diff --git a/client.c b/client.c
index ca55b78..aa78959 100644
--- a/client.c
+++ b/client.c
@@ -52,7 +52,7 @@
 
 union sockaddr_in46 {
   struct sockaddr_in in4;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   struct sockaddr_in6 in6;
 #endif
   struct sockaddr u;
@@ -160,7 +160,7 @@ open_io(const char *hostname, int port)
       his_addr.in4.sin_port = htons(port);
       his_addr_len = sizeof (his_addr.in4);
       break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
     case IPADDR_INET6:
       sock_fd = socket(AF_INET6, SOCK_DGRAM, 0);
 
@@ -187,7 +187,7 @@ open_io(const char *hostname, int port)
     recv_errqueue = 1;
   }
 #endif
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
 #ifdef IPV6_RECVERR
   if (ip.family == IPADDR_INET6 &&
       !setsockopt(sock_fd, IPPROTO_IPV6, IPV6_RECVERR, &on_off, sizeof(on_off))) {
@@ -1412,7 +1412,7 @@ submit_request(CMD_Request *request, CMD_Reply *reply, int *reply_auth_ok)
                       (where_from.u.sa_family == AF_INET &&
                        (where_from.in4.sin_addr.s_addr != his_addr.in4.sin_addr.s_addr ||
                         where_from.in4.sin_port != his_addr.in4.sin_port)) ||
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
                       (where_from.u.sa_family == AF_INET6 &&
                        (memcmp(where_from.in6.sin6_addr.s6_addr, his_addr.in6.sin6_addr.s6_addr,
                                sizeof (where_from.in6.sin6_addr.s6_addr)) != 0 ||
diff --git a/cmdmon.c b/cmdmon.c
index 58a6c90..7cfab0f 100644
--- a/cmdmon.c
+++ b/cmdmon.c
@@ -54,7 +54,7 @@
 
 union sockaddr_in46 {
   struct sockaddr_in in4;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   struct sockaddr_in6 in6;
 #endif
   struct sockaddr u;
@@ -62,7 +62,7 @@ union sockaddr_in46 {
 
 /* File descriptors for command and monitoring sockets */
 static int sock_fd4;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
 static int sock_fd6;
 #endif
 
@@ -207,7 +207,7 @@ prepare_socket(int family, int port_number)
   }
 #endif
 
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   if (family == AF_INET6) {
 #ifdef IPV6_V6ONLY
     /* Receive IPv6 packets only */
@@ -233,7 +233,7 @@ prepare_socket(int family, int port_number)
       else
         my_addr.in4.sin_addr.s_addr = htonl(INADDR_ANY);
       break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
     case AF_INET6:
       my_addr_len = sizeof (my_addr.in6);
       my_addr.in6.sin6_family = family;
@@ -304,7 +304,7 @@ CAM_Initialise(int family)
     sock_fd4 = prepare_socket(AF_INET, port_number);
   else
     sock_fd4 = -1;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   if (port_number && (family == IPADDR_UNSPEC || family == IPADDR_INET6))
     sock_fd6 = prepare_socket(AF_INET6, port_number);
   else
@@ -312,7 +312,7 @@ CAM_Initialise(int family)
 #endif
 
   if (port_number && sock_fd4 < 0
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
       && sock_fd6 < 0
 #endif
       ) {
@@ -333,7 +333,7 @@ CAM_Finalise(void)
     close(sock_fd4);
   }
   sock_fd4 = -1;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   if (sock_fd6 >= 0) {
     SCH_RemoveInputFileHandler(sock_fd6);
     close(sock_fd6);
@@ -687,7 +687,7 @@ transmit_reply(CMD_Reply *msg, union sockaddr_in46 *where_to, int auth_len)
       sock_fd = sock_fd4;
       addrlen = sizeof (where_to->in4);
       break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
     case AF_INET6:
       sock_fd = sock_fd6;
       addrlen = sizeof (where_to->in6);
@@ -711,7 +711,7 @@ transmit_reply(CMD_Reply *msg, union sockaddr_in46 *where_to, int auth_len)
         ip.addr.in4 = ntohl(where_to->in4.sin_addr.s_addr);
         port = ntohs(where_to->in4.sin_port);
         break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
       case AF_INET6:
         ip.family = IPADDR_INET6;
         memcpy(ip.addr.in6, (where_to->in6.sin6_addr.s6_addr), sizeof(ip.addr.in6));
@@ -1659,7 +1659,7 @@ read_from_cmd_socket(void *anything)
       remote_port = ntohs(where_from.in4.sin_port);
       localhost = (remote_ip.addr.in4 == 0x7f000001UL);
       break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
     case AF_INET6:
       remote_ip.family = IPADDR_INET6;
       memcpy(&remote_ip.addr.in6, where_from.in6.sin6_addr.s6_addr,
diff --git a/configure b/configure
index 3f898bd..c2e54d1 100755
--- a/configure
+++ b/configure
@@ -112,7 +112,7 @@ For better control, use the options below.
   --disable-pps          Disable PPS refclock driver
   --disable-ipv6         Disable IPv6 support
   --disable-rtc          Don't include RTC even on Linux
-  --disable-linuxcaps    Disable Linux capabilities support
+  --disable-linuxcaps    Disable libcap (Linux capabilities) support
   --disable-asyncdns     Disable asynchronous name resolving
   --disable-forcednsretry Don't retry on permanent DNS error
   --with-ntp-era=SECONDS Specify earliest assumed NTP time in seconds
@@ -183,7 +183,7 @@ EXTRA_OBJECTS=""
 EXTRA_DEFS=""
 SYSDEFS=""
 
-debug=0
+feat_debug=0
 feat_cmdmon=1
 feat_ntp=1
 feat_refclock=1
@@ -194,8 +194,8 @@ try_nss=1
 try_tomcrypt=1
 feat_rtc=1
 try_rtc=0
-feat_linuxcaps=1
-try_linuxcaps=0
+feat_droproot=1
+try_libcap=0
 readline_lib=""
 readline_inc=""
 ncurses_lib=""
@@ -215,7 +215,7 @@ for option
 do
     case "$option" in
     --enable-debug )
-      debug=1
+      feat_debug=1
     ;;
     --disable-readline )
       feat_readline=0
@@ -290,7 +290,7 @@ do
       feat_pps=0
     ;;
     --disable-linuxcaps)
-      feat_linuxcaps=0
+      feat_droproot=0
     ;;
     --disable-asyncdns)
       feat_asyncdns=0
@@ -355,7 +355,7 @@ case $SYSTEM in
     ;;
     Linux* )
         EXTRA_OBJECTS="sys_generic.o sys_linux.o wrap_adjtimex.o"
-        try_linuxcaps=1
+        try_libcap=1
         try_rtc=1
         try_setsched=1
         try_lockmem=1
@@ -404,6 +404,11 @@ case $SYSTEM in
     ;;
 esac
 
+if [ $feat_debug = "1" ]; then
+  add_def FEAT_DEBUG
+fi
+add_def DEBUG $feat_debug
+
 if [ $feat_cmdmon = "1" ]; then
   add_def FEAT_CMDMON
   EXTRA_OBJECTS="$EXTRA_OBJECTS cmdmon.o manual.o pktlength.o"
@@ -488,7 +493,7 @@ if [ $feat_ipv6 = "1" ] && \
     n.sin6_addr = in6addr_any;
     return !inet_ntop(AF_INET6, &n.sin6_addr.s6_addr, p, sizeof(p));'
 then
-  add_def HAVE_IPV6
+  add_def FEAT_IPV6
   if test_code 'in6_pktinfo' 'sys/socket.h netinet/in.h' '' '' '
     return sizeof(struct in6_pktinfo);'
   then
@@ -538,17 +543,17 @@ if [ "x$timepps_h" != "x" ] && \
     struct timespec ts;
     return time_pps_fetch(h, PPS_TSFMT_TSPEC, &i, &ts);'
 then
-  add_def HAVE_PPSAPI
+  add_def FEAT_PPS
 fi
 
-if [ $feat_linuxcaps = "1" ] && [ $try_linuxcaps = "1" ] && \
+if [ $feat_droproot = "1" ] && [ $try_libcap = "1" ] && \
   test_code \
-    linuxcaps \
+    libcap \
     'sys/types.h pwd.h sys/prctl.h sys/capability.h grp.h' \
     '' '-lcap' \
     'prctl(PR_SET_KEEPCAPS, 1);cap_set_proc(cap_from_text("cap_sys_time=ep"));'
 then
-    add_def FEAT_LINUXCAPS
+    add_def FEAT_PRIVDROP
     EXTRA_LIBS="$EXTRA_LIBS -lcap"
 fi
 
@@ -659,7 +664,7 @@ if [ $try_nss = "1" ]; then
     HASH_COMPILE="$test_cflags"
     HASH_LINK="$test_link"
     LIBS="$LIBS $HASH_LINK"
-    add_def GENERATE_SHA1_KEY
+    add_def FEAT_SECHASH
   fi
 fi
 
@@ -671,7 +676,7 @@ if [ "x$HASH_LINK" = "x" ] && [ $try_tomcrypt = "1" ]; then
     HASH_COMPILE="-I/usr/include/tomcrypt"
     HASH_LINK="-ltomcrypt"
     LIBS="$LIBS $HASH_LINK"
-    add_def GENERATE_SHA1_KEY
+    add_def FEAT_SECHASH
   fi
 fi
 
@@ -730,7 +735,6 @@ if [ "x$SETCHRONYVARDIR" != "x" ]; then
   CHRONYVARDIR=$SETCHRONYVARDIR
 fi
 
-add_def DEBUG $debug
 add_def DEFAULT_CONF_FILE "\"$SYSCONFDIR/chrony.conf\""
 add_def DEFAULT_USER "\"$default_user\""
 add_def MAIL_PROGRAM "\"$mail_program\""
diff --git a/keys.c b/keys.c
index 9025fea..6c326ad 100644
--- a/keys.c
+++ b/keys.c
@@ -63,7 +63,7 @@ static int cache_key_pos;
 static int
 generate_key(unsigned long key_id)
 {
-#ifdef GENERATE_SHA1_KEY
+#ifdef FEAT_SECHASH
   unsigned char key[20];
   const char *hashname = "SHA1";
 #else
diff --git a/nameserv.c b/nameserv.c
index f8a4b63..56a3a4a 100644
--- a/nameserv.c
+++ b/nameserv.c
@@ -71,7 +71,7 @@ DNS_Name2IPAddress(const char *name, IPAddr *addr)
         addr->addr.in4 = ntohl(((struct sockaddr_in *)ai->ai_addr)->sin_addr.s_addr);
         result = 1;
         break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
       case AF_INET6:
         addr->family = IPADDR_INET6;
         memcpy(&addr->addr.in6, &((struct sockaddr_in6 *)ai->ai_addr)->sin6_addr.s6_addr, sizeof (addr->addr.in6));
@@ -115,7 +115,7 @@ DNS_IPAddress2Name(IPAddr *ip_addr, char *name, int len)
 {
   char *result = NULL;
 
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   struct sockaddr_in in4;
   struct sockaddr_in6 in6;
   char hbuf[NI_MAXHOST];
@@ -151,7 +151,7 @@ DNS_IPAddress2Name(IPAddr *ip_addr, char *name, int len)
       addr = htonl(ip_addr->addr.in4);
       host = gethostbyaddr((const char *) &addr, sizeof (ip_addr), AF_INET);
       break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
     case IPADDR_INET6:
       host = gethostbyaddr((const void *) ip_addr->addr.in6, sizeof (ip_addr->addr.in6), AF_INET6);
       break;
diff --git a/ntp_io.c b/ntp_io.c
index e0f7aea..1af88a2 100644
--- a/ntp_io.c
+++ b/ntp_io.c
@@ -43,7 +43,7 @@
 
 union sockaddr_in46 {
   struct sockaddr_in in4;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   struct sockaddr_in6 in6;
 #endif
   struct sockaddr u;
@@ -52,7 +52,7 @@ union sockaddr_in46 {
 /* The server/peer and client sockets for IPv4 and IPv6 */
 static int server_sock_fd4;
 static int client_sock_fd4;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
 static int server_sock_fd6;
 static int client_sock_fd6;
 #endif
@@ -116,7 +116,7 @@ prepare_socket(int family, int port_number, int client_only)
       my_addr_len = sizeof (my_addr.in4);
 
       break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
     case AF_INET6:
       if (!client_only)
         CNF_GetBindAddress(IPADDR_INET6, &bind_address);
@@ -181,7 +181,7 @@ prepare_socket(int family, int port_number, int client_only)
     }
 #endif
   }
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   else if (family == AF_INET6) {
 #ifdef IPV6_V6ONLY
     /* Receive IPv6 packets only */
@@ -226,7 +226,7 @@ prepare_separate_client_socket(int family)
   switch (family) {
     case IPADDR_INET4:
       return prepare_socket(AF_INET, 0, 1);
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
     case IPADDR_INET6:
       return prepare_socket(AF_INET6, 0, 1);
 #endif
@@ -252,7 +252,7 @@ connect_socket(int sock_fd, NTP_Remote_Address *remote_addr)
       addr.in4.sin_addr.s_addr = htonl(remote_addr->ip_addr.addr.in4);
       addr.in4.sin_port = htons(remote_addr->port);
       break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
     case IPADDR_INET6:
       addr_len = sizeof (addr.in6);
       addr.in6.sin6_family = AF_INET6;
@@ -306,7 +306,7 @@ NIO_Initialise(int family)
 
   server_sock_fd4 = INVALID_SOCK_FD;
   client_sock_fd4 = INVALID_SOCK_FD;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   server_sock_fd6 = INVALID_SOCK_FD;
   client_sock_fd6 = INVALID_SOCK_FD;
 #endif
@@ -321,7 +321,7 @@ NIO_Initialise(int family)
         client_sock_fd4 = server_sock_fd4;
     }
   }
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   if (family == IPADDR_UNSPEC || family == IPADDR_INET6) {
     if (server_port)
       server_sock_fd6 = prepare_socket(AF_INET6, server_port, 0);
@@ -335,11 +335,11 @@ NIO_Initialise(int family)
 #endif
 
   if ((server_port && server_sock_fd4 == INVALID_SOCK_FD
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
        && server_sock_fd6 == INVALID_SOCK_FD
 #endif
       ) || (!separate_client_sockets && client_sock_fd4 == INVALID_SOCK_FD
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
        && client_sock_fd6 == INVALID_SOCK_FD
 #endif
       )) {
@@ -356,7 +356,7 @@ NIO_Finalise(void)
     close_socket(client_sock_fd4);
   close_socket(server_sock_fd4);
   server_sock_fd4 = client_sock_fd4 = INVALID_SOCK_FD;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   if (server_sock_fd6 != client_sock_fd6)
     close_socket(client_sock_fd6);
   close_socket(server_sock_fd6);
@@ -386,7 +386,7 @@ NIO_GetClientSocket(NTP_Remote_Address *remote_addr)
     switch (remote_addr->ip_addr.family) {
       case IPADDR_INET4:
         return client_sock_fd4;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
       case IPADDR_INET6:
         return client_sock_fd6;
 #endif
@@ -404,7 +404,7 @@ NIO_GetServerSocket(NTP_Remote_Address *remote_addr)
   switch (remote_addr->ip_addr.family) {
     case IPADDR_INET4:
       return server_sock_fd4;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
     case IPADDR_INET6:
       return server_sock_fd6;
 #endif
@@ -429,7 +429,7 @@ NIO_IsServerSocket(int sock_fd)
 {
   return sock_fd != INVALID_SOCK_FD &&
     (sock_fd == server_sock_fd4
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
      || sock_fd == server_sock_fd6
 #endif
     );
@@ -490,7 +490,7 @@ read_from_socket(void *anything)
         remote_addr.ip_addr.addr.in4 = ntohl(where_from.in4.sin_addr.s_addr);
         remote_addr.port = ntohs(where_from.in4.sin_port);
         break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
       case AF_INET6:
         remote_addr.ip_addr.family = IPADDR_INET6;
         memcpy(&remote_addr.ip_addr.addr.in6, where_from.in6.sin6_addr.s6_addr,
@@ -589,7 +589,7 @@ send_packet(void *packet, int packetlen, NTP_Remote_Address *remote_addr, NTP_Lo
       remote.in4.sin_port = htons(remote_addr->port);
       remote.in4.sin_addr.s_addr = htonl(remote_addr->ip_addr.addr.in4);
       break;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
     case IPADDR_INET6:
       /* Don't set address with connected socket */
       if (local_addr->sock_fd != server_sock_fd6 && separate_client_sockets)
diff --git a/refclock_pps.c b/refclock_pps.c
index b17f496..cd3cd83 100644
--- a/refclock_pps.c
+++ b/refclock_pps.c
@@ -29,7 +29,7 @@
 
 #include "refclock.h"
 
-#if HAVE_PPSAPI
+#if FEAT_PPS
 
 #if defined(HAVE_SYS_TIMEPPS_H)
 #include <sys/timepps.h>
diff --git a/sys.c b/sys.c
index 765af09..6b6aff4 100644
--- a/sys.c
+++ b/sys.c
@@ -97,7 +97,7 @@ SYS_Finalise(void)
 
 void SYS_DropRoot(char *user)
 {
-#if defined(LINUX) && defined (FEAT_LINUXCAPS)
+#if defined(LINUX) && defined (FEAT_PRIVDROP)
   SYS_Linux_DropRoot(user);
 #else
   LOG_FATAL(LOGF_Sys, "dropping root privileges not supported");
diff --git a/sys_linux.c b/sys_linux.c
index a8af8df..b342505 100644
--- a/sys_linux.c
+++ b/sys_linux.c
@@ -44,7 +44,7 @@ int SchedPriority = 0;
 int LockAll = 0;
 #endif
 
-#ifdef FEAT_LINUXCAPS
+#ifdef FEAT_PRIVDROP
 #include <sys/types.h>
 #include <pwd.h>
 #include <sys/prctl.h>
@@ -352,7 +352,7 @@ SYS_Linux_Finalise(void)
 
 /* ================================================== */
 
-#ifdef FEAT_LINUXCAPS
+#ifdef FEAT_PRIVDROP
 void
 SYS_Linux_DropRoot(char *user)
 {
diff --git a/sysincl.h b/sysincl.h
index adf1997..b0f587c 100644
--- a/sysincl.h
+++ b/sysincl.h
@@ -78,7 +78,7 @@
 
 #endif
 
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
 /* For inet_ntop() */
 #include <arpa/inet.h>
 #endif
diff --git a/util.c b/util.c
index 08fc0cd..aedf2c9 100644
--- a/util.c
+++ b/util.c
@@ -277,7 +277,7 @@ UTI_IPToString(IPAddr *addr)
       break;
     case IPADDR_INET6:
       ip6 = addr->addr.in6;
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
       inet_ntop(AF_INET6, ip6, result, BUFFER_LENGTH);
 #else
       snprintf(result, BUFFER_LENGTH, "%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x:%02x%02x",
@@ -296,7 +296,7 @@ UTI_IPToString(IPAddr *addr)
 int
 UTI_StringToIP(const char *addr, IPAddr *ip)
 {
-#ifdef HAVE_IPV6
+#ifdef FEAT_IPV6
   struct in_addr in4;
   struct in6_addr in6;