Fix esp_mbedtls_write API

Fix esp_wolfssl_write API
Closes https://github.com/espressif/esp-idf/issues/7461

components/esp-tls/esp_tls.h

@@ -436,7 +436,11 @@ int esp_tls_conn_http_new_async(const char *url, const esp_tls_cfg_t *cfg, esp_t
  *             -  0  if write operation was not successful. The underlying
  *                   connection was closed.
  *             - <0  if write operation was not successful, because either an 
- *                   error occured or an action must be taken by the calling process.   
+ *                   error occured or an action must be taken by the calling process.
+ *             - ESP_TLS_ERR_SSL_WANT_READ/
+ *               ESP_TLS_ERR_SSL_WANT_WRITE.
+ *                  if the handshake is incomplete and waiting for data to be available for reading.
+ *                  In this case this functions needs to be called again when the underlying transport is ready for operation.
  */
 static inline ssize_t esp_tls_conn_write(esp_tls_t *tls, const void *data, size_t datalen)
 {

components/esp-tls/esp_tls_mbedtls.c

@@ -161,9 +161,9 @@ ssize_t esp_mbedtls_write(esp_tls_t *tls, const char *data, size_t datalen)
                 ESP_LOGE(TAG, "write error :%d:", ret);
                 return ret;
             } else {
-                // Exitting the tls-write process as less than desired datalen are writable
+                // Exiting the tls-write process as less than desired datalen are writable
                 ESP_LOGD(TAG, "mbedtls_ssl_write() returned %d, already written %d, exitting...", ret, written);
-                return written;
+                return (written > 0) ? written : ret;
             }
         }
         written += ret;

components/esp-tls/esp_tls_wolfssl.c

@@ -170,7 +170,7 @@ ssize_t esp_wolfssl_read(esp_tls_t *tls, char *data, size_t datalen)
 ssize_t esp_wolfssl_write(esp_tls_t *tls, const char *data, size_t datalen)
 {
     ssize_t ret = wolfSSL_write( (WOLFSSL *)tls->priv_ssl, (unsigned char *) data, datalen);
-    if (ret < 0) {
+    if (ret <= 0) {
         ret = wolfSSL_get_error( (WOLFSSL *)tls->priv_ssl, ret);
         if (ret != ESP_TLS_ERR_SSL_WANT_READ  && ret != ESP_TLS_ERR_SSL_WANT_WRITE) {
             ESP_INT_EVENT_TRACKER_CAPTURE(tls->error_handle, ERR_TYPE_WOLFSSL, -ret);