Add options controlling maximum h2 frame sizes

doc/src/manual/cowboy_http2.asciidoc

@@ -26,6 +26,8 @@ opts() :: #{
     max_concurrent_streams         => non_neg_integer() | infinity,
     max_decode_table_size          => non_neg_integer(),
     max_encode_table_size          => non_neg_integer(),
+    max_frame_size_received        => 16384..16777215,
+    max_frame_size_sent            => 16384..16777215 | infinity,
     middlewares                    => [module()],
     preface_timeout                => timeout(),
     shutdown_timeout               => timeout(),
@@ -84,6 +86,19 @@ max_encode_table_size (4096)::
     value to what the client advertises and choose the smallest one as the
     encoder's header table size.
 
+max_frame_size_received (16384)::
+    Maximum size of the frames received by the server. This value is
+    advertised to the remote endpoint which can then decide to use
+    any value lower or equal for its frame sizes.
+
+max_frame_size_sent (infinity)::
+    Maximum size of the frames sent by the server. This option allows
+    setting an upper limit to the frame sizes instead of blindly
+    following the client's advertised maximum.
++
+    Note that actual frame sizes may be lower than the limit when
+    there is not enough space left in the flow control window.
+
 middlewares ([cowboy_router, cowboy_handler])::
     Middlewares to run for every request.
 
@@ -100,7 +115,8 @@ stream_handlers ([cowboy_stream_h])::
 
 * *2.4*: Add the options `initial_connection_window_size`,
          `initial_stream_window_size`, `max_concurrent_streams`,
-         `max_decode_table_size` and `max_encode_table_size`
+         `max_decode_table_size`, `max_encode_table_size`,
+         `max_frame_size_received` and `max_frame_size_sent`
          to configure HTTP/2 SETTINGS.
 * *2.4*: Add the experimental option `enable_connect_protocol`.
 * *2.0*: Protocol introduced.

src/cowboy_http2.erl

@@ -32,6 +32,8 @@
 	max_concurrent_streams => non_neg_integer() | infinity,
 	max_decode_table_size => non_neg_integer(),
 	max_encode_table_size => non_neg_integer(),
+	max_frame_size_received => 16384..16777215,
+	max_frame_size_sent => 16384..16777215 | infinity,
 	middlewares => [module()],
 	preface_timeout => timeout(),
 	shutdown_timeout => timeout(),
@@ -89,7 +91,7 @@
 	%% the final settings handling will be very different.
 	local_settings = #{
 %		header_table_size => 4096,
-%		enable_push => false, %% We are the server. Push is never enabled.
+%		enable_push => false, %% We are the server. Push is never enabled for clients.
 %		max_concurrent_streams => infinity,
 		initial_window_size => 65535,
 		max_frame_size => 16384
@@ -215,9 +217,10 @@ settings_init(State, Opts) ->
 		max_concurrent_streams, infinity),
 	S2 = setting_from_opt(S1, Opts, initial_stream_window_size,
 		initial_window_size, 65535),
-	%% @todo max_frame_size
+	S3 = setting_from_opt(S2, Opts, max_frame_size_received,
+		max_frame_size, 16384),
 	%% @todo max_header_list_size
-	Settings = setting_from_opt(S2, Opts, enable_connect_protocol,
+	Settings = setting_from_opt(S3, Opts, enable_connect_protocol,
 		enable_connect_protocol, false),
 	State#state{next_settings=Settings}.
 
@@ -810,10 +813,15 @@ send_data(State=#state{local_window=ConnWindow},
 		Stream=#stream{local_window=StreamWindow}, IsFin, Data, In)
 		when ConnWindow =< 0; StreamWindow =< 0 ->
 	{State, queue_data(Stream, IsFin, Data, In)};
-send_data(State=#state{socket=Socket, transport=Transport, local_window=ConnWindow},
+send_data(State=#state{socket=Socket, transport=Transport, opts=Opts,
+		remote_settings=RemoteSettings, local_window=ConnWindow},
 		Stream=#stream{id=StreamID, local_window=StreamWindow}, IsFin, Data, In) ->
-	MaxFrameSize = 16384, %% @todo Use the real SETTINGS_MAX_FRAME_SIZE set by the client.
-	MaxSendSize = min(min(ConnWindow, StreamWindow), MaxFrameSize),
+	RemoteMaxFrameSize = maps:get(max_frame_size, RemoteSettings, 16384),
+	ConfiguredMaxFrameSize = maps:get(max_frame_size_sent, Opts, infinity),
+	MaxSendSize = min(
+		min(ConnWindow, StreamWindow),
+		min(RemoteMaxFrameSize, ConfiguredMaxFrameSize)
+	),
 	case Data of
 		{sendfile, Offset, Bytes, Path} when Bytes =< MaxSendSize ->
 			Transport:send(Socket, cow_http2:data_header(StreamID, IsFin, Bytes)),

test/http2_SUITE.erl

@@ -28,15 +28,19 @@ groups() -> [{clear, [parallel], ct_helper:all(?MODULE)}].
 init_routes(_) -> [
 	{"localhost", [
 		{"/", hello_h, []},
+		{"/echo/:key", echo_h, []},
 		{"/resp_iolist_body", resp_iolist_body_h, []}
 	]}
 ].
 
-%% Do a prior knowledge handshake (function copied from rfc7540_SUITE).
+%% Do a prior knowledge handshake (function originally copied from rfc7540_SUITE).
 do_handshake(Config) ->
+	do_handshake(#{}, Config).
+
+do_handshake(Settings, Config) ->
 	{ok, Socket} = gen_tcp:connect("localhost", config(port, Config), [binary, {active, false}]),
 	%% Send a valid preface.
-	ok = gen_tcp:send(Socket, ["PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n", cow_http2:settings(#{})]),
+	ok = gen_tcp:send(Socket, ["PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n", cow_http2:settings(Settings)]),
 	%% Receive the server preface.
 	{ok, << Len:24 >>} = gen_tcp:recv(Socket, 3, 1000),
 	{ok, << 4:8, 0:40, _:Len/binary >>} = gen_tcp:recv(Socket, 6 + Len, 1000),
@@ -81,6 +85,38 @@ initial_connection_window_size(Config) ->
 	ConfiguredSize = Size + 65535,
 	ok.
 
+max_frame_size_sent(Config) ->
+	doc("Confirm that frames sent by Cowboy are limited in size "
+		"by the max_frame_size_sent configuration value."),
+	MaxFrameSize = 20000,
+	ProtoOpts = #{
+		env => #{dispatch => cowboy_router:compile(init_routes(Config))},
+		max_frame_size_sent => MaxFrameSize
+	},
+	{ok, _} = cowboy:start_clear(name(), [{port, 0}], ProtoOpts),
+	Port = ranch:get_port(name()),
+	{ok, Socket} = do_handshake(#{max_frame_size => MaxFrameSize + 10000}, [{port, Port}|Config]),
+	%% Send a request with a 30000 bytes body.
+	{HeadersBlock, _} = cow_hpack:encode([
+		{<<":method">>, <<"POST">>},
+		{<<":scheme">>, <<"http">>},
+		{<<":authority">>, <<"localhost">>}, %% @todo Correct port number.
+		{<<":path">>, <<"/echo/read_body">>}
+	]),
+	ok = gen_tcp:send(Socket, [
+		cow_http2:headers(1, nofin, HeadersBlock),
+		cow_http2:data(1, nofin, <<0:16384/unit:8>>),
+		cow_http2:data(1, fin, <<0:13616/unit:8>>)
+	]),
+	%% Receive a HEADERS frame as a response.
+	{ok, <<Len:24, 1:8, _:40>>} = gen_tcp:recv(Socket, 9, 6000),
+	{ok, _} = gen_tcp:recv(Socket, Len, 6000),
+	%% The DATA frames following must have lengths of 20000
+	%% and then 10000 due to the limit.
+	{ok, <<20000:24, 0:8, _:40, _:20000/unit:8>>} = gen_tcp:recv(Socket, 20009, 6000),
+	{ok, <<10000:24, 0:8, _:40, _:10000/unit:8>>} = gen_tcp:recv(Socket, 10009, 6000),
+	ok.
+
 preface_timeout_infinity(Config) ->
 	doc("Ensure infinity for preface_timeout is accepted."),
 	ProtoOpts = #{

test/rfc7540_SUITE.erl

@@ -1277,65 +1277,63 @@ max_frame_size_reject_larger_than_default(Config) ->
 	{ok, << _:24, 7:8, _:72, 6:32 >>} = gen_tcp:recv(Socket, 17, 6000),
 	ok.
 
-%% @todo We need configurable SETTINGS in Cowboy for these tests.
-%%	max_frame_size_config_reject_too_small(Config) ->
-%%		doc("SETTINGS_MAX_FRAME_SIZE configuration values smaller than "
-%%			"16384 must be rejected. (RFC7540 6.5.2)"),
-%%		%% @todo This requires us to have a configurable SETTINGS in Cowboy.
-%%		todo.
-%%
-%%	max_frame_size_config_reject_too_large(Config) ->
-%%		doc("SETTINGS_MAX_FRAME_SIZE configuration values larger than "
-%%			"16777215 must be rejected. (RFC7540 6.5.2)"),
-%%		%% @todo This requires us to have a configurable SETTINGS in Cowboy.
-%%		todo.
-%%
-%%	max_frame_size_allow_exactly_custom(Config) ->
-%%		doc("An endpoint that sets SETTINGS_MAX_FRAME_SIZE must allow frames "
-%%			"of up to that size. (RFC7540 4.2, RFC7540 6.5.2)"),
-%%		%% @todo This requires us to have a configurable SETTINGS in Cowboy.
-%%		todo.
-%%
-%%	max_frame_size_reject_larger_than_custom(Config) ->
-%%		doc("An endpoint that sets SETTINGS_MAX_FRAME_SIZE must reject frames "
-%%			"of up to that size with a FRAME_SIZE_ERROR connection error. (RFC7540 4.2, RFC7540 6.5.2)"),
-%%		%% @todo This requires us to have a configurable SETTINGS in Cowboy.
-%%		todo.
-
-%% @todo How do I test this?
-%%
-%%	max_frame_size_client_default_respect_limits(Config) ->
-%%		doc("The server must not send frame sizes of more "
-%%			"than 16384 by default. (RFC7540 4.1, RFC7540 4.2)"),
-
-%% This is about the client sending a SETTINGS frame.
-max_frame_size_client_override_reject_too_small(Config) ->
-	doc("A SETTINGS_MAX_FRAME_SIZE smaller than 16384 must be rejected "
-		"with a PROTOCOL_ERROR connection error. (RFC7540 6.5.2)"),
+max_frame_size_allow_exactly_custom(Config0) ->
+	doc("An endpoint that sets SETTINGS_MAX_FRAME_SIZE must allow frames "
+		"of up to that size. (RFC7540 4.2, RFC7540 6.5.2)"),
+	%% Create a new listener that sets the maximum frame size to 30000.
+	Config = cowboy_test:init_http(name(), #{
+		env => #{dispatch => cowboy_router:compile(init_routes(Config0))},
+		max_frame_size_received => 30000
+	}, Config0),
+	%% Do the handshake.
 	{ok, Socket} = do_handshake(Config),
-	%% Send a SETTINGS frame with a SETTINGS_MAX_FRAME_SIZE lower than 16384.
-	ok = gen_tcp:send(Socket, << 6:24, 4:8, 0:40, 5:16, 16383:32 >>),
-	%% Receive a PROTOCOL_ERROR connection error.
-	{ok, << _:24, 7:8, _:72, 1:32 >>} = gen_tcp:recv(Socket, 17, 6000),
+	%% Send a HEADERS frame initiating a stream followed by
+	%% a single 30000 bytes DATA frame.
+	Headers = [
+		{<<":method">>, <<"POST">>},
+		{<<":scheme">>, <<"http">>},
+		{<<":authority">>, <<"localhost">>}, %% @todo Correct port number.
+		{<<":path">>, <<"/long_polling">>}
+	],
+	{HeadersBlock, _} = cow_hpack:encode(Headers),
+	ok = gen_tcp:send(Socket, [
+		cow_http2:headers(1, nofin, HeadersBlock),
+		cow_http2:data(1, fin, <<0:30000/unit:8>>)
+	]),
+	%% Receive a proper response.
+	{ok, << Len2:24, 1:8, _:40 >>} = gen_tcp:recv(Socket, 9, 6000),
+	{ok, _} = gen_tcp:recv(Socket, Len2, 6000),
+	%% No errors follow due to our sending of a 25000 bytes frame.
+	{error, timeout} = gen_tcp:recv(Socket, 0, 1000),
 	ok.
 
-%% This is about the client sending a SETTINGS frame.
-max_frame_size_client_override_reject_too_large(Config) ->
-	doc("A SETTINGS_MAX_FRAME_SIZE larger than 16777215 must be rejected "
-		"with a PROTOCOL_ERROR connection error. (RFC7540 6.5.2)"),
+max_frame_size_reject_larger_than_custom(Config0) ->
+	doc("An endpoint that sets SETTINGS_MAX_FRAME_SIZE must reject frames "
+		"of up to that size with a FRAME_SIZE_ERROR connection error. (RFC7540 4.2, RFC7540 6.5.2)"),
+	%% Create a new listener that sets the maximum frame size to 30000.
+	Config = cowboy_test:init_http(name(), #{
+		env => #{dispatch => cowboy_router:compile(init_routes(Config0))},
+		max_frame_size_received => 30000
+	}, Config0),
+	%% Do the handshake.
 	{ok, Socket} = do_handshake(Config),
-	%% Send a SETTINGS frame with a SETTINGS_MAX_FRAME_SIZE larger than 16777215.
-	ok = gen_tcp:send(Socket, << 6:24, 4:8, 0:40, 5:16, 16777216:32 >>),
-	%% Receive a PROTOCOL_ERROR connection error.
-	{ok, << _:24, 7:8, _:72, 1:32 >>} = gen_tcp:recv(Socket, 17, 6000),
+	%% Send a HEADERS frame initiating a stream followed by
+	%% a single DATA frame larger than 30000 bytes.
+	Headers = [
+		{<<":method">>, <<"POST">>},
+		{<<":scheme">>, <<"http">>},
+		{<<":authority">>, <<"localhost">>}, %% @todo Correct port number.
+		{<<":path">>, <<"/long_polling">>}
+	],
+	{HeadersBlock, _} = cow_hpack:encode(Headers),
+	ok = gen_tcp:send(Socket, [
+		cow_http2:headers(1, nofin, HeadersBlock),
+		cow_http2:data(1, fin, <<0:30001/unit:8>>)
+	]),
+	%% Receive a FRAME_SIZE_ERROR connection error.
+	{ok, << _:24, 7:8, _:72, 6:32 >>} = gen_tcp:recv(Socket, 17, 6000),
 	ok.
 
-%% @todo How do I test this?
-%%
-%%	max_frame_size_client_custom_respect_limits(Config) ->
-%%		doc("The server must not send frame sizes of more than "
-%%			"client's advertised limits. (RFC7540 4.1, RFC7540 4.2)"),
-
 %% I am using FRAME_SIZE_ERROR here because the information in the
 %% frame header tells us this frame is at least 1 byte long, while
 %% the given length is smaller; i.e. it is too small to contain
@@ -2422,7 +2420,7 @@ continuation_with_extension_frame_interleaved_error(Config) ->
 %   incomplete SETTINGS frame MUST be treated as a connection error
 %   (Section 5.4.1) of type PROTOCOL_ERROR.
 
-%% (RFC7540 6.5.2)
+%% Settings.
 
 settings_header_table_size_client(Config) ->
 	doc("The SETTINGS_HEADER_TABLE_SIZE setting can be used to "
@@ -2581,7 +2579,7 @@ settings_max_concurrent_streams_0(Config0) ->
 settings_initial_window_size(Config0) ->
 	doc("The SETTINGS_INITIAL_WINDOW_SIZE setting can be used to "
 		"change the initial window size of streams. (RFC7540 6.5.2)"),
-	%% Create a new listener that allows only a single concurrent stream.
+	%% Create a new listener that sets initial window sizes to 100000.
 	Config = cowboy_test:init_http(name(), #{
 		env => #{dispatch => cowboy_router:compile(init_routes(Config0))},
 		initial_connection_window_size => 100000,
@@ -2630,7 +2628,7 @@ settings_initial_window_size_after_ack(Config0) ->
 	doc("The SETTINGS_INITIAL_WINDOW_SIZE setting can be used to "
 		"change the initial window size of streams. It is applied "
 		"to all existing streams upon receipt of the SETTINGS ack. (RFC7540 6.5.2)"),
-	%% Create a new listener that allows only a single concurrent stream.
+	%% Create a new listener that sets the initial stream window sizes to 0.
 	Config = cowboy_test:init_http(name(), #{
 		env => #{dispatch => cowboy_router:compile(init_routes(Config0))},
 		initial_stream_window_size => 0
@@ -2670,7 +2668,7 @@ settings_initial_window_size_before_ack(Config0) ->
 	doc("The SETTINGS_INITIAL_WINDOW_SIZE setting can be used to "
 		"change the initial window size of streams. It is only "
 		"applied upon receipt of the SETTINGS ack. (RFC7540 6.5.2)"),
-	%% Create a new listener that allows only a single concurrent stream.
+	%% Create a new listener that sets the initial stream window sizes to 0.
 	Config = cowboy_test:init_http(name(), #{
 		env => #{dispatch => cowboy_router:compile(init_routes(Config0))},
 		initial_stream_window_size => 0
@@ -2711,13 +2709,56 @@ settings_initial_window_size_before_ack(Config0) ->
 	{error, timeout} = gen_tcp:recv(Socket, 0, 1000),
 	ok.
 
-%   SETTINGS_MAX_FRAME_SIZE (0x5):
-%      The initial value is 2^14 (16,384) octets.  The value advertised
-%      by an endpoint MUST be between this initial value and the maximum
-%      allowed frame size (2^24-1 or 16,777,215 octets), inclusive.
-%      Values outside this range MUST be treated as a connection error
-%      (Section 5.4.1) of type PROTOCOL_ERROR.
-%
+settings_max_frame_size(Config0) ->
+	doc("The SETTINGS_MAX_FRAME_SIZE setting can be used to "
+		"change the maximum frame size allowed. (RFC7540 6.5.2)"),
+	%% Create a new listener that sets the maximum frame size to 30000.
+	Config = cowboy_test:init_http(name(), #{
+		env => #{dispatch => cowboy_router:compile(init_routes(Config0))},
+		max_frame_size_received => 30000
+	}, Config0),
+	%% Do the handshake.
+	{ok, Socket} = do_handshake(Config),
+	%% Send a HEADERS frame initiating a stream followed by
+	%% a single 25000 bytes DATA frame.
+	Headers = [
+		{<<":method">>, <<"POST">>},
+		{<<":scheme">>, <<"http">>},
+		{<<":authority">>, <<"localhost">>}, %% @todo Correct port number.
+		{<<":path">>, <<"/long_polling">>}
+	],
+	{HeadersBlock, _} = cow_hpack:encode(Headers),
+	ok = gen_tcp:send(Socket, [
+		cow_http2:headers(1, nofin, HeadersBlock),
+		cow_http2:data(1, fin, <<0:25000/unit:8>>)
+	]),
+	%% Receive a proper response.
+	{ok, << Len2:24, 1:8, _:40 >>} = gen_tcp:recv(Socket, 9, 6000),
+	{ok, _} = gen_tcp:recv(Socket, Len2, 6000),
+	%% No errors follow due to our sending of a 25000 bytes frame.
+	{error, timeout} = gen_tcp:recv(Socket, 0, 1000),
+	ok.
+
+settings_max_frame_size_reject_too_small(Config) ->
+	doc("A SETTINGS_MAX_FRAME_SIZE smaller than 16384 must be rejected "
+		"with a PROTOCOL_ERROR connection error. (RFC7540 6.5.2)"),
+	{ok, Socket} = do_handshake(Config),
+	%% Send a SETTINGS frame with a SETTINGS_MAX_FRAME_SIZE lower than 16384.
+	ok = gen_tcp:send(Socket, << 6:24, 4:8, 0:40, 5:16, 16383:32 >>),
+	%% Receive a PROTOCOL_ERROR connection error.
+	{ok, << _:24, 7:8, _:72, 1:32 >>} = gen_tcp:recv(Socket, 17, 6000),
+	ok.
+
+settings_max_frame_size_reject_too_large(Config) ->
+	doc("A SETTINGS_MAX_FRAME_SIZE larger than 16777215 must be rejected "
+		"with a PROTOCOL_ERROR connection error. (RFC7540 6.5.2)"),
+	{ok, Socket} = do_handshake(Config),
+	%% Send a SETTINGS frame with a SETTINGS_MAX_FRAME_SIZE larger than 16777215.
+	ok = gen_tcp:send(Socket, << 6:24, 4:8, 0:40, 5:16, 16777216:32 >>),
+	%% Receive a PROTOCOL_ERROR connection error.
+	{ok, << _:24, 7:8, _:72, 1:32 >>} = gen_tcp:recv(Socket, 17, 6000),
+	ok.
+
 %   SETTINGS_MAX_HEADER_LIST_SIZE (0x6):  This advisory setting informs a
 %      peer of the maximum size of header list that the sender is
 %      prepared to accept, in octets.  The value is based on the