fix(http2): avoid buffering Upgraded writes without send capacity#4102
Open
seanmonstar wants to merge 3 commits into
Open
fix(http2): avoid buffering Upgraded writes without send capacity#4102seanmonstar wants to merge 3 commits into
Upgraded writes without send capacity#4102seanmonstar wants to merge 3 commits into
Conversation
seanmonstar
force-pushed
the
sean/lsnkptrokswk
branch
from
78cea2f to
d57b9a9
Compare
…adedSendStreamTask Fix a backpressure bypass bug in UpgradedSendStreamTask::tick() where poll_capacity() returning Poll::Pending caused a 'break 'capacity' that fell through to rx.poll_next() -> send_data(), pushing data into the h2 send buffer without available capacity. This broke the HTTP/2 flow control chain, causing unbounded memory growth (OOM) when downstream consumers were slower than upstream producers. The fix changes 'break 'capacity' to 'return Poll::Pending', which correctly suspends the task until a WINDOW_UPDATE frame restores send capacity. The now-unused 'capacity label is also removed. This bug was introduced in hyper v1.8.0 (PR #3967) and affects v1.8.0, v1.8.1, and v1.9.0. A single HTTP/2 CONNECT tunnel with asymmetric upstream/downstream speeds could trigger OOM within seconds. Add four integration tests covering H2 CONNECT backpressure scenarios: - h2_connect_backpressure_respected: small window + large data transfer - h2_connect_zero_window_then_release: normal path regression guard - h2_connect_reset_during_backpressure: RST_STREAM error propagation - h2_connect_backpressure_bidirectional: bidirectional data + backpressure
When poll_capacity returns Pending, defer the return and check poll_reset first. This ensures the reset waker is registered via poll_reset (which shares the same send_task slot in h2 internally), enabling earlier RST_STREAM detection without an extra poll round-trip. While h2 internally calls notify_send() on RST_STREAM/EOF/error (so poll_capacity's waker alone would eventually be woken), polling poll_reset here provides immediate detection if RST_STREAM has already arrived, avoiding one unnecessary suspend/wake cycle. The h2_has_capacity flag cleanly separates the capacity check from the control flow, making the manual select-over-3-futures pattern more readable.
seanmonstar
force-pushed
the
sean/lsnkptrokswk
branch
from
d57b9a9 to
650bfac
Compare
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This continues #4050, with changes based on the feedback I left on the PR.