anti-clockhop changes from Dave Mills

bk: 42646d1dksGv88IKXkOMMdVrLTlokg

diff --git a/include/ntp.h b/include/ntp.h
index 9167bd47511c4cbe482c16c5427a00878110fce4..2c600702d7df0cb5bf460e8ef76c038f7ed21037 100644 (file)
--- a/include/ntp.h
+++ b/include/ntp.h
@@ -127,8 +127,7 @@ typedef char s_char;
 #define MAXDISTANCE    1.      /* max root distance */
 #define CLOCK_SGATE    3.      /* popcorn spike gate */
 #define HUFFPUFF       900     /* huff-n'-puff sample interval (s) */
-#define HYST           .5      /* anti-clockhop hysteresis */
-#define HYST_TC                .875    /* anti-clockhop hysteresis decay */
+#define HOPPER         3       /* anti-clockhop threshold */
 #define MAX_TTL                8       /* max ttl mapping vector size */
 #define NTP_MAXEXTEN   1024    /* max extension field size */
 
@@ -339,7 +338,6 @@ struct peer {
        double  jitter;         /* peer jitter (squares) */
        double  disp;           /* peer dispersion */
        double  estbdelay;      /* clock offset to broadcast server */
-       double  hyst;           /* anti-clockhop hysteresis */
 
        /*
         * End of clear-to-zero area

diff --git a/ntpd/ntp_proto.c b/ntpd/ntp_proto.c
index 1b09f264e1d69db1d4eea1cabbd85fcff6b257f8..27a5675e8c8e338dd25b470b4ba5f89f31712d3d 100644 (file)
--- a/ntpd/ntp_proto.c
+++ b/ntpd/ntp_proto.c
@@ -66,6 +66,7 @@ static        u_char leap_consensus;  /* consensus of survivor leap bits */
 static double sys_mindist = MINDISTANCE; /* selection threshold (s) */
 static double sys_maxdist = MAXDISTANCE; /* selection ceiling (s) */
 double sys_jitter;             /* system jitter (s) */
+int    sys_hopper;             /* anticlockhop counter */
 keyid_t        sys_private;            /* private value for session seed */
 int    sys_manycastserver;     /* respond to manycast client pkts */
 int    peer_ntpdate;           /* active peers in ntpdate mode */
@@ -165,10 +166,11 @@ transmit(
        if (peer->burst == 0) {
                u_char oreach;
 
+               if (peer == sys_peer)
+                       sys_hopper++;
                oreach = peer->reach;
                peer->outdate = current_time;
                peer->reach <<= 1;
-               peer->hyst *= HYST_TC;
                if (!peer->reach) {
 
                        /*
@@ -1931,11 +1933,6 @@ clock_select(void)
         * configured, his association raft is drowned as well, but only
         * if at at least eight poll intervals have gone. We must leave
         * at least one peer to collect the million bucks.
-        *
-        * Note the hysteresis gimmick that increases the effective
-        * distance for those rascals that have not made the final cut.
-        * This is to discourage clockhopping. Note also the prejudice
-        * against lower stratum peers if the floor is elevated.
         */
        j = 0;
        for (i = 0; i < nlist; i++) {
@@ -1957,7 +1954,6 @@ clock_select(void)
                 * hasn't been heard for awhile.
                 */
                d = root_distance(peer) + peer->stratum * sys_maxdist;
-               d *= 1. - peer->hyst;
                if (j >= NTP_MAXCLOCK) {
                        if (d >= synch[j - 1])
                                continue;
@@ -2092,15 +2088,8 @@ clock_select(void)
         * stratum. Note that the head of the list is at the lowest
         * stratum and that unsynchronized peers cannot survive this
         * far.
-        *
-        * Fiddle for hysteresis. Pump it up for a peer only if the peer
-        * stratum is at least the floor and there are enough survivors.
-        * This minimizes the pain when tossing out rascals beneath the
-        * floorboard. Don't count peers with stratum above the ceiling.
-        * Manycast is sooo complicated.
         */
        leap_consensus = 0;
-       typesystem = peer_list[0];
        for (i = nlist - 1; i >= 0; i--) {
                peer = peer_list[i];
                leap_consensus |= peer->leap;
@@ -2108,18 +2097,30 @@ clock_select(void)
                sys_survivors++;
                if (peer->flags & FLAG_PREFER)
                        sys_prefer = peer;
+               if (peer == osys_peer)
+                       typesystem = peer;
 #ifdef REFCLOCK
                if (peer->refclktype == REFCLK_ATOM_PPS)
                        sys_pps = peer;
 #endif /* REFCLOCK */
 #if DEBUG
                if (debug > 1)
-                       printf("cluster: survivor %s metric %.6f hyst %.6f\n",
-                           ntoa(&peer_list[i]->srcadr), synch[i],
-                           peer_list[i]->hyst);
+                       printf("cluster: survivor %s metric %.6f\n",
+                           ntoa(&peer_list[i]->srcadr), synch[i]);
 #endif
        }
 
+       /*
+        * Anticlockhop provision. Keep the current system peer if it is
+        * a survivor but not first in the list. But do that only HOPPER
+        * times.
+        */
+       if (osys_peer == NULL || typesystem == NULL || typesystem ==
+           peer_list[0] || sys_hopper > HOPPER) {
+               typesystem = peer_list[0];
+               sys_hopper = 0;
+       }
+
        /*
         * In manycast client mode we may have spooked a sizeable number
         * of peers that we don't need. If there are at least
@@ -2174,9 +2175,9 @@ clock_select(void)
        } else {
 
                /*
-                * Otherwise, choose the head of the survivor list.
+                * Otherwise, choose the anticlockhopper.
                 */ 
-               sys_peer = peer_list[0];
+               sys_peer = typesystem;
                sys_peer->status = CTL_PST_SEL_SYSPEER;
                clock_combine(peer_list, nlist);
                sys_jitter = SQRT(SQUARE(sys_peer->jitter) +
@@ -2189,14 +2190,9 @@ clock_select(void)
        }
 
        /*
-        * We have found the alpha male. Mark its scent and ding the
-        * anticlockhop hysteresis.
+        * We have found the alpha male.
         */
        sys_peer->flags |= FLAG_SYSPEER;
-       if (osurv >= sys_minclock)
-               sys_peer->hyst = HYST;
-       else
-               sys_peer->hyst = 0;
        if (osys_peer != sys_peer) {
                char *src;