esp_http_server: Provide apps an option to let http_server ignore sess_ctx changes

By default, if a URI handler changes the http session context,
the webserver internally clears the older context after the handler
returns. However, if applications want to change this behavior and
manage the allocation/de-allocation/freeing themselves and let the
server handle only the "socket close" case, this commit provides such
an option.

components/esp_http_server/include/esp_http_server.h

@@ -362,6 +362,18 @@ typedef struct httpd_req {
      * function for freeing the session context, please specify that here.
      */
     httpd_free_ctx_fn_t free_ctx;
+
+    /**
+     * Flag indicating if Session Context changes should be ignored
+     *
+     * By default, if you change the sess_ctx in some URI handler, the http server
+     * will internally free the earlier context (if non NULL), after the URI handler
+     * returns. If you want to manage the allocation/reallocation/freeing of
+     * sess_ctx yourself, set this flag to true, so that the server will not
+     * perform any checks on it. The context will be cleared by the server
+     * (by calling free_ctx or free()) only if the socket gets closed.
+     */
+    bool ignore_sess_ctx_changes;
 } httpd_req_t;
 
 /**

components/esp_http_server/src/esp_httpd_priv.h

@@ -60,6 +60,7 @@ struct thread_data {
 struct sock_db {
     int fd;                                 /*!< The file descriptor for this socket */
     void *ctx;                              /*!< A custom context for this socket */
+    bool ignore_sess_ctx_changes;           /*!< Flag indicating if session context changes should be ignored */
     void *transport_ctx;                    /*!< A custom 'transport' context for this socket, to be used by send/recv/pending */
     httpd_handle_t handle;                  /*!< Server handle */
     httpd_free_ctx_fn_t free_ctx;      /*!< Function for freeing the context */

components/esp_http_server/src/httpd_parse.c

@@ -588,6 +588,7 @@ static void init_req(httpd_req_t *r, httpd_config_t *config)
     r->user_ctx = 0;
     r->sess_ctx = 0;
     r->free_ctx = 0;
+    r->ignore_sess_ctx_changes = 0;
 }
 
 static void init_req_aux(struct httpd_req_aux *ra, httpd_config_t *config)
@@ -607,13 +608,14 @@ static void httpd_req_cleanup(httpd_req_t *r)
 {
     struct httpd_req_aux *ra = r->aux;
 
-    /* Retrieve session info from the request into the socket database */
-    if (ra->sd->ctx != r->sess_ctx) {
-        /* Free previous context */
+    /* Check if the context has changed and needs to be cleared */ 
+    if ((r->ignore_sess_ctx_changes == false) && (ra->sd->ctx != r->sess_ctx)) {
         httpd_sess_free_ctx(ra->sd->ctx, ra->sd->free_ctx);
-        ra->sd->ctx = r->sess_ctx;
     }
+    /* Retrieve session info from the request into the socket database. */
+    ra->sd->ctx = r->sess_ctx;
     ra->sd->free_ctx = r->free_ctx;
+    ra->sd->ignore_sess_ctx_changes = r->ignore_sess_ctx_changes;
 
     /* Clear out the request and request_aux structures */
     ra->sd = NULL;
@@ -641,6 +643,7 @@ esp_err_t httpd_req_new(struct httpd_data *hd, struct sock_db *sd)
     /* Copy session info to the request */
     r->sess_ctx = sd->ctx;
     r->free_ctx = sd->free_ctx;
+    r->ignore_sess_ctx_changes = sd->ignore_sess_ctx_changes;
     /* Parse request */
     esp_err_t err = httpd_parse_req(hd);
     if (err != ESP_OK) {