Realtek-rtl8195am-Network Socket Updates

This PR addresses the issue of #8124.
It updates and enriches the wifi connection error type to adapt the Network Socket test plan requirement.
In the meantime, it increases the heap size that allows the transmission of larger packet size.

Description
1. Increase heap size in lwipstack\mbed_lib.json to fulfill bursty TCP and UDP transmission requirement.
2. Modify and enrich wifi connection error types in TARGET_AMEBA\RTWInterface.cpp to adapt the decision logic of the wifi test cases.
3. Add new static constants in TARGET_AMEBA\RTWInterface.h, including 'SSID_MAX_LENGTH', 'PASSPHRASE_MAX_LENGTH' and 'PASSPHRASE_MIN_LENGTH' to help verifying the validity of ssid and passphrase.

Pull request type
[x] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

features/lwipstack/mbed_lib.json

@@ -115,7 +115,8 @@
     },
     "target_overrides": {
         "REALTEK_RTL8195AM": {
-            "tcpip-thread-stacksize": 1600
+            "tcpip-thread-stacksize": 1600,
+            "mem-size": 12800
         },
         "UBLOX_EVK_ODIN_W2": {
             "pbuf-pool-size" :  10

targets/TARGET_Realtek/TARGET_AMEBA/RTWInterface.cpp

@@ -104,29 +104,38 @@ RTWInterface::~RTWInterface()
  */
 nsapi_error_t RTWInterface::set_credentials(const char *ssid, const char *pass, nsapi_security_t security)
 {
-    if (!ssid) {
+    _security = security;
+    // Check if ssid is empty
+    if (!ssid) { 
         return NSAPI_ERROR_PARAMETER;
     }
 
-    switch (security) {
-        case NSAPI_SECURITY_WPA:
-        case NSAPI_SECURITY_WPA2:
-        case NSAPI_SECURITY_WPA_WPA2:
-        case NSAPI_SECURITY_WEP:
-            if ((strlen(pass) < 8) || (strlen(pass) > 63)) { // 802.11 password 8-63 characters
-                return NSAPI_ERROR_PARAMETER;
-            }
-            break;
-        case NSAPI_SECURITY_NONE:
-            break;
-        default:
-            return NSAPI_ERROR_PARAMETER;
+    // Check if ssid is too long
+    int ssid_length = strlen(ssid);
+
+    if (ssid_length > 0 && ssid_length <= SSID_MAX_LENGTH) {
+        memset(_ssid, 0, sizeof(_ssid));
+        strncpy(_ssid, ssid, sizeof(_ssid));
+    } else {
+        return NSAPI_ERROR_PARAMETER;
     }
 
-    strncpy(_ssid, ssid, 255);
-    strncpy(_pass, pass, 255);
-    _security = security;
-
+    // Check if it is an open access point 
+    if (_security != NSAPI_SECURITY_NONE) {
+    // Check if passphase is empty
+        if (!pass) {
+            return NSAPI_ERROR_PARAMETER;
+        }
+        // Check if passphase too long
+        if (strlen(pass) >= PASSPHRASE_MIN_LENGTH && strlen(pass) <= PASSPHRASE_MAX_LENGTH ) {
+            memset(_pass, 0, sizeof(_pass));
+            strncpy(_pass, pass, sizeof(_pass));
+        } else {
+            return NSAPI_ERROR_PARAMETER;
+        }
+    } else { // It is an open access point
+        memset(_pass, 0, sizeof(_pass));
+    }
     return NSAPI_ERROR_OK;
 }
 
@@ -135,11 +144,15 @@ nsapi_error_t RTWInterface::connect()
     int ret;
     rtw_security_t sec;
 
-    if (!_ssid || (!_pass && _security != NSAPI_SECURITY_NONE)) {
-        printf("Invalid credentials\r\n");
-        return NSAPI_ERROR_PARAMETER;
+    // Check if the ssid is empty 
+    if (strlen(_ssid) == 0) {
+        return NSAPI_ERROR_NO_SSID;
     }
-
+    // Check the security is empty and the passphase is valid 
+    if ((_security != NSAPI_SECURITY_NONE) && (strlen(_pass) < PASSPHRASE_MIN_LENGTH)) {
+            return NSAPI_ERROR_PARAMETER;
+    }
+    // Based on security type set, adapt to Ameba SDK format
     switch (_security) {
         case NSAPI_SECURITY_WPA:
         case NSAPI_SECURITY_WPA2:
@@ -155,22 +168,24 @@ nsapi_error_t RTWInterface::connect()
         default:
             return NSAPI_ERROR_PARAMETER;
     }
-
+    // Check if channel number is valid
     if (_channel > 0 && _channel < 14) {
         uint8_t pscan_config = PSCAN_ENABLE;
-        wifi_set_pscan_chan(&_channel, &pscan_config, 1);
+        wifi_set_pscan_chan(&_channel, &pscan_config, 1); // Indicate which channel will be scanned
     }
-
-    ret = wifi_connect(_ssid, sec, _pass, strlen(_ssid), strlen(_pass), 0, (void *)NULL);
+    ret = wifi_connect(_ssid, sec, _pass, strlen(_ssid), strlen(_pass), 0, (void *)NULL); // Join a WiFi network
+    // Check if the WiFi is connected. Return RTW_SUCCESS for succeful; Return RTW_ERROR for error
     if (ret != RTW_SUCCESS) {
-        printf("failed: %d\r\n", ret);
-        return NSAPI_ERROR_NO_CONNECTION;
+        if(_ssid == "NULL"){
+            return NSAPI_ERROR_PARAMETER;
+        }
+        else{
+            printf("failed: %d\r\n", ret);
+            return NSAPI_ERROR_NO_CONNECTION;
+        }
     }
-
     rtw_emac.wlan_emac_link_change(true);
-
     ret = EMACInterface::connect();
-
     return ret;
 }
 
@@ -200,7 +215,7 @@ nsapi_error_t RTWInterface::scan(WiFiAccessPoint *res, unsigned count)
 nsapi_error_t RTWInterface::set_channel(uint8_t channel)
 {
     _channel = channel;
-    return NSAPI_ERROR_OK;
+    return NSAPI_ERROR_UNSUPPORTED;
 }
 
 int8_t RTWInterface::get_rssi()
@@ -215,8 +230,11 @@ int8_t RTWInterface::get_rssi()
 nsapi_error_t RTWInterface::connect(const char *ssid, const char *pass,
                             nsapi_security_t security, uint8_t channel)
 {
-    set_credentials(ssid, pass, security);
     set_channel(channel);
+    int err = set_credentials(ssid, pass, security);
+    if(err) {
+        return err;
+    }
     return connect();
 }
 

targets/TARGET_Realtek/TARGET_AMEBA/RTWInterface.h

@@ -112,5 +112,8 @@ protected:
     char _pass[256];
     nsapi_security_t _security;
     uint8_t _channel;
+    static const int SSID_MAX_LENGTH = 32; //The longest ssid
+    static const int PASSPHRASE_MAX_LENGTH = 63; //The longest passphrase
+    static const int PASSPHRASE_MIN_LENGTH = 8; // The shortest passphrase
 };
 #endif