%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2016. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%%     http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
%% A simple boot_server at a CP.
%%
%% This server should know about which slaves (DP's or whatever) to boot.
%% File's (with absolute path name) will be fetched.
%%

-module(erl_boot_server).

-include("inet_boot.hrl").

-behaviour(gen_server).

%% API functions.
-export([start/1, start_link/1, add_slave/1, delete_slave/1,
	 add_subnet/2, delete_subnet/2,
	 which_slaves/0]).

%% Exports for testing (dont't remove; tests suites depend on them).
-export([would_be_booted/1]).

%% Internal exports
-export([init/1,handle_call/3,handle_cast/2,handle_info/2,terminate/2]).
-export([code_change/3]).
-export([boot_init/1, boot_accept/3]).

-record(state, 
	{
	  priority = 0,  %% priority of this server
	  version = ""   :: string(),	%% Version handled i.e "4.5.3" etc
	  udp_sock,      %% listen port for broadcase requests
	  udp_port,      %% port number must be ?EBOOT_PORT!
	  listen_sock,   %% listen sock for incoming file requests
	  listen_port,   %% listen port number
	  slaves,        %% list of accepted ip addresses
	  bootp          :: pid(),	%% boot process
	  prim_state     %% state for efile code loader
	 }).
-type state() :: #state{}.

-define(single_addr_mask, {255, 255, 255, 255}).

-type ip4_address() :: {0..255,0..255,0..255,0..255}.

-spec start(Slaves) -> {'ok', Pid} | {'error', What} when
      Slaves :: [Host],
      Host :: atom(),
      Pid :: pid(),
      What :: any().

start(Slaves) ->
    case check_arg(Slaves) of
	{ok, AL} ->
	    gen_server:start({local,boot_server}, erl_boot_server, AL, []);
	_ ->
	    {error, {badarg, Slaves}}
    end.

-spec start_link(Slaves) -> {'ok', Pid} | {'error', What} when
      Slaves :: [Host],
      Host :: atom(),
      Pid :: pid(),
      What :: any().

start_link(Slaves) ->
    case check_arg(Slaves) of
	{ok, AL} ->
	    gen_server:start_link({local,boot_server},
				  erl_boot_server, AL, []);
	_ ->
	    {error, {badarg, Slaves}}
    end.

check_arg(Slaves) ->
    check_arg(Slaves, []).

check_arg([Slave|Rest], Result) ->
    case inet:getaddr(Slave, inet) of
	{ok, IP} ->
	    check_arg(Rest, [{?single_addr_mask, IP}|Result]);
	_ ->
	    error
    end;
check_arg([], Result) ->
    {ok, Result};
check_arg(_, _Result) ->
    error.

-spec add_slave(Slave) -> 'ok' | {'error', What} when
      Slave :: Host,
      Host :: atom(),
      What :: any().

add_slave(Slave) ->
    case inet:getaddr(Slave, inet) of
	{ok,IP} ->
	    gen_server:call(boot_server, {add, {?single_addr_mask, IP}});
	_ ->
	    {error, {badarg, Slave}}
    end.

-spec delete_slave(Slave) -> 'ok' | {'error', What} when
      Slave :: Host,
      Host :: atom(),
      What :: any().

delete_slave(Slave) ->
    case inet:getaddr(Slave, inet) of
	{ok,IP} ->
	    gen_server:call(boot_server, {delete, {?single_addr_mask, IP}});
	_ ->
	    {error, {badarg, Slave}}
    end.

-spec add_subnet(Mask :: ip4_address(), Addr :: ip4_address()) ->
	'ok' | {'error', any()}.

add_subnet(Mask, Addr) when is_tuple(Mask), is_tuple(Addr) ->
    case member_address(Addr, [{Mask, Addr}]) of
	true ->
	    gen_server:call(boot_server, {add, {Mask, Addr}});
	false ->
	    {error, empty_subnet}
    end.

-spec delete_subnet(Mask :: ip4_address(), Addr :: ip4_address()) -> 'ok'.

delete_subnet(Mask, Addr) when is_tuple(Mask), is_tuple(Addr) ->
    gen_server:call(boot_server, {delete, {Mask, Addr}}).

-spec which_slaves() -> Slaves when
      Slaves :: [Host],
      Host :: atom().

which_slaves() ->
    gen_server:call(boot_server, which).

%% Given a host name or IP address, returns true if a host
%% having that IP address would be accepted for booting, and
%% false otherwise.  (Convenient for testing.)

would_be_booted(Addr) ->
    {ok, IP} = inet:getaddr(Addr, inet),
    member_address(IP, which_slaves()).

int16(X) when is_integer(X) ->
    [(X bsr 8) band 16#ff, (X) band 16#ff].

%% Check if an address is a member

member_address(IP, [{{MA, MB, MC, MD}, {EA, EB, EC, ED}}|Rest]) ->
    {A, B, C, D} = IP,
    if A band MA =:= EA,
       B band MB =:= EB,
       C band MC =:= EC,
       D band MD =:= ED ->
	    true;
       true ->
	    member_address(IP, Rest)
    end;
member_address(_, []) ->
    false.

%% ------------------------------------------------------------
%% call-back functions.
%% ------------------------------------------------------------

-spec init([atom()]) -> {'ok', state()}.

init(Slaves) ->
    {ok, U} = gen_udp:open(?EBOOT_PORT, []),
    {ok, L} = gen_tcp:listen(0, [binary,{packet,4}]),
    {ok, Port} = inet:port(L),
    {ok, UPort} = inet:port(U),
    Ref = make_ref(),
    Pid = proc_lib:spawn_link(?MODULE, boot_init, [Ref]),
    ok = gen_tcp:controlling_process(L, Pid),
    Pid ! {Ref, L},
    %% We trap exit inorder to restart boot_init and udp_port 
    process_flag(trap_exit, true),
    {ok, #state{priority = 0,
		version = erlang:system_info(version),
		udp_sock = U,
		udp_port = UPort,
		listen_sock = L,
		listen_port = Port,
		slaves = ordsets:from_list(Slaves),
		bootp = Pid
	       }}.

-spec handle_call('which' | {'add',atom()} | {'delete',atom()}, _, state()) ->
        {'reply', 'ok' | [atom()], state()}.

handle_call({add,Address}, _, S0) ->
    Slaves = ordsets:add_element(Address, S0#state.slaves),
    S0#state.bootp ! {slaves, Slaves},
    {reply, ok, S0#state{slaves = Slaves}};
handle_call({delete,Address}, _, S0) ->
    Slaves = ordsets:del_element(Address, S0#state.slaves),
    S0#state.bootp ! {slaves, Slaves},
    {reply, ok, S0#state{slaves = Slaves}};
handle_call(which, _, S0) ->
    {reply, ordsets:to_list(S0#state.slaves), S0}.

-spec handle_cast(term(), [atom()]) -> {'noreply', [atom()]}.

handle_cast(_, Slaves) ->
    {noreply, Slaves}.

-spec handle_info(term(), state()) -> {'noreply', state()}.

handle_info({udp, U, IP, Port, Data}, S0) ->
    Token = ?EBOOT_REQUEST ++ S0#state.version,
    Valid = member_address(IP, ordsets:to_list(S0#state.slaves)),
    %% check that the connecting node is valid and has the same
    %% erlang version as the boot server node
    case {Valid,Data,Token} of
	{true,Token,Token} ->
	    case gen_udp:send(U,IP,Port,[?EBOOT_REPLY,S0#state.priority,
                                         int16(S0#state.listen_port),
                                         S0#state.version])
            of
                ok -> ok;
                {error, not_owner} ->
                    error_logger:error_msg("** Illegal boot server connection attempt: "
				   "not owner of ~w ** ~n", [U]);
                {error, Reason} ->
                    Err = file:format_error(Reason),
                    error_logger:error_msg("** Illegal boot server connection attempt: "
				   "~w POSIX error ** ~n", [U, Err])
            end,
	    {noreply,S0};
	{false,_,_} ->
	    error_logger:error_msg("** Illegal boot server connection attempt: "
				   "~w is not a valid address ** ~n", [IP]),
	    {noreply,S0};
	{true,_,_} ->
	    case catch string:substr(Data, 1, length(?EBOOT_REQUEST)) of
		?EBOOT_REQUEST ->
		    Vsn = string:substr(Data, length(?EBOOT_REQUEST)+1, length(Data)),
		    error_logger:error_msg("** Illegal boot server connection attempt: "
					   "client version is ~s ** ~n", [Vsn]);
		_ ->
		    error_logger:error_msg("** Illegal boot server connection attempt: "
					   "unrecognizable request ** ~n", [])
	    end,
	    {noreply,S0}
    end;
handle_info(_Info, S0) ->
    {noreply,S0}.

-spec terminate(term(), state()) -> 'ok'.

terminate(_Reason, _S0) ->
    ok.

-spec code_change(term(), state(), term()) -> {'ok', state()}.

code_change(_Vsn, State, _Extra) ->
    {ok, State}.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
%% Boot server 
%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

-spec boot_init(reference()) -> no_return().

boot_init(Tag) ->
    receive
	{Tag, Listen} ->
	    process_flag(trap_exit, true),
	    boot_main(Listen)
    end.

boot_main(Listen) ->
    Tag = make_ref(),
    Pid = proc_lib:spawn_link(?MODULE, boot_accept, [self(), Listen, Tag]),
    boot_main(Listen, Tag, Pid).

boot_main(Listen, Tag, Pid) ->
    receive
	{Tag, _} ->
	    boot_main(Listen);
	{'EXIT', Pid, _} -> 
	    boot_main(Listen);
	{'EXIT', _, Reason} ->
	    exit(Pid, kill),
	    exit(Reason);
	{tcp_closed, Listen} ->
	    exit(closed)
    end.

boot_accept(Server, Listen, Tag) ->
    Reply = gen_tcp:accept(Listen),
    unlink(Server),
    Server ! {Tag, continue},
    case Reply of
	{ok, Socket} ->
	    {ok, {IP, _Port}} = inet:peername(Socket),
	    true = member_address(IP, which_slaves()),
	    PS = erl_prim_loader:prim_init(),
	    boot_loop(Socket, PS)
    end.

boot_loop(Socket, PS) ->
    receive
	{tcp, Socket, Data} ->
	    PS2 = handle_command(Socket, PS, Data),
	    boot_loop(Socket, PS2);
	{tcp_closed, Socket} ->
	    true
    end.

handle_command(S, PS, Msg) ->
    case catch binary_to_term(Msg) of
	{get,File} ->
	    {Res, PS2} = erl_prim_loader:prim_get_file(PS, File),
	    send_file_result(S, get, Res),
	    PS2;
	{list_dir,Dir} ->
	    {Res, PS2} = erl_prim_loader:prim_list_dir(PS, Dir),
	    send_file_result(S, list_dir, Res),
	    PS2;
	{read_file_info,File} ->
	    {Res, PS2} = erl_prim_loader:prim_read_file_info(PS, File, true),
	    send_file_result(S, read_file_info, Res),
	    PS2;
        {read_link_info,File} ->
            {Res, PS2} = erl_prim_loader:prim_read_file_info(PS, File, false),
            send_file_result(S, read_link_info, Res),
            PS2;
	get_cwd ->
	    {Res, PS2} = erl_prim_loader:prim_get_cwd(PS, []),
	    send_file_result(S, get_cwd, Res),
	    PS2;
	{get_cwd,Drive} ->
	    {Res, PS2} = erl_prim_loader:prim_get_cwd(PS, [Drive]),
	    send_file_result(S, get_cwd, Res),
	    PS2;
	{'EXIT',Reason} ->
	    send_result(S, {error,Reason}),
	    PS;
	_Other ->
	    send_result(S, {error,unknown_command}),
	    PS
    end.

send_file_result(S, Cmd, Result) ->
    send_result(S, {Cmd,Result}).

send_result(S, Term) ->
    case gen_tcp:send(S, term_to_binary(Term)) of
	ok ->
	    ok;
	Error ->
	    error_logger:error_msg("** Boot server could not send result "
				   "to socket: ~w** ~n", [Error]),
	    ok
    end.
