Application shutdown can hang if there are DNS lookups on-going that don't get answers

Any network operation that does QHostInfo::lookupHost launches a new task into global QThreadPool instance. If this DNS lookup starts and for whatever reason there is no reply from a DNS server and the application is closing, it will hang there for 20-30seconds before actually exiting as it is waiting for the QThreadPool to finish.

In Windows 8 there seems to be DnsQueryEx function which could do asynchronous lookups and provides means to cancel the request in case the application wants to quit. Perhaps this could be used without a worker thread+getnameinfo.