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http2: fix endless loop when writing empty string #18924

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http2: fix endless loop when writing empty string #18924

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9b72053
http2: fix endless loop when writing empty string
addaleax Feb 22, 2018
74f489c
test: check endless loop while writing empty string
XadillaX Feb 11, 2018
b702ba3
[squash] extend test case
addaleax Feb 22, 2018
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http2: fix endless loop when writing empty string 
Refs: #18673
Fixes: #18169
Refs: https://github.com/nodejs/node/blob/v9.5.0/src/node_http2.cc#L1481-L1484
Refs: https://github.com/nodejs/node/blob/v9.5.0/lib/_http_outgoing.js#L659-L661
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@addaleax
addaleax committed Feb 22, 2018
commit 9b72053f633ce90cf32916b8c577315cd57e2dc5
14 changes: 13 additions & 1 deletion src/node_http2.cc
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Expand Up @@ -2184,6 +2184,17 @@ ssize_t Http2Stream::Provider::Stream::OnRead(nghttp2_session* handle,

size_t amount = 0; // amount of data being sent in this data frame.

// Remove all empty chunks from the head of the queue.
// This is done here so that .write('', cb) is still a meaningful way to
// find out when the HTTP2 stream wants to consume data, and because the
// StreamBase API allows empty input chunks.
while (!stream->queue_.empty() && stream->queue_.front().buf.len == 0) {
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@XadillaX XadillaX Feb 24, 2018

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One question, if we remove the empty buffer and do nothing, will the header be sent?

Refs: https://github.com/nodejs/node/pull/18673/files#diff-696b2cc418addca5f3fe5020058f8b15R1622

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@addaleax addaleax Feb 24, 2018

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@XadillaX Hm – I’m not sure I can wrap my head around everything, but this code here is only ever called by nghttp2 after the headers were sent anyway… does that answer your question?

So, yes, writing an empty buffer would trigger the headers to be sent, as I understand it.

WriteWrap* finished = stream->queue_.front().req_wrap;
stream->queue_.pop();
if (finished != nullptr)
finished->Done(0);
}

if (!stream->queue_.empty()) {
DEBUG_HTTP2SESSION2(session, "stream %d has pending outbound data", id);
amount = std::min(stream->available_outbound_length_, length);
Expand All @@ -2197,7 +2208,8 @@ ssize_t Http2Stream::Provider::Stream::OnRead(nghttp2_session* handle,
}
}

if (amount == 0 && stream->IsWritable() && stream->queue_.empty()) {
if (amount == 0 && stream->IsWritable()) {
CHECK(stream->queue_.empty());
DEBUG_HTTP2SESSION2(session, "deferring stream %d", id);
return NGHTTP2_ERR_DEFERRED;
}
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