload (reported at most once per minute)\n");
-				stamp_last = stamp_now;
 			}
+			stamp_last = stamp_now;
+			err_last = err;
 		}
 	}
 	for (int i = 0; i < q->len; ++i) {