--- a/src/lib/lib-event-private.h	Wed Dec 04 19:39:10 2019 +0200
+++ b/src/lib/lib-event-private.h	Fri Nov 29 15:25:21 2019 +0200
@@ -1,6 +1,11 @@
 #ifndef LIB_EVENT_PRIVATE_H
 #define LIB_EVENT_PRIVATE_H
 
+struct event_pointer {
+	const char *key;
+	void *value;
+};
+
 struct event {
 	struct event_passthrough event_passthrough;
 	/* linked list of all events, newest first */
@@ -17,6 +22,7 @@
 	void *log_prefix_callback_context;
 	event_log_message_callback_t *log_message_callback;
 	void *log_message_callback_context;
+	ARRAY(struct event_pointer) pointers;
 	enum log_type min_log_level;
 	bool log_prefix_from_system_pool:1;
 	bool log_prefix_replace:1;

--- a/src/lib/lib-event.c	Wed Dec 04 19:39:10 2019 +0200
+++ b/src/lib/lib-event.c	Fri Nov 29 15:25:21 2019 +0200
@@ -591,6 +591,40 @@
 	return event->min_log_level;
 }
 
+struct event *event_set_ptr(struct event *event, const char *key, void *value)
+{
+	struct event_pointer *p;
+
+	if (!array_is_created(&event->pointers))
+		p_array_init(&event->pointers, event->pool, 4);
+	else {
+		/* replace existing pointer if the key already exists */
+		array_foreach_modifiable(&event->pointers, p) {
+			if (strcmp(p->key, key) == 0) {
+				p->value = value;
+				return event;
+			}
+		}
+	}
+	p = array_append_space(&event->pointers);
+	p->key = p_strdup(event->pool, key);
+	p->value = value;
+	return event;
+}
+
+void *event_get_ptr(struct event *event, const char *key)
+{
+	const struct event_pointer *p;
+
+	if (!array_is_created(&event->pointers))
+		return NULL;
+	array_foreach(&event->pointers, p) {
+		if (strcmp(p->key, key) == 0)
+			return p->value;
+	}
+	return NULL;
+}
+
 struct event_category *event_category_find_registered(const char *name)
 {
 	struct event_category *const *catp;

--- a/src/lib/lib-event.h	Wed Dec 04 19:39:10 2019 +0200
+++ b/src/lib/lib-event.h	Fri Nov 29 15:25:21 2019 +0200
@@ -100,19 +100,20 @@
    Only the fields in the events themselves are checked. Parent events' fields are not checked. */
 bool event_has_all_fields(struct event *event, const struct event *other);
 
-/* Returns the source event duplicated into a new event. */
+/* Returns the source event duplicated into a new event. Event pointers are
+   dropped. */
 struct event *event_dup(const struct event *source);
 /* Returns a flattened version of the source event.
    Both categories and fields will be flattened.
    A new reference to the source event is returned if no flattening was
-   needed. */
+   needed. Event pointers are dropped if a new event was created. */
 struct event *event_flatten(struct event *src);
 /* Returns a minimized version of the source event.
    Remove parents with no fields or categories, attempt to flatten fields
    and categories to avoid sending one-off parent events.  (There is a more
    detailed description in a comment above the function implementation.)
    A new reference to the source event is returned if no simplification
-   occured. */
+   occured. Event pointers are dropped if a new event was created. */
 struct event *event_minimize(struct event *src);
 /* Copy all categories from source to dest.
    Only the categories in source event itself are copied.
@@ -238,6 +239,15 @@
 struct event *event_set_min_log_level(struct event *event, enum log_type level);
 enum log_type event_get_min_log_level(const struct event *event);
 
+/* Add an internal pointer to an event. It can be looked up only with
+   event_get_ptr(). The keys are in their own namespace and won't conflict
+   with event fields. The pointers are specific to this specific event only -
+   they will be dropped from any duplicated/flattened/minimized events. */
+struct event *event_set_ptr(struct event *event, const char *key, void *value);
+/* Return a pointer set with event_set_ptr(), or NULL if it doesn't exist.
+   The pointer is looked up only from the event itself, not its parents. */
+void *event_get_ptr(struct event *event, const char *key);
+
 /* Add NULL-terminated list of categories to the event. The categories pointer
    doesn't need to stay valid afterwards, but the event_category structs
    themselves must be. Returns the event parameter. */