fix: remove padded_len() u8 overflow in DATA frame padding release#914
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padded_len() returned Option<u8> and computed pad_len + 1 to account for the pad length field byte. When pad_len=255 (the maximum per RFC 7540 Section 6.1), 255u8 + 1 overflows to 0, causing the auto-release in recv_data() to release 0 bytes instead of 256. This leaks 256 bytes of flow control capacity per frame for both the stream and connection windows. Remove padded_len() entirely (it had a single call site) and compute padding overhead inline as flow_controlled_len() - payload().len(), which does not rely on details of the payload construction at all, making it more robust, and uses usize arithmetic and cannot overflow.
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padded_len() returned Option and computed pad_len + 1 to account for the pad length field byte. When pad_len=255 (the maximum per RFC 7540 Section 6.1), 255u8 + 1 overflows to 0, causing the auto-release in recv_data() to release 0 bytes instead of 256. This leaks 256 bytes of flow control capacity per frame for both the stream and connection windows.
Remove padded_len() entirely (it had a single call site) and compute padding overhead inline as flow_controlled_len() - payload().len(), which does not rely on details of the payload construction at all, making it more robust, and uses usize arithmetic and cannot overflow.
(Just required formatting to merge from previous PR)
Closes #908