CP-308544 Promote legacy default ntp servers (#6727)

For example, the legacy default ntp servers are
`[0-3].centos.pool.ntp.org`, and current default ntp servers are
`[0-3].xenserver.pool.ntp.org`. After update or upgrade, the legacy
default ntp servers are recognized and changed to current default ntp
servers. The mode is `ntp_mode_default` as well.
Add a new config option named legacy-default-ntp-servers. It will be
defined in xapi.conf.d/xenserver.conf (the same with
default-ntp-servers)

Author: changlei-li

ocaml/xapi/xapi_globs.ml

@@ -1420,6 +1420,8 @@ let failed_login_alert_freq = ref 3600
 
 let default_ntp_servers = ref []
 
+let legacy_default_ntp_servers = ref []
+
 let other_options =
   [
     gen_list_option "sm-plugins"
@@ -1902,6 +1904,11 @@ let other_options =
     , (fun () -> !ntp_client_path)
     , "Path to the ntp client binary"
     )
+  ; gen_list_option "legacy-default-ntp-servers"
+      "space-separated list of legacy default NTP servers"
+      (fun s -> s)
+      (fun s -> s)
+      legacy_default_ntp_servers
   ; gen_list_option "default-ntp-servers"
       "space-separated list of default NTP servers"
       (fun s -> s)

ocaml/xapi/xapi_host.ml

@@ -3530,6 +3530,7 @@ let disable_ntp ~__context ~self =
   Db.Host.set_ntp_enabled ~__context ~self ~value:false
 
 let sync_ntp_config ~__context ~host =
+  Xapi_host_ntp.promote_legacy_default_servers () ;
   let servers = Xapi_host_ntp.get_servers_from_conf () in
   let is_ntp_dhcp_enabled = Xapi_host_ntp.is_ntp_dhcp_enabled () in
   let ntp_mode =

ocaml/xapi/xapi_host_ntp.ml

@@ -12,6 +12,10 @@
  * GNU Lesser General Public License for more details.
  *)
 
+module D = Debug.Make (struct let name = "xapi_host_ntp" end)
+
+open D
+
 let ( // ) = Filename.concat
 
 let ntp_dhcp_server_path interface =
@@ -155,3 +159,19 @@ let get_servers_status () =
           None
     )
     lines
+
+let promote_legacy_default_servers () =
+  let servers = get_servers_from_conf () in
+  let legacy = !Xapi_globs.legacy_default_ntp_servers in
+  let defaults = !Xapi_globs.default_ntp_servers in
+  if
+    legacy <> []
+    && defaults <> []
+    && Xapi_stdext_std.Listext.List.set_equiv servers legacy
+  then (
+    info "Promoting legacy default NTP servers (%s) to new default servers (%s)"
+      (String.concat "," servers)
+      (String.concat "," defaults) ;
+    set_servers_in_conf defaults ;
+    restart_ntp_service ()
+  )

ocaml/xapi/xapi_host_ntp.mli

@@ -20,6 +20,8 @@ val set_servers_in_conf : string list -> unit
 
 val clear_servers_in_conf : unit -> unit
 
+val promote_legacy_default_servers : unit -> unit
+
 val restart_ntp_service : unit -> unit
 
 val enable_ntp_service : unit -> unit