{
  "id": "embedded/lwip-tcp-dup-ack-retransmit",
  "signature": "lwIP: TCP connection lost, too many duplicate ACKs triggered retransmit timeout on socket 3",
  "signature_zh": "lwIP：TCP连接丢失，过多重复ACK导致套接字3重传超时",
  "regex": "lwIP.*TCP connection lost.*duplicate ACKs.*retransmit timeout.*socket [0-9]+",
  "domain": "embedded",
  "category": "network_error",
  "subcategory": null,
  "root_cause": "Persistent packet loss due to network congestion or faulty PHY, causing lwIP TCP to enter retransmission timeout and close the connection.",
  "root_cause_type": "generic",
  "root_cause_zh": "由于网络拥塞或有故障的PHY导致持续丢包，使lwIP TCP进入重传超时并关闭连接。",
  "versions": [
    {
      "version": "lwIP v2.1.3",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "FreeRTOS+TCP v3.1.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "STM32F769",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "Increase TCP retransmission timeout in lwIP config (TCP_RTO_MIN)",
      "why_fails": "Delays detection of genuine connection loss and may cause application-level timeouts; does not fix underlying packet loss.",
      "fail_rate": 0.65,
      "condition": "",
      "sources": []
    },
    {
      "action": "Disable TCP Nagle algorithm to send smaller packets",
      "why_fails": "Reduces throughput and may increase ACK overhead; does not address duplicate ACK cause.",
      "fail_rate": 0.7,
      "condition": "",
      "sources": []
    },
    {
      "action": "Replace PHY chip with a different model",
      "why_fails": "Expensive and time-consuming; the issue may be due to PCB layout or driver configuration, not the PHY itself.",
      "fail_rate": 0.5,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Enable lwIP TCP keepalive to detect stale connections early and implement application-level retry logic.",
      "success_rate": 0.8,
      "how": "Enable lwIP TCP keepalive to detect stale connections early and implement application-level retry logic.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Improve PHY stability by adding external pull-up resistors on TX and RX lines and verifying MDC/MDIO timing per datasheet.",
      "success_rate": 0.7,
      "how": "Improve PHY stability by adding external pull-up resistors on TX and RX lines and verifying MDC/MDIO timing per datasheet.",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [
    "Enable lwIP TCP keepalive to detect stale connections early and implement application-level retry logic.",
    "Improve PHY stability by adding external pull-up resistors on TX and RX lines and verifying MDC/MDIO timing per datasheet."
  ],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": "https://www.nongnu.org/lwip/2_1_x/index.html",
  "official_doc_section": null,
  "error_code": null,
  "verification_tier": "ai_generated",
  "confidence": 0.86,
  "fix_success_rate": 0.75,
  "resolvable": "partial",
  "first_seen": "2024-09-15",
  "last_confirmed": "2024-06-01",
  "last_updated": "2024-06-01",
  "evidence_count": 1,
  "tags": [],
  "locale": "en",
  "aliases": []
}