fix(esp_http_server): Add support for custom HTTP status codes

Closes https://github.com/espressif/esp-idf/issues/12399

components/esp_http_server/include/esp_http_server.h

@@ -1293,6 +1293,30 @@ esp_err_t httpd_resp_set_hdr(httpd_req_t *r, const char *field, const char *valu
  */
 esp_err_t httpd_resp_send_err(httpd_req_t *req, httpd_err_code_t error, const char *msg);
 
+/**
+ * @brief   For sending out custom error code in response to HTTP request.
+ *
+ * @note
+ *  - This API is supposed to be called only from the context of
+ *    a URI handler where httpd_req_t* request pointer is valid.
+ *  - Once this API is called, all request headers are purged, so
+ *    request headers need be copied into separate buffers if
+ *    they are required later.
+ *  - If you wish to send additional data in the body of the
+ *    response, please use the lower-level functions directly.
+ *
+ * @param[in] req     Pointer to the HTTP request for which the response needs to be sent
+ * @param[in] status  Error status to send
+ * @param[in] msg     Error message string
+ *
+ * @return
+ *  - ESP_OK : On successfully sending the response packet
+ *  - ESP_ERR_INVALID_ARG : Null arguments
+ *  - ESP_ERR_HTTPD_RESP_SEND   : Error in raw send
+ *  - ESP_ERR_HTTPD_INVALID_REQ : Invalid request pointer
+ */
+esp_err_t httpd_resp_send_custom_err(httpd_req_t *req, const char *status, const char *msg);
+
 /**
  * @brief   Helper function for HTTP 404
  *

components/esp_http_server/src/httpd_txrx.c

@@ -483,6 +483,45 @@ esp_err_t httpd_resp_send_err(httpd_req_t *req, httpd_err_code_t error, const ch
     return ret;
 }
 
+esp_err_t httpd_resp_send_custom_err(httpd_req_t *req, const char *status, const char *msg)
+{
+    ESP_LOGW(TAG, LOG_FMT("%s - %s"), status, msg);
+
+    /* Set error code in HTTP response */
+    httpd_resp_set_status(req, status);
+    httpd_resp_set_type(req, HTTPD_TYPE_TEXT);
+
+#ifdef CONFIG_HTTPD_ERR_RESP_NO_DELAY
+    /* Use TCP_NODELAY option to force socket to send data in buffer
+     * This ensures that the error message is sent before the socket
+     * is closed */
+    struct httpd_req_aux *ra = req->aux;
+    int nodelay = 1;
+    if (setsockopt(ra->sd->fd, IPPROTO_TCP, TCP_NODELAY, &nodelay, sizeof(nodelay)) < 0) {
+        /* If failed to turn on TCP_NODELAY, throw warning and continue */
+        ESP_LOGW(TAG, LOG_FMT("error calling setsockopt : %d"), errno);
+        nodelay = 0;
+    }
+#endif
+
+    /* Send HTTP error message */
+    esp_err_t ret = httpd_resp_send(req, msg, HTTPD_RESP_USE_STRLEN);
+
+#ifdef CONFIG_HTTPD_ERR_RESP_NO_DELAY
+    /* If TCP_NODELAY was set successfully above, time to disable it */
+    if (nodelay == 1) {
+        nodelay = 0;
+        if (setsockopt(ra->sd->fd, IPPROTO_TCP, TCP_NODELAY, &nodelay, sizeof(nodelay)) < 0) {
+            /* If failed to turn off TCP_NODELAY, throw error and
+             * return failure to signal for socket closure */
+            ESP_LOGE(TAG, LOG_FMT("error calling setsockopt : %d"), errno);
+            return ESP_ERR_INVALID_STATE;
+        }
+    }
+#endif
+    return ret;
+}
+
 esp_err_t httpd_register_err_handler(httpd_handle_t handle,
                                      httpd_err_code_t error,
                                      httpd_err_handler_func_t err_handler_fn)