[WS] Fix wslay multi-frame message parsing (again) #102128
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We incorrectly assumed that the `payload_length` in the recv start callback of wslay was the final message size, but according to the WebSocket protocol, the payload length always refers to the current frame's payload size. The protocol, in fact, do not include a "message payload" length on purpose to allow sending messages of unknown size without forcing the sender to buffer the whole message (RFC6455 Section 5.4). This means a receiving peer has no way to know beforehand how long a message will be, and needs instead to keep track of the length of each frame until the FIN one is received to properly reconstruct the message at the end.
akien-mga
approved these changes
Jan 30, 2025
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Thanks! |
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I belatedly noticed this issue in beta2, and can confirm that this PR fixes it for me :-) |
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We incorrectly assumed that the
payload_lengthin the recv start callback of wslay was the final message size, but according to the WebSocket protocol, the payload length always refers to the current frame's payload size.The protocol, in fact, do not include a "message payload" length on purpose to allow sending messages of unknown size without forcing the sender to buffer the whole message (RFC6455 Section 5.4).
This means a receiving peer has no way to know beforehand how long a message will be, and needs instead to keep track of the length of each frame until the FIN one is received to properly reconstruct the message at the end.
Fixes #101811 .
Closes #102038 .