Fix RAK4631 Ethernet gateway API connection loss after W5100S brownout

src/mesh/api/ServerAPI.cpp

@@ -1,7 +1,10 @@
 #include "ServerAPI.h"
+#include "Throttle.h"
 #include "configuration.h"
 #include <Arduino.h>
 
+#define TCP_IDLE_TIMEOUT_MS (15 * 60 * 1000UL)
+
 template <typename T>
 ServerAPI<T>::ServerAPI(T &_client) : StreamAPI(&client), concurrency::OSThread("ServerAPI"), client(_client)
 {
@@ -28,6 +31,12 @@ template <typename T> bool ServerAPI<T>::checkIsConnected()
 template <class T> int32_t ServerAPI<T>::runOnce()
 {
     if (client.connected()) {
+        if (lastContactMsec > 0 && !Throttle::isWithinTimespanMs(lastContactMsec, TCP_IDLE_TIMEOUT_MS)) {
+            LOG_WARN("TCP connection timeout, no data for %lu ms", (unsigned long)(millis() - lastContactMsec));
+            close();
+            enabled = false;
+            return 0;
+        }
         return StreamAPI::runOncePart();
     } else {
         LOG_INFO("Client dropped connection, suspend API service");
@@ -57,7 +66,7 @@ template <class T, class U> int32_t APIServerPort<T, U>::runOnce()
 #else
     auto client = U::available();
 #endif
-#elif defined(ARCH_RP2040)
+#elif defined(ARCH_RP2040) || defined(ARCH_NRF52)
     auto client = U::accept();
 #else
     auto client = U::available();

src/mesh/api/ethServerAPI.cpp

@@ -17,6 +17,15 @@ void initApiServer(int port)
     }
 }
 
+void deInitApiServer()
+{
+    if (apiPort) {
+        LOG_INFO("Deinit API server");
+        delete apiPort;
+        apiPort = nullptr;
+    }
+}
+
 ethServerAPI::ethServerAPI(EthernetClient &_client) : ServerAPI(_client)
 {
     LOG_INFO("Incoming ethernet connection");

src/mesh/api/ethServerAPI.h

@@ -24,4 +24,5 @@ class ethServerPort : public APIServerPort<ethServerAPI, EthernetServer>
 };
 
 void initApiServer(int port = SERVER_API_DEFAULT_PORT);
+void deInitApiServer();
 #endif

src/mesh/eth/ethClient.cpp

@@ -32,6 +32,64 @@ static Periodic *ethEvent;
 static int32_t reconnectETH()
 {
     if (config.network.eth_enabled) {
+
+        // Detect W5100S chip reset by verifying the MAC address register.
+        // PoE power instability can brownout the W5100S while the MCU keeps running,
+        // causing all chip registers (MAC, IP, sockets) to revert to defaults.
+        uint8_t currentMac[6];
+        Ethernet.MACAddress(currentMac);
+
+        uint8_t expectedMac[6];
+        getMacAddr(expectedMac);
+        expectedMac[0] &= 0xfe;
+
+        if (memcmp(currentMac, expectedMac, 6) != 0) {
+            LOG_WARN("W5100S MAC mismatch (chip reset detected), reinitializing Ethernet");
+
+            syslog.disable();
+#if !MESHTASTIC_EXCLUDE_SOCKETAPI
+            deInitApiServer();
+#endif
+
+#ifdef PIN_ETHERNET_RESET
+            pinMode(PIN_ETHERNET_RESET, OUTPUT);
+            digitalWrite(PIN_ETHERNET_RESET, LOW);
+            delay(100);
+            digitalWrite(PIN_ETHERNET_RESET, HIGH);
+            delay(100);
+#endif
+
+#ifdef RAK11310
+            ETH_SPI_PORT.setSCK(PIN_SPI0_SCK);
+            ETH_SPI_PORT.setTX(PIN_SPI0_MOSI);
+            ETH_SPI_PORT.setRX(PIN_SPI0_MISO);
+            ETH_SPI_PORT.begin();
+#endif
+            Ethernet.init(ETH_SPI_PORT, PIN_ETHERNET_SS);
+
+            int status = 0;
+            if (config.network.address_mode == meshtastic_Config_NetworkConfig_AddressMode_DHCP) {
+                status = Ethernet.begin(expectedMac);
+            } else if (config.network.address_mode == meshtastic_Config_NetworkConfig_AddressMode_STATIC) {
+                Ethernet.begin(expectedMac, config.network.ipv4_config.ip, config.network.ipv4_config.dns,
+                               config.network.ipv4_config.gateway, config.network.ipv4_config.subnet);
+                status = 1;
+            }
+
+            if (status == 0) {
+                LOG_ERROR("Ethernet re-initialization failed, will retry");
+                return 5000;
+            }
+
+            LOG_INFO("Ethernet reinitialized - IP %u.%u.%u.%u", Ethernet.localIP()[0], Ethernet.localIP()[1],
+                     Ethernet.localIP()[2], Ethernet.localIP()[3]);
+
+            ethStartupComplete = false;
+#ifndef DISABLE_NTP
+            ntp_renew = 0;
+#endif
+        }
+
         Ethernet.maintain();
         if (!ethStartupComplete) {
             // Start web server