doc: update NEWS

Accept HW timestamp only if it doesn't differ from the kernel/daemon
timestamp by more than one second.

NEWS

@@ -16,14 +16,20 @@ 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
+* Allow rate limiting with very short intervals
 * 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,
+   (using new request/reply types), new fields and flags in NTP source request
-   new commands: refresh, serverstats
+   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"
@@ -2266,11 +2297,11 @@ process_cmd_ntpdata(char *line)
                  "Version         : %u\n"
                  "Mode            : %M\n"
                  "Stratum         : %u\n"
-               "Poll            : %d\n"
+                 "Poll interval   : %d (%.0f seconds)\n"
-               "Precision       : %.9f seconds\n"
+                 "Precision       : %d (%.9f seconds)\n"
                  "Root delay      : %.6f seconds\n"
                  "Root dispersion : %.6f seconds\n"
-               "Reference ID    : %R\n"
+                 "Reference ID    : %R (%s)\n"
                  "Reference time  : %T\n"
                  "Offset          : %+.9f seconds\n"
                  "Peer delay      : %.9f seconds\n"
@@ -2290,10 +2321,14 @@ 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,
+                 (unsigned long)ntohl(reply.data.ntp_data.ref_id),
+                 reply.data.ntp_data.stratum <= 1 ?
+                   UTI_RefidToString(ntohl(reply.data.ntp_data.ref_id)) : "",
+                 &ref_time,
                  UTI_FloatNetworkToHost(reply.data.ntp_data.offset),
                  UTI_FloatNetworkToHost(reply.data.ntp_data.peer_delay),
                  UTI_FloatNetworkToHost(reply.data.ntp_data.peer_dispersion),
@@ -2309,6 +2344,7 @@ 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;
 
@@ -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;
@@ -325,6 +339,9 @@ CLG_Initialise(void)
   records = NULL;
 
   expand_hashtable();
+
+  UTI_GetRandomBytes(&ts_offset, sizeof (ts_offset));
+  ts_offset %= NSEC_PER_SEC / (1U << TS_FRAC);
 }
 
 /* ================================================== */
@@ -345,6 +362,12 @@ 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 +392,12 @@ 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 */

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

@@ -194,10 +194,10 @@ static char *pidfile;
 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 ntp_ratelimit_leak = 2;
 static int cmd_ratelimit_enabled = 0;
-static int cmd_ratelimit_interval = 1;
+static int cmd_ratelimit_interval = -4;
-static int cmd_ratelimit_burst = 16;
+static int cmd_ratelimit_burst = 8;
 static int cmd_ratelimit_leak = 2;
 
 /* Smoothing constants */
@@ -223,7 +223,13 @@ static char *leapsec_tz = NULL;
 /* Name of the user to which will be dropped root privileges. */
 static char *user;
 
-/* Array of strings for interfaces with HW timestamping */
+typedef struct {
+  char *name;
+  double tx_comp;
+  double rx_comp;
+} HwTs_Interface;
+
+/* Array of HwTs_Interface */
 static ARR_Instance hwts_interfaces;
 
 typedef struct {
@@ -327,7 +333,7 @@ CNF_Initialise(int r)
 {
   restarted = r;
 
-  hwts_interfaces = ARR_CreateInstance(sizeof (char *));
+  hwts_interfaces = ARR_CreateInstance(sizeof (HwTs_Interface));
 
   init_sources = ARR_CreateInstance(sizeof (IPAddr));
   ntp_sources = ARR_CreateInstance(sizeof (NTP_Source));
@@ -354,7 +360,7 @@ CNF_Finalise(void)
   unsigned int i;
 
   for (i = 0; i < ARR_GetSize(hwts_interfaces); i++)
-    Free(*(char **)ARR_GetElement(hwts_interfaces, i));
+    Free(((HwTs_Interface *)ARR_GetElement(hwts_interfaces, i))->name);
   ARR_DestroyInstance(hwts_interfaces);
 
   for (i = 0; i < ARR_GetSize(ntp_sources); i++)
@@ -1245,8 +1251,39 @@ parse_tempcomp(char *line)
 static void
 parse_hwtimestamp(char *line)
 {
-  check_number_of_args(line, 1);
+  HwTs_Interface *iface;
-  *(char **)ARR_GetNewElement(hwts_interfaces) = Strdup(line);
+  char *p;
+  int n;
+
+  if (!*line) {
+    command_parse_error();
+    return;
+  }
+
+  p = line;
+  line = CPS_SplitWord(line);
+
+  iface = ARR_GetNewElement(hwts_interfaces);
+  iface->name = Strdup(p);
+  iface->tx_comp = 0.0;
+  iface->rx_comp = 0.0;
+
+  for (p = line; *p; line += n, p = line) {
+    line = CPS_SplitWord(line);
+
+    if (!strcasecmp(p, "rxcomp")) {
+      if (sscanf(line, "%lf%n", &iface->rx_comp, &n) != 1)
+        break;
+    } else if (!strcasecmp(p, "txcomp")) {
+      if (sscanf(line, "%lf%n", &iface->tx_comp, &n) != 1)
+        break;
+    } else {
+      break;
+    }
+  }
+
+  if (*p)
+    command_parse_error();
 }
 
 /* ================================================== */
@@ -1930,8 +1967,18 @@ CNF_GetInitStepThreshold(void)
 
 /* ================================================== */
 
-ARR_Instance
+int
-CNF_GetHwTsInterfaces(void)
+CNF_GetHwTsInterface(unsigned int index, char **name, double *tx_comp, double *rx_comp)
 {
-  return hwts_interfaces;
+  HwTs_Interface *iface;
+
+  if (index >= ARR_GetSize(hwts_interfaces))
+    return 0;
+
+  iface = ARR_GetElement(hwts_interfaces, index);
+  *name = iface->name;
+  *tx_comp = iface->tx_comp;
+  *rx_comp = iface->rx_comp;
+
+  return 1;
 }

conf.h

@@ -29,7 +29,6 @@
 #define GOT_CONF_H
 
 #include "addressing.h"
-#include "array.h"
 #include "reference.h"
 
 extern void CNF_Initialise(int restarted);
@@ -120,6 +119,6 @@ extern char *CNF_GetHwclockFile(void);
 extern int CNF_GetInitSources(void);
 extern double CNF_GetInitStepThreshold(void);
 
-extern ARR_Instance CNF_GetHwTsInterfaces(void);
+extern int CNF_GetHwTsInterface(unsigned int index, char **name, double *tx_comp, double *rx_comp);
 
 #endif /* GOT_CONF_H */

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
@@ -629,6 +633,7 @@ fi
 RECVMMSG_CODE='
   struct mmsghdr hdr;
   return !recvmmsg(0, &hdr, 1, MSG_DONTWAIT, 0);'
+if [ $try_recvmmsg = "1" ]; then
   if test_code 'recvmmsg()' 'sys/socket.h' '' "$EXTRA_LIBS" "$RECVMMSG_CODE"; then
     add_def HAVE_RECVMMSG
   else
@@ -639,6 +644,7 @@ else
       add_def HAVE_RECVMMSG
     fi
   fi
+fi
 
 if [ $feat_timestamping = "1" ] && [ $try_timestamping = "1" ] &&
   test_code 'SW/HW timestamping' 'sys/types.h sys/socket.h linux/net_tstamp.h

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
@@ -159,9 +160,8 @@ synchronisation only if they agree with the trusted and required source.
 *xleave*:::
 This option enables an interleaved mode which allows the server or the peer to
 send transmit timestamps captured after the actual transmission (e.g. when the
-server or the peer is running *chronyd* with HW timestamping enabled by the
+server or the peer is running *chronyd* with software (kernel) or hardware
-<<hwtimestamp,*hwtimestamp*>> directive). This can significantly improve the
+timestamping). This can significantly improve the accuracy of the measurements.
-accuracy of the measurements.
 +
 The interleaved mode is compatible with servers that support only the basic
 mode, but peers must both support and have enabled the interleaved mode,
@@ -993,7 +993,7 @@ both a client of its servers, and a server to other clients.
 Examples of the use of the directive are as follows:
 +
 ----
-allow foo.example.net
+allow 1.2.3.4
 allow 1.2
 allow 3.4.5
 allow 6.7.8/22
@@ -1004,7 +1004,8 @@ allow ::/0
 allow
 ----
 +
-The first directive allows the named node to be an NTP client of this computer.
+The first directive allows a node with IPv4 address _1.2.3.4_ to be an NTP
+client of this computer.
 The second directive allows any node with an IPv4 address of the form _1.2.x.y_
 (with _x_ and _y_ arbitrary) to be an NTP client of this computer. Likewise,
 the third directive allows any node with an IPv4 address of the form _3.4.5.x_
@@ -1045,6 +1046,10 @@ Within a configuration file this capability is probably rather moot; however,
 it is of greater use for reconfiguration at run-time via *chronyc* with the
 <<chronyc.adoc#allow,*allow all*>> command.
 +
+The directive allows a hostname to be specified instead of an IP address, but
+the name must be resolvable when *chronyd* is started (i.e. *chronyd* needs
+to be started when the network is already up and DNS is working).
++
 Note, if the <<initstepslew,*initstepslew*>> directive is used in the
 configuration file, each of the computers listed in that directive must allow
 client access by this computer for it to work.
@@ -1237,7 +1242,10 @@ 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.
+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
@@ -1249,20 +1257,20 @@ 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
+rate is defined as a power of 1/2 and it is 2 by default, i.e. on average at
-least every eighth request has a response. The minimum value is 1 and the
+least every fourth request has a response. The minimum value is 1 and the
 maximum value is 4.
 ::
 +
 An example use of the directive is:
 +
 ----
-ratelimit interval 4 burst 4
+ratelimit interval 1 burst 16
 ----
 +
-This would reduce the response rate for IP addresses that send packets on
+This would reduce the response rate for IP addresses sending packets on average
-average more frequently than once per 16 seconds or send packets in bursts
+more than once per 2 seconds, or sending packets in bursts of more than 16
-of more than 4 packets.
+packets, by up to 75% (with default *leak* of 2).
 
 [[smoothtime]]*smoothtime* _max-freq_ _max-wander_ [*leaponly*]::
 The *smoothtime* directive can be used to enable smoothing of the time that
@@ -1391,8 +1399,8 @@ 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
+localhost are never limited and the default interval is -4 (16 packets per
-burst is 16, and the default leak rate is 2.
+second).
 +
 An example of the use of the directive is:
 +
@@ -1772,17 +1780,18 @@ sendmail binary.
 
 === Miscellaneous
 
-[[hwtimestamp]]*hwtimestamp* _interface_::
+[[hwtimestamp]]*hwtimestamp* _interface_ [_option_]...::
 This directive enables hardware timestamping of NTP packets sent to and
 received from the specified network interface. The network interface controller
 (NIC) uses its own clock to accurately timestamp the actual transmissions and
 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
+system clock. In order to get the best results, both sides receiving and
-timestamping on both sides receiving and sending the packets (i.e. server and
+sending NTP packets (i.e. server and client, or two peers) need to use HW
-client, or both peers), and also enable the interleaved mode with the *xleave*
+timestamping. If the server or peer supports the interleaved mode, it needs to
-option in the <<server,*server*>> or the <<peer,*peer*>> directive.
+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
@@ -1799,10 +1808,28 @@ 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*.
 +
-An example of the directive is:
+If the specified interface is _*_, *chronyd* will try to enable HW timestamping
+on all available interfaces.
++
+The *hwtimestamp* directive has the following options:
++
+*txcomp* _compensation_:::
+This option specifies the difference in seconds between the actual transmission
+time at the physical layer and the reported transmit timestamp. This value will
+be added to transmit timestamps obtained from the NIC. The default value is 0.
+*rxcomp* _compensation_:::
+This option specifies the difference in seconds between the reported receive
+timestamp and the actual reception time at the physical layer. This value will
+be subtracted from receive timestamps obtained from the NIC. The default value
+is 0.
+::
++
+Examples of the directive are:
 +
 ----
 hwtimestamp eth0
+hwtimestamp eth1 txcomp 300e-9 rxcomp 645e-9
+hwtimestamp *
 ----
 
 [[include]]*include* _pattern_::
@@ -2211,24 +2238,34 @@ information to be saved.
 *chronyd* can be configured to operate as a public NTP server, e.g. to join the
 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
+allow client access from all addresses. It is recommended to find at least four
-few good servers, and possibly combine them with a random selection of other
+good servers (e.g. from the pool, or on the NTP homepage). If the server has a
-servers in the pool. Rate limiting can be enabled to not waste too much
+hardware reference clock (e.g. a GPS receiver), it can be specified by the
-bandwidth on misconfigured and broken NTP clients. The *-r* option with the
+<<refclock,*refclock*>> directive.
-*dumpdir* directive shortens the time for which *chronyd* will not serve time
-to its clients when it needs to be restarted for any reason.
 
-The configuration file might be:
+The amount of memory used for logging client accesses can be increased in order
+to enable clients to use the interleaved mode even when the server has a large
+number of clients, and better support rate limiting if it is enabled by the
+<<ratelimit,*ratelimit*>> directive. The system timezone database, if it is
+kept up to date and includes the *right/UTC* timezone, can be used as a
+reliable source to determine when a leap second will be applied to UTC. The
+*-r* option with the <<dumpdir,*dumpdir*>> directive shortens the time in which
+*chronyd* will not be able to serve time to its clients when it needs to be
+restarted (e.g. after upgrading to a newer version, or a change in the
+configuration).
+
+The configuration file could look like:
 
 ----
 server foo.example.net iburst
 server bar.example.net iburst
 server baz.example.net iburst
-pool pool.ntp.org iburst
+server qux.example.net iburst
 makestep 1.0 3
 rtcsync
 allow
-ratelimit interval 2 burst 10
+clientloglimit 100000000
+leapsectz right/UTC
 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
+NTP-specific information about the specified NTP source, or all NTP sources if
-shown below.
+no address was specified. An example of the output is shown below.
 +
 ----
 Remote address  : 203.0.113.15 (CB00710F)
@@ -454,11 +454,11 @@ Leap status     : Normal
 Version         : 4
 Mode            : Server
 Stratum         : 1
-Poll            : 10
+Poll interval   : 10 (1024 seconds)
-Precision       : 0.000000060 seconds
+Precision       : -24 (0.000000060 seconds)
 Root delay      : 0.000015 seconds
 Root dispersion : 0.000015 seconds
-Reference ID    : 50505331
+Reference ID    : 47505300 (GPS)
 Reference time  : Fri Nov 25 15:22:12 2016
 Offset          : -0.000060878 seconds
 Peer delay      : 0.000175634 seconds
@@ -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
 

hwclock.c

@@ -55,6 +55,9 @@ struct HCL_Instance_Record {
   /* Number of samples */
   int n_samples;
 
+  /* Maximum error of the last sample */
+  double last_err;
+
   /* Flag indicating the offset and frequency values are valid */
   int valid_coefs;
 
@@ -151,6 +154,7 @@ HCL_AccumulateSample(HCL_Instance clock, struct timespec *hw_ts,
   clock->n_samples++;
   clock->hw_ref = *hw_ts;
   clock->local_ref = *local_ts;
+  clock->last_err = err;
 
   /* Get new coefficients */
   clock->valid_coefs =
@@ -196,9 +200,9 @@ HCL_CookTime(HCL_Instance clock, struct timespec *raw, struct timespec *cooked,
   offset = clock->offset + elapsed / clock->frequency;
   UTI_AddDoubleToTimespec(&clock->local_ref, offset, cooked);
 
-  /* Estimation of the error is not implemented yet */
+  /* Fow now, just return the error of the last sample */
   if (err)
-    *err = 0.0;
+    *err = clock->last_err;
 
   return 1;
 }

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

@@ -1412,12 +1412,8 @@ receive_packet(NCR_Instance inst, NTP_Local_Address *local_addr,
       sample_rx_tss = rx_ts->source;
     }
 
-    /* Work out 'delay' relative to the source's time */
+    /* Calculate delay */
-    delay = (1.0 - (source_freq_lo + source_freq_hi) / 2.0) *
+    delay = fabs(local_interval - remote_interval);
-              local_interval - remote_interval;
-
-    /* Clamp delay to avoid misleading results later */
-    delay = fabs(delay);
     if (delay < precision)
       delay = precision;
     
@@ -1439,7 +1435,8 @@ receive_packet(NCR_Instance inst, NTP_Local_Address *local_addr,
     skew = (source_freq_hi - source_freq_lo) / 2.0;
     
     /* and then calculate peer dispersion */
-    dispersion = precision + inst->local_tx.err + rx_ts_err + skew * fabs(local_interval);
+    dispersion = MAX(precision, MAX(inst->local_tx.err, rx_ts_err)) +
+                 skew * fabs(local_interval);
     
     /* Additional tests required to pass before accumulating the sample */
 
@@ -1453,11 +1450,12 @@ 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
+    /* Test B requires in the basic client mode that the ratio of the round
-       minimum one currently in the stats data register is less than an
+       trip delay to the minimum one currently in the stats data register is
-       administrator-defined value */
+       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
@@ -1608,13 +1606,14 @@ receive_packet(NCR_Instance inst, NTP_Local_Address *local_addr,
                      UTI_DiffTimespecsToDouble(&inst->local_rx.ts, &inst->local_tx.ts));
 
       if (kod_rate) {
+        LOG(LOGS_WARN, LOGF_NtpCore, "Received KoD RATE from %s",
+            UTI_IPToString(&inst->remote_addr.ip_addr));
+
         /* Back off for a while and stop ongoing burst */
         delay_time += 4 * (1UL << inst->minpoll);
 
         if (inst->opmode == MD_BURST_WAS_OFFLINE || inst->opmode == MD_BURST_WAS_ONLINE) {
           inst->burst_good_samples_to_go = 0;
-          LOG(LOGS_WARN, LOGF_NtpCore, "Received KoD RATE from %s, burst sampling stopped",
-              UTI_IPToString(&inst->remote_addr.ip_addr));
         }
       }
 

ntp_io.c

@@ -364,8 +364,12 @@ NIO_Initialise(int family)
 #ifdef HAVE_LINUX_TIMESTAMPING
   NIO_Linux_Initialise();
 #else
-  if (ARR_GetSize(CNF_GetHwTsInterfaces()))
+  if (1) {
+    double tx_comp, rx_comp;
+    char *name;
+    if (CNF_GetHwTsInterface(0, &name, &tx_comp, &rx_comp))
       LOG_FATAL(LOGF_NtpIO, "HW timestamping not supported");
+  }
 #endif
 
   recv_messages = ARR_CreateInstance(sizeof (struct Message));

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>
@@ -65,12 +66,18 @@ struct Interface {
   /* Start of UDP data at layer 2 for IPv4 and IPv6 */
   int l2_udp4_ntp_start;
   int l2_udp6_ntp_start;
+  /* Compensation of errors in TX and RX timestamping */
+  double tx_comp;
+  double rx_comp;
   HCL_Instance clock;
 };
 
 /* Number of PHC readings per HW clock sample */
 #define PHC_READINGS 10
 
+/* Maximum acceptable offset between HW and daemon/kernel timestamp */
+#define MAX_TS_DELAY 1.0
+
 /* Array of Interfaces */
 static ARR_Instance interfaces;
 
@@ -84,15 +91,22 @@ static int permanent_ts_options;
 /* ================================================== */
 
 static int
-add_interface(const char *name)
+add_interface(const char *name, double tx_comp, double rx_comp)
 {
   struct ethtool_ts_info ts_info;
   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;
@@ -158,13 +172,42 @@ add_interface(const char *name)
   iface->l2_udp4_ntp_start = 42;
   iface->l2_udp6_ntp_start = 62;
 
+  iface->tx_comp = tx_comp;
+  iface->rx_comp = rx_comp;
+
   iface->clock = HCL_CreateInstance();
 
+  DEBUG_LOG(LOGF_NtpIOLinux, "Enabled HW timestamping on %s", name);
+
   return 1;
 }
 
 /* ================================================== */
 
+static int
+add_all_interfaces(double tx_comp, double rx_comp)
+{
+  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, tx_comp, rx_comp))
+      r = 1;
+  }
+  
+  freeifaddrs(ifaddr);
+
+  /* Return success if at least one interface was added */
+  return r;
+}
+
+/* ================================================== */
+
 static void
 update_interface_speed(struct Interface *iface)
 {
@@ -199,22 +242,33 @@ update_interface_speed(struct Interface *iface)
 void
 NIO_Linux_Initialise(void)
 {
-  ARR_Instance config_hwts_ifaces;
+  double tx_comp, rx_comp;
-  char *if_name;
+  char *name;
   unsigned int i;
+  int hwts;
 
   interfaces = ARR_CreateInstance(sizeof (struct Interface));
 
-  config_hwts_ifaces = CNF_GetHwTsInterfaces();
+  /* Enable HW timestamping on specified interfaces.  If "*" was specified, try
+     all interfaces.  If no interface was specified, enable SW timestamping. */
 
-  /* Enable HW timestamping on all specified interfaces.  If no interface was
+  for (i = hwts = 0; CNF_GetHwTsInterface(i, &name, &tx_comp, &rx_comp); i++) {
-     specified, use SW timestamping. */
+    if (!strcmp("*", name))
-  if (ARR_GetSize(config_hwts_ifaces)) {
+      continue;
-    for (i = 0; i < ARR_GetSize(config_hwts_ifaces); i++) {
+    if (!add_interface(name, tx_comp, rx_comp))
-      if_name = *(char **)ARR_GetElement(config_hwts_ifaces, i);
+      LOG_FATAL(LOGF_NtpIO, "Could not enable HW timestamping on %s", name);
-      if (!add_interface(if_name))
+    hwts = 1;
-        LOG_FATAL(LOGF_NtpIO, "Could not enable HW timestamping on %s", if_name);
   }
+
+  for (i = 0; CNF_GetHwTsInterface(i, &name, &tx_comp, &rx_comp); i++) {
+    if (strcmp("*", name))
+      continue;
+    if (add_all_interfaces(tx_comp, rx_comp))
+      hwts = 1;
+    break;
+  }
+
+  if (hwts) {
     ts_flags = SOF_TIMESTAMPING_RAW_HARDWARE | SOF_TIMESTAMPING_RX_HARDWARE;
     ts_tx_flags = SOF_TIMESTAMPING_TX_HARDWARE;
   } else {
@@ -368,8 +422,8 @@ static void
 process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
                      NTP_Local_Timestamp *local_ts, int rx_ntp_length, int family)
 {
-  struct timespec sample_phc_ts, sample_local_ts;
+  struct timespec sample_phc_ts, sample_local_ts, ts;
-  double sample_delay, rx_correction;
+  double sample_delay, rx_correction, ts_delay, err;
   int l2_length;
 
   if (HCL_NeedsNewSample(iface->clock, &local_ts->ts)) {
@@ -395,9 +449,23 @@ process_hw_timestamp(struct Interface *iface, struct timespec *hw_ts,
     UTI_AddDoubleToTimespec(hw_ts, rx_correction, hw_ts);
   }
 
-  if (!HCL_CookTime(iface->clock, hw_ts, &local_ts->ts, &local_ts->err))
+  if (!rx_ntp_length && iface->tx_comp)
+    UTI_AddDoubleToTimespec(hw_ts, iface->tx_comp, hw_ts);
+  else if (rx_ntp_length && iface->rx_comp)
+    UTI_AddDoubleToTimespec(hw_ts, -iface->rx_comp, hw_ts);
+
+  if (!HCL_CookTime(iface->clock, hw_ts, &ts, &err))
     return;
 
+  ts_delay = UTI_DiffTimespecsToDouble(&local_ts->ts, &ts);
+
+  if (fabs(ts_delay) > MAX_TS_DELAY) {
+    DEBUG_LOG(LOGF_NtpIOLinux, "Unacceptable timestamp delay %.9f", ts_delay);
+    return;
+  }
+
+  local_ts->ts = ts;
+  local_ts->err = err;
   local_ts->source = NTP_TS_HARDWARE;
 }
 
@@ -487,7 +555,7 @@ NIO_Linux_ProcessMessage(NTP_Remote_Address *remote_addr, NTP_Local_Address *loc
       if (!UTI_IsZeroTimespec(&ts3.ts[0])) {
         LCL_CookTime(&ts3.ts[0], &local_ts->ts, &local_ts->err);
         local_ts->source = NTP_TS_KERNEL;
-      } else {
+      } else if (!UTI_IsZeroTimespec(&ts3.ts[2])) {
         iface = get_interface(if_index);
         if (iface) {
           process_hw_timestamp(iface, &ts3.ts[2], local_ts, !is_tx ? length : 0,

sources.c

@@ -425,10 +425,11 @@ SRC_UpdateReachability(SRC_Instance inst, int reachable)
   }
 
   /* Try to replace NTP sources that are unreachable, falsetickers, or
-     have root distance larger than the allowed maximum */
+     have root distance or jitter larger than the allowed maximums */
   if (inst->type == SRC_NTP &&
       ((!inst->reachability && inst->reachability_size == SOURCE_REACH_BITS) ||
-       inst->status == SRC_FALSETICKER || inst->status == SRC_BAD_DISTANCE)) {
+       inst->status == SRC_BAD_DISTANCE || inst->status == SRC_JITTERY ||
+       inst->status == SRC_FALSETICKER)) {
     NSR_HandleBadSource(inst->ip_addr);
   }
 }

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 = CLAMP(MIN_WEIGHT_SD, sd, min_distance);
-      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 = CLAMP(MIN_SKEW, inst->skew, MAX_SKEW);
-      inst->skew = MIN_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 */