feat: add ResetRTO API for immediate recovery#344
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Implement `ResetRTO` at both the `KCP` and `UDPSession` levels to reset retransmission timers for all unacknowledged segments. When network connectivity is restored after an interruption, existing retransmission timers might have exponentially backed off, causing unnecessary delays. This feature allows the application layer to hint the underlying session to reset the RTO and schedule retransmissions immediately. By design, `UDPSession.ResetRTO()` avoids a synchronous `flush` to prevent immediate I/O bursts and minimize lock contention. The actual retransmissions are naturally picked up by the background `update()` tick, governed by the configured `interval` (e.g., 10ms-100ms via SetNoDelay), providing a smooth and predictable recovery.
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Changed the module path directly instead of using a replace directive, as `go install` does not support `go mod replace`. This ensures downstream users can install and build the binary properly via `go install`. We will consider switching back to the upstream repository if the maintainer merges the PR (kcp-go#344) in the future.
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Fixes #343.
Introduces
ResetRTO()to help applications quickly resume data delivery once they detect that network connectivity has been restored.This is highly beneficial in mobile or volatile network environments. When the application detects link restoration (e.g., cellular to Wi-Fi handover) via out-of-band signals, it can use this API to resume data delivery immediately without waiting for long penalizing RTO timers to expire.