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Add the max_concurrent_streams h2 option

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Loïc Hoguin 2018-04-25 21:32:58 +02:00
parent 8bd55941aa
commit 7373822b86
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4 changed files with 104 additions and 46 deletions
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8
doc/src/manual/cowboy_http2.asciidoc
View file

@ -21,6 +21,7 @@ opts() :: #{
enable_connect_protocol => boolean(),
env => cowboy_middleware:env(),
inactivity_timeout => timeout(),
max_concurrent_streams => non_neg_integer() | infinity,
max_decode_table_size => non_neg_integer(),
max_encode_table_size => non_neg_integer(),
middlewares => [module()],
@ -55,6 +56,9 @@ env (#{})::
inactivity_timeout (300000)::
Time in ms with nothing received at all before Cowboy closes the connection.
max_concurrent_streams (infinity)::
Maximum number of concurrent streams allowed on the connection.
max_decode_table_size (4096)::
Maximum header table size used by the decoder. This is the value advertised
to the client. The client can then choose a header table size equal or lower
@ -79,7 +83,9 @@ stream_handlers ([cowboy_stream_h])::
== Changelog
* *2.4*: Add the options `max_decode_table_size` and `max_encode_table_size`.
* *2.4*: Add the options `max_concurrent_streams`,
`max_decode_table_size` and `max_encode_table_size`
to configure HTTP/2 SETTINGS.
* *2.4*: Add the experimental option `enable_connect_protocol`.
* *2.0*: Protocol introduced.

23
src/cowboy_http2.erl
View file

@ -27,6 +27,7 @@
enable_connect_protocol => boolean(),
env => cowboy_middleware:env(),
inactivity_timeout => timeout(),
max_concurrent_streams => non_neg_integer() | infinity,
max_decode_table_size => non_neg_integer(),
max_encode_table_size => non_neg_integer(),
middlewares => [module()],
@ -206,11 +207,12 @@ init(Parent, Ref, Socket, Transport, Opts, Peer, Sock, Cert, Buffer, _Settings,
settings_init(State, Opts) ->
S0 = setting_from_opt(#{}, Opts, max_decode_table_size,
header_table_size, 4096),
%% @todo max_concurrent_streams + enforce it
S1 = setting_from_opt(S0, Opts, max_concurrent_streams,
max_concurrent_streams, infinity),
%% @todo initial_window_size
%% @todo max_frame_size
%% @todo max_header_list_size
Settings = setting_from_opt(S0, Opts, enable_connect_protocol,
Settings = setting_from_opt(S1, Opts, enable_connect_protocol,
enable_connect_protocol, false),
State#state{next_settings=Settings}.
@ -868,13 +870,24 @@ terminate_all_streams([#stream{id=StreamID, state=StreamState}|Tail], Reason) ->
stream_decode_init(State=#state{decode_state=DecodeState0}, StreamID, IsFin, HeaderBlock) ->
try cow_hpack:decode(HeaderBlock, DecodeState0) of
{Headers, DecodeState} ->
stream_pseudo_headers_init(State#state{decode_state=DecodeState},
stream_enforce_concurrency_limit(State#state{decode_state=DecodeState},
StreamID, IsFin, Headers)
catch _:_ ->
terminate(State, {connection_error, compression_error,
'Error while trying to decode HPACK-encoded header block. (RFC7540 4.3)'})
end.
stream_enforce_concurrency_limit(State=#state{opts=Opts, streams=Streams},
StreamID, IsFin, Headers) ->
MaxConcurrentStreams = maps:get(max_concurrent_streams, Opts, infinity),
case length(Streams) < MaxConcurrentStreams of
true ->
stream_pseudo_headers_init(State, StreamID, IsFin, Headers);
false ->
stream_refused(State, StreamID,
'Maximum number of concurrent streams has been reached. (RFC7540 5.1.2)')
end.
stream_pseudo_headers_init(State=#state{local_settings=LocalSettings},
StreamID, IsFin, Headers0) ->
IsExtendedConnectEnabled = maps:get(enable_connect_protocol, LocalSettings, false),
@ -1045,6 +1058,10 @@ stream_malformed(State=#state{socket=Socket, transport=Transport}, StreamID, _)
Transport:send(Socket, cow_http2:rst_stream(StreamID, protocol_error)),
State.
stream_refused(State=#state{socket=Socket, transport=Transport}, StreamID, _) ->
Transport:send(Socket, cow_http2:rst_stream(StreamID, refused_stream)),
State.
stream_early_error(State0=#state{ref=Ref, opts=Opts, peer=Peer,
local_settings=#{initial_window_size := RemoteWindow},
remote_settings=#{initial_window_size := LocalWindow},

3
test/h2spec_SUITE.erl
View file

@ -30,7 +30,8 @@ init_per_suite(Config) ->
skip;
_ ->
cowboy_test:init_http2(h2spec, #{
env => #{dispatch => init_dispatch()}
env => #{dispatch => init_dispatch()},
max_concurrent_streams => 100
}, Config)
end.

116
test/rfc7540_SUITE.erl
View file

@ -49,6 +49,7 @@ init_routes(_) -> [
{"localhost", [
{"/", hello_h, []},
{"/echo/:key", echo_h, []},
{"/long_polling", long_polling_h, []},
{"/resp/:key[/:arg]", resp_h, []}
]}
].
@ -2263,34 +2264,6 @@ reject_streamid_lower(Config) ->
% frame so that the client is forced to open a new connection for new
% streams.
%% @todo We need this option too. (RFC7540 5.1.2)
% A peer can limit the number of concurrently active streams using the
% SETTINGS_MAX_CONCURRENT_STREAMS parameter (see Section 6.5.2) within
% a SETTINGS frame. The maximum concurrent streams setting is specific
% to each endpoint and applies only to the peer that receives the
% setting. That is, clients specify the maximum number of concurrent
% streams the server can initiate, and servers specify the maximum
% number of concurrent streams the client can initiate.
%
% Streams that are in the "open" state or in either of the "half-
% closed" states count toward the maximum number of streams that an
% endpoint is permitted to open. Streams in any of these three states
% count toward the limit advertised in the
% SETTINGS_MAX_CONCURRENT_STREAMS setting. Streams in either of the
% "reserved" states do not count toward the stream limit.
%
% Endpoints MUST NOT exceed the limit set by their peer. An endpoint
% that receives a HEADERS frame that causes its advertised concurrent
% stream limit to be exceeded MUST treat this as a stream error
% (Section 5.4.2) of type PROTOCOL_ERROR or REFUSED_STREAM. The choice
% of error code determines whether the endpoint wishes to enable
% automatic retry (see Section 8.1.4) for details).
%
% An endpoint that wishes to reduce the value of
% SETTINGS_MAX_CONCURRENT_STREAMS to a value that is below the current
% number of open streams can either close streams that exceed the new
% value or allow streams to complete.
%% (RFC7540 5.2.1)
% 3. Flow control is directional with overall control provided by the
% receiver. A receiver MAY choose to set any window size that it
@ -2539,21 +2512,72 @@ settings_header_table_size_server(Config0) ->
% 0. An endpoint that has both set this parameter to 0 and had it
% acknowledged MUST treat the receipt of a PUSH_PROMISE frame as a
% connection error (Section 5.4.1) of type PROTOCOL_ERROR.
%% @todo settings_disable_push
settings_max_concurrent_streams(Config0) ->
doc("The SETTINGS_MAX_CONCURRENT_STREAMS setting can be used to "
"restrict the number of concurrent streams. (RFC7540 5.1.2, RFC7540 6.5.2)"),
%% Create a new listener that allows only a single concurrent stream.
Config = cowboy_test:init_http(name(), #{
env => #{dispatch => cowboy_router:compile(init_routes(Config0))},
max_concurrent_streams => 1
}, Config0),
{ok, Socket} = do_handshake(Config),
%% Send two HEADERS frames as two separate streams.
Headers = [
{<<":method">>, <<"GET">>},
{<<":scheme">>, <<"http">>},
{<<":authority">>, <<"localhost">>}, %% @todo Correct port number.
{<<":path">>, <<"/long_polling">>}
],
{ReqHeadersBlock1, EncodeState} = cow_hpack:encode(Headers),
{ReqHeadersBlock2, _} = cow_hpack:encode(Headers, EncodeState),
ok = gen_tcp:send(Socket, [
cow_http2:headers(1, fin, ReqHeadersBlock1),
cow_http2:headers(3, fin, ReqHeadersBlock2)
]),
%% Receive a REFUSED_STREAM stream error.
{ok, << _:24, 3:8, _:8, 3:32, 7:32 >>} = gen_tcp:recv(Socket, 13, 6000),
ok.
settings_max_concurrent_streams_0(Config0) ->
doc("The SETTINGS_MAX_CONCURRENT_STREAMS setting can be set to "
"0 to refuse all incoming streams. (RFC7540 5.1.2, RFC7540 6.5.2)"),
%% Create a new listener that allows only a single concurrent stream.
Config = cowboy_test:init_http(name(), #{
env => #{dispatch => cowboy_router:compile(init_routes(Config0))},
max_concurrent_streams => 0
}, Config0),
{ok, Socket} = do_handshake(Config),
%% Send a HEADERS frame.
{HeadersBlock, _} = cow_hpack:encode([
{<<":method">>, <<"GET">>},
{<<":scheme">>, <<"http">>},
{<<":authority">>, <<"localhost">>}, %% @todo Correct port number.
{<<":path">>, <<"/long_polling">>}
]),
ok = gen_tcp:send(Socket, cow_http2:headers(1, fin, HeadersBlock)),
%% Receive a REFUSED_STREAM stream error.
{ok, << _:24, 3:8, _:8, 1:32, 7:32 >>} = gen_tcp:recv(Socket, 13, 6000),
ok.
%% @todo The client can limit the number of concurrent streams too. (RFC7540 5.1.2)
%
% SETTINGS_MAX_CONCURRENT_STREAMS (0x3): Indicates the maximum number
% of concurrent streams that the sender will allow. This limit is
% directional: it applies to the number of streams that the sender
% permits the receiver to create. Initially, there is no limit to
% this value. It is recommended that this value be no smaller than
% 100, so as to not unnecessarily limit parallelism.
%
% A value of 0 for SETTINGS_MAX_CONCURRENT_STREAMS SHOULD NOT be
% treated as special by endpoints. A zero value does prevent the
% creation of new streams; however, this can also happen for any
% limit that is exhausted with active streams. Servers SHOULD only
% set a zero value for short durations; if a server does not wish to
% accept requests, closing the connection is more appropriate.
% A peer can limit the number of concurrently active streams using the
% SETTINGS_MAX_CONCURRENT_STREAMS parameter (see Section 6.5.2) within
% a SETTINGS frame. The maximum concurrent streams setting is specific
% to each endpoint and applies only to the peer that receives the
% setting. That is, clients specify the maximum number of concurrent
% streams the server can initiate, and servers specify the maximum
% number of concurrent streams the client can initiate.
%
% Endpoints MUST NOT exceed the limit set by their peer. An endpoint
% that receives a HEADERS frame that causes its advertised concurrent
% stream limit to be exceeded MUST treat this as a stream error
% (Section 5.4.2) of type PROTOCOL_ERROR or REFUSED_STREAM. The choice
% of error code determines whether the endpoint wishes to enable
% automatic retry (see Section 8.1.4) for details).
% SETTINGS_INITIAL_WINDOW_SIZE (0x4):
% Values above the maximum flow-control window size of 2^31-1 MUST
% be treated as a connection error (Section 5.4.1) of type
@ -2566,6 +2590,16 @@ settings_header_table_size_server(Config0) ->
% Values outside this range MUST be treated as a connection error
% (Section 5.4.1) of type PROTOCOL_ERROR.
%
% 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
% uncompressed size of header fields, including the length of the
% name and value in octets plus an overhead of 32 octets for each
% header field.
%
% For any given request, a lower limit than what is advertised MAY
% be enforced. The initial value of this setting is unlimited.
%
% An endpoint that receives a SETTINGS frame with any unknown or
% unsupported identifier MUST ignore that setting. (6.5.2 and 6.5.3)