BG96: Add correct get_ip_address implementation

The default get_ip_address implementation was not working for
BG9x. Furthermore the cellular connect routine tries to get the
address multiple times, which added around 2 seconds of
unnecessary delay to the connection. This commit adds the correct
implementation using the AT+QIACT? command.

Author: boraozgen

connectivity/drivers/cellular/QUECTEL/BG96/QUECTEL_BG96_CellularStack.cpp

@@ -20,6 +20,7 @@
 #include "QUECTEL/BG96/QUECTEL_BG96_CellularStack.h"
 #include "CellularLog.h"
 #include "netsocket/TLSSocket.h"
+#include "CellularUtil.h"
 
 // Ref: Quectel_BG96_SSL_AT_Commands_Manual, ch 2.1.1 AT+QSSLCFG
 static const int BG96_SUPPORTED_SSL_VERSION     = 4; // All
@@ -157,6 +158,40 @@ nsapi_error_t QUECTEL_BG96_CellularStack::socket_connect(nsapi_socket_t handle,
     return err;
 }
 
+nsapi_error_t QUECTEL_BG96_CellularStack::get_ip_address(SocketAddress *address)
+{
+    if (!address) {
+        return NSAPI_ERROR_PARAMETER;
+    }
+    _at.lock();
+
+    _at.cmd_start_stop("+QIACT", "?");
+    _at.resp_start("+QIACT:");
+
+    int32_t context_type = 0;
+
+    if (_at.info_resp()) {
+        _at.skip_param(); // ID
+        _at.skip_param(); // State
+
+        context_type = _at.read_int();
+        if (context_type == 1) {
+            _stack_type = IPV4_STACK;
+        } else if (context_type == 2) {
+            _stack_type = IPV6_STACK;
+        }
+
+        if (_at.read_string(_ip, PDP_IPV6_SIZE) != -1) {
+            mbed_cellular_util::convert_ipv6(_ip);
+            address->set_ip_address(_ip);
+        }
+    }
+    _at.resp_stop();
+    _at.unlock();
+
+    return (context_type > 0) ? NSAPI_ERROR_OK : NSAPI_ERROR_NO_ADDRESS;
+}
+
 void QUECTEL_BG96_CellularStack::urc_qiurc_recv()
 {
     urc_qiurc(URC_RECV);

connectivity/drivers/cellular/QUECTEL/BG96/QUECTEL_BG96_CellularStack.h

@@ -47,6 +47,8 @@ class QUECTEL_BG96_CellularStack : public AT_CellularStack {
 
     virtual nsapi_error_t socket_connect(nsapi_socket_t handle, const SocketAddress &address);
 
+    virtual nsapi_error_t get_ip_address(SocketAddress *address);
+
 #ifdef MBED_CONF_CELLULAR_OFFLOAD_DNS_QUERIES
     virtual nsapi_error_t gethostbyname(const char *host, SocketAddress *address, nsapi_version_t version, const char *interface_name);
     virtual nsapi_value_or_error_t gethostbyname_async(const char *host, hostbyname_cb_t callback, nsapi_version_t version = NSAPI_UNSPEC,