fixed missing interface / scope_id copy.

Reduce the minimum number of samples required by the filter from
min(4, length) to 1.

This makes the filtering less confusing. The sample lifetime is limited
to one poll and the default filtering of the SOCK refclock (where the
maximum number of samples per poll is unknown) is identical to the other
refclocks.

A concern with potential variability in number of samples per poll below
4 is switching between different calculations of dispersion in
combine_selected_samples() in samplefilt.c.

The 106-refclock test shows how the order of refclocks in the config can
impact the first filtered sample and selection. If the PPS refclock
follows SHM, a single low-quality PPS sample is accepted in the same
poll where SHM is selected and the initial clock correction started,
which causes larger skew later and delays the first selection of the PPS
refclock.

.gitignore

@@ -26,3 +26,9 @@ tags
 /test/unit/Makefile
 /test/unit/*.test
 /test/unit/*.o
+
+# Build
+/cmake-build-*/
+
+# IDE
+/.idea/

CMakeLists.txt

@@ -0,0 +1,46 @@
+cmake_minimum_required(VERSION 3.10)
+project(chrony)
+
+# Directories configuration
+set(SYSCONFDIR "/etc")
+set(BINDIR "/usr/local/bin")
+set(SBINDIR "/usr/local/sbin")
+set(LOCALSTATEDIR "/var")
+set(CHRONYVARDIR "/var/lib/chrony")
+set(DESTDIR "")
+
+# Compiler and flags
+set(CMAKE_C_FLAGS "-g -D_FORTIFY_SOURCE=2 -fPIE -fstack-protector-strong --param=ssp-buffer-size=4 -Wmissing-prototypes -Wall -pthread")
+set(CMAKE_EXE_LINKER_FLAGS "-pie -Wl,-z,relro,-z,now")
+
+# Targets
+add_executable(chronyd
+        sys_generic.c sys_linux.c sys_timex.c sys_posix.c cmdmon.c manual.c pktlength.c ntp_auth.c ntp_core.c ntp_ext.c ntp_io.c
+        ntp_sources.c addrfilt.c clientlog.c keys.c nameserv.c refclock.c refclock_phc.c refclock_pps.c refclock_shm.c
+        refclock_sock.c nameserv_async.c hwclock.c ntp_io_linux.c rtc_linux.c hash_intmd5.c cmac_gnutls.c
+        nts_ntp_client.c
+        array.c cmdparse.c conf.c leapdb.c local.c logging.c main.c memory.c quantiles.c reference.c regress.c rtc.c samplefilt.c
+        sched.c socket.c sources.c sourcestats.c stubs.c smooth.c sys.c sys_null.c tempcomp.c util.c
+        nts_ntp_auth.c siv_gnutls.c nts_ke_client.c nts_ke_session.c nts_ntp_server.c nts_ke_server.c
+)
+add_executable(chronyc
+        array.c client.c cmdparse.c getdate.c memory.c nameserv.c pktlength.c socket.c util.c hash_intmd5.c cmac_gnutls.c)
+
+# Libraries
+target_link_libraries(chronyd m gnutls)
+target_link_libraries(chronyc m edit gnutls)
+
+# Install commands
+install(TARGETS chronyd DESTINATION ${DESTDIR}${SBINDIR})
+install(TARGETS chronyc DESTINATION ${DESTDIR}${BINDIR})
+
+# Docs
+add_custom_target(docs
+        COMMAND ${CMAKE_MAKE_PROGRAM} -C doc docs
+        COMMENT "Building documentation"
+)
+
+add_custom_target(install-docs
+        COMMAND ${CMAKE_MAKE_PROGRAM} -C doc install-docs
+        COMMENT "Installing documentation"
+)

addressing.h

@@ -45,7 +45,7 @@ typedef struct {
     uint32_t id;
   } addr;
   uint16_t family;
-  uint16_t _pad;
+  uint16_t interface;
 } IPAddr;
 
 typedef struct {

doc/chrony.conf.adoc

@@ -661,14 +661,13 @@ value is the estimated precision of the system clock.
 Maximum allowed dispersion for filtered samples (in seconds). Samples with
 larger estimated dispersion are ignored. By default, this limit is disabled.
 *filter* _samples_:::
-This option sets the length of the median filter which is used to reduce the
-noise in the measurements. With each poll about 40 percent of the stored
-samples are discarded and one final sample is calculated as an average of the
-remaining samples. If the length is 4 or more, at least 4 samples have to be
-collected between polls. For lengths below 4, the filter has to be full. The
-default is 64. With drivers that perform their own polling (PPS, PHC, SHM), the
-maximum value is adjusted to the number of driver polls per source poll, i.e.
-2^(_poll_ - _dpoll_).
+This option sets the maximum number of samples that can be stored in the median
+filter between polls of the source. The filter combines about 60 percent of the
+samples closest to the median offset into one sample. If more samples are
+received by the driver between polls, the oldest samples will be dropped. One
+sample per poll is sufficient for the source to be selectable. The default
+is 64. Note that the PHC driver has additional filtering based on the reading
+delay.
 *prefer*:::
 Prefer this source over other selectable sources without the *prefer* option.
 *noselect*:::

refclock.c

@@ -233,12 +233,10 @@ RCL_AddRefclock(RefclockParameters *params)
     if (inst->driver_poll > inst->poll)
       inst->driver_poll = inst->poll;
 
+    /* Adjust the filter length to save memory if the expected number
+       of samples is smaller */
     max_samples = 1 << (inst->poll - inst->driver_poll);
     if (max_samples < params->filter_length) {
-      if (max_samples < 4) {
-        LOG(LOGS_WARN, "Setting filter length for %s to %d",
-            UTI_RefidToString(inst->ref_id), max_samples);
-      }
       params->filter_length = max_samples;
     }
   }
@@ -246,11 +244,9 @@ RCL_AddRefclock(RefclockParameters *params)
   if (inst->driver->init && !inst->driver->init(inst))
     LOG_FATAL("refclock %s initialisation failed", params->driver_name);
 
-  /* Require the filter to have at least 4 samples to produce a filtered
-     sample, or be full for shorter lengths, and combine 60% of samples
-     closest to the median */
-  inst->filter = SPF_CreateInstance(MIN(params->filter_length, 4), params->filter_length,
-                                    params->max_dispersion, 0.6);
+  /* Don't require more than one sample per poll and combine 60% of the
+     samples closest to the median offset */
+  inst->filter = SPF_CreateInstance(1, params->filter_length, params->max_dispersion, 0.6);
 
   inst->source = SRC_CreateNewInstance(inst->ref_id, SRC_REFCLOCK, 0, params->sel_options,
                                        NULL, params->min_samples, params->max_samples,

socket.c

@@ -1785,6 +1785,7 @@ SCK_IPSockAddrToSockaddr(IPSockAddr *ip_sa, struct sockaddr *sa, int sa_length)
         return 0;
       memset(sa, 0, sizeof (struct sockaddr_in6));
       sa->sa_family = AF_INET6;
+      ((struct sockaddr_in6 *)sa)->sin6_scope_id = ip_sa->ip_addr.interface;
       memcpy(&((struct sockaddr_in6 *)sa)->sin6_addr.s6_addr, ip_sa->ip_addr.addr.in6,
              sizeof (((struct sockaddr_in6 *)sa)->sin6_addr.s6_addr));
       ((struct sockaddr_in6 *)sa)->sin6_port = htons(ip_sa->port);

test/simulation/106-refclock

@@ -89,9 +89,9 @@ Root delay      : 0\.000000001 seconds
 	check_file_messages "20.* PPS1.*- N " 60 63 refclocks.log || test_fail
 	rm -f tmp/refclocks.log
 
-	min_sync_time=80
-	max_sync_time=180
-	chronyc_start=220
+	min_sync_time=180
+	max_sync_time=260
+	chronyc_start=270
 	client_conf="
 refclock SHM 0 refid NMEA offset 0.35 delay 0.1
 refclock PPS /dev/pps0
@@ -112,6 +112,30 @@ Root delay      : 0\.000000001 seconds
 	check_file_messages "20.* PPS1.*[0-9] N " 800 960  refclocks.log || test_fail
 	check_file_messages "20.* PPS1.*- N " 50 63 refclocks.log || test_fail
 	rm -f tmp/refclocks.log
+
+	min_sync_time=80
+	max_sync_time=180
+	chronyc_start=220
+	# Swapped order of SHM and PPS impacts first accepted sample
+	client_conf="
+refclock PPS /dev/pps0
+refclock SHM 0 refid NMEA offset 0.35 delay 0.1
+logdir tmp
+log refclocks
+maxupdateskew 10000"
+
+	run_test || test_fail
+	check_chronyd_exit || test_fail
+	check_source_selection || test_fail
+	check_sync || test_fail
+	check_chronyc_output "^Reference ID.*50505330 \(PPS0\)
+Stratum.*: 1
+.*
+Root delay      : 0\.000000001 seconds
+.*$" || test_fail
+
+	check_file_messages "20.* PPS0.*[0-9] N " 800 960  refclocks.log || test_fail
+	check_file_messages "20.* PPS0.*- N " 50 63 refclocks.log || test_fail
 fi
 
 export CLKNETSIM_PHC_JITTER_OFF=$[2 * 25 * 492]

util.c

@@ -32,6 +32,9 @@
 #include "logging.h"
 #include "memory.h"
 #include "util.h"
+
+#include <net/if.h>
+
 #include "hash.h"
 
 #define NSEC_PER_SEC 1000000000
@@ -302,13 +305,21 @@ UTI_IPToString(const IPAddr *addr)
       break;
     case IPADDR_INET6:
       ip6 = addr->addr.in6;
+      uint16_t interface = addr->interface;
 #ifdef FEAT_IPV6
+      // compose the IPv6
       inet_ntop(AF_INET6, ip6, result, BUFFER_LENGTH);
+      // if used, append the interface name
+      if (interface != 0) {
+        char* result_if_delimiter = result + strlen(result);
+        *result_if_delimiter = '%';
+        if_indextoname(interface, result_if_delimiter + 1);
+      }
 #else
       assert(BUFFER_LENGTH >= 40);
       for (a = 0; a < 8; a++)
         snprintf(result + a * 5, 40 - a * 5, "%04x:",
-                 (unsigned int)(ip6[2 * a] << 8 | ip6[2 * a + 1]));
+                 (unsigned int)(ip6[2 * a] << 8 | ip6[2 * a + 1]));_pad
 #endif
       break;
     case IPADDR_ID:
@@ -332,15 +343,35 @@ UTI_StringToIP(const char *addr, IPAddr *ip)
 
   if (inet_pton(AF_INET, addr, &in4) > 0) {
     ip->family = IPADDR_INET4;
-    ip->_pad = 0;
+    ip->interface = 0;
     ip->addr.in4 = ntohl(in4.s_addr);
     return 1;
   }
 
 #ifdef FEAT_IPV6
-  if (inet_pton(AF_INET6, addr, &in6) > 0) {
+  // split the address into an IP and an interface.
+  char addr_ip[INET6_ADDRSTRLEN];
+  strncpy(addr_ip, addr, sizeof(addr_ip));
+  char *addr_if = strchr(addr_ip, '%');
+
+  // prepare the interface index
+  unsigned int addr_if_index = 0;
+  // check if an interface is specified
+  if (addr_if != NULL) {
+    // split the string into two string, by replacing the "%" into an end-of-string
+    *addr_if = '\0';
+    // the interface will now start on the next character
+    addr_if++;
+
+    // get the index of the interface
+    addr_if_index = if_nametoindex(addr_if);
+    if (addr_if_index == 0)
+      return 0;
+  }
+
+  if (inet_pton(AF_INET6, addr_ip, &in6) > 0) {
     ip->family = IPADDR_INET6;
-    ip->_pad = 0;
+    ip->interface = addr_if_index;
     memcpy(ip->addr.in6, in6.s6_addr, sizeof (ip->addr.in6));
     return 1;
   }
@@ -366,7 +397,7 @@ UTI_StringToIdIP(const char *addr, IPAddr *ip)
 {
   if (sscanf(addr, "ID#%"SCNu32, &ip->addr.id) == 1) {
     ip->family = IPADDR_ID;
-    ip->_pad = 0;
+    ip->interface = 0;
     return 1;
   }
 
@@ -466,6 +497,7 @@ UTI_IPHostToNetwork(const IPAddr *src, IPAddr *dest)
       break;
     case IPADDR_INET6:
       memcpy(dest->addr.in6, src->addr.in6, sizeof (dest->addr.in6));
+      dest->interface = src->interface;
       break;
     case IPADDR_ID:
       dest->addr.id = htonl(src->addr.id);
@@ -481,7 +513,7 @@ void
 UTI_IPNetworkToHost(const IPAddr *src, IPAddr *dest)
 {
   dest->family = ntohs(src->family);
-  dest->_pad = 0;
+  dest->interface = src->interface;
 
   switch (dest->family) {
     case IPADDR_INET4: