[ONME-2844] Supporting non-blocking connect()

A few new error codes are added to nsapi_error_t and
support for non-blocking socket connect is added.
Nanostack's connect call will be non-blocking.
Whereas LWIP connect call is currently blocking, and it could be changed now
to be non-blocking.

Author: Hasnain Virk

features/netsocket/TCPSocket.cpp

@@ -39,10 +39,47 @@ nsapi_error_t TCPSocket::connect(const SocketAddress &address)
     _lock.lock();
     nsapi_error_t ret;
 
-    if (!_socket) {
-        ret = NSAPI_ERROR_NO_SOCKET;
-    } else {
+    // If this assert is hit then there are two threads
+    // performing a send at the same time which is undefined
+    // behavior
+    MBED_ASSERT(!_write_in_progress);
+    _write_in_progress = true;
+
+    bool blocking_connect_in_progress = false;
+
+    while (true) {
+        if (!_socket) {
+            ret = NSAPI_ERROR_NO_SOCKET;
+            break;
+        }
+
+        _pending = 0;
         ret = _stack->socket_connect(_socket, address);
+        if ((_timeout == 0) || !(ret == NSAPI_ERROR_IN_PROGRESS || ret == NSAPI_ERROR_ALREADY)) {
+            break;
+        } else {
+            blocking_connect_in_progress = true;
+
+            int32_t count;
+
+            // Release lock before blocking so other threads
+            // accessing this object aren't blocked
+            _lock.unlock();
+            count = _write_sem.wait(_timeout);
+            _lock.lock();
+
+            if (count < 1) {
+                // Semaphore wait timed out so break out and return
+                break;
+            }
+        }
+    }
+
+    _write_in_progress = false;
+
+    /* Non-blocking connect gives "EISCONN" once done - convert to OK for blocking mode if we became connected during this call */
+    if (ret == NSAPI_ERROR_IS_CONNECTED && blocking_connect_in_progress) {
+        ret = NSAPI_ERROR_OK;
     }
 
     _lock.unlock();
@@ -81,9 +118,8 @@ nsapi_size_or_error_t TCPSocket::send(const void *data, nsapi_size_t size)
         }
 
         _pending = 0;
-        nsapi_size_or_error_t sent = _stack->socket_send(_socket, data, size);
-        if ((0 == _timeout) || (NSAPI_ERROR_WOULD_BLOCK != sent)) {
-            ret = sent;
+        ret = _stack->socket_send(_socket, data, size);
+        if ((_timeout == 0) || (ret != NSAPI_ERROR_WOULD_BLOCK)) {
             break;
         } else {
             int32_t count;
@@ -125,9 +161,8 @@ nsapi_size_or_error_t TCPSocket::recv(void *data, nsapi_size_t size)
         }
 
         _pending = 0;
-        nsapi_size_or_error_t recv = _stack->socket_recv(_socket, data, size);
-        if ((0 == _timeout) || (NSAPI_ERROR_WOULD_BLOCK != recv)) {
-            ret = recv;
+        ret = _stack->socket_recv(_socket, data, size);
+        if ((_timeout == 0) || (ret != NSAPI_ERROR_WOULD_BLOCK)) {
             break;
         } else {
             int32_t count;

features/netsocket/nsapi_types.h

@@ -48,6 +48,9 @@ enum nsapi_error {
     NSAPI_ERROR_DHCP_FAILURE  = -3010,     /*!< DHCP failed to complete successfully */
     NSAPI_ERROR_AUTH_FAILURE  = -3011,     /*!< connection to access point failed */
     NSAPI_ERROR_DEVICE_ERROR  = -3012,     /*!< failure interfacing with the network processor */
+    NSAPI_ERROR_IN_PROGRESS   = -3013,     /*!< operation (eg connect) in progress */
+    NSAPI_ERROR_ALREADY       = -3014,     /*!< operation (eg connect) already in progress */
+    NSAPI_ERROR_IS_CONNECTED  = -3015,     /*!< socket is already connected */
 };
 
 /** Type used to represent error codes