[TCP] Implement Zero window probe#35
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- Fixed bug in smooth average RTT calculation - Actually assign calculated RTO value (previously fixed to 1s) - Enforce min/max RTO according to RFC - Enforce Karn to only account for new ACK in RTO calculation
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Pull request overview
This PR extends wolfIP’s TCP behavior to better handle stalled connections by adding a zero-window persist/probe mechanism, while also introducing related TCP RTO/control-RTO updates and accompanying unit tests.
Changes:
- Add TCP persist timer logic and a 1-byte “zero window probe” send path when the peer advertises a zero receive window.
- Add/adjust TCP RTO tracking (SRTT/RTTVAR, Karn handling via
PKT_FLAG_WAS_RETRANS) and implement control-segment (SYN/FIN) retransmission timing with retry caps. - Expand unit tests to cover new RTO/control-RTO behaviors and basic persist/probe behavior; update README TCP feature list.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.
| File | Description |
|---|---|
src/wolfip.c |
Implements persist/probe logic, RFC6298-style RTO updates, Karn handling, and control-segment RTO retries. |
src/test/unit/unit.c |
Adds/updates unit tests for control-RTO, RTO math, Karn skip-on-retrans, and persist/probe basics. |
README.md |
Documents TCP RTO computation support in the feature matrix. |
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danielinux
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Feb 20, 2026
Fix: probe_seq may be set to snd_una when snd_una falls within an existing queued segment
danielinux
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Feb 20, 2026
Proper clean-up on close: Manage ACK in TCP_LAST_ACK state.
danielinux
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Closing in favor of #36 |
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Based on previous PR #34