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On STOP_SENDING reception, an error is notified to the stream layer as no more data can be responded. However, this is not done if the stream instance is not allocated (already freed for example). The issue occurs if STOP_SENDING is received and the stream instance is instantiated after it. It happens if a STREAM frame is received after it with H3 HEADERS, which is valid in QUIC protocol due to UDP packet reordering. In this case, stream layer is never notified about the underlying error. Instead, reponse buffers are silently purged by the MUX in qmux_strm_snd_buf(). This is suboptimal as there is no point in exchanging data from the server if it cannot be eventually transferred back to the client. However, aside from this consideration, no other issue occured. However, this is not the case with QUIC mux-to-mux implementation. Now, if mux-to-mux is used, qmux_strm_snd_buf() is bypassed and response if transferred via nego_ff/done_ff callbacks. However, these functions did not checked if QCS is already locally closed. This causes a crash when qcc_send_stream() is called via done_ff. To fix this crash, there is several approach, one of them would be to adjust nego_ff/done_ff QUIC callbacks. However, another method has been chosen. Now stream layer is flagged on error just after its instantiation if the stream is already locally closed. This ensures that mux-to-mux won't try to emit data as se_nego_ff() check if the opposide SD is not on error before continuing. Note that an alternative solution could be to not instantiate at all stream layer if QCS is already locally closed. This is the most optimal solution as it reduce unnecessary allocations and task processing. However, it's not easy to implement so the easier bug fix has been chosen for the moment. This patch is labelled as MEDIUM as it can change behavior of all QCS instances, wheter mux-to-mux is used or not, and thus could reveal other architecture issues. This should fix latest crash occurence on github issue #2392. It should be backported up to 2.6, until a necessary period of observation. |
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The HAProxy documentation has been split into a number of different files for ease of use. Please refer to the following files depending on what you're looking for : - INSTALL for instructions on how to build and install HAProxy - BRANCHES to understand the project's life cycle and what version to use - LICENSE for the project's license - CONTRIBUTING for the process to follow to submit contributions The more detailed documentation is located into the doc/ directory : - doc/intro.txt for a quick introduction on HAProxy - doc/configuration.txt for the configuration's reference manual - doc/lua.txt for the Lua's reference manual - doc/SPOE.txt for how to use the SPOE engine - doc/network-namespaces.txt for how to use network namespaces under Linux - doc/management.txt for the management guide - doc/regression-testing.txt for how to use the regression testing suite - doc/peers.txt for the peers protocol reference - doc/coding-style.txt for how to adopt HAProxy's coding style - doc/internals for developer-specific documentation (not all up to date)