cgrates: make sure ctx is released on backup node

when cgrates ctx is being replicated, we need to release it when the
dialog is destroyed, otherwise it will leak.

Many thanks for @NicoFrLy on GitHub for reporting it.
Close #3656

Author: razvancrainea

modules/cgrates/cgrates_acc.c

@@ -111,11 +111,24 @@ static inline struct cgr_acc_ctx *cgr_get_acc_ctx(void)
 	return ctx->acc;
 }
 
-struct cgr_acc_ctx *cgr_tryget_acc_ctx(void)
+static struct cgr_acc_ctx *cgr_fetch_acc_ctx(struct dlg_cell *dlg)
 {
-	struct cgr_acc_ctx *acc_ctx;
 	int_str ctxstr;
 	int val_type;
+
+	/* search for the accounting ctx */
+	if (cgr_dlgb.fetch_dlg_value(dlg, &cgr_ctx_str, &val_type, &ctxstr, 0) < 0)
+		return NULL;
+	if (ctxstr.s.len != sizeof(struct cgr_acc_ctx *)) {
+		LM_BUG("Invalid ctx pointer size %d\n", ctxstr.s.len);
+		return NULL;
+	}
+	return *(struct cgr_acc_ctx **)ctxstr.s.s;
+}
+
+struct cgr_acc_ctx *cgr_tryget_acc_ctx(void)
+{
+	struct cgr_acc_ctx *acc_ctx;
 	struct cgr_kv *kv;
 	struct list_head *l, *sl;
 	struct list_head *t, *st;
@@ -132,14 +145,8 @@ struct cgr_acc_ctx *cgr_tryget_acc_ctx(void)
 	dlg = cgr_dlgb.get_dlg();
 	if (!dlg) /* dialog not found yet, moving later */
 		return NULL;
-	/* search for the accounting ctx */
-	if (cgr_dlgb.fetch_dlg_value(dlg, &cgr_ctx_str, &val_type, &ctxstr, 0) < 0)
-		return NULL;
-	if (ctxstr.s.len != sizeof(struct cgr_acc_ctx *)) {
-		LM_BUG("Invalid ctx pointer size %d\n", ctxstr.s.len);
-		return NULL;
-	}
-	acc_ctx = *(struct cgr_acc_ctx **)ctxstr.s.s;
+
+	acc_ctx = cgr_fetch_acc_ctx(dlg);
 	if (!acc_ctx) /* nothing to do now */
 		return NULL;
 
@@ -856,6 +863,16 @@ static void cgr_dlg_onwrite(struct dlg_cell *dlg, int type,
 		pkg_free(sessions_kvs);
 }
 
+static void cgr_dlg_destroy(struct dlg_cell *dlg, int type,
+		struct dlg_cb_params *_params)
+{
+	struct cgr_acc_ctx *ctx = cgr_fetch_acc_ctx(dlg);
+	if (ctx)
+		cgr_ref_acc_ctx(ctx, -1, "destroy");
+	else
+		LM_DBG("context already released\n");
+}
+
 int w_cgr_acc(struct sip_msg* msg, void *flag_c, str* acc_c, str *dst_c,
 		str *tag_c)
 {
@@ -962,6 +979,10 @@ int w_cgr_acc(struct sip_msg* msg, void *flag_c, str* acc_c, str *dst_c,
 			LM_ERR("cannot register callback for context serialization!\n");
 			return -1;
 		}
+
+		if (cgr_dlgb.register_dlgcb(dlg, DLGCB_DESTROY,
+					cgr_dlg_destroy, NULL, NULL) != 0)
+			LM_ERR("cannot register callback for context release! context might leak!\n");
 		ctx->engaged = 1;
 	}
 
@@ -1277,6 +1298,16 @@ void cgr_loaded_callback(struct dlg_cell *dlg, int type,
 		LM_ERR("cannot register callback for database accounting\n");
 		goto internal_error;
 	}
+	if (cgr_dlgb.register_dlgcb(dlg, DLGCB_WRITE_VP,
+				cgr_dlg_onwrite, ctx, NULL) != 0) {
+		LM_ERR("cannot register callback for context serialization!\n");
+		goto internal_error;
+	}
+
+	if (cgr_dlgb.register_dlgcb(dlg, DLGCB_DESTROY,
+				cgr_dlg_destroy, NULL, NULL) != 0)
+		LM_ERR("cannot register callback for context release! context might leak!\n");
+	ctx->engaged = 1;
 	LM_DBG("successfully loaded acc ctx=%p\n", ctx);
 	return;
 internal_error: