[Bug 2114] Correctly calculate sntp's synch distance

bk: 50bc819bU_KtL3W18IfmJGN6XE6uNA

diff --git a/ChangeLog b/ChangeLog
index cd21308ee339eccf00a5c9da1ab6534da7eff390..d9d939422e327a56006386c92256cec9131f7046 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,4 @@
+* [Bug 2114] Correctly calculate sntp's synch distance.
 (4.2.7p330) 2012/12/03 Released by Harlan Stenn <stenn@ntp.org>
 * autogen doc cleanup
 (4.2.7p329) 2012/12/01 Released by Harlan Stenn <stenn@ntp.org>

diff --git a/sntp/main.c b/sntp/main.c
index ae297f7ef4796ce9766018a4e1b66225f908f25e..ec76c14aaf4ac5bd2d41fc0880e2c09a22051f5d 100644 (file)
--- a/sntp/main.c
+++ b/sntp/main.c
@@ -358,7 +358,7 @@ open_sockets(
                /* Register an NTP callback for recv/timeout */
                ev_sock6 = event_new(base, sock6,
                                     EV_TIMEOUT | EV_READ | EV_PERSIST,
-                                    &sock_cb, NULL);
+                                    &sock_cb, NULL);
                if (NULL == ev_sock6) {
                        msyslog(LOG_ERR,
                                "open_sockets: event_new(base, sock6) failed!");
@@ -694,7 +694,7 @@ xmt(
 
 
 /*
- * timeout_queries()  -- give up on unrequited NTP queries
+ * timeout_queries() -- give up on unrequited NTP queries
  */
 void
 timeout_queries(void)
@@ -1249,7 +1249,7 @@ handle_pkt(
                if (0 == stratum)
                                stratum = 16;
 
-               if (synch_distance > 0) {
+               if (synch_distance > 0.) {
                        cnt = snprintf(disptxt, sizeof(disptxt),
                                       " +/- %f", synch_distance);
                        if (cnt >= sizeof(disptxt))
@@ -1305,12 +1305,57 @@ offset_calculation(
        NTOHL_FP(&rpkt->xmt, &p_xmt);
 
        *precision = LOGTOD(rpkt->precision);
-       TRACE(3, ("offset_calculation: precision: %f\n", *precision));
 
+       TRACE(3, ("offset_calculation: LOGTOD(rpkt->precision): %f\n", *precision));
+
+       /* Compute offset etc. */
+       tmp = p_rec;
+       L_SUB(&tmp, &p_org);
+       LFPTOD(&tmp, t21);
+       TVTOTS(tv_dst, &dst);
+       dst.l_ui += JAN_1970;
+       tmp = p_xmt;
+       L_SUB(&tmp, &dst);
+       LFPTOD(&tmp, t34);
+       *offset = (t21 + t34) / 2.;
+       delta = t21 - t34;
+
+       // synch_distance is:
+       // (peer->delay + peer->rootdelay) / 2 + peer->disp
+       // + peer->rootdisp + clock_phi * (current_time - peer->update)
+       // + peer->jitter;
+       //
+       // and peer->delay = fabs(peer->offset - p_offset) * 2;
+       // and peer->offset needs history, so we're left with
+       // p_offset = (t21 + t34) / 2.;
+       // peer->disp = 0; (we have no history to augment this)
+       // clock_phi = 15e-6; 
+       // peer->jitter = LOGTOD(sys_precision); (we have no history to augment this)
+       // and ntp_proto.c:set_sys_tick_precision() should get us sys_precision.
+       //
+       // so our answer seems to be:
+       //
+       // (fabs(t21 + t34) + peer->rootdelay) / 3.
+       // + 0 (peer->disp)
+       // + peer->rootdisp
+       // + 15e-6 (clock_phi)
+       // + LOGTOD(sys_precision)
+
+       INSIST( FPTOD(p_rdly) >= 0. );
+#if 1
+       *synch_distance = (fabs(t21 + t34) + FPTOD(p_rdly)) / 3.
+               + 0.
+               + FPTOD(p_rdsp)
+               + 15e-6
+               + 0.    /* LOGTOD(sys_precision) when we can get it */
+               ;
+       INSIST( *synch_distance >= 0. );
+#else
        *synch_distance = (FPTOD(p_rdly) + FPTOD(p_rdsp))/2.0;
+#endif
 
 #ifdef DEBUG
-       if (debug > 2) {
+       if (debug > 3) {
                printf("sntp rootdelay: %f\n", FPTOD(p_rdly));
                printf("sntp rootdisp: %f\n", FPTOD(p_rdsp));
                printf("sntp syncdist: %f\n", *synch_distance);
@@ -1328,21 +1373,11 @@ offset_calculation(
        }
 #endif
 
-       /* Compute offset etc. */
-       tmp = p_rec;
-       L_SUB(&tmp, &p_org);
-       LFPTOD(&tmp, t21);
-       TVTOTS(tv_dst, &dst);
-       dst.l_ui += JAN_1970;
-       tmp = p_xmt;
-       L_SUB(&tmp, &dst);
-       LFPTOD(&tmp, t34);
-       *offset = (t21 + t34) / 2.;
-       delta = t21 - t34;
-
        TRACE(3, ("sntp offset_calculation:\trec - org t21: %.6f\n"
                  "\txmt - dst t34: %.6f\tdelta: %.6f\toffset: %.6f\n",
                  t21, t34, delta, *offset));
+
+       return;
 }