presence: fix several issues when using build_notify_body_t

* use the custom content type body if provided
* populate the actual pres_ev_t list element with the build_notify_body_t
  function
* use a proper free function for the notify body string in case of error
* improve comment-docs for build_notify_body_t

modules/presence/event_list.c

@@ -226,6 +226,7 @@ int add_event(pres_ev_t* event)
 	ev->aux_free_body= event->aux_free_body;
 	ev->free_body= event->free_body;
 	ev->build_empty_pres_info= event->build_empty_pres_info;
+	ev->build_notify_body= event->build_notify_body;
 	ev->default_expires= event->default_expires;
 
 	if(not_in_list)

modules/presence/event_list.h

@@ -73,13 +73,14 @@ typedef int (get_rules_doc_t)(str* user, str* domain, str** rules_doc);
  * subscribe, instead of pushing a notify with a body built from the published
  * presentities, you can dynamically build with this function whatever 
  * body you want to be returned with the body
+ * A free_body_t function must also be provided if this function is used.
  * Input data: presentity SIP URI and the SUBSCRIBE's body
- * Output data: * the body (may be empty string if nothing to return); it must
+ * Output data: * the body (may be NULL if nothing to return); it must
  *                be a pkg allocated str and separate pkg allocated body
  *              * the content-type string - must be a pkg mem chunk 
  *                holding the CT body; note that the str itself is managed by
  *                the upper/calling layer, so just use/write into it.
- * Returns : body str upon success, NULL upon error
+ * Returns : body str or NULL (on error or no body to be returned)
  */
 typedef str* (build_notify_body_t)(str *pres_uri, str *subs_body,
 		str *ct_type);

modules/presence/notify.c

@@ -219,12 +219,16 @@ int build_str_hdr(subs_t* subs, int is_body, str* hdr, str *ct_body,
 		p += CRLF_LEN;
 	}
 
-	if(is_body && subs->event->content_type.s && subs->event->content_type.len)
+	if (!ct_body->len &&
+		subs->event->content_type.s && subs->event->content_type.len)
+		ct_body = &subs->event->content_type;
+
+	if(is_body && ct_body->len)
 	{
 		memcpy(p,"Content-Type: ", 14);
 		p += 14;
-		memcpy(p, subs->event->content_type.s , subs->event->content_type.len);
-		p += subs->event->content_type.len;
+		memcpy(p, ct_body->s , ct_body->len);
+		p += ct_body->len;
 		memcpy(p, CRLF, CRLF_LEN);
 		p += CRLF_LEN;
 	}
@@ -2052,6 +2056,7 @@ int send_notify_request(subs_t* subs, subs_t * watcher_subs,
 				} else if (subs->event->build_notify_body) {
 					notify_body = subs->event->build_notify_body(
 						&subs->pres_uri, &subs->subs_body, &ct_body);
+					free_fct = subs->event->free_body;
 				} else {
 					notify_body = get_p_notify_body(subs->pres_uri,
 							subs->event, 0, 0, (subs->contact.s)?&subs->contact:NULL,
@@ -2200,8 +2205,8 @@ int send_notify_request(subs_t* subs, subs_t * watcher_subs,
 				if(subs->event->type& WINFO_TYPE)
 					xmlFree(notify_body->s);
 				else
-				if(subs->event->apply_auth_nbody== NULL && subs->event->agg_nbody== NULL)
-					pkg_free(notify_body->s);
+				if(free_fct)
+					free_fct(notify_body->s);
 				else
 				subs->event->free_body(notify_body->s);
 			}