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Fix Lightway#203 DTLS13 retransmission issue #323

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kp-mariappan-ramasamy merged 3 commits into from
Jan 20, 2026
Merged

Fix Lightway#203 DTLS13 retransmission issue #323

kp-mariappan-ramasamy merged 3 commits into from
Jan 20, 2026
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@kp-mariappan-ramasamy kp-mariappan-ramasamy commented Jan 7, 2026 •
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Fix for expressvpn/lightway#203

Wolfssl DTLS restricts retransmission within 1 sec which break our logic to scale the timer by 1/10.

This patch fixes it, by allowing wolfssl to take the timer value in milli seconds

From this PR:
https://github.com/wolfSSL/wolfssl/pull/9623/changes

@kp-mariappan-ramasamy kp-mariappan-ramasamy requested a review from a team as a code owner January 7, 2026 12:00
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github-actions bot commented Jan 7, 2026 •
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Code coverage summary for 2c93868:

Filename                             Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
wolfssl-sys/src/lib.rs                    25                 0   100.00%           2                 0   100.00%          13                 0   100.00%           0                 0         -
wolfssl/src/aes256.rs                    166                 8    95.18%          11                 0   100.00%         124                 4    96.77%           0                 0         -
wolfssl/src/chacha20_poly1305.rs          75                 2    97.33%           5                 0   100.00%          66                 2    96.97%           0                 0         -
wolfssl/src/context.rs                   401               173    56.86%          41                14    65.85%         286               110    61.54%           0                 0         -
wolfssl/src/error.rs                      45                13    71.11%           5                 1    80.00%          44                11    75.00%           0                 0         -
wolfssl/src/lib.rs                        81                15    81.48%          11                 1    90.91%          72                13    81.94%           0                 0         -
wolfssl/src/rng.rs                        72                10    86.11%           6                 0   100.00%          42                 3    92.86%           0                 0         -
wolfssl/src/ssl.rs                      1285               376    70.74%          84                25    70.24%         837               250    70.13%           0                 0         -
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                                   2150               597    72.23%         165                41    75.15%        1484               393    73.52%           0                 0         -

✅ Region coverage 72% passes
✅ Line coverage 73% passes

@kp-mariappan-ramasamy
wolfssl-sys: fix dtls13-rtx-timer.patch for wolfssl 5.8.4
5cfdc44 
Adjust patch context and line numbers to match actual wolfssl 5.8.4 source:
- test_dtls.c: File ends at line 2259, not 2489. Updated context to match
  test_dtls_memio_wolfio_stateless instead of test_dtls_mtu_split_messages
- test_dtls.h: Fixed function declaration order and line numbers
@kp-mariappan-ramasamy
wolfssl-sys: Set DTLS13_MIN_RTX_INTERVAL as 100 ms
c8fe800 
I ran three iterations of Lightway client and observe the packet
capture before and after the configuration:

BEFORE (1000ms RTX)

| Run | Intervals (ms)                 |
|-----|--------------------------------|
| 1   | 101 → 1403 → 1601 → 3200       |
| 2   | 100 → 202 → 1203 → 1602 → 3202 |
| 3   | 101 → 602 → 801 → 1602 → 3202  |

---
AFTER (100ms RTX)

| Run | Intervals (ms)                      |
|-----|-------------------------------------|
| 1   | 102 → 201 → 401 → 801 → 1602 → 3201 |
| 2   | 101 → 201 → 401 → 801 → 1601 → 3201 |
| 3   | 100 → 201 → 401 → 801 → 1601 → 3201 |

- Consistent exponential backoff: 100ms → 200ms → 400ms → 800ms → 1600ms → 3200ms
- All 3 runs show identical behavior

The retransmission timing now follows the expected exponential backoff
pattern consistently across all test runs.
@kp-mariappan-ramasamy kp-mariappan-ramasamy merged commit 32f5df7 into main Jan 20, 2026
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@kp-mariappan-ramasamy kp-mariappan-ramasamy deleted the fix-rtx branch January 20, 2026 04:33
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@kp-thomas-yau kp-thomas-yau kp-thomas-yau approved these changes

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