Better handling of wifi disconnect (#231)

When network interface is down, some nasty things happen, for instance tcp_connect returns without ever calling error callback.
This change adds some workarounds for that: before doing a tcp connect and DNS resolve we check if there is a route available.
Also added a listener for wifi events which stops (aborts) all the WiFiClients and WiFiUDPs when wifi is disconnected. This should
help libraries detect disconnect properly.

libraries/ESP8266WiFi/src/ESP8266WiFi.cpp

@@ -33,6 +33,8 @@ extern "C" {
 #include "lwip/dns.h"
 }
 
+#include "WiFiClient.h"
+#include "WiFiUdp.h"
 
 extern "C" void esp_schedule();
 extern "C" void esp_yield();
@@ -42,6 +44,7 @@ ESP8266WiFiClass::ESP8266WiFiClass()
 , _useClientMode(false)
 , _useStaticIp(false)
 {
+    wifi_set_event_handler_cb((wifi_event_handler_cb_t)&ESP8266WiFiClass::_eventCallback);
 }
 
 void ESP8266WiFiClass::mode(WiFiMode m)
@@ -588,6 +591,17 @@ void ESP8266WiFiClass::_smartConfigCallback(uint32_t st, void* result)
     }
 }
 
+void ESP8266WiFiClass::_eventCallback(void* arg)
+{
+    System_Event_t* event = reinterpret_cast<System_Event_t*>(arg);
+    DEBUGV("wifi evt: %d\r\n", event->event);
+
+    if (event->event == EVENT_STAMODE_DISCONNECTED) {
+        WiFiClient::stopAll();
+        WiFiUDP::stopAll();
+    }
+}
+
 void ESP8266WiFiClass::printDiag(Print& p)
 {
     const char* modes[] = {"NULL", "STA", "AP", "STA+AP"};

libraries/ESP8266WiFi/src/ESP8266WiFi.h

@@ -313,6 +313,7 @@ protected:
     static void _scanDone(void* result, int status);
     void * _getScanInfoByIndex(int i);
     static void _smartConfigCallback(uint32_t status, void* result);
+    static void _eventCallback(void *event);
     bool _smartConfigStarted = false;
     bool _smartConfigDone = false;
 

libraries/ESP8266WiFi/src/WiFiClient.cpp

@@ -34,26 +34,35 @@ extern "C"
 #include "WiFiClient.h"
 #include "WiFiServer.h"
 #include "lwip/opt.h"
+#include "lwip/ip.h"
 #include "lwip/tcp.h"
 #include "lwip/inet.h"
+#include "lwip/netif.h"
 #include "cbuf.h"
 #include "include/ClientContext.h"
 #include "c_types.h"
 
 uint16_t WiFiClient::_localPort = 0;
 
+template<>
+WiFiClient* SList<WiFiClient>::_s_first = 0;
+
+
 WiFiClient::WiFiClient() 
 : _client(0)
 {
+    WiFiClient::_add(this);
 }
 
 WiFiClient::WiFiClient(ClientContext* client) : _client(client)
 {
     _client->ref();
+    WiFiClient::_add(this);
 }
 
 WiFiClient::~WiFiClient()
 {
+    WiFiClient::_remove(this);
     if (_client)
         _client->unref();
 }
@@ -63,6 +72,7 @@ WiFiClient::WiFiClient(const WiFiClient& other)
     _client = other._client;
     if (_client)
         _client->ref();
+    WiFiClient::_add(this);
 }
 
 WiFiClient& WiFiClient::operator=(const WiFiClient& other)
@@ -88,9 +98,21 @@ int WiFiClient::connect(const char* host, uint16_t port)
 
 int WiFiClient::connect(IPAddress ip, uint16_t port) 
 {
+    ip_addr_t addr;
+    addr.addr = ip;
+
     if (_client)
         stop();
 
+    // if the default interface is down, tcp_connect exits early without
+    // ever calling tcp_err
+    // http://lists.gnu.org/archive/html/lwip-devel/2010-05/msg00001.html
+    netif* interface = ip_route(&addr);
+    if (!interface) {
+        DEBUGV("no route to host\r\n");
+        return 1;
+    }
+
     tcp_pcb* pcb = tcp_new();
     if (!pcb)
         return 0;
@@ -99,8 +121,6 @@ int WiFiClient::connect(IPAddress ip, uint16_t port)
         pcb->local_port = _localPort++;
     }
 
-    ip_addr_t addr;
-    addr.addr = ip;
     tcp_arg(pcb, this);
     tcp_err(pcb, &WiFiClient::_s_err);
     tcp_connect(pcb, &addr, port, reinterpret_cast<tcp_connected_fn>(&WiFiClient::_s_connected));
@@ -257,3 +277,14 @@ void WiFiClient::_s_err(void* arg, int8_t err)
     reinterpret_cast<WiFiClient*>(arg)->_err(err);
 }
 
+void WiFiClient::stopAll()
+{
+    for (WiFiClient* it = _s_first; it; it = it->_next) {
+        ClientContext* c = it->_client;
+        if (c) {
+            c->abort();
+            c->unref();
+            it->_client = 0;
+        }
+    }
+}

libraries/ESP8266WiFi/src/WiFiClient.h

@@ -26,11 +26,12 @@
 #include "Client.h"
 #include "IPAddress.h"
 #include <memory>
+#include "include/slist.h"
 
 class ClientContext;
 class WiFiServer;
 
-class WiFiClient : public Client {
+class WiFiClient : public Client, public SList<WiFiClient> {
 protected:
   WiFiClient(ClientContext* client);
 
@@ -89,6 +90,8 @@ public:
 
   using Print::write;
 
+  static void stopAll();
+
 private:
 
   static int8_t _s_connected(void* arg, void* tpcb, int8_t err);
@@ -99,7 +102,6 @@ private:
 
   ClientContext* _client;
   static uint16_t _localPort;
-
 };
 
 

libraries/ESP8266WiFi/src/WiFiUdp.cpp

@@ -40,14 +40,22 @@ extern "C"
 #include "lwip/mem.h"
 #include "include/UdpContext.h"
 
+
+template<>
+WiFiUDP* SList<WiFiUDP>::_s_first = 0;
+
 /* Constructor */
-WiFiUDP::WiFiUDP() : _ctx(0) {}
+WiFiUDP::WiFiUDP() : _ctx(0) 
+{
+    WiFiUDP::_add(this);
+}
 
 WiFiUDP::WiFiUDP(const WiFiUDP& other)
 {
     _ctx = other._ctx;
     if (_ctx)
         _ctx->ref();
+    WiFiUDP::_add(this);
 }
 
 WiFiUDP& WiFiUDP::operator=(const WiFiUDP& rhs)
@@ -60,6 +68,7 @@ WiFiUDP& WiFiUDP::operator=(const WiFiUDP& rhs)
 
 WiFiUDP::~WiFiUDP()
 {
+    WiFiUDP::_remove(this);
     if (_ctx)
         _ctx->unref();
 }
@@ -258,3 +267,11 @@ uint16_t WiFiUDP::localPort()
 
     return _ctx->getLocalPort();
 }
+
+void WiFiUDP::stopAll()
+{
+    for (WiFiUDP* it = _s_first; it; it = it->_next) {
+        it->stop();
+    }
+}
+

libraries/ESP8266WiFi/src/WiFiUdp.h

@@ -23,12 +23,13 @@
 #define WIFIUDP_H
 
 #include <Udp.h>
+#include <include/slist.h>
 
 #define UDP_TX_PACKET_MAX_SIZE 8192
 
 class UdpContext;
 
-class WiFiUDP : public UDP {
+class WiFiUDP : public UDP, public SList<WiFiUDP> {
 private:
   UdpContext* _ctx;
 
@@ -103,6 +104,8 @@ public:
   // Return the local port for outgoing packets
   uint16_t localPort();
 
+  static void stopAll();
+
 };
 
 #endif //WIFIUDP_H

libraries/ESP8266WiFi/src/include/slist.h

@@ -0,0 +1,38 @@
+#ifndef SLIST_H
+#define SLIST_H
+
+template<typename T>
+class SList {
+public:
+  SList() : _next(0) { }
+
+protected:
+
+  static void _add(T* self) {
+    T* tmp = _s_first;
+    _s_first = self;
+    self->_next = tmp;
+  }
+
+  static void _remove(T* self) {
+    if (_s_first == self) {
+      _s_first = self->_next;
+      self->_next = 0;
+      return;
+    }
+
+    for (T* prev = _s_first; prev->_next; _s_first = _s_first->_next) {
+      if (prev->_next == self) {
+        prev->_next = self->_next;
+        self->_next = 0;
+        return;
+      }
+    }
+  }
+
+  static T* _s_first;
+  T* _next;
+};
+
+
+#endif //SLIST_H