tests/qtest: optimize migrate_set_ports

Do not query connection parameters if all port numbers are known.  This is
more efficient, and also solves a problem for the cpr-transfer test.
At the point where cpr-transfer calls migrate_qmp and migrate_set_ports,
the monitor is not connected and queries are not allowed.  Port=0 is
never used for cpr-transfer.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Link: https://lore.kernel.org/r/1736967650-129648-19-git-send-email-steven.sistare@oracle.com
Signed-off-by: Fabiano Rosas <farosas@suse.de>

tests/qtest/migration/migration-util.c

@@ -135,25 +135,32 @@ migrate_get_connect_qdict(QTestState *who)
 
 void migrate_set_ports(QTestState *to, QList *channel_list)
 {
-    QDict *addr;
+    g_autoptr(QDict) addr = NULL;
     QListEntry *entry;
     const char *addr_port = NULL;
 
-    addr = migrate_get_connect_qdict(to);
-
     QLIST_FOREACH_ENTRY(channel_list, entry) {
         QDict *channel = qobject_to(QDict, qlist_entry_obj(entry));
         QDict *addrdict = qdict_get_qdict(channel, "addr");
 
-        if (qdict_haskey(addrdict, "port") &&
-            qdict_haskey(addr, "port") &&
-            (strcmp(qdict_get_str(addrdict, "port"), "0") == 0)) {
+        if (!qdict_haskey(addrdict, "port") ||
+            strcmp(qdict_get_str(addrdict, "port"), "0")) {
+            continue;
+        }
+
+        /*
+         * Fetch addr only if needed, so tests that are not yet connected to
+         * the monitor do not query it.  Such tests cannot use port=0.
+         */
+        if (!addr) {
+            addr = migrate_get_connect_qdict(to);
+        }
+
+        if (qdict_haskey(addr, "port")) {
             addr_port = qdict_get_str(addr, "port");
             qdict_put_str(addrdict, "port", addr_port);
         }
     }
-
-    qobject_unref(addr);
 }
 
 bool migrate_watch_for_events(QTestState *who, const char *name,