Add more flow control tests to rfc7540 and fix related issues

src/cowboy_http2.erl

@@ -400,10 +400,17 @@ frame(State=#state{client_streamid=LastStreamID}, {rst_stream, StreamID, _})
 frame(State, {rst_stream, StreamID, Reason}) ->
 	stream_terminate(State, StreamID, {stream_error, Reason, 'Stream reset requested by client.'});
 %% SETTINGS frame.
-frame(State=#state{socket=Socket, transport=Transport, remote_settings=Settings0},
+frame(State0=#state{socket=Socket, transport=Transport, remote_settings=Settings0},
 		{settings, Settings}) ->
 	Transport:send(Socket, cow_http2:settings_ack()),
-	State#state{remote_settings=maps:merge(Settings0, Settings)};
+	State = State0#state{remote_settings=maps:merge(Settings0, Settings)},
+	case Settings of
+		#{initial_window_size := NewWindowSize} ->
+			OldWindowSize = maps:get(initial_window_size, Settings0, 65535),
+			update_stream_windows(State, NewWindowSize - OldWindowSize);
+		_ ->
+			State
+	end;
 %% Ack for a previously sent SETTINGS frame.
 frame(State=#state{next_settings=_NextSettings}, settings_ack) ->
 	%% @todo Apply SETTINGS that require synchronization.
@@ -426,7 +433,7 @@ frame(State, Frame={goaway, _, _, _}) ->
 	terminate(State, {stop, Frame, 'Client is going away.'});
 %% Connection-wide WINDOW_UPDATE frame.
 frame(State=#state{local_window=ConnWindow}, {window_update, Increment})
-		when ConnWindow + Increment > 2147483647 ->
+		when ConnWindow + Increment > 16#7fffffff ->
 	terminate(State, {connection_error, flow_control_error,
 		'The flow control window must not be greater than 2^31-1. (RFC7540 6.9.1)'});
 frame(State=#state{local_window=ConnWindow}, {window_update, Increment}) ->
@@ -438,7 +445,7 @@ frame(State=#state{client_streamid=LastStreamID}, {window_update, StreamID, _})
 		'WINDOW_UPDATE frame received on a stream in idle state. (RFC7540 5.1)'});
 frame(State0=#state{streams=Streams0}, {window_update, StreamID, Increment}) ->
 	case lists:keyfind(StreamID, #stream.id, Streams0) of
-		#stream{local_window=StreamWindow} when StreamWindow + Increment > 2147483647 ->
+		#stream{local_window=StreamWindow} when StreamWindow + Increment > 16#7fffffff ->
 			stream_reset(State0, StreamID, {stream_error, flow_control_error,
 				'The flow control window must not be greater than 2^31-1. (RFC7540 6.9.1)'});
 		Stream0 = #stream{local_window=StreamWindow} ->
@@ -656,6 +663,15 @@ status(<< H, T, U, _/bits >>) when H >= $1, H =< $9, T >= $0, T =< $9, U >= $0,
 send_data(State=#state{streams=Streams}) ->
 	resume_streams(State, Streams, []).
 
+%% When SETTINGS_INITIAL_WINDOW_SIZE changes we need to update
+%% the stream windows for all active streams and perhaps resume
+%% sending data.
+update_stream_windows(State=#state{streams=Streams0}, Increment) ->
+	Streams = [
+		S#stream{local_window=StreamWindow + Increment}
+	|| S=#stream{local_window=StreamWindow} <- Streams0],
+	resume_streams(State, Streams, []).
+
 resume_streams(State, [], Acc) ->
 	State#state{streams=lists:reverse(Acc)};
 %% While technically we should never get < 0 here, let's be on the safe side.

test/rfc7540_SUITE.erl

@@ -2622,9 +2622,9 @@ window_update_reject_overflow(Config) ->
 		"window to exceed 2^31-1 must be rejected with a "
 		"FLOW_CONTROL_ERROR connection error. (RFC7540 6.9.1)"),
 	{ok, Socket} = do_handshake(Config),
-	%% Send connection-wide WINDOW_UPDATE frame that causes the window to overflow.
+	%% Send a connection-wide WINDOW_UPDATE frame that causes the window to overflow.
 	ok = gen_tcp:send(Socket, [
-		cow_http2:window_update(2147483647)
+		cow_http2:window_update(16#7fffffff)
 	]),
 	%% Receive a FLOW_CONTROL_ERROR connection error.
 	{ok, << _:24, 7:8, _:72, 3:32 >>} = gen_tcp:recv(Socket, 17, 6000),
@@ -2645,8 +2645,89 @@ window_update_reject_overflow_stream(Config) ->
 	]),
 	ok = gen_tcp:send(Socket, [
 		cow_http2:headers(1, fin, HeadersBlock),
-		cow_http2:window_update(1, 2147483647)
+		cow_http2:window_update(1, 16#7fffffff)
 	]),
 	%% Receive a FLOW_CONTROL_ERROR stream error.
 	{ok, << _:24, 3:8, _:8, 1:32, 3:32 >>} = gen_tcp:recv(Socket, 13, 6000),
 	ok.
+
+settings_initial_window_size_changes(Config) ->
+	doc("When the value of SETTINGS_INITIAL_WINDOW_SIZE changes, the server "
+		"must adjust the size of the flow control windows of the active "
+		"streams. (RFC7540 6.9.2)"),
+	{ok, Socket} = do_handshake(Config),
+	%% Set SETTINGS_INITIAL_WINDOW_SIZE to 0 to prevent sending of DATA.
+	ok = gen_tcp:send(Socket, cow_http2:settings(#{initial_window_size => 0})),
+	%% Receive the SETTINGS ack.
+	{ok, << 0:24, 4:8, 1:8, 0:32 >>} = gen_tcp:recv(Socket, 9, 1000),
+	%% Send a HEADERS frame.
+	{HeadersBlock, _} = cow_hpack:encode([
+		{<<":method">>, <<"GET">>},
+		{<<":scheme">>, <<"http">>},
+		{<<":authority">>, <<"localhost">>}, %% @todo Correct port number.
+		{<<":path">>, <<"/">>}
+	]),
+	ok = gen_tcp:send(Socket, cow_http2:headers(1, fin, HeadersBlock)),
+	%% Receive a response but no DATA frames are coming.
+	{ok, << SkipLen:24, 1:8, _:8, 1:32 >>} = gen_tcp:recv(Socket, 9, 1000),
+	{ok, _} = gen_tcp:recv(Socket, SkipLen, 1000),
+	{error, timeout} = gen_tcp:recv(Socket, 9, 1000),
+	%% Set SETTINGS_INITIAL_WINDOW_SIZE to a larger value.
+	ok = gen_tcp:send(Socket, cow_http2:settings(#{initial_window_size => 5})),
+	%% Receive the SETTINGS ack.
+	{ok, << 0:24, 4:8, 1:8, 0:32 >>} = gen_tcp:recv(Socket, 9, 1000),
+	%% Receive a DATA frame of that size and no other.
+	{ok, << 5:24, 0:8, 0:8, 1:32, "Hello" >>} = gen_tcp:recv(Socket, 14, 1000),
+	{error, timeout} = gen_tcp:recv(Socket, 9, 1000),
+	%% Set SETTINGS_INITIAL_WINDOW_SIZE to exactly the size in the body.
+	ok = gen_tcp:send(Socket, cow_http2:settings(#{initial_window_size => 12})),
+	%% Receive the SETTINGS ack.
+	{ok, << 0:24, 4:8, 1:8, 0:32 >>} = gen_tcp:recv(Socket, 9, 1000),
+	%% Receive the rest of the response.
+	{ok, << 7:24, 0:8, 1:8, 1:32, " world!" >>} = gen_tcp:recv(Socket, 16, 1000),
+	ok.
+
+settings_initial_window_size_changes_negative(Config) ->
+	doc("When the value of SETTINGS_INITIAL_WINDOW_SIZE changes, the server "
+		"must adjust the size of the flow control windows of the active "
+		"streams even if their window end up negative. (RFC7540 6.9.2)"),
+	{ok, Socket} = do_handshake(Config),
+	%% Set SETTINGS_INITIAL_WINDOW_SIZE to 5.
+	ok = gen_tcp:send(Socket, cow_http2:settings(#{initial_window_size => 5})),
+	%% Receive the SETTINGS ack.
+	{ok, << 0:24, 4:8, 1:8, 0:32 >>} = gen_tcp:recv(Socket, 9, 1000),
+	%% Send a HEADERS frame.
+	{HeadersBlock, _} = cow_hpack:encode([
+		{<<":method">>, <<"GET">>},
+		{<<":scheme">>, <<"http">>},
+		{<<":authority">>, <<"localhost">>}, %% @todo Correct port number.
+		{<<":path">>, <<"/">>}
+	]),
+	ok = gen_tcp:send(Socket, cow_http2:headers(1, fin, HeadersBlock)),
+	%% Receive a response with a single DATA frame of the initial size we set.
+	{ok, << SkipLen:24, 1:8, _:8, 1:32 >>} = gen_tcp:recv(Socket, 9, 1000),
+	{ok, _} = gen_tcp:recv(Socket, SkipLen, 1000),
+	{ok, << 5:24, 0:8, 0:8, 1:32, "Hello" >>} = gen_tcp:recv(Socket, 14, 1000),
+	{error, timeout} = gen_tcp:recv(Socket, 9, 1000),
+	%% Set SETTINGS_INITIAL_WINDOW_SIZE to 0 to make the stream's window negative.
+	ok = gen_tcp:send(Socket, cow_http2:settings(#{initial_window_size => 0})),
+	%% Receive the SETTINGS ack.
+	{ok, << 0:24, 4:8, 1:8, 0:32 >>} = gen_tcp:recv(Socket, 9, 1000),
+	%% Set SETTINGS_INITIAL_WINDOW_SIZE to exactly the size in the body.
+	ok = gen_tcp:send(Socket, cow_http2:settings(#{initial_window_size => 12})),
+	%% Receive the SETTINGS ack.
+	{ok, << 0:24, 4:8, 1:8, 0:32 >>} = gen_tcp:recv(Socket, 9, 1000),
+	%% Receive the rest of the response.
+	{ok, << 7:24, 0:8, 1:8, 1:32, " world!" >>} = gen_tcp:recv(Socket, 16, 1000),
+	ok.
+
+settings_initial_window_size_reject_overflow(Config) ->
+	doc("A SETTINGS_INITIAL_WINDOW_SIZE that causes a flow control window "
+		"to exceed 2^31-1 must be rejected with a FLOW_CONTROL_ERROR "
+		"connection error. (RFC7540 6.9.2)"),
+	{ok, Socket} = do_handshake(Config),
+	%% Set SETTINGS_INITIAL_WINDOW_SIZE to 2^31.
+	ok = gen_tcp:send(Socket, cow_http2:settings(#{initial_window_size => 16#80000000})),
+	%% Receive a FLOW_CONTROL_ERROR connection error.
+	{ok, << _:24, 7:8, _:72, 3:32 >>} = gen_tcp:recv(Socket, 17, 6000),
+	ok.