Cellular: notify global up after we have IP address

CellularContext now tries to get an IP address after connect and before
sending NSAPI_STATUS_GLOBAL_UP. Even if we don't the IP address from
the modem we will send NSAPI_STATUS_GLOBAL_UP and return success.
Modem has an ip address but for some reason some modems don't
give it to us.

UNITTESTS/features/cellular/framework/AT/at_cellularcontext/at_cellularcontexttest.cpp

@@ -537,7 +537,7 @@ TEST_F(TestAT_CellularContext, connect_disconnect_sync)
     ATHandler_stub::read_string_index = 2;
     ASSERT_EQ(ctx1.connect(),  NSAPI_ERROR_OK);
 
-    ASSERT_EQ(network_cb_count, 5);
+    ASSERT_EQ(network_cb_count, 4);
 
     ASSERT_EQ(ctx1.disconnect(), NSAPI_ERROR_OK);
     ATHandler_stub::resp_info_true_counter = 1;
@@ -704,7 +704,7 @@ TEST_F(TestAT_CellularContext, connect_disconnect_async)
     data.status_data = CellularNetwork::Attached;
     ctx1.cellular_callback((nsapi_event_t)CellularAttachNetwork, (intptr_t)&data);
 
-    ASSERT_EQ(network_cb_count, 5);
+    ASSERT_EQ(network_cb_count, 4);
     ASSERT_EQ(ctx1.connect(), NSAPI_ERROR_IS_CONNECTED);
     EXPECT_TRUE(ctx1.is_connected() == true);
     ASSERT_EQ(ctx1.disconnect(), NSAPI_ERROR_NO_MEMORY);

UNITTESTS/features/cellular/framework/AT/at_cellularstack/at_cellularstacktest.cpp

@@ -175,7 +175,7 @@ TEST_F(TestAT_CellularStack, test_AT_CellularStack_get_ip_address)
     ATHandler at(&fh1, que, 0, ",");
 
     MyStack st(at, 0, IPV6_STACK);
-    EXPECT_EQ(strlen(st.get_ip_address()), 0);
+    EXPECT_TRUE(st.get_ip_address() == NULL);
 
     char table[] = "1.2.3.4.5.65.7.8.9.10.11\0";
     ATHandler_stub::ssize_value = -1;

UNITTESTS/features/cellular/framework/AT/at_cellularstack/unittest.cmake

@@ -28,4 +28,5 @@ set(unittest-test-sources
   stubs/NetworkStack_stub.cpp
   stubs/SocketAddress_stub.cpp
   stubs/mbed_assert_stub.c
+  stubs/ThisThread_stub.cpp
 )

features/cellular/framework/API/CellularContext.h

@@ -344,6 +344,12 @@ class CellularContext : public CellularInterface {
      */
     virtual void do_connect();
 
+    /** After we have connected successfully we must check that we have a valid IP address.
+     *  Some modems/networks don't give IP address right after connect so we must poll it for a while.
+     *  Whether we get IP address or not, this methods sends NSAPI_STATUS_GLOBAL_UP to application.
+     */
+    void validate_ip_address();
+
     // member variables needed in target override methods
     NetworkStack *_stack; // must be pointer because of PPP
     pdp_type_t _pdp_type;

features/cellular/framework/AT/AT_CellularContext.cpp

@@ -587,7 +587,6 @@ void AT_CellularContext::do_connect()
     }
 #else
     _is_connected = true;
-    call_network_cb(NSAPI_STATUS_GLOBAL_UP);
 #endif
 }
 

features/cellular/framework/AT/AT_CellularStack.cpp

@@ -18,6 +18,7 @@
 #include "AT_CellularStack.h"
 #include "CellularUtil.h"
 #include "CellularLog.h"
+#include "ThisThread.h"
 
 using namespace mbed_cellular_util;
 using namespace mbed;
@@ -54,41 +55,31 @@ int AT_CellularStack::find_socket_index(nsapi_socket_t handle)
 
 /** NetworkStack
  */
-
 const char *AT_CellularStack::get_ip_address()
 {
     _at.lock();
 
     _at.cmd_start_stop("+CGPADDR", "=", "%d", _cid);
-
     _at.resp_start("+CGPADDR:");
 
+    int len = -1;
     if (_at.info_resp()) {
-
         _at.skip_param();
 
-        int len = _at.read_string(_ip, NSAPI_IPv4_SIZE);
-        if (len == -1) {
-            _ip[0] = '\0';
-            _at.resp_stop();
-            _at.unlock();
-            // no IPV4 address, return
-            return NULL;
-        }
+        len = _at.read_string(_ip, NSAPI_IPv4_SIZE);
 
-        // in case stack type is not IPV4 only, try to look also for IPV6 address
-        if (_stack_type != IPV4_STACK) {
+        if (len != -1 && _stack_type != IPV4_STACK) {
+            // in case stack type is not IPV4 only, try to look also for IPV6 address
             (void)_at.read_string(_ip, PDP_IPV6_SIZE);
         }
     }
-
     _at.resp_stop();
     _at.unlock();
 
     // we have at least IPV4 address
     convert_ipv6(_ip);
 
-    return _ip;
+    return len != -1 ? _ip : NULL;
 }
 
 nsapi_error_t AT_CellularStack::socket_stack_init()

features/cellular/framework/device/CellularContext.cpp

@@ -87,6 +87,30 @@ void CellularContext::set_authentication_type(AuthenticationType type)
     _authentication_type = type;
 }
 
+void CellularContext::validate_ip_address()
+{
+    const int IP_MAX_TRIES = 10; // maximum of 2 seconds as we wait 200ms between tries
+    const int IP_WAIT_INTERVAL = 200; // 200 ms between retries
+    const char *ip = NULL;
+    int i = 0;
+
+    while (1) {
+        ip = get_ip_address();
+        if (ip || i >= IP_MAX_TRIES) {
+            if (ip == NULL) {
+                tr_warning("Connected but no local ip address");
+            } else {
+                tr_info("Cellular local IP: %s", ip);
+            }
+            break;
+        }
+        rtos::ThisThread::sleep_for(IP_WAIT_INTERVAL);
+        i++;
+    }
+
+    call_network_cb(NSAPI_STATUS_GLOBAL_UP);
+}
+
 void CellularContext::do_connect_with_retry()
 {
     if (_cb_data.final_try) {
@@ -97,6 +121,9 @@ void CellularContext::do_connect_with_retry()
     }
     do_connect();
     if (_cb_data.error == NSAPI_ERROR_OK) {
+        // Some modems don't get the ip address right after connect so we must
+        // validate it but even if we don't get ip we still send NSAPI_STATUS_GLOBAL_UP
+        validate_ip_address();
         return;
     }