New option resource_conflict defines server action (thanks to Lee Boynton)(EJAB-650)

doc/guide.tex

@@ -1243,6 +1243,16 @@ defines in what format the users passwords are stored:
     This format allows clients to authenticate using: \term{SASL PLAIN} and \term{SASL SCRAM-SHA-1}.
 \end{description}
 
+The option \option{resource\_conflict} defines the action when a client attempts to
+login to an account with a resource that is already connected.
+The option syntax is:
+\esyntax{\{resource\_conflict, setresource|closenew|closeold\}.}
+The possible values match exactly the three possibilities described in
+\footahref{http://tools.ietf.org/html/rfc6120\#section-7.7.2.2}{XMPP Core: section 7.7.2.2}.
+The default value is \term{closeold}.
+If the client uses old Jabber Non-SASL authentication (\xepref{0078}),
+then this option is not respected, and the action performed is \term{closeold}.
+
 Examples:
 \begin{itemize}
 \item To use internal Mnesia storage with hashed passwords on all virtual hosts:

src/ejabberd_c2s.erl

@@ -907,6 +907,29 @@ wait_for_sasl_response(closed, StateData) ->
     {stop, normal, StateData}.
 
 
+resource_conflict_action(U, S, R) ->
+    OptionRaw = case ejabberd_sm:is_existing_resource(U, S, R) of
+		    true ->
+			ejabberd_config:get_local_option({resource_conflict,binary_to_list(S)});
+		    false ->
+			acceptnew
+		end,
+    Option = case OptionRaw of
+		 setresource -> setresource;
+		 closeold -> acceptnew; %% ejabberd_sm will close old session
+		 closenew -> closenew;
+		 acceptnew -> acceptnew;
+		 _ -> acceptnew %% default ejabberd behavior
+	     end,
+    case Option of
+	acceptnew ->
+	    {accept_resource, R};
+	closenew ->
+	    closenew;
+	setresource ->
+	    Rnew = lists:concat([randoms:get_string() | tuple_to_list(now())]),
+	    {accept_resource, Rnew}
+    end.
 
 wait_for_bind({xmlstreamelement, El}, StateData) ->
     try
@@ -923,11 +946,17 @@ wait_for_bind({xmlstreamelement, El}, StateData) ->
 	%%send_element(StateData,
 	%%	     exmpp_stream:features([exmpp_server_session:feature()
 	%%				    | RosterVersioningFeature])),
-	JID = exmpp_jid:make(StateData#state.user, StateData#state.server, R),
-	Res = exmpp_server_binding:bind(El, JID),
-	send_element(StateData, Res),
-	fsm_next_state(wait_for_session,
+	case resource_conflict_action(StateData#state.user, StateData#state.server, list_to_binary(R)) of
+	closenew ->
+		send_element(StateData, ?SERRT_CONFLICT), %% (Lang, "Replaced by new connection")),
+		fsm_next_state(wait_for_bind, StateData);
+	{accept_resource, R2} ->
+		JID = exmpp_jid:make(StateData#state.user, StateData#state.server, R2),
+		Res = exmpp_server_binding:bind(El, JID),
+		send_element(StateData, Res),
+		fsm_next_state(wait_for_session,
 		       StateData#state{resource = exmpp_jid:resource(JID), jid = JID})
+	end
     catch
 	throw:{stringprep, resourceprep, _, _} ->
 	    Err = exmpp_server_binding:error(El, 'bad-request'),

src/ejabberd_sm.erl

@@ -59,6 +59,7 @@
 	 get_session_pid/1,
 	 get_user_info/3,
 	 get_user_ip/1,
+	 is_existing_resource/3,
 	 migrate/1
 	]).
 
@@ -727,16 +728,12 @@ check_for_sessions_to_replace(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']}]),
+    SIDs = get_resource_sessions(JID),
     if
 	SIDs == [] -> ok;
 	true ->
+	    %% A connection exist with the same resource. We replace it:
 	    MaxSID = lists:max(SIDs),
 	    lists:foreach(
 	      fun({_, Pid} = S) when S /= MaxSID ->
@@ -745,6 +742,17 @@ check_existing_resources(JID) ->
 	      end, SIDs)
     end.
 
+is_existing_resource(U, S, R) ->
+    [] /= get_resource_sessions(exmpp_jid:make(U, S, R)).
+
+get_resource_sessions(JID) ->
+    USR = {exmpp_jid:prep_node(JID),
+           exmpp_jid:prep_domain(JID),
+           exmpp_jid:prep_resource(JID)},
+    mnesia:dirty_select(
+	     session,
+	     [{#session{sid = '$1', usr = USR, _ = '_'}, [], ['$1']}]).
+
 check_max_sessions(JID) ->
     %% If the max number of sessions for a given is reached, we replace the
     %% first one