From: Dave Hart <hart@ntp.org>
Date: Sun, 7 Mar 2010 20:01:29 +0000 (+0000)
Subject: rate limit ntpdate packets to 2s interval per server to stay
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f4442b6dd31350ceaf67fca288ce027a0dd4973a;p=thirdparty%2Fntp.git

rate limit ntpdate packets to 2s interval per server to stay
  within the "restrict ... limited" default limit set by
  "discard minimum 1", plus 1s of enforcement slop.
Respect KoD rate-limiting responses from ntpd.


bk: 4b940619s_-nhP0lOxdfHzVzJKOvXg
---

diff --git a/ntpdate/ntpdate.c b/ntpdate/ntpdate.c
index 082c5b089a..a906ae283d 100644
--- a/ntpdate/ntpdate.c
+++ b/ntpdate/ntpdate.c
@@ -58,7 +58,7 @@ struct timeval timeout = {0,0};
 #elif defined(SYS_WINNT)
 /*
  * Windows does not abort a select select call if SIGALRM goes off
- * so a 200 ms timeout is needed
+ * so a 200 ms timeout is needed (TIMER_HZ is 5).
  */
 struct sock_timeval timeout = {0,1000000/TIMER_HZ};
 #else
@@ -419,8 +419,18 @@ ntpdatemain (
 			} else {
 				sys_timeout = ((LFPTOFP(&tmp) * TIMER_HZ)
 					   + 0x8000) >> 16;
-				if (sys_timeout == 0)
-				sys_timeout = 1;
+				/*
+				 * No less than 1s between requests to
+				 * a server to stay within ntpd's
+				 * default "discard minimum 1" (and 1s
+				 * enforcement slop).  That is enforced
+				 * only if the nondefault limited
+				 * restriction is in place, such as with
+				 * "restrict ... limited" and "restrict
+				 * ... kod limited".
+				 */
+				if (MINTIMEOUT < sys_timeout)
+					sys_timeout = MINTIMEOUT;
 			}
 			break;
 		case 'v':
@@ -828,6 +838,19 @@ receive(
 	if (!is_authentic)
 		server->trust |= 1;
 
+	/*
+	 * Check for a KoD (rate limiting) response, cease and decist.
+	 */
+	if (LEAP_NOTINSYNC == PKT_LEAP(rpkt->li_vn_mode) &&
+	    STRATUM_PKT_UNSPEC == rpkt->stratum &&
+	    !memcmp("RATE", &rpkt->refid, 4)) {
+		msyslog(LOG_ERR, "%s rate limit response from server.\n",
+			stoa(&rbufp->recv_srcadr));
+		server->event_time = 0;
+		complete_servers++;
+		return;
+	}
+
 	/*
 	 * Looks good.	Record info from the packet.
 	 */
@@ -845,8 +868,9 @@ receive(
 	 * Make sure the server is at least somewhat sane.	If not, try
 	 * again.
 	 */
-	if (L_ISZERO(&rec) || !L_ISHIS(&server->org, &rec)) {
-		transmit(server);
+	if (L_ISZERO(&rec) || !L_ISHIS(&server->org, &rec)
+	    || L_ISEQU(&rec, &server->org)) {
+		server->event_time = current_time + sys_timeout;
 		return;
 	}
 
@@ -895,10 +919,10 @@ receive(
 	}
 
 	/*
-	 * Shift this data in, then transmit again.
+	 * Shift this data in, then schedule another transmit.
 	 */
 	server_data(server, (s_fp) di, &ci, 0);
-	transmit(server);
+	server->event_time = current_time + sys_timeout;
 }
 
 
@@ -1346,12 +1370,16 @@ addserver(
 			/* Name server is unusable. Exit after failing on the
 			   first server, in order to shorten the timeout caused
 			   by waiting for resolution of several servers */
-			fprintf(stderr, "Name server cannot be used, exiting");
-			msyslog(LOG_ERR, "name server cannot be used, reason: %s\n", gai_strerror(error));
+			fprintf(stderr, "Exiting, name server cannot be used: %s (%d)",
+				gai_strerror(error), error);
+			msyslog(LOG_ERR, "name server cannot be used: %s (%d)\n",
+				gai_strerror(error), error);
 			exit(1);
 		}
-		fprintf(stderr, "Error : %s\n", gai_strerror(error));
-		msyslog(LOG_ERR, "can't find host %s\n", serv);
+		fprintf(stderr, "Error resolving %s: %s (%d)\n", serv,
+			gai_strerror(error), error);
+		msyslog(LOG_ERR, "Can't find host %s: %s (%d)\n", serv,
+			gai_strerror(error), error);
 		return;
 	}
 #ifdef DEBUG
diff --git a/ntpdate/ntpdate.h b/ntpdate/ntpdate.h
index 00bc3ff061..75fba42910 100644
--- a/ntpdate/ntpdate.h
+++ b/ntpdate/ntpdate.h
@@ -91,7 +91,8 @@ struct server {
 /*
  * Some defaults
  */
-#define	DEFTIMEOUT	5		/* 5 timer increments */
+#define	MINTIMEOUT	(2 * TIMER_HZ)	/* 2s min. between packets */
+#define	DEFTIMEOUT	MINTIMEOUT	/*   (to the same server) */
 #define	DEFSAMPLES	4		/* get 4 samples per server */
 #define	DEFPRECISION	(-5)		/* the precision we claim */
 #define	DEFMAXPERIOD	60		/* maximum time to wait */