mid-registrar: Avoid generating De-REGISTER from Passive node

    * enhance the usrloc API with a contact ownership checking function
    * mid-registrar now only generates De-REGISTER for owned contacts

Credits to Giovanni Maruzzelli for detailed reporting and instructions
on how to reproduce this issue!

Fixes #2559

(cherry picked from commit 4128f67)

modules/mid_registrar/ulcb.c

@@ -229,15 +229,14 @@ void mid_reg_ct_event(void *binding, ul_cb_type type)
 
 	LM_DBG("Contact callback (%d): contact='%.*s'\n", type, c->c.len, c->c.s);
 
-	if (type & (UL_CONTACT_DELETE|UL_CONTACT_EXPIRE)) {
-		if (reg_mode == MID_REG_THROTTLE_CT) {
-			skip_dereg = ul.get_ucontact_key(c, &ul_key_skip_dereg);
-			if (skip_dereg && skip_dereg->i == 1)
-				return;
-
-			if (unregister_contact(c) != 0)
-				LM_ERR("failed to unregister contact\n");
-		}
+	if (type & (UL_CONTACT_DELETE|UL_CONTACT_EXPIRE)
+	        && reg_mode == MID_REG_THROTTLE_CT) {
+		skip_dereg = ul.get_ucontact_key(c, &ul_key_skip_dereg);
+		if ((skip_dereg && skip_dereg->i == 1) || !ul.is_my_ucontact(c))
+			return;
+
+		if (unregister_contact(c) != 0)
+			LM_ERR("failed to unregister contact\n");
 	}
 }
 

modules/usrloc/dlist.c

@@ -716,7 +716,7 @@ get_domain_mem_ucontacts(udomain_t *d,void *buf, int *len, unsigned int flags,
 				/* a lot slower than fetching all tags before the outermost
 				 * loop, but at least we have proper responsiveness to tag
 				 * switches! */
-				if (pinging_mode == PMD_OWNERSHIP && !is_my_contact(c))
+				if (pinging_mode == PMD_OWNERSHIP && !_is_my_ucontact(c))
 					continue;
 
 				needed = (int)((c->received.s?

modules/usrloc/ucontact.c

@@ -1045,3 +1045,8 @@ int_str_t *put_ucontact_key(ucontact_t* _ct, const str* _key,
 {
 	return kv_put(_ct->kv_storage, _key, _val);
 }
+
+int is_my_ucontact(ucontact_t *c)
+{
+	return _is_my_ucontact(c);
+}

modules/usrloc/ucontact.h

@@ -199,6 +199,7 @@ typedef struct {
 
 int ucontact_coords_cmp(ucontact_coords a, ucontact_coords b);
 void free_ucontact_coords(ucontact_coords coords);
+int is_my_ucontact(ucontact_t *c);
 
 /*! \brief
  * ancient time used for marking the contacts forced to expired

modules/usrloc/ul_cluster.h

@@ -50,7 +50,7 @@ extern str ul_shtag_key;
 extern str contact_repl_cap;
 
 int ul_init_cluster(void);
-#define is_my_contact(__ct) \
+#define _is_my_ucontact(__ct) \
 	(!__ct->shtag.s || \
 	 clusterer_api.shtag_get(&__ct->shtag, location_cluster) \
 		== SHTAG_STATE_ACTIVE)

modules/usrloc/usrloc.c

@@ -78,6 +78,7 @@ int bind_usrloc(usrloc_api_t* api)
 	api->delete_ucontact_from_coords = delete_ucontact_from_coords;
 	api->ucontact_coords_cmp         = ucontact_coords_cmp;
 	api->free_ucontact_coords        = free_ucontact_coords;
+	api->is_my_ucontact              = is_my_ucontact;
 	api->next_contact_id             = next_contact_id;
 	api->update_sipping_latency      = update_sipping_latency;
 	api->raise_ev_ct_refresh         = ul_raise_ct_refresh_event;

modules/usrloc/usrloc.h

@@ -326,6 +326,15 @@ typedef struct usrloc_api {
 	 */
 	void (*free_ucontact_coords) (ucontact_coords coords);
 
+	/**
+	 * Check if an ucontact is logically owned by the current OpenSIPS node.
+	 * Always returns true in single node setups or if a contact does not have
+	 * an ownership tag attached.
+	 *
+	 * Return: 1 (true), 0 (false)
+	 */
+	int (*is_my_ucontact) (ucontact_t *c);
+
 	/**
 	 * Generate the next contact ID of a given record.  Returns a different
 	 * contact ID on each new call, rotating across CLABEL_MASK values.