inet: delayed/avoided read of /etc/resolv.conf and /etc/hosts

The 'file' and 'dns' lookup methods configuration files
are now read and parsed at the time of the first lookup
instead of at boot time when per default none of these
lookup methods are used.

2 files changed, 69 insertions, 41 deletions

diff --git a/lib/kernel/src/inet_config.erl b/lib/kernel/src/inet_config.erl
index b5317f72f5..cba38359e1 100644
--- a/lib/kernel/src/inet_config.erl
+++ b/lib/kernel/src/inet_config.erl
@@ -130,21 +130,25 @@ init() ->
 	{unix,_} ->
 	    %% The Etc variable enables us to run tests with other 
 	    %% configuration files than the normal ones 
-	    Etc = case os:getenv("ERL_INET_ETC_DIR") of
-		      false -> ?DEFAULT_ETC;
-		      _EtcDir -> 
-			  _EtcDir			
-		  end,
+	    Etc =
+		case os:getenv("ERL_INET_ETC_DIR") of
+		    false ->
+			?DEFAULT_ETC;
+		    _EtcDir ->
+			_EtcDir
+		end,
 	    case inet_db:res_option(resolv_conf) of
 		undefined ->
-		    inet_db:set_resolv_conf(filename:join(Etc,
-							  ?DEFAULT_RESOLV));
+		    inet_db:res_option(
+		      resolv_conf_name,
+		      filename:join(Etc, ?DEFAULT_RESOLV));
 		_ -> ok
 	    end,
 	    case inet_db:res_option(hosts_file) of
 		undefined ->
-		    inet_db:set_hosts_file(filename:join(Etc,
-							 ?DEFAULT_HOSTS));
+		    inet_db:res_option(
+		      hosts_file_name,
+		      filename:join(Etc, ?DEFAULT_HOSTS));
 		_ -> ok
 	    end;
 	_ -> ok
diff --git a/lib/kernel/src/inet_db.erl b/lib/kernel/src/inet_db.erl
index 211847014f..9cdffb5f2c 100644
--- a/lib/kernel/src/inet_db.erl
+++ b/lib/kernel/src/inet_db.erl
@@ -425,7 +425,9 @@ res_optname(usevc) -> res_usevc;
 res_optname(edns) -> res_edns;
 res_optname(udp_payload_size) -> res_udp_payload_size;
 res_optname(resolv_conf) -> res_resolv_conf;
+res_optname(resolv_conf_name) -> res_resolv_conf;
 res_optname(hosts_file) -> res_hosts_file;
+res_optname(hosts_file_name) -> res_hosts_file;
 res_optname(_) -> undefined.
 
 res_check_option(nameserver, NSs) -> %% Legacy
@@ -458,9 +460,15 @@ res_check_option(udp_payload_size, S) when is_integer(S), S >= 512 -> true;
 res_check_option(resolv_conf, "") -> true;
 res_check_option(resolv_conf, F) ->
     res_check_option_absfile(F);
+res_check_option(resolv_conf_name, "") -> true;
+res_check_option(resolv_conf_name, F) ->
+    res_check_option_absfile(F);
 res_check_option(hosts_file, "") -> true;
 res_check_option(hosts_file, F) ->
     res_check_option_absfile(F);
+res_check_option(hosts_file_name, "") -> true;
+res_check_option(hosts_file_name, F) ->
+    res_check_option_absfile(F);
 res_check_option(_, _) -> false.
 
 res_check_option_absfile(F) ->
@@ -503,7 +511,7 @@ res_update_hosts() ->
     res_update(res_hosts_file, res_hosts_file_tm, res_hosts_file_info,
 	       set_hosts_file_tm, fun set_hosts_file/1).
 
-res_update(Tag, TagTm, TagInfo, CallTag, SetFun) ->
+res_update(Tag, TagTm, TagInfo, TagSetTm, SetFun) ->
     case db_get(TagTm) of
 	undefined -> ok;
 	TM ->
@@ -522,12 +530,12 @@ res_update(Tag, TagTm, TagInfo, CallTag, SetFun) ->
 							 atime = undefined},
 				    case db_get(TagInfo) of
 					Finfo ->
-					    call({CallTag, Now});
+					    call({TagSetTm, Now});
 					_ ->
 					    SetFun(File)
 				    end;
 				_ ->
-				    call({CallTag, Now}),
+				    call({TagSetTm, Now}),
 				    error
 			    end
 		    end;
@@ -974,37 +982,46 @@ handle_call(Request, From, #state{db=Db}=State) ->
 		    {reply, error, State}
 	    end;
 
+	{res_set, hosts_file_name=Option, Fname} ->
+	    handle_set_file(
+	      Option, Fname, res_hosts_file_tm, res_hosts_file_info,
+	      undefined, From, State);
+	{res_set, resolv_conf_name=Option, Fname} ->
+	    handle_set_file(
+	      Option, Fname, res_resolv_conf_tm, res_resolv_conf_info,
+	      undefined, From, State);
+
 	{res_set, hosts_file=Option, Fname} ->
-	    handle_set_file(Option, Fname,
-			    res_hosts_file_tm, res_hosts_file_info,
-			    fun (Bin) ->
-				    case inet_parse:hosts(Fname,
-							  {chars,Bin}) of
-					{ok,Opts} ->
-					    [{load_hosts_file,Opts}];
-					_ -> error
-				    end
-			    end,
-			    From, State);
+	    handle_set_file(
+	      Option, Fname, res_hosts_file_tm, res_hosts_file_info,
+	      fun (Bin) ->
+		      case inet_parse:hosts(
+			     Fname, {chars,Bin}) of
+			  {ok,Opts} ->
+			      [{load_hosts_file,Opts}];
+			  _ -> error
+		      end
+	      end,
+	      From, State);
 	%%
 	{res_set, resolv_conf=Option, Fname} ->
-	    handle_set_file(Option, Fname,
-			    res_resolv_conf_tm, res_resolv_conf_info,
-			    fun (Bin) ->
-				    case inet_parse:resolv(Fname,
-							  {chars,Bin}) of
-					{ok,Opts} ->
-					    [del_ns,
-					     clear_search,
-					     clear_cache
-					     |[Opt ||
-						  {T,_}=Opt <- Opts,
-						  (T =:= nameserver orelse
-						   T =:= search)]];
-					_ -> error
-				    end
-			    end,
-			    From, State);
+	    handle_set_file(
+	      Option, Fname, res_resolv_conf_tm, res_resolv_conf_info,
+	      fun (Bin) ->
+		      case inet_parse:resolv(
+			     Fname, {chars,Bin}) of
+			  {ok,Opts} ->
+			      [del_ns,
+			       clear_search,
+			       clear_cache
+			       |[Opt ||
+				    {T,_}=Opt <- Opts,
+				    (T =:= nameserver orelse
+				     T =:= search)]];
+			  _ -> error
+		      end
+	      end,
+	      From, State);
 	%%
 	{res_set, Opt, Value} ->
 	    case res_optname(Opt) of
@@ -1156,6 +1173,12 @@ handle_set_file(Option, Fname, TagTm, TagInfo, ParseFun, From,
 	    ets:delete(Db, TagInfo),
 	    ets:delete(Db, TagTm),
 	    handle_set_file(ParseFun, <<>>, From, State);
+	true when ParseFun =:= undefined ->
+	    File = filename:flatten(Fname),
+	    ets:insert(Db, {res_optname(Option), File}),
+	    ets:insert(Db, {TagInfo, undefined}),
+	    ets:insert(Db, {TagTm, 0}),
+	    {reply,ok,State};
 	true ->
 	    File = filename:flatten(Fname),
 	    ets:insert(Db, {res_optname(Option), File}),
@@ -1178,7 +1201,8 @@ handle_set_file(Option, Fname, TagTm, TagInfo, ParseFun, From,
 
 handle_set_file(ParseFun, Bin, From, State) ->
     case ParseFun(Bin) of
-	error -> {reply,error,State};
+	error ->
+	    {reply,error,State};
 	Opts ->
 	    handle_rc_list(Opts, From, State)
     end.