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http2: strictly limit number on concurrent streams
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Strictly limit the number of concurrent streams based on the
current setting of the MAX_CONCURRENT_STREAMS setting

Backport-PR-URL: #18050
Backport-PR-URL: #20456
PR-URL: #16766
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Anatoli Papirovski <[email protected]>
Reviewed-By: Sebastiaan Deckers <[email protected]>
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jasnell authored and MylesBorins committed May 2, 2018
1 parent 9a4bac2 commit c915bc5
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Showing 3 changed files with 80 additions and 1 deletion.
19 changes: 18 additions & 1 deletion src/node_http2.cc
Original file line number Diff line number Diff line change
Expand Up @@ -656,6 +656,16 @@ inline Http2Stream* Http2Session::FindStream(int32_t id) {
return s != streams_.end() ? s->second : nullptr;
}

inline bool Http2Session::CanAddStream() {
uint32_t maxConcurrentStreams =
nghttp2_session_get_local_settings(
session_, NGHTTP2_SETTINGS_MAX_CONCURRENT_STREAMS);
size_t maxSize =
std::min(streams_.max_size(), static_cast<size_t>(maxConcurrentStreams));
// We can add a new stream so long as we are less than the current
// maximum on concurrent streams
return streams_.size() < maxSize;
}

inline void Http2Session::AddStream(Http2Stream* stream) {
CHECK_GE(++statistics_.stream_count, 0);
Expand Down Expand Up @@ -766,7 +776,14 @@ inline int Http2Session::OnBeginHeadersCallback(nghttp2_session* handle,

Http2Stream* stream = session->FindStream(id);
if (stream == nullptr) {
new Http2Stream(session, id, frame->headers.cat);
if (session->CanAddStream()) {
new Http2Stream(session, id, frame->headers.cat);
} else {
// Too many concurrent streams being opened
nghttp2_submit_rst_stream(**session, NGHTTP2_FLAG_NONE, id,
NGHTTP2_ENHANCE_YOUR_CALM);
return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
}
} else {
// If the stream has already been destroyed, ignore.
if (stream->IsDestroyed())
Expand Down
2 changes: 2 additions & 0 deletions src/node_http2.h
Original file line number Diff line number Diff line change
Expand Up @@ -835,6 +835,8 @@ class Http2Session : public AsyncWrap {
// Returns pointer to the stream, or nullptr if stream does not exist
inline Http2Stream* FindStream(int32_t id);

inline bool CanAddStream();

// Adds a stream instance to this session
inline void AddStream(Http2Stream* stream);

Expand Down
60 changes: 60 additions & 0 deletions test/parallel/test-http2-too-many-streams.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,60 @@
'use strict';

const common = require('../common');
if (!common.hasCrypto)
common.skip('missing crypto');

const Countdown = require('../common/countdown');
const http2 = require('http2');
const assert = require('assert');

// Test that the maxConcurrentStreams setting is strictly enforced

const server = http2.createServer({ settings: { maxConcurrentStreams: 1 } });

let c = 0;

server.on('stream', common.mustCall((stream) => {
// Because we only allow one open stream at a time,
// c should never be greater than 1.
assert.strictEqual(++c, 1);
stream.respond();
// Force some asynchronos stuff.
setImmediate(() => {
stream.end('ok');
assert.strictEqual(--c, 0);
});
}, 3));

server.listen(0, common.mustCall(() => {
const client = http2.connect(`http://localhost:${server.address().port}`);

const countdown = new Countdown(3, common.mustCall(() => {
server.close();
client.destroy();
}));

client.on('remoteSettings', common.mustCall(() => {
assert.strictEqual(client.remoteSettings.maxConcurrentStreams, 1);

{
const req = client.request();
req.resume();
req.on('close', () => {
countdown.dec();

setImmediate(() => {
const req = client.request();
req.resume();
req.on('close', () => countdown.dec());
});
});
}

{
const req = client.request();
req.resume();
req.on('close', () => countdown.dec());
}
}));
}));

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