xmpp.chapril.org-ejabberd/src/ejabberd_sm.erl

%%%----------------------------------------------------------------------
%%% File    : ejabberd_sm.erl
%%% Author  : Alexey Shchepin <alexey@process-one.net>
%%% Purpose : Session manager
%%% Created : 24 Nov 2002 by Alexey Shchepin <alexey@process-one.net>
%%%
%%%
%%% ejabberd, Copyright (C) 2002-2009   ProcessOne
%%%
%%% This program is free software; you can redistribute it and/or
%%% modify it under the terms of the GNU General Public License as
%%% published by the Free Software Foundation; either version 2 of the
%%% License, or (at your option) any later version.
%%%
%%% This program is distributed in the hope that it will be useful,
%%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
%%% General Public License for more details.
%%%
%%% You should have received a copy of the GNU General Public License
%%% along with this program; if not, write to the Free Software
%%% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
%%% 02111-1307 USA
%%%
%%%----------------------------------------------------------------------

-module(ejabberd_sm).
-author('alexey@process-one.net').

-behaviour(gen_server).

%% API
-export([start_link/0,
	 route/3,
	 open_session/3, close_session/2,
	 check_in_subscription/6,
	 bounce_offline_message/3,
	 disconnect_removed_user/2,
	 get_user_resources/2,
	 set_presence/5,
	 unset_presence/4,
	 close_session_unset_presence/3,
	 dirty_get_sessions_list/0,
	 dirty_get_my_sessions_list/0,
	 get_vh_session_list/1,
	 register_iq_handler/4,
	 register_iq_handler/5,
	 unregister_iq_handler/2,
	 connected_users/0,
	 connected_users_number/0,
	 user_resources/2,
	 get_session_pid/1,
	 get_user_info/3,
	 get_user_ip/1
	]).

%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
	 terminate/2, code_change/3]).

-include_lib("exmpp/include/exmpp.hrl").

-include("ejabberd.hrl").
-include("ejabberd_commands.hrl").
-include("mod_privacy.hrl").

-record(session, {sid, usr, us, priority, info}).
-record(state, {}).

%% default value for the maximum number of user connections
-define(MAX_USER_SESSIONS, infinity).

% These are the namespace already declared by the stream opening. This is
% used at serialization time.
-define(DEFAULT_NS, ?NS_JABBER_CLIENT).
-define(PREFIXED_NS, [
  {?NS_XMPP, ?NS_XMPP_pfx}, {?NS_DIALBACK, ?NS_DIALBACK_pfx}
]).


-define(IS_BINARY_OR_UNDEF(X),
            (is_binary(X) orelse X == 'undefined')).
%%====================================================================
%% API
%%====================================================================
%%--------------------------------------------------------------------
%% Function: start_link() -> {ok,Pid} | ignore | {error,Error}
%% Description: Starts the server
%%--------------------------------------------------------------------
start_link() ->
    gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).

route(FromOld, ToOld, #xmlelement{} = PacketOld) ->
    catch throw(for_stacktrace), % To have a stacktrace.
    io:format("~nSM: old #xmlelement:~n~p~n~p~n~n",
      [PacketOld, erlang:get_stacktrace()]),
    % XXX OLD FORMAT: From, To, Packet.
    From = jlib:from_old_jid(FromOld),
    To = jlib:from_old_jid(ToOld),
    Packet = exmpp_xml:xmlelement_to_xmlel(PacketOld, [?NS_JABBER_CLIENT],
      [{?NS_XMPP, ?NS_XMPP_pfx}]),
    route(From, To, Packet);
route(From, To, Packet) ->
    case catch do_route(From, To, Packet) of
	{'EXIT', Reason} ->
	    ?ERROR_MSG("~p~nwhen processing: ~p",
		       [Reason, {From, To, Packet}]);
	_ ->
	    ok
    end.

open_session(SID, JID, Info) when ?IS_JID(JID) ->
    set_session(SID, JID, undefined, Info),
    check_for_sessions_to_replace(JID),
    ejabberd_hooks:run(sm_register_connection_hook, exmpp_jid:prep_domain(JID),
		       [SID, JID, Info]).

close_session(SID, JID ) when ?IS_JID(JID)-> 
    Info = case mnesia:dirty_read({session, SID}) of
	[] -> [];
	[#session{info=I}] -> I
    end,
    F = fun() ->
		mnesia:delete({session, SID})
	end,
    mnesia:sync_dirty(F),
    ejabberd_hooks:run(sm_remove_connection_hook, exmpp_jid:prep_domain(JID),
		       [SID, JID, Info]).

check_in_subscription(Acc, User, Server, _JID, _Type, _Reason) 
        when is_binary(User), is_binary(Server)->
    case ejabberd_auth:is_user_exists(binary_to_list(User), binary_to_list(Server)) of
	true ->
	    Acc;
	false ->
	    {stop, false}
    end.

bounce_offline_message(From, To, Packet) ->
    Err = exmpp_stanza:reply_with_error(Packet, 'service-unavailable'),
    ejabberd_router:route(To, From, Err),
    stop.

disconnect_removed_user(User, Server) ->
    ejabberd_sm:route(exmpp_jid:make(),
		      exmpp_jid:make(User, 
                                      Server),
                      #xmlel{name = 'broadcast',
                        children = [{exit, "User removed"}]}).

get_user_resources(User, Server) 
    when is_binary(User), is_binary(Server) ->
    US = {User, Server},
    case catch mnesia:dirty_index_read(session, US, #session.us) of
	{'EXIT', _Reason} ->
	    [];
	Ss ->
	    [element(3, S#session.usr) || S <- clean_session_list(Ss)]
    end.

get_user_ip(JID) when ?IS_JID(JID) ->
    USR = {exmpp_jid:prep_node(JID), 
           exmpp_jid:prep_domain(JID), 
           exmpp_jid:prep_resource(JID)},
    case mnesia:dirty_index_read(session, USR, #session.usr) of
	[] ->
	    undefined;
	Ss ->
	    Session = lists:max(Ss),
	    proplists:get_value(ip, Session#session.info)
    end.

get_user_info(User, Server, Resource) 
    when is_binary(User), 
         is_binary(Server),
         is_binary(Resource) ->
    LUser = exmpp_stringprep:nodeprep(User),
    LServer = exmpp_stringprep:nameprep(Server),
    LResource = exmpp_stringprep:resourceprep(Resource),
    USR = {LUser, 
           LServer, 
           LResource},
    case mnesia:dirty_index_read(session, USR, #session.usr) of
	[] ->
	    offline;
	Ss ->
	    Session = lists:max(Ss),
	    Node = node(element(2, Session#session.sid)),
	    Conn = proplists:get_value(conn, Session#session.info),
	    IP = proplists:get_value(ip, Session#session.info),
	    [{node, Node}, {conn, Conn}, {ip, IP}]
    end.

set_presence(SID, JID, Priority, Presence, Info) when ?IS_JID(JID) ->
    set_session(SID, JID, Priority, Info),
    ejabberd_hooks:run(set_presence_hook, 
           exmpp_jid:prep_domain(JID),
		       [exmpp_jid:prep_node(JID), 
                exmpp_jid:prep_domain(JID), 
                exmpp_jid:prep_resource(JID), 
                Presence]).

unset_presence(SID, JID, Status, Info) when ?IS_JID(JID)->
    set_session(SID, JID, undefined, Info),
    ejabberd_hooks:run(unset_presence_hook, 
               exmpp_jid:prep_domain(JID),
		       [exmpp_jid:prep_node(JID), 
                exmpp_jid:prep_domain(JID), 
                exmpp_jid:prep_resource(JID), 
                Status]).

close_session_unset_presence(SID, JID, Status) when ?IS_JID(JID) ->
    close_session(SID, JID),
    ejabberd_hooks:run(unset_presence_hook, 
               exmpp_jid:prep_domain(JID),
		       [exmpp_jid:prep_node(JID), 
                exmpp_jid:prep_domain(JID), 
                exmpp_jid:prep_resource(JID), 
                Status]).

get_session_pid(JID) when ?IS_JID(JID) ->
    USR = {exmpp_jid:prep_node(JID), 
           exmpp_jid:prep_domain(JID), 
           exmpp_jid:prep_resource(JID)},
    case catch mnesia:dirty_index_read(session, USR, #session.usr) of
	[#session{sid = {_, Pid}}] -> Pid;
	_ -> none
    end.

dirty_get_sessions_list() ->
    mnesia:dirty_select(
      session,
      [{#session{usr = '$1', _ = '_'},
	[],
	['$1']}]).

dirty_get_my_sessions_list() ->
    mnesia:dirty_select(
      session,
      [{#session{sid = {'_', '$1'}, _ = '_'},
	[{'==', {node, '$1'}, node()}],
	['$_']}]).

get_vh_session_list(Server) when is_binary(Server) ->
    LServer = exmpp_stringprep:nameprep(Server),
    mnesia:dirty_select(
      session,
      [{#session{usr = '$1', _ = '_'},
	[{'==', {element, 2, '$1'}, LServer}],
	['$1']}]).

register_iq_handler(Host, XMLNS, Module, Fun) ->
    ejabberd_sm ! {register_iq_handler, Host, XMLNS, Module, Fun}.

register_iq_handler(Host, XMLNS, Module, Fun, Opts) ->
    ejabberd_sm ! {register_iq_handler, Host, XMLNS, Module, Fun, Opts}.

unregister_iq_handler(Host, XMLNS) ->
    ejabberd_sm ! {unregister_iq_handler, Host, XMLNS}.


%%====================================================================
%% gen_server callbacks
%%====================================================================

%%--------------------------------------------------------------------
%% Function: init(Args) -> {ok, State} |
%%                         {ok, State, Timeout} |
%%                         ignore               |
%%                         {stop, Reason}
%% Description: Initiates the server
%%--------------------------------------------------------------------
init([]) ->
    update_tables(),
    mnesia:create_table(session,
			[{ram_copies, [node()]},
			 {attributes, record_info(fields, session)}]),
    mnesia:add_table_index(session, usr),
    mnesia:add_table_index(session, us),
    mnesia:add_table_copy(session, node(), ram_copies),
    mnesia:subscribe(system),
    ets:new(sm_iqtable, [named_table]),
    lists:foreach(
      fun(Host) ->
          HostB = list_to_binary(Host),
	      ejabberd_hooks:add(roster_in_subscription, HostB,
				 ejabberd_sm, check_in_subscription, 20),
	      ejabberd_hooks:add(offline_message_hook, HostB,
				 ejabberd_sm, bounce_offline_message, 100),
	      ejabberd_hooks:add(remove_user, HostB,
				 ejabberd_sm, disconnect_removed_user, 100)
      end, ?MYHOSTS),
    ejabberd_commands:register_commands(commands()),

    {ok, #state{}}.

%%--------------------------------------------------------------------
%% Function: %% handle_call(Request, From, State) -> {reply, Reply, State} |
%%                                      {reply, Reply, State, Timeout} |
%%                                      {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, Reply, State} |
%%                                      {stop, Reason, State}
%% Description: Handling call messages
%%--------------------------------------------------------------------
handle_call(_Request, _From, State) ->
    Reply = ok,
    {reply, Reply, State}.

%%--------------------------------------------------------------------
%% Function: handle_cast(Msg, State) -> {noreply, State} |
%%                                      {noreply, State, Timeout} |
%%                                      {stop, Reason, State}
%% Description: Handling cast messages
%%--------------------------------------------------------------------
handle_cast(_Msg, State) ->
    {noreply, State}.

%%--------------------------------------------------------------------
%% Function: handle_info(Info, State) -> {noreply, State} |
%%                                       {noreply, State, Timeout} |
%%                                       {stop, Reason, State}
%% Description: Handling all non call/cast messages
%%--------------------------------------------------------------------
handle_info({route, FromOld, ToOld, #xmlelement{} = PacketOld}, State) ->
    catch throw(for_stacktrace), % To have a stacktrace.
    io:format("~nSM: old #xmlelement:~n~p~n~p~n~n",
      [PacketOld, erlang:get_stacktrace()]),
    % XXX OLD FORMAT: From, To, Packet.
    From = jlib:from_old_jid(FromOld),
    To = jlib:from_old_jid(ToOld),
    Packet = exmpp_xml:xmlelement_to_xmlel(PacketOld, [?NS_JABBER_CLIENT],
      [{?NS_XMPP, ?NS_XMPP_pfx}]),
    handle_info({route, From, To, Packet}, State);
handle_info({route, From, To, Packet}, State) ->
    case catch do_route(From, To, Packet) of
	{'EXIT', Reason} ->
	    ?ERROR_MSG("~p~nwhen processing: ~p",
		       [Reason, {From, To, Packet}]);
	_ ->
	    ok
    end,
    {noreply, State};
handle_info({mnesia_system_event, {mnesia_down, Node}}, State) ->
    clean_table_from_bad_node(Node),
    {noreply, State};
handle_info({register_iq_handler, Host, XMLNS, Module, Function}, State) ->
    ets:insert(sm_iqtable, {{XMLNS, Host}, Module, Function}),
    {noreply, State};
handle_info({register_iq_handler, Host, XMLNS, Module, Function, Opts}, State) ->
    ets:insert(sm_iqtable, {{XMLNS, Host}, Module, Function, Opts}),
    {noreply, State};
handle_info({unregister_iq_handler, Host, XMLNS}, State) ->
    case ets:lookup(sm_iqtable, {XMLNS, Host}) of
	[{_, Module, Function, Opts}] ->
	    gen_iq_handler:stop_iq_handler(Module, Function, Opts);
	_ ->
	    ok
    end,
    ets:delete(sm_iqtable, {XMLNS, Host}),
    {noreply, State};
handle_info(_Info, State) ->
    {noreply, State}.

%%--------------------------------------------------------------------
%% Function: terminate(Reason, State) -> void()
%% Description: This function is called by a gen_server when it is about to
%% terminate. It should be the opposite of Module:init/1 and do any necessary
%% cleaning up. When it returns, the gen_server terminates with Reason.
%% The return value is ignored.
%%--------------------------------------------------------------------
terminate(_Reason, _State) ->
    ejabberd_commands:unregister_commands(commands()),
    ok.

%%--------------------------------------------------------------------
%% Func: code_change(OldVsn, State, Extra) -> {ok, NewState}
%% Description: Convert process state when code is changed
%%--------------------------------------------------------------------
code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------

set_session(SID, JID, Priority, Info) ->
    US = {exmpp_jid:prep_node(JID), exmpp_jid:prep_domain(JID)},
    USR = {exmpp_jid:prep_node(JID), 
           exmpp_jid:prep_domain(JID), 
           exmpp_jid:prep_resource(JID)},
    F = fun() ->
		mnesia:write(#session{sid = SID,
				      usr = USR,
				      us = US,
				      priority = Priority,
				      info = Info})
	end,
    mnesia:sync_dirty(F).

clean_table_from_bad_node(Node) ->
    F = fun() ->
		Es = mnesia:select(
		       session,
		       [{#session{sid = {'_', '$1'}, _ = '_'},
			 [{'==', {node, '$1'}, Node}],
			 ['$_']}]),
		lists:foreach(fun(E) ->
				      mnesia:delete({session, E#session.sid})
			      end, Es)
	end,
    mnesia:sync_dirty(F).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

do_route(From, To, Packet) ->
    ?DEBUG("session manager~n\tfrom ~p~n\tto ~p~n\tpacket ~P~n",
	   [From, To, Packet, 8]),
    case exmpp_jid:prep_resource(To) of
	undefined ->
	    case Packet of
		_ when ?IS_PRESENCE(Packet) ->
		    {Pass, _Subsc} =
			case exmpp_presence:get_type(Packet) of
			    'subscribe' ->
				Reason = exmpp_presence:get_status(Packet),
				{is_privacy_allow(From, To, Packet) andalso
				 ejabberd_hooks:run_fold(
				   roster_in_subscription,
				   exmpp_jid:prep_domain(To),
				   false,
				   [exmpp_jid:prep_node(To), exmpp_jid:prep_domain(To), From, subscribe, Reason]),
				 true};
			    'subscribed' ->
				{is_privacy_allow(From, To, Packet) andalso
				 ejabberd_hooks:run_fold(
				   roster_in_subscription,
				   exmpp_jid:prep_domain(To),
				   false,
				   [exmpp_jid:prep_node(To), exmpp_jid:prep_domain(To), From, subscribed, <<>>]),
				 true};
			    'unsubscribe' ->
				{is_privacy_allow(From, To, Packet) andalso
				 ejabberd_hooks:run_fold(
				   roster_in_subscription,
				   exmpp_jid:prep_domain(To),
				   false,
				   [exmpp_jid:prep_node(To), exmpp_jid:prep_domain(To), From, unsubscribe, <<>>]),
				 true};
			    'unsubscribed' ->
				{is_privacy_allow(From, To, Packet) andalso
				 ejabberd_hooks:run_fold(
				   roster_in_subscription,
				   exmpp_jid:prep_domain(To),
				   false,
				   [exmpp_jid:prep_node(To), exmpp_jid:prep_domain(To), From, unsubscribed, <<>>]),
				 true};
			    _ ->
				{true, false}
			end,
		    if Pass ->
			    PResources = get_user_present_resources(
					   exmpp_jid:prep_node(To), exmpp_jid:prep_domain(To)),
			    lists:foreach(
			      fun({_, R}) ->
				      do_route(
					From,
					exmpp_jid:full(To, R),
					Packet)
			      end, PResources);
		       true ->
			    ok
		    end;
		_ when ?IS_MESSAGE(Packet) ->
		    route_message(From, To, Packet);
		_ when ?IS_IQ(Packet) ->
		    process_iq(From, To, Packet);
		#xmlel{name = 'broadcast'} ->
		    lists:foreach(
		      fun(R) ->
			      do_route(From,
				       exmpp_jid:full(To, R),
				       Packet)
		      end, get_user_resources(exmpp_jid:prep_node(To), 
                                      exmpp_jid:prep_domain(To)));
		_ ->
		    ok
	    end;
	_ ->
	    USR = {exmpp_jid:prep_node(To),
               exmpp_jid:prep_domain(To),
               exmpp_jid:prep_resource(To)},
	    case mnesia:dirty_index_read(session, USR, #session.usr) of
		[] ->
		    case Packet of
			_ when ?IS_MESSAGE(Packet) ->
			    route_message(From, To, Packet);
			_ when ?IS_IQ(Packet) ->
			    case exmpp_iq:get_type(Packet) of
				'error' -> ok;
				'result' -> ok;
				_ ->
				    Err =
					exmpp_iq:error(Packet,
                                          'service-unavailable'),
				    ejabberd_router:route(To, From, Err)
			    end;
			_ ->
			    ?DEBUG("packet droped~n", [])
		    end;
		Ss ->
		    Session = lists:max(Ss),
		    Pid = element(2, Session#session.sid),
		    ?DEBUG("sending to process ~p~n", [Pid]),
		    Pid ! {route, From, To, Packet}
	    end
    end.

%% The default list applies to the user as a whole,
%% and is processed if there is no active list set
%% for the target session/resource to which a stanza is addressed,
%% or if there are no current sessions for the user.
is_privacy_allow(From, To, Packet) ->
    User = exmpp_jid:prep_node(To), 
    Server = exmpp_jid:prep_domain(To),
    PrivacyList = ejabberd_hooks:run_fold(privacy_get_user_list, Server,
					  #userlist{}, [User, Server]),
    is_privacy_allow(From, To, Packet, PrivacyList).

%% Check if privacy rules allow this delivery
%% Function copied from ejabberd_c2s.erl
is_privacy_allow(From, To, Packet, PrivacyList) ->
    User = exmpp_jid:prep_node(To), 
    Server = exmpp_jid:prep_domain(To),
    allow == ejabberd_hooks:run_fold(
	       privacy_check_packet, Server,
	       allow,
	       [User,
		Server,
		PrivacyList,
		{From, To, Packet},
		in]).

route_message(From, To, Packet) ->
    LUser = exmpp_jid:prep_node(To),
    LServer = exmpp_jid:prep_domain(To),
    PrioRes = get_user_present_resources(LUser, LServer),
    case catch lists:max(PrioRes) of
	{Priority, _R} when is_integer(Priority), Priority >= 0 ->
	    lists:foreach(
	      %% Route messages to all priority that equals the max, if
	      %% positive
	      fun({P, R}) when P == Priority ->
		      USR = {LUser, LServer, R},
		      case mnesia:dirty_index_read(session, USR, #session.usr) of
			  [] ->
			      ok; % Race condition
			  Ss ->
			      Session = lists:max(Ss),
			      Pid = element(2, Session#session.sid),
			      ?DEBUG("sending to process ~p~n", [Pid]),
			      Pid ! {route, From, To, Packet}
		      end;
		 %% Ignore other priority:
		 ({_Prio, _Res}) ->
		      ok
	      end,
	      PrioRes);
	_ ->
	    case exmpp_message:get_type(Packet) of
		'error' ->
		    ok;
		'groupchat' ->
		    bounce_offline_message(From, To, Packet);
		'headline' ->
		    bounce_offline_message(From, To, Packet);
		_ ->
		    case ejabberd_auth:is_user_exists(exmpp_jid:prep_node_as_list(To), 
                                              exmpp_jid:prep_domain_as_list(To)) of
			true ->
			    ejabberd_hooks:run(offline_message_hook,
					       exmpp_jid:prep_domain(To),
					       [From, To, Packet]);
			_ ->
			    Err = exmpp_stanza:reply_with_error(
				    Packet, 'service-unaivailable'),
			    ejabberd_router:route(To, From, Err)
		    end
	    end
    end.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

clean_session_list(Ss) ->
    clean_session_list(lists:keysort(#session.usr, Ss), []).

clean_session_list([], Res) ->
    Res;
clean_session_list([S], Res) ->
    [S | Res];
clean_session_list([S1, S2 | Rest], Res) ->
    if
	S1#session.usr == S2#session.usr ->
	    if
		S1#session.sid > S2#session.sid ->
		    clean_session_list([S1 | Rest], Res);
		true ->
		    clean_session_list([S2 | Rest], Res)
	    end;
	true ->
	    clean_session_list([S2 | Rest], [S1 | Res])
    end.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

get_user_present_resources(LUser, LServer) ->
    US = {LUser, LServer},
    case catch mnesia:dirty_index_read(session, US, #session.us) of
	{'EXIT', _Reason} ->
	    [];
	Ss ->
	    [{S#session.priority, element(3, S#session.usr)} ||
		S <- clean_session_list(Ss), is_integer(S#session.priority)]
    end.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% On new session, check if some existing connections need to be replace
check_for_sessions_to_replace(JID) ->
    %% TODO: Depending on how this is executed, there could be an unneeded
    %% replacement for max_sessions. We need to check this at some point.
    check_existing_resources(JID),
    check_max_sessions(JID).

check_existing_resources(JID) ->
    USR = {exmpp_jid:prep_node(JID),
           exmpp_jid:prep_domain(JID),
           exmpp_jid:prep_resource(JID)},
    %% A connection exist with the same resource. We replace it:
    SIDs = mnesia:dirty_select(
	     session,
	     [{#session{sid = '$1', usr = USR, _ = '_'}, [], ['$1']}]),
    if
	SIDs == [] -> ok;
	true ->
	    MaxSID = lists:max(SIDs),
	    lists:foreach(
	      fun({_, Pid} = S) when S /= MaxSID ->
		      Pid ! replaced;
		 (_) -> ok
	      end, SIDs)
    end.

check_max_sessions(JID) ->
    %% If the max number of sessions for a given is reached, we replace the
    %% first one
    SIDs = mnesia:dirty_select(
	     session,
	     [{#session{sid = '$1', 
                    us = {exmpp_jid:prep_node(JID), exmpp_jid:prep_domain(JID)},
                    _ = '_'}, [],
	       ['$1']}]),
    MaxSessions = get_max_user_sessions(JID),
    if
	length(SIDs) =< MaxSessions ->
	    ok;
	true ->
	    {_, Pid} = lists:min(SIDs),
	    Pid ! replaced
    end.


%% Get the user_max_session setting
%% This option defines the max number of time a given users are allowed to
%% log in
%% Defaults to infinity
get_max_user_sessions(JID) ->
    case acl:match_rule(
	   exmpp_jid:prep_domain_as_list(JID), max_user_sessions, exmpp_jid:bare(JID)) of
	Max when is_integer(Max) -> Max;
	infinity -> infinity;
	_ -> ?MAX_USER_SESSIONS
    end.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

process_iq(From, To, Packet) ->
    case exmpp_iq:xmlel_to_iq(Packet) of
	#iq{kind = request, ns = XMLNS} = IQ_Rec ->
        LServer = exmpp_jid:prep_domain(To),
	    case ets:lookup(sm_iqtable, {XMLNS, LServer}) of
		[{_, Module, Function}] ->
		    ResIQ = Module:Function(From, To, IQ_Rec),
		    if
			ResIQ /= ignore ->
			    Reply = exmpp_iq:iq_to_xmlel(ResIQ, To, From),
			    ejabberd_router:route(To, From, Reply);
			true ->
			    ok
		    end;
		[{_, Module, Function, Opts}] ->
		    gen_iq_handler:handle(LServer, 
                      Module, Function, Opts, From, To, IQ_Rec);
		[] ->
		    Err = exmpp_iq:error(Packet, 'service-unavailable'),
		    ejabberd_router:route(To, From, Err)
	    end;
	#iq{kind = response} ->
	    ok;
	_ ->
	    Err = exmpp_iq:error(Packet, 'bad-request'),
	    ejabberd_router:route(To, From, Err),
	    ok
    end.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% ejabberd commands

commands() ->
	[
     #ejabberd_commands{name = connected_users,
		       tags = [session],
		       desc = "List all established sessions",
		       module = ?MODULE, function = connected_users,
		       args = [],
		       result = {connected_users, {list, {sessions, string}}}},
     #ejabberd_commands{name = connected_users_number,
		       tags = [session, stats],
		       desc = "Get the number of established sessions",
		       module = ?MODULE, function = connected_users_number,
		       args = [],
		       result = {num_sessions, integer}},
     #ejabberd_commands{name = user_resources,
		       tags = [session],
		       desc = "List user's connected resources",
		       module = ?MODULE, function = user_resources,
		       args = [{user, string}, {host, string}],
		       result = {resources, {list, {resource, string}}}}
	].

connected_users() ->
    USRs = dirty_get_sessions_list(),
    SUSRs = lists:sort(USRs),
    lists:map(fun({U, S, R}) -> [U, $@, S, $/, R] end, SUSRs).

connected_users_number() ->
    length(dirty_get_sessions_list()).

user_resources(User, Server) ->
    Resources =  get_user_resources(list_to_binary(User), 
                                    list_to_binary(Server)),
    lists:sort(Resources).


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% Update Mnesia tables

update_tables() ->
    case catch mnesia:table_info(session, attributes) of
	[ur, user, node] ->
	    mnesia:delete_table(session);
	[ur, user, pid] ->
	    mnesia:delete_table(session);
	[usr, us, pid] ->
	    mnesia:delete_table(session);
	[sid, usr, us, priority] ->
	    mnesia:delete_table(session);
	[sid, usr, us, priority, info] ->
	    ok;
	{'EXIT', _} ->
	    ok
    end,
    case lists:member(presence, mnesia:system_info(tables)) of
	true ->
	    mnesia:delete_table(presence);
	false ->
	    ok
    end,
    case lists:member(local_session, mnesia:system_info(tables)) of
	true ->
	    mnesia:delete_table(local_session);
	false ->
	    ok
    end.