doc: update NEWS

Change the default interval of both NTP and command rate limiting to -10
(1024 packets per second) and the burst to 16. The default NTP leak is 2
(rate limiting is enabled by default) and the default command leak is 0
(rate limiting is disabled by default).

NEWS

@@ -16,14 +16,21 @@ Enhancements
 * Add -t option to chronyd to exit after specified time
 * Add partial protection against replay attacks on symmetric mode
 * Don't reset polling interval when switching sources to online state
+* Enable NTP response rate limiting by default
+  (1024 packets per second per IP address and 25% leak)
 * Improve maximum server throughput on Linux and NetBSD
 * Remove dump files after start
 * Add tab-completion to chronyc with libedit/readline
 * Add ntpdata command to print details about NTP measurements
+* Allow all source options to be set in add server/peer command
 * Indicate truncated addresses/hostnames in chronyc output
 * Print reference IDs as hexadecimal numbers to avoid confusion with
   IPv4 addresses
 
+Bug fixes
+---------
+* Fix crash with disabled asynchronous name resolving
+
 New in version 2.4.1
 ====================
 

candm.h

@@ -362,8 +362,8 @@ typedef struct {
    domain socket.
 
    Version 6 (no authentication) : changed format of client accesses by index
-   (using new request/reply types), new flags in NTP source request and report,
-   new commands: refresh, serverstats
+   (using new request/reply types), new fields and flags in NTP source request
+   and report, new commands: ntpdata, refresh, serverstats
  */
 
 #define PROTO_VERSION_NUMBER 6
@@ -672,6 +672,7 @@ typedef struct {
   uint32_t total_tx_count;
   uint32_t total_rx_count;
   uint32_t total_valid_count;
+  uint32_t reserved[4];
   int32_t EOR;
 } RPY_NTPData;
 

client.c

@@ -1191,7 +1191,7 @@ give_help(void)
     "\0\0"
     "NTP sources:\0\0"
     "activity\0Check how many NTP sources are online/offline\0"
-    "ntpdata <address>\0Display information about last valid measurement\0"
+    "ntpdata [<address>]\0Display information about last valid measurement\0"
     "add server <address> [options]\0Add new NTP server\0"
     "add peer <address> [options]\0Add new NTP peer\0"
     "delete <address>\0Remove server or peer\0"
@@ -2244,11 +2244,39 @@ process_cmd_ntpdata(char *line)
   CMD_Reply reply;
   IPAddr remote_addr, local_addr;
   struct timespec ref_time;
+  uint32_t i, n_sources;
+  uint16_t mode;
+  int specified_addr;
 
+  if (*line) {
+    specified_addr = 1;
+    n_sources = 1;
+  } else {
+    specified_addr = 0;
+    request.command = htons(REQ_N_SOURCES);
+    if (!request_reply(&request, &reply, RPY_N_SOURCES, 0))
+      return 0;
+    n_sources = ntohl(reply.data.n_sources.n_sources);
+  }
+
+  for (i = 0; i < n_sources; i++) {
+    if (specified_addr) {
       if (DNS_Name2IPAddress(line, &remote_addr, 1) != DNS_Success) {
         LOG(LOGS_ERR, LOGF_Client, "Could not get address for hostname");
         return 0;
       }
+    } else {
+      request.command = htons(REQ_SOURCE_DATA);
+      request.data.source_data.index = htonl(i);
+      if (!request_reply(&request, &reply, RPY_SOURCE_DATA, 0))
+        return 0;
+
+      mode = ntohs(reply.data.source_data.mode);
+      if (mode != RPY_SD_MD_CLIENT && mode != RPY_SD_MD_PEER)
+        continue;
+
+      UTI_IPNetworkToHost(&reply.data.source_data.ip_addr, &remote_addr);
+    }
 
     request.command = htons(REQ_NTP_DATA);
     UTI_IPHostToNetwork(&remote_addr, &request.data.ntp_data.ip_addr);
@@ -2259,6 +2287,9 @@ process_cmd_ntpdata(char *line)
     UTI_IPNetworkToHost(&reply.data.ntp_data.local_addr, &local_addr);
     UTI_TimespecNetworkToHost(&reply.data.ntp_data.ref_time, &ref_time);
 
+    if (!specified_addr && !csv_mode)
+      printf("\n");
+
     print_report("Remote address  : %s (%R)\n"
                  "Remote port     : %u\n"
                  "Local address   : %s (%R)\n"
@@ -2266,8 +2297,8 @@ process_cmd_ntpdata(char *line)
                  "Version         : %u\n"
                  "Mode            : %M\n"
                  "Stratum         : %u\n"
-               "Poll            : %d\n"
-               "Precision       : %.9f seconds\n"
+                 "Poll interval   : %d (%.0f seconds)\n"
+                 "Precision       : %d (%.9f seconds)\n"
                  "Root delay      : %.6f seconds\n"
                  "Root dispersion : %.6f seconds\n"
                  "Reference ID    : %R\n"
@@ -2290,7 +2321,8 @@ process_cmd_ntpdata(char *line)
                  UTI_IPToString(&local_addr), (unsigned long)UTI_IPToRefid(&local_addr),
                  reply.data.ntp_data.leap, reply.data.ntp_data.version,
                  reply.data.ntp_data.mode, reply.data.ntp_data.stratum,
-               reply.data.ntp_data.poll, UTI_Log2ToDouble(reply.data.ntp_data.precision),
+                 reply.data.ntp_data.poll, UTI_Log2ToDouble(reply.data.ntp_data.poll),
+                 reply.data.ntp_data.precision, UTI_Log2ToDouble(reply.data.ntp_data.precision),
                  UTI_FloatNetworkToHost(reply.data.ntp_data.root_delay),
                  UTI_FloatNetworkToHost(reply.data.ntp_data.root_dispersion),
                  (unsigned long)ntohl(reply.data.ntp_data.ref_id), &ref_time,
@@ -2309,6 +2341,7 @@ process_cmd_ntpdata(char *line)
                  (unsigned long)ntohl(reply.data.ntp_data.total_rx_count),
                  (unsigned long)ntohl(reply.data.ntp_data.total_valid_count),
                  REPORT_END);
+  }
 
   return 1;
 }

clientlog.c

@@ -86,6 +86,10 @@ static unsigned int max_slots;
 #define TS_FRAC 4
 #define INVALID_TS 0
 
+/* Static offset included in conversion to the fixed-point timestamps to
+   randomise their alignment */
+static uint32_t ts_offset;
+
 /* Request rates are saved in the record as 8-bit scaled log2 values */
 #define RATE_SCALE 4
 #define MIN_RATE (-14 * RATE_SCALE)
@@ -95,7 +99,7 @@ static unsigned int max_slots;
    number of tokens spent on response are determined from configured
    minimum inverval between responses (in log2) and burst length. */
 
-#define MIN_LIMIT_INTERVAL (-TS_FRAC)
+#define MIN_LIMIT_INTERVAL (-15 - TS_FRAC)
 #define MAX_LIMIT_INTERVAL 12
 #define MIN_LIMIT_BURST 1
 #define MAX_LIMIT_BURST 255
@@ -105,7 +109,8 @@ static uint16_t max_cmd_tokens;
 static uint16_t ntp_tokens_per_packet;
 static uint16_t cmd_tokens_per_packet;
 
-/* Reduction of token rates to avoid overflow of 16-bit counters */
+/* Reduction of token rates to avoid overflow of 16-bit counters.  Negative
+   shift is used for coarse limiting with intervals shorter than -TS_FRAC. */
 static int ntp_token_shift;
 static int cmd_token_shift;
 
@@ -114,7 +119,7 @@ static int cmd_token_shift;
    prevent an attacker sending requests with spoofed source address
    from blocking responses to the address completely. */
 
-#define MIN_LEAK_RATE 1
+#define MIN_LEAK_RATE 0
 #define MAX_LEAK_RATE 4
 
 static int ntp_leak_rate;
@@ -133,6 +138,8 @@ static uint32_t total_ntp_drops;
 static uint32_t total_cmd_drops;
 static uint32_t total_record_drops;
 
+#define NSEC_PER_SEC 1000000000U
+
 /* ================================================== */
 
 static int expand_hashtable(void);
@@ -271,11 +278,18 @@ set_bucket_params(int interval, int burst, uint16_t *max_tokens,
   interval = CLAMP(MIN_LIMIT_INTERVAL, interval, MAX_LIMIT_INTERVAL);
   burst = CLAMP(MIN_LIMIT_BURST, burst, MAX_LIMIT_BURST);
 
-  /* Find smallest shift with which the maximum number fits in 16 bits */
+  if (interval >= -TS_FRAC) {
+    /* Find the smallest shift with which the maximum number fits in 16 bits */
     for (*token_shift = 0; *token_shift < interval + TS_FRAC; (*token_shift)++) {
       if (burst << (TS_FRAC + interval - *token_shift) < 1U << 16)
         break;
     }
+  } else {
+    /* Coarse rate limiting */
+    *token_shift = interval + TS_FRAC;
+    *tokens_per_packet = 1;
+    burst = MAX(1U << -*token_shift, burst);
+  }
 
   *tokens_per_packet = 1U << (TS_FRAC + interval - *token_shift);
   *max_tokens = *tokens_per_packet * burst;
@@ -291,29 +305,19 @@ CLG_Initialise(void)
 {
   int interval, burst, leak_rate;
 
-  max_ntp_tokens = max_cmd_tokens = 0;
-  ntp_tokens_per_packet = cmd_tokens_per_packet = 0;
-  ntp_token_shift = cmd_token_shift = 0;
-  ntp_leak_rate = cmd_leak_rate = 0;
-
-  if (CNF_GetNTPRateLimit(&interval, &burst, &leak_rate)) {
+  CNF_GetNTPRateLimit(&interval, &burst, &leak_rate);
   set_bucket_params(interval, burst, &max_ntp_tokens, &ntp_tokens_per_packet,
                     &ntp_token_shift);
   ntp_leak_rate = CLAMP(MIN_LEAK_RATE, leak_rate, MAX_LEAK_RATE);
-  }
 
-  if (CNF_GetCommandRateLimit(&interval, &burst, &leak_rate)) {
+  CNF_GetCommandRateLimit(&interval, &burst, &leak_rate);
   set_bucket_params(interval, burst, &max_cmd_tokens, &cmd_tokens_per_packet,
                     &cmd_token_shift);
   cmd_leak_rate = CLAMP(MIN_LEAK_RATE, leak_rate, MAX_LEAK_RATE);
-  }
 
   active = !CNF_GetNoClientLog();
-  if (!active) {
-    if (ntp_leak_rate || cmd_leak_rate)
-      LOG_FATAL(LOGF_ClientLog, "ratelimit cannot be used with noclientlog");
+  if (!active)
     return;
-  }
 
   /* Calculate the maximum number of slots that can be allocated in the
      configured memory limit.  Take into account expanding of the hash
@@ -325,6 +329,9 @@ CLG_Initialise(void)
   records = NULL;
 
   expand_hashtable();
+
+  UTI_GetRandomBytes(&ts_offset, sizeof (ts_offset));
+  ts_offset %= NSEC_PER_SEC / (1U << TS_FRAC);
 }
 
 /* ================================================== */
@@ -345,6 +352,12 @@ get_ts_from_timespec(struct timespec *ts)
 {
   uint32_t sec = ts->tv_sec, nsec = ts->tv_nsec;
 
+  nsec += ts_offset;
+  if (nsec >= NSEC_PER_SEC) {
+    nsec -= NSEC_PER_SEC;
+    sec++;
+  }
+
   /* This is fast and accurate enough */
   return sec << TS_FRAC | (140740U * (nsec >> 15)) >> (32 - TS_FRAC);
 }
@@ -369,7 +382,12 @@ update_record(struct timespec *now, uint32_t *last_hit, uint32_t *hits,
   if (prev_hit == INVALID_TS || (int32_t)interval < 0)
     return;
 
+  if (token_shift >= 0)
     new_tokens = (now_ts >> token_shift) - (prev_hit >> token_shift);
+  else if (now_ts - prev_hit > max_tokens)
+    new_tokens = max_tokens;
+  else
+    new_tokens = (now_ts - prev_hit) << -token_shift;
   *tokens = MIN(*tokens + new_tokens, max_tokens);
 
   /* Convert the interval to scaled and rounded log2 */
@@ -502,7 +520,7 @@ CLG_LimitNTPResponseRate(int index)
   Record *record;
   int drop;
 
-  if (!ntp_tokens_per_packet)
+  if (!ntp_leak_rate)
     return 0;
 
   record = ARR_GetElement(records, index);
@@ -543,7 +561,7 @@ CLG_LimitCommandResponseRate(int index)
 {
   Record *record;
 
-  if (!cmd_tokens_per_packet)
+  if (!cmd_leak_rate)
     return 0;
 
   record = ARR_GetElement(records, index);

cmdmon.c

@@ -1232,6 +1232,7 @@ handle_ntp_data(CMD_Request *rx_message, CMD_Reply *tx_message)
   tx_message->data.ntp_data.total_tx_count = htonl(report.total_tx_count);
   tx_message->data.ntp_data.total_rx_count = htonl(report.total_rx_count);
   tx_message->data.ntp_data.total_valid_count = htonl(report.total_valid_count);
+  memset(tx_message->data.ntp_data.reserved, 0xff, sizeof (tx_message->data.ntp_data.reserved));
 }
 
 /* ================================================== */

conf.c

@@ -66,8 +66,7 @@ static void parse_log(char *);
 static void parse_mailonchange(char *);
 static void parse_makestep(char *);
 static void parse_maxchange(char *);
-static void parse_ratelimit(char *line, int *enabled, int *interval,
-                            int *burst, int *leak);
+static void parse_ratelimit(char *line, int *interval, int *burst, int *leak);
 static void parse_refclock(char *);
 static void parse_smoothtime(char *);
 static void parse_source(char *line, NTP_Source_Type type, int pool);
@@ -191,14 +190,12 @@ static char *ntp_signd_socket = NULL;
 static char *pidfile;
 
 /* Rate limiting parameters */
-static int ntp_ratelimit_enabled = 0;
-static int ntp_ratelimit_interval = 3;
-static int ntp_ratelimit_burst = 8;
-static int ntp_ratelimit_leak = 3;
-static int cmd_ratelimit_enabled = 0;
-static int cmd_ratelimit_interval = 1;
+static int ntp_ratelimit_interval = -10;
+static int ntp_ratelimit_burst = 16;
+static int ntp_ratelimit_leak = 2;
+static int cmd_ratelimit_interval = -10;
 static int cmd_ratelimit_burst = 16;
-static int cmd_ratelimit_leak = 2;
+static int cmd_ratelimit_leak = 0;
 
 /* Smoothing constants */
 static double smooth_max_freq = 0.0; /* in ppm */
@@ -455,8 +452,7 @@ CNF_ParseLine(const char *filename, int number, char *line)
   } else if (!strcasecmp(command, "cmdport")) {
     parse_int(p, &cmd_port);
   } else if (!strcasecmp(command, "cmdratelimit")) {
-    parse_ratelimit(p, &cmd_ratelimit_enabled, &cmd_ratelimit_interval,
-                    &cmd_ratelimit_burst, &cmd_ratelimit_leak);
+    parse_ratelimit(p, &cmd_ratelimit_interval, &cmd_ratelimit_burst, &cmd_ratelimit_leak);
   } else if (!strcasecmp(command, "combinelimit")) {
     parse_double(p, &combine_limit);
   } else if (!strcasecmp(command, "corrtimeratio")) {
@@ -536,8 +532,7 @@ CNF_ParseLine(const char *filename, int number, char *line)
   } else if (!strcasecmp(command, "port")) {
     parse_int(p, &ntp_port);
   } else if (!strcasecmp(command, "ratelimit")) {
-    parse_ratelimit(p, &ntp_ratelimit_enabled, &ntp_ratelimit_interval,
-                    &ntp_ratelimit_burst, &ntp_ratelimit_leak);
+    parse_ratelimit(p, &ntp_ratelimit_interval, &ntp_ratelimit_burst, &ntp_ratelimit_leak);
   } else if (!strcasecmp(command, "refclock")) {
     parse_refclock(p);
   } else if (!strcasecmp(command, "reselectdist")) {
@@ -642,13 +637,11 @@ parse_source(char *line, NTP_Source_Type type, int pool)
 /* ================================================== */
 
 static void
-parse_ratelimit(char *line, int *enabled, int *interval, int *burst, int *leak)
+parse_ratelimit(char *line, int *interval, int *burst, int *leak)
 {
   int n, val;
   char *opt;
 
-  *enabled = 1;
-
   while (*line) {
     opt = line;
     line = CPS_SplitWord(line);
@@ -1830,22 +1823,20 @@ CNF_GetLockMemory(void)
 
 /* ================================================== */
 
-int CNF_GetNTPRateLimit(int *interval, int *burst, int *leak)
+void CNF_GetNTPRateLimit(int *interval, int *burst, int *leak)
 {
   *interval = ntp_ratelimit_interval;
   *burst = ntp_ratelimit_burst;
   *leak = ntp_ratelimit_leak;
-  return ntp_ratelimit_enabled;
 }
 
 /* ================================================== */
 
-int CNF_GetCommandRateLimit(int *interval, int *burst, int *leak)
+void CNF_GetCommandRateLimit(int *interval, int *burst, int *leak)
 {
   *interval = cmd_ratelimit_interval;
   *burst = cmd_ratelimit_burst;
   *leak = cmd_ratelimit_leak;
-  return cmd_ratelimit_enabled;
 }
 
 /* ================================================== */

conf.h

@@ -102,8 +102,8 @@ extern void CNF_SetupAccessRestrictions(void);
 extern int CNF_GetSchedPriority(void);
 extern int CNF_GetLockMemory(void);
 
-extern int CNF_GetNTPRateLimit(int *interval, int *burst, int *leak);
-extern int CNF_GetCommandRateLimit(int *interval, int *burst, int *leak);
+extern void CNF_GetNTPRateLimit(int *interval, int *burst, int *leak);
+extern void CNF_GetCommandRateLimit(int *interval, int *burst, int *leak);
 extern void CNF_GetSmooth(double *max_freq, double *max_wander, int *leap_only);
 extern void CNF_GetTempComp(char **file, double *interval, char **point_file, double *T0, double *k0, double *k1, double *k2);
 

configure

@@ -219,6 +219,7 @@ try_lockmem=0
 feat_asyncdns=1
 feat_forcednsretry=1
 try_clock_gettime=1
+try_recvmmsg=1
 feat_timestamping=1
 try_timestamping=0
 feat_ntp_signd=0
@@ -400,6 +401,9 @@ case $OPERATINGSYSTEM in
         echo "Configuring for " $SYSTEM
     ;;
     FreeBSD)
+        # recvmmsg() seems to be broken on FreeBSD 11.0 and it's just
+        # a wrapper around recvmsg()
+        try_recvmmsg=0
         EXTRA_OBJECTS="sys_generic.o sys_netbsd.o sys_timex.o"
         add_def FREEBSD
         if [ $feat_droproot = "1" ]; then
@@ -629,15 +633,17 @@ fi
 RECVMMSG_CODE='
   struct mmsghdr hdr;
   return !recvmmsg(0, &hdr, 1, MSG_DONTWAIT, 0);'
-if test_code 'recvmmsg()' 'sys/socket.h' '' "$EXTRA_LIBS" "$RECVMMSG_CODE"; then
+if [ $try_recvmmsg = "1" ]; then
+  if test_code 'recvmmsg()' 'sys/socket.h' '' "$EXTRA_LIBS" "$RECVMMSG_CODE"; then
     add_def HAVE_RECVMMSG
-else
+  else
     if test_code 'recvmmsg() with _GNU_SOURCE' 'sys/socket.h' '-D_GNU_SOURCE' \
       "$EXTRA_LIBS" "$RECVMMSG_CODE"
     then
       add_def _GNU_SOURCE
       add_def HAVE_RECVMMSG
     fi
+  fi
 fi
 
 if [ $feat_timestamping = "1" ] && [ $try_timestamping = "1" ] &&

doc/chrony.conf.adoc

@@ -110,7 +110,8 @@ round-trip delay of 0.3 seconds or more should be ignored. The default value is
 This option is similar to the maxdelay option above. *chronyd* keeps a record
 of the minimum round-trip delay amongst the previous measurements that it has
 buffered. If a measurement has a round trip delay that is greater than the
-maxdelayratio times the minimum delay, it will be rejected.
+maxdelayratio times the minimum delay, it will be rejected. This option works
+only in the *server* directive when not in the interleaved mode.
 *maxdelaydevratio* _ratio_:::
 If a measurement has a ratio of the increase in the round-trip delay from the
 minimum delay amongst the previous measurements to the standard deviation of
@@ -1220,8 +1221,8 @@ source port used in NTP client requests can be set by the
 <<acquisitionport,*acquisitionport*>> directive.
 
 [[ratelimit]]*ratelimit* [_option_]...::
-This directive enables response rate limiting for NTP packets. Its purpose is
-to reduce network traffic with misconfigured or broken NTP clients that are
+This directive configures response rate limiting for NTP packets. Its purpose
+is to reduce network traffic with misconfigured or broken NTP clients that are
 polling the server too frequently. The limits are applied to individual IP
 addresses. If multiple clients share one IP address (e.g. multiple hosts behind
 NAT), the sum of their traffic will be limited. If a client that increases its
@@ -1236,33 +1237,40 @@ in any order):
 +
 *interval*:::
 This option sets the minimum interval between responses. It is defined as a
-power of 2 in seconds. The default value is 3 (8 seconds). The minimum value
-is -4 and the maximum value is 12.
+power of 2 in seconds. The default value is -10 (1/1024 of a second, or 1024
+packets per second). The minimum value is -19 (524288 packets per second) and
+the maximum value is 12 (one packet per 4096 seconds). Note that with values
+below -4 the rate limiting is coarse (responses are allowed in bursts, even if
+the interval between them is shorter than the specified interval).
 *burst*:::
 This option sets the maximum number of responses that can be sent in a burst,
 temporarily exceeding the limit specified by the *interval* option. This is
 useful for clients that make rapid measurements on start (e.g. *chronyd* with
-the *iburst* option). The default value is 8. The minimum value is 1 and the
+the *iburst* option). The default value is 16. The minimum value is 1 and the
 maximum value is 255.
 *leak*:::
 This option sets the rate at which responses are randomly allowed even if the
 limits specified by the *interval* and *burst* options are exceeded. This is
 necessary to prevent an attacker who is sending requests with a spoofed
 source address from completely blocking responses to that address. The leak
-rate is defined as a power of 1/2 and it is 3 by default, i.e. on average at
-least every eighth request has a response. The minimum value is 1 and the
-maximum value is 4.
+rate is defined as a power of 1/2 and it is 2 by default, i.e. on average at
+least every fourth request has a response. The minimum value is 0, which
+disables the rate limiting, and the maximum value is 4 (one response per 16
+requests).
 ::
 +
 An example use of the directive is:
 +
 ----
-ratelimit interval 4 burst 4
+ratelimit interval 1 burst 8
 ----
 +
-This would reduce the response rate for IP addresses that send packets on
-average more frequently than once per 16 seconds or send packets in bursts
-of more than 4 packets.
+This would reduce the response rate for IP addresses sending packets on average
+more than once per 2 seconds, or sending packets in bursts of more than 8
+packets, by up to 75% (with default *leak* of 2).
++
+Rate limiting can be disabled by setting the *leak* option to 0, or by the
+<<noclientlog,*noclientlog*>> directive.
 
 [[smoothtime]]*smoothtime* _max-freq_ _max-wander_ [*leaponly*]::
 The *smoothtime* directive can be used to enable smoothing of the time that
@@ -1389,16 +1397,18 @@ This would make *chronyd* use UDP 257 as its command port. (*chronyc* would
 need to be run with the *-p 257* switch to inter-operate correctly.)
 
 [[cmdratelimit]]*cmdratelimit* [_option_]...::
-This directive enables response rate limiting for command packets. It is
-similar to the <<ratelimit,*ratelimit*>> directive, except responses to
-localhost are never limited and the default interval is 1 (2 seconds), the default
-burst is 16, and the default leak rate is 2.
+This directive is identical to the <<ratelimit,*ratelimit*>> directive, except
+it configures rate limiting for command packets and responses to localhost are
+never limited. It is disabled by default (the default *leak* is 0).
 +
 An example of the use of the directive is:
 +
 ----
-cmdratelimit interval 2
+cmdratelimit interval -2 burst 128 leak 2
 ----
++
+This would reduce response rate for addresses that send more than 4 requests
+per second, or bursts of more than 128 packets, by up to 75%.
 
 === Real-time clock (RTC)
 
@@ -1779,10 +1789,11 @@ received from the specified network interface. The network interface controller
 receptions, avoiding processing and queueing delays in the kernel, network
 driver, and hardware. This can significantly improve the accuracy of the
 timestamps and the measured offset, which is used for synchronisation of the
-system clock. In order to get best results, it is necessary to enable HW
-timestamping on both sides receiving and sending the packets (i.e. server and
-client, or both peers), and also enable the interleaved mode with the *xleave*
-option in the <<server,*server*>> or the <<peer,*peer*>> directive.
+system clock. In order to get the best results, both sides receiving and
+sending NTP packets (i.e. server and client, or two peers) need to use HW
+timestamping. If the server or peer supports the interleaved mode, it needs to
+be enabled by the *xleave* option in the <<server,*server*>> or the
+<<peer,*peer*>> directive.
 +
 This directive is supported on Linux 3.19 and newer. The NIC must support HW
 timestamping, which can be verified with the *ethtool -T* command. The list of
@@ -1799,6 +1810,9 @@ interfaces. The timestamping used in measurements is indicated in the
 _measurements.log_ file if enabled by the <<log,*log measurements*>> directive,
 and the <<chronyc.adoc#ntpdata,*ntpdata*>> report in *chronyc*.
 +
+If the specified interface is _*_, *chronyd* will try to enable HW timestamping
+on all available interfaces.
++
 An example of the directive is:
 +
 ----
@@ -2213,7 +2227,7 @@ http://www.pool.ntp.org/en/join.html[pool.ntp.org] project. The configuration
 is similar to the NTP client with permanent connection, except it needs to
 allow client access from all addresses. It is recommended to handpick at least
 few good servers, and possibly combine them with a random selection of other
-servers in the pool. Rate limiting can be enabled to not waste too much
+servers in the pool. The rate limiting interval can be increased to save more
 bandwidth on misconfigured and broken NTP clients. The *-r* option with the
 *dumpdir* directive shortens the time for which *chronyd* will not serve time
 to its clients when it needs to be restarted for any reason.
@@ -2228,7 +2242,7 @@ pool pool.ntp.org iburst
 makestep 1.0 3
 rtcsync
 allow
-ratelimit interval 2 burst 10
+ratelimit interval 1
 driftfile @CHRONYVARDIR@/drift
 dumpdir @CHRONYRUNDIR@
 dumponexit

doc/chronyc.adoc

@@ -441,10 +441,10 @@ the offline state.
 the name of the server or peer was not resolved to an address yet; this source is
 not visible in the *sources* and *sourcestats* reports.
 
-[[ntpdata]]*ntpdata* _address_::
+[[ntpdata]]*ntpdata* [_address_]::
 The *ntpdata* command displays the last valid measurement and other
-NTP-specific information about the NTP source. An example of the output is
-shown below.
+NTP-specific information about the specified NTP source, or all NTP sources if
+no address was specified. An example of the output is shown below.
 +
 ----
 Remote address  : 203.0.113.15 (CB00710F)
@@ -454,8 +454,8 @@ Leap status     : Normal
 Version         : 4
 Mode            : Server
 Stratum         : 1
-Poll            : 10
-Precision       : 0.000000060 seconds
+Poll interval   : 10 (1024 seconds)
+Precision       : -24 (0.000000060 seconds)
 Root delay      : 0.000015 seconds
 Root dispersion : 0.000015 seconds
 Reference ID    : 50505331
@@ -489,7 +489,7 @@ reference ID.
 *Version*:::
 *Mode*:::
 *Stratum*:::
-*Poll*:::
+*Poll interval*:::
 *Precision*:::
 *Root delay*:::
 *Root dispersion*:::

examples/chrony-wait.service

@@ -9,7 +9,7 @@ Wants=time-sync.target
 Type=oneshot
 # Wait up to ~10 minutes for chronyd to synchronize and the remaining
 # clock correction to be less than 0.1 seconds
-ExecStart=/usr/bin/chronyc waitsync 600 0.1 0.0 1
+ExecStart=/usr/bin/chronyc -h 127.0.0.1,::1 waitsync 600 0.1 0.0 1
 RemainAfterExit=yes
 StandardOutput=null
 

nameserv_async.c

@@ -113,6 +113,9 @@ DNS_Name2IPAddressAsync(const char *name, DNS_NameResolveHandler handler, void *
     LOG_FATAL(LOGF_Nameserv, "pipe() failed");
   }
 
+  UTI_FdSetCloexec(inst->pipe[0]);
+  UTI_FdSetCloexec(inst->pipe[1]);
+
   resolving_threads++;
   assert(resolving_threads <= 1);
 

ntp_core.c

@@ -1453,11 +1453,12 @@ receive_packet(NCR_Instance inst, NTP_Local_Address *local_addr,
             !(inst->mode == MODE_ACTIVE && interleaved_packet &&
               delay > UTI_Log2ToDouble(message->poll - 1));
 
-    /* Test B requires that the ratio of the round trip delay to the
-       minimum one currently in the stats data register is less than an
-       administrator-defined value */
+    /* Test B requires in the basic client mode that the ratio of the round
+       trip delay to the minimum one currently in the stats data register is
+       less than an administrator-defined value */
     testB = inst->max_delay_ratio <= 1.0 ||
-            (delay - dispersion) / SST_MinRoundTripDelay(stats) <= inst->max_delay_ratio;
+            !(inst->mode == MODE_CLIENT && !interleaved_packet &&
+              (delay - dispersion) / SST_MinRoundTripDelay(stats) > inst->max_delay_ratio);
 
     /* Test C requires that the ratio of the increase in delay from the minimum
        one in the stats data register to the standard deviation of the offsets

ntp_io_linux.c

@@ -28,6 +28,7 @@
 
 #include "sysincl.h"
 
+#include <ifaddrs.h>
 #include <linux/errqueue.h>
 #include <linux/ethtool.h>
 #include <linux/net_tstamp.h>
@@ -90,9 +91,16 @@ add_interface(const char *name)
   struct hwtstamp_config ts_config;
   struct ifreq req;
   int sock_fd, if_index, phc_index, phc_fd;
+  unsigned int i;
   struct Interface *iface;
   char phc_path[64];
 
+  /* Check if the interface was not already added */
+  for (i = 0; i < ARR_GetSize(interfaces); i++) {
+    if (!strcmp(name, ((struct Interface *)ARR_GetElement(interfaces, i))->name))
+      return 1;
+  }
+
   sock_fd = socket(AF_INET, SOCK_DGRAM, 0);
   if (sock_fd < 0)
     return 0;
@@ -160,11 +168,37 @@ add_interface(const char *name)
 
   iface->clock = HCL_CreateInstance();
 
+  DEBUG_LOG(LOGF_NtpIOLinux, "Enabled HW timestamping on %s", name);
+
   return 1;
 }
 
 /* ================================================== */
 
+static int
+add_all_interfaces(void)
+{
+  struct ifaddrs *ifaddr, *ifa;
+  int r;
+
+  if (getifaddrs(&ifaddr)) {
+    DEBUG_LOG(LOGF_NtpIOLinux, "getifaddrs() failed : %s", strerror(errno));
+    return 0;
+  }
+
+  for (r = 0, ifa = ifaddr; ifa; ifa = ifa->ifa_next) {
+    if (add_interface(ifa->ifa_name))
+      r = 1;
+  }
+  
+  freeifaddrs(ifaddr);
+
+  /* Return success if at least one interface was added */
+  return r;
+}
+
+/* ================================================== */
+
 static void
 update_interface_speed(struct Interface *iface)
 {
@@ -202,19 +236,34 @@ NIO_Linux_Initialise(void)
   ARR_Instance config_hwts_ifaces;
   char *if_name;
   unsigned int i;
+  int wildcard, hwts;
 
   interfaces = ARR_CreateInstance(sizeof (struct Interface));
 
   config_hwts_ifaces = CNF_GetHwTsInterfaces();
 
-  /* Enable HW timestamping on all specified interfaces.  If no interface was
-     specified, use SW timestamping. */
-  if (ARR_GetSize(config_hwts_ifaces)) {
+  /* Enable HW timestamping on specified interfaces.  If "*" was specified, try
+     all interfaces.  If no interface was specified, enable SW timestamping. */
+
+  for (i = wildcard = 0; i < ARR_GetSize(config_hwts_ifaces); i++) {
+    if (!strcmp("*", *(char **)ARR_GetElement(config_hwts_ifaces, i)))
+      wildcard = 1;
+  }
+
+  if (!wildcard && ARR_GetSize(config_hwts_ifaces)) {
     for (i = 0; i < ARR_GetSize(config_hwts_ifaces); i++) {
       if_name = *(char **)ARR_GetElement(config_hwts_ifaces, i);
       if (!add_interface(if_name))
         LOG_FATAL(LOGF_NtpIO, "Could not enable HW timestamping on %s", if_name);
     }
+    hwts = 1;
+  } else if (wildcard && add_all_interfaces()) {
+    hwts = 1;
+  } else {
+    hwts = 0;
+  }
+
+  if (hwts) {
     ts_flags = SOF_TIMESTAMPING_RAW_HARDWARE | SOF_TIMESTAMPING_RX_HARDWARE;
     ts_tx_flags = SOF_TIMESTAMPING_TX_HARDWARE;
   } else {

sourcestats.c

@@ -47,8 +47,12 @@
    2000ppm, which would be pretty bad */
 #define WORST_CASE_FREQ_BOUND (2000.0/1.0e6)
 
-/* The minimum allowed skew */
+/* The minimum and maximum assumed skew */
 #define MIN_SKEW 1.0e-12
+#define MAX_SKEW 1.0e+02
+
+/* The minimum assumed std dev for weighting */
+#define MIN_WEIGHT_SD 1.0e-9
 
 /* The asymmetry of network jitter when all jitter is in one direction */
 #define MAX_ASYMMETRY 0.5
@@ -507,8 +511,7 @@ SST_DoNewRegression(SST_Stats inst)
     /* And now, work out the weight vector */
 
     sd = mean_distance - min_distance;
-    if (sd > min_distance || sd <= 0.0)
-      sd = min_distance;
+    sd = CLAMP(MIN_WEIGHT_SD, sd, min_distance);
 
     for (i=0; i<inst->n_samples; i++) {
       sd_weight = 1.0 + SD_TO_DIST_RATIO * (peer_distances[i] - min_distance) / sd;
@@ -539,9 +542,7 @@ SST_DoNewRegression(SST_Stats inst)
     inst->std_dev = sqrt(est_var);
     inst->nruns = nruns;
 
-    if (inst->skew < MIN_SKEW)
-      inst->skew = MIN_SKEW;
-
+    inst->skew = CLAMP(MIN_SKEW, inst->skew, MAX_SKEW);
     stress = fabs(old_freq - inst->estimated_frequency) / old_skew;
 
     DEBUG_LOG(LOGF_SourceStats, "off=%e freq=%e skew=%e n=%d bs=%d runs=%d asym=%f arun=%d",
@@ -844,6 +845,8 @@ SST_SaveToFile(SST_Stats inst, FILE *out)
             inst->strata[j]);
 
   }
+
+  fprintf(out, "%d\n", inst->asymmetry_run);
 }
 
 /* ================================================== */
@@ -898,6 +901,10 @@ SST_LoadFromFile(SST_Stats inst, FILE *in)
         UTI_NormaliseTimespec(&inst->sample_times[i]);
       }
     }
+
+    /* This field was not saved in older versions */
+    if (!fgets(line, sizeof(line), in) || sscanf(line, "%d\n", &inst->asymmetry_run) != 1)
+      inst->asymmetry_run = 0;
   } else {
     inst->n_samples = 0; /* Load abandoned if any sign of corruption */
     return 0;

stubs.c

@@ -42,6 +42,7 @@
 #include "privops.h"
 #include "refclock.h"
 #include "sched.h"
+#include "util.h"
 
 #ifndef FEAT_ASYNCDNS
 
@@ -51,10 +52,11 @@ struct DNS_Async_Instance {
   const char *name;
   DNS_NameResolveHandler handler;
   void *arg;
+  int pipe[2];
 };
 
 static void
-resolve_name(void *anything)
+resolve_name(int fd, int event, void *anything)
 {
   struct DNS_Async_Instance *inst;
   IPAddr addrs[DNS_MAX_ADDRESSES];
@@ -62,6 +64,11 @@ resolve_name(void *anything)
   int i;
 
   inst = (struct DNS_Async_Instance *)anything;
+
+  SCH_RemoveFileHandler(inst->pipe[0]);
+  close(inst->pipe[0]);
+  close(inst->pipe[1]);
+
   status = PRV_Name2IPAddress(inst->name, addrs, DNS_MAX_ADDRESSES);
 
   for (i = 0; status == DNS_Success && i < DNS_MAX_ADDRESSES &&
@@ -83,7 +90,16 @@ DNS_Name2IPAddressAsync(const char *name, DNS_NameResolveHandler handler, void *
   inst->handler = handler;
   inst->arg = anything;
 
-  SCH_AddTimeoutByDelay(0.0, resolve_name, inst);
+  if (pipe(inst->pipe))
+    LOG_FATAL(LOGF_Nameserv, "pipe() failed");
+
+  UTI_FdSetCloexec(inst->pipe[0]);
+  UTI_FdSetCloexec(inst->pipe[1]);
+
+  SCH_AddFileHandler(inst->pipe[0], SCH_FILE_INPUT, resolve_name, inst);
+
+  if (write(inst->pipe[1], "", 1) < 0)
+    ;
 }
 
 #endif /* !FEAT_ASYNCDNS */