sources: relax selection of non-trusted sources

When the selection has some trusted sources, don't require non-trusted
sources to be contained in the best interval as that can usually pass
only one source if the best interval is the interval of the source, or
no source at all if the best interval is an intersection of multiple
sources.

Relax the requirement for non-trusted sources to be contained in the
best interval of trusted sources alone instead of all sources in the
trusted interval.

diff --git a/sources.c b/sources.c
index fb6a61b3ff780ce7cc5d07bbd8c7691b5a2f8ae5..e272743832d43296a2e2b9870a75de093ad0b848 100644 (file)
--- a/sources.c
+++ b/sources.c
@@ -761,6 +761,7 @@ SRC_SelectSource(SRC_Instance updated_inst)
   double src_offset, src_offset_sd, src_frequency, src_frequency_sd, src_skew;
   double src_root_delay, src_root_dispersion;
   double best_lo, best_hi, distance, sel_src_distance, max_score;
+  double best_trust_lo, best_trust_hi;
   double first_sample_ago, max_reach_sample_ago;
   NTP_Leap leap_status;
 
@@ -989,7 +990,7 @@ SRC_SelectSource(SRC_Instance updated_inst)
 
   trust_depth = best_trust_depth = 0;
   depth = best_depth = 0;
-  best_lo = best_hi = 0.0;
+  best_lo = best_hi = best_trust_lo = best_trust_hi = 0.0;
 
   for (i = 0; i < n_endpoints; i++) {
     switch (sort_list[i].tag) {
@@ -999,14 +1000,20 @@ SRC_SelectSource(SRC_Instance updated_inst)
           trust_depth++;
         if (trust_depth > best_trust_depth ||
             (trust_depth == best_trust_depth && depth > best_depth)) {
-          best_trust_depth = trust_depth;
+          if (trust_depth > best_trust_depth) {
+            best_trust_depth = trust_depth;
+            best_trust_lo = sort_list[i].offset;
+          }
           best_depth = depth;
           best_lo = sort_list[i].offset;
         }
         break;
       case HIGH:
-        if (trust_depth == best_trust_depth && depth == best_depth)
-          best_hi = sort_list[i].offset;
+        if (trust_depth == best_trust_depth) {
+          if (depth == best_depth)
+            best_hi = sort_list[i].offset;
+          best_trust_hi = sort_list[i].offset;
+        }
         if (sources[sort_list[i].index]->sel_options & SRC_SELECT_TRUST)
           trust_depth--;
         depth--;
@@ -1045,22 +1052,26 @@ SRC_SelectSource(SRC_Instance updated_inst)
       continue;
 
     /* Check if source's interval contains the best interval, or is wholly
-       contained within it.  If there are any trusted sources the first
-       condition is applied only to them to not allow non-trusted sources to
-       move the final offset outside the interval. */
-    if (((!best_trust_depth || sources[i]->sel_options & SRC_SELECT_TRUST) &&
-         sources[i]->sel_info.lo_limit <= best_lo &&
+       contained within it.  If there are any trusted sources, other sources
+       are required to be wholly contained within the best interval of the
+       trusted sources to not allow non-trusted sources to move the final
+       offset outside the trusted interval. */
+    if ((sources[i]->sel_info.lo_limit <= best_lo &&
          sources[i]->sel_info.hi_limit >= best_hi) ||
         (sources[i]->sel_info.lo_limit >= best_lo &&
          sources[i]->sel_info.hi_limit <= best_hi)) {
 
+      if (!(best_trust_depth == 0 || (sources[i]->sel_options & SRC_SELECT_TRUST) ||
+            (sources[i]->sel_info.lo_limit >= best_trust_lo &&
+             sources[i]->sel_info.hi_limit <= best_trust_hi))) {
+        mark_source(sources[i], SRC_UNTRUSTED);
+        continue;
+      }
+
       sel_sources[n_sel_sources++] = i;
 
       if (sources[i]->sel_options & SRC_SELECT_REQUIRE)
         sel_req_source = 0;
-    } else if (sources[i]->sel_info.lo_limit <= best_lo &&
-               sources[i]->sel_info.hi_limit >= best_hi) {
-      mark_source(sources[i], SRC_UNTRUSTED);
     } else {
       mark_source(sources[i], SRC_FALSETICKER);
     }