litespeedtech / litespeedtech/lsquic
ECN mirroring can differ between mini_conn and full_conn
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Description
Hi,
we analyzed whether ECN with QUIC can be used in the wild [1] and found that some LiteSpeed Server instances first mirror ECN counters but then stop to do so leading to failed ECN validation. The behavior can also be seen in the interop runner between, e.g., picoquic and lsquic [2].
We found that the mini_conn part of lsquic always sends ECN counters in ACKs while the full_conn follows the "Enable ECN support" flag and can thus stop mirroring ECN.
Is this behavior intended?
Best,
Constantin
[1] https://arxiv.org/abs/2309.14273
[2] https://interop.seemann.io/logs/2023-10-19T00:02/lsquic_picoquic/http3/client/test_log.txt
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Research direction
Start by comparing ECN counter handling in the mini_conn and full_conn paths, then reproduce the mismatch through the interop runner using the linked picoquic and lsquic test log. Done means determining whether both paths should mirror ECN counters consistently and preventing the observed ECN validation failure.
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Assessment
- Tech stack
- c
- Domain
- networking
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100