Cellular: Fix BG96 offloaded DNS query for new API

Fixed following issues in BG96 offloaded DNS:
- Fixed mbed-os 6 API change for asynchronous DNS callback. Return value is no longer
  an error value but in success case the amount of DNS records
- Asynchronous request returns request ID instead of NSAPI_ERROR_OK. BG96 supports only
  one asynchronouse DNS query at the time, so ID 1 is used.
- BG96 does not support multi-ip DNS responses, so disabled multi-ip tests

TESTS/netsocket/dns/asynchronous_dns_multi_ip.cpp

@@ -15,7 +15,7 @@
  * limitations under the License.
  */
 
-#if defined(MBED_CONF_RTOS_PRESENT)
+#if defined(MBED_CONF_RTOS_PRESENT) && !defined(MBED_CONF_CELLULAR_OFFLOAD_DNS_QUERIES)
 
 #include "mbed.h"
 #include "greentea-client/test_env.h"
@@ -118,4 +118,4 @@ void ASYNCHRONOUS_DNS_MULTI_IP()
     TEST_ASSERT_EQUAL(0, result_dns_failure);
     TEST_ASSERT_EQUAL(0, result_exp_timeout);
 }
-#endif // defined(MBED_CONF_RTOS_PRESENT)
+#endif // defined(MBED_CONF_RTOS_PRESENT) && !defined(MBED_CONF_CELLULAR_OFFLOAD_DNS_QUERIES)

TESTS/netsocket/dns/dns_tests.h

@@ -73,7 +73,10 @@ struct dns_application_data_multi_ip {
 
 extern const char dns_test_hosts[MBED_CONF_APP_DNS_TEST_HOSTS_NUM][DNS_TEST_HOST_LEN];
 extern const char dns_test_hosts_second[MBED_CONF_APP_DNS_TEST_HOSTS_NUM][DNS_TEST_HOST_LEN];
+
+#ifndef MBED_CONF_CELLULAR_OFFLOAD_DNS_QUERIES
 extern const char dns_test_hosts_multi_ip[MBED_CONF_APP_DNS_SIMULT_QUERIES][DNS_TEST_HOST_LEN];
+#endif
 
 /*
  * Utility functions

TESTS/netsocket/dns/main.cpp

@@ -42,7 +42,10 @@ NetworkInterface *net;
 
 const char dns_test_hosts[MBED_CONF_APP_DNS_TEST_HOSTS_NUM][DNS_TEST_HOST_LEN] = MBED_CONF_APP_DNS_TEST_HOSTS;
 const char dns_test_hosts_second[MBED_CONF_APP_DNS_TEST_HOSTS_NUM][DNS_TEST_HOST_LEN] = MBED_CONF_APP_DNS_TEST_HOSTS_SECOND;
+
+#ifndef MBED_CONF_CELLULAR_OFFLOAD_DNS_QUERIES
 const char dns_test_hosts_multi_ip[MBED_CONF_APP_DNS_SIMULT_QUERIES][DNS_TEST_HOST_LEN] = MBED_CONF_APP_DNS_TEST_MULTI_IP_HOSTS;
+#endif
 
 // Callback used for asynchronous DNS result
 void hostbyname_cb(void *data, nsapi_error_t result, SocketAddress *address)
@@ -221,8 +224,10 @@ Case cases[] = {
     Case("SYNCHRONOUS_DNS", SYNCHRONOUS_DNS),
     Case("SYNCHRONOUS_DNS_MULTIPLE", SYNCHRONOUS_DNS_MULTIPLE),
     Case("SYNCHRONOUS_DNS_INVALID", SYNCHRONOUS_DNS_INVALID),
+#ifndef MBED_CONF_CELLULAR_OFFLOAD_DNS_QUERIES
     Case("SYNCHRONOUS_DNS_MULTI_IP", SYNCHRONOUS_DNS_MULTI_IP),
     Case("ASYNCHRONOUS_DNS_MULTI_IP", ASYNCHRONOUS_DNS_MULTI_IP),
+#endif
 };
 
 Specification specification(test_setup, cases, greentea_teardown, greentea_continue_handlers);

TESTS/netsocket/dns/synchronous_dns_multi_ip.cpp

@@ -15,6 +15,8 @@
  * limitations under the License.
  */
 
+#if !defined(MBED_CONF_CELLULAR_OFFLOAD_DNS_QUERIES)
+
 #include "mbed.h"
 #include "greentea-client/test_env.h"
 #include "unity.h"
@@ -84,3 +86,5 @@ void SYNCHRONOUS_DNS_MULTI_IP()
     TEST_ASSERT_EQUAL(0, result_dns_failure);
     TEST_ASSERT_EQUAL(0, result_exp_timeout);
 }
+
+#endif // !defined(MBED_CONF_CELLULAR_OFFLOAD_DNS_QUERIES)

features/cellular/framework/targets/QUECTEL/BG96/QUECTEL_BG96_CellularStack.cpp

@@ -29,6 +29,8 @@ static const char BG96_SUPPORTED_CIPHER_SUITE[] = "0xFFFF"; // Support all
 //       Later can be expanded to support multiple contexts. Modem supports IDs 0-5.
 static const int sslctxID = 0;
 
+static const int BG96_ASYNC_DNS_QUERY_ID = 1; // BG96 driver only supports one request, so using id 1
+
 using namespace mbed;
 
 QUECTEL_BG96_CellularStack::QUECTEL_BG96_CellularStack(ATHandler &atHandler, int cid, nsapi_ip_stack_t stack_type, AT_CellularDevice &device) :
@@ -191,7 +193,7 @@ void QUECTEL_BG96_CellularStack::urc_qiurc_dnsgip()
     }
     SocketAddress address;
     if (read_dnsgip(address, _dns_version)) {
-        _dns_callback(NSAPI_ERROR_OK, &address);
+        _dns_callback(1, &address);
     } else {
         _dns_callback(NSAPI_ERROR_DNS_FAILURE, NULL);
     }
@@ -496,7 +498,7 @@ nsapi_value_or_error_t QUECTEL_BG96_CellularStack::gethostbyname_async(const cha
         _dns_version = version;
     }
 
-    return _at.unlock_return_error() ? NSAPI_ERROR_DNS_FAILURE : NSAPI_ERROR_OK;
+    return _at.unlock_return_error() ? NSAPI_ERROR_DNS_FAILURE : BG96_ASYNC_DNS_QUERY_ID;
 }
 
 nsapi_error_t QUECTEL_BG96_CellularStack::gethostbyname_async_cancel(int id)