Undo #1864, fix LWIP offline error (#1979)

Fixes #1973

The periodic LWIP pump/Ethernet packet reader async_context stopped
firing occasionally under high packet loads, causing the LWIP stack
to become unresponsive to any incoming data.

Re-implement the 2-step process for polling (like the CYW43 driver
from the RPI folks does) and undoes #1864 change.

libraries/lwIP_Ethernet/src/LwipEthernet.cpp

@@ -31,6 +31,7 @@ bool __ethernetContextInitted = false;
 
 // Async context that pumps the ethernet controllers
 static async_context_threadsafe_background_t lwip_ethernet_async_context_threadsafe_background;
+static async_when_pending_worker_t always_pending_update_timeout_worker;
 static async_at_time_worker_t ethernet_timeout_worker;
 static async_context_t *_context = nullptr;
 
@@ -127,10 +128,12 @@ static async_context_t *lwip_ethernet_init_default_async_context(void) {
     return NULL;
 }
 
+uint32_t __ethernet_timeout_reached_calls = 0;
 static uint32_t _pollingPeriod = 20;
 // This will only be called under the protection of the async context mutex, so no re-entrancy checks needed
-static void ethernet_timeout_reached(async_context_t *context, __unused async_at_time_worker_t *worker) {
+static void ethernet_timeout_reached(__unused async_context_t *context, __unused async_at_time_worker_t *worker) {
     assert(worker == &ethernet_timeout_worker);
+    __ethernet_timeout_reached_calls++;
     for (auto handlePacket : _handlePacketList) {
         handlePacket.second();
     }
@@ -141,6 +144,11 @@ static void ethernet_timeout_reached(async_context_t *context, __unused async_at
 #else
     sys_check_timeouts();
 #endif
+}
+
+static void update_next_timeout(async_context_t *context, async_when_pending_worker_t *worker) {
+    assert(worker == &always_pending_update_timeout_worker);
+    worker->work_pending = true;
     async_context_add_at_time_worker_in_ms(context, &ethernet_timeout_worker, _pollingPeriod);
 }
 
@@ -158,7 +166,9 @@ void __startEthernetContext() {
     _context = lwip_ethernet_init_default_async_context();
 #endif
     ethernet_timeout_worker.do_work = ethernet_timeout_reached;
-    async_context_add_at_time_worker_in_ms(_context, &ethernet_timeout_worker, _pollingPeriod);
+    always_pending_update_timeout_worker.work_pending = true;
+    always_pending_update_timeout_worker.do_work = update_next_timeout;
+    async_context_add_when_pending_worker(_context, &always_pending_update_timeout_worker);
     __ethernetContextInitted = true;
 }
 

libraries/lwIP_Ethernet/src/LwipIntfDev.h

@@ -137,6 +137,13 @@ public:
         _spiSettings = s;
     }
 
+    uint32_t packetsReceived() {
+        return _packetsReceived;
+    }
+    uint32_t packetsSent() {
+        return _packetsSent;
+    }
+
     // ESP8266WiFi API compatibility
 
     wl_status_t status();
@@ -172,6 +179,9 @@ protected:
 
     // Packet handler number
     int _phID = -1;
+
+    uint32_t _packetsReceived = 0;
+    uint32_t _packetsSent = 0;
 };
 
 
@@ -416,7 +426,7 @@ err_t LwipIntfDev<RawDev>::linkoutput_s(netif* netif, struct pbuf* pbuf) {
     LwipIntfDev* lid = (LwipIntfDev*)netif->state;
     ethernet_arch_lwip_begin();
     uint16_t len = lid->sendFrame((const uint8_t*)pbuf->payload, pbuf->len);
-
+    lid->_packetsSent++;
 #if PHY_HAS_CAPTURE
     if (phy_capture) {
         phy_capture(lid->_netif.num, (const char*)pbuf->payload, pbuf->len, /*out*/ 1,
@@ -530,6 +540,8 @@ err_t LwipIntfDev<RawDev>::handlePackets() {
             return ERR_BUF;
         }
 
+        _packetsReceived++;
+
         err_t err = _netif.input(pbuf, &_netif);
 
 #if PHY_HAS_CAPTURE