Add waitsync command

chrony.texi

@@ -2898,6 +2898,7 @@ password:
 @item @code{sources}
 @item @code{sourcestats}
 @item @code{tracking}
+@item @code{waitsync}
 @end itemize
 
 All other commands require a password to have been specified previously,
@@ -2958,6 +2959,7 @@ interface.
 * timeout command::             Set initial response timeout
 * tracking command::            Display system clock performance
 * trimrtc command::             Correct the RTC time to the current system time
+* waitsync command::            Wait until synchronised
 * writertc command::            Write the RTC parameters to file.
 @end menu
 @c }}}
@@ -4188,6 +4190,31 @@ across machine reboots even if the @code{trimrtc} command is never used
 corrected, in a manner compatible with @code{chronyd} using it to
 maintain accurate time across machine reboots.
 @c }}}
+@c {{{ waitsync
+@node waitsync command
+@subsubsection waitsync
+The @code{waitsync} command waits for @code{chronyd} to synchronise.
+
+Up to three optional arguments can be specified, the first is the maximum
+number of tries in 10 second intervals before giving up and returning a
+non-zero error code.  When 0 is specified, or there are no arguments, the
+number of tries will not be limited.
+
+The second and third arguments are the maximum allowed remaining correction of
+the system clock and the maximum allowed skew (in ppm) as reported by the
+@code{tracking} command (@pxref{tracking command}) in the @code{System time}
+and @code{Skew} fields.  If not specified or zero, the value will not be
+checked.
+
+An example is
+
+@example
+waitsync 60 0.01
+@end example
+
+which will wait up to about 10 minutes for @code{chronyd} to synchronise to a
+source and the remaining correction to be less than 10 milliseconds.
+@c }}}
 @c {{{ writertc
 @node writertc command
 @subsubsection writertc

client.c

@@ -1234,6 +1234,7 @@ give_help(void)
   printf("sourcestats [-v] : Display estimation information about current sources\n");
   printf("tracking : Display system time information\n");
   printf("trimrtc : Correct RTC relative to system clock\n");
+  printf("waitsync [max-tries [max-correction [max-skew]]] : Wait until synchronised\n");
   printf("writertc : Save RTC parameters to file\n");
   printf("\n");
   printf("dns -n|+n : Disable/enable resolving IP addresses to hostnames\n");
@@ -2402,6 +2403,56 @@ process_cmd_reselect(CMD_Request *msg, char *line)
 
 /* ================================================== */
 
+static int
+process_cmd_waitsync(char *line)
+{
+  CMD_Request request;
+  CMD_Reply reply;
+  uint32_t ref_id, a, b, c, d;
+  double correction, skew_ppm, max_correction, max_skew_ppm;
+  int ret = 0, max_tries, i;
+
+  max_tries = 0;
+  max_correction = 0.0;
+  max_skew_ppm = 0.0;
+
+  sscanf(line, "%d %lf %lf", &max_tries, &max_correction, &max_skew_ppm);
+
+  request.command = htons(REQ_TRACKING);
+
+  for (i = 1; ; i++) {
+    if (request_reply(&request, &reply, RPY_TRACKING, 0)) {
+      ref_id = ntohl(reply.data.tracking.ref_id);
+      a = (ref_id >> 24);
+      b = (ref_id >> 16) & 0xff;
+      c = (ref_id >> 8) & 0xff;
+      d = (ref_id) & 0xff;
+
+      correction = UTI_FloatNetworkToHost(reply.data.tracking.current_correction);
+      correction = fabs(correction);
+      skew_ppm = UTI_FloatNetworkToHost(reply.data.tracking.skew_ppm);
+
+      printf("try: %d, refid: %d.%d.%d.%d, correction: %.9f, skew: %.3f\n",
+          i, a, b, c, d, correction, skew_ppm);
+
+      if (ref_id != 0 && ref_id != 0x7f7f0101L /* LOCAL refid */ &&
+          (max_correction == 0.0 || correction <= max_correction) &&
+          (max_skew_ppm == 0.0 || skew_ppm <= max_skew_ppm)) {
+        ret = 1;
+      }
+    }
+
+    if (!ret && (!max_tries || i < max_tries)) {
+      sleep(10);
+    } else {
+      break;
+    }
+  }
+  return ret;
+}
+
+/* ================================================== */
+
 static int
 process_cmd_dns(const char *line)
 {
@@ -2579,6 +2630,9 @@ process_line(char *line, int *quit)
     do_normal_submit = process_cmd_reselectdist(&tx_message, p+12);
   } else if (!strncmp(p, "reselect", 8)) {
     process_cmd_reselect(&tx_message, p+8);
+  } else if (!strncmp(p, "waitsync", 8)) {
+    ret = process_cmd_waitsync(p+8);
+    do_normal_submit = 0;
   } else if (!strncmp(p, "dns ", 4)) {
     ret = process_cmd_dns(p+4);
     do_normal_submit = 0;