So are things 'bound to star' checked somewhere else in the path? I don't understand why the hash table wouldn't just have entries for each of the receiving connections still.
There is only one listener bound to star, instead of 16k listeners for every IP. Thus, the hash bucket mapping to port 53 has only one entry instead of 16k.
It works out the same for the application: 1 fd or 16k fds doesn't really matter if you're using epoll, and that single fd can accept connections to any of those 16k IP addresses.
It works out the same for the application: 1 fd or 16k fds doesn't really matter if you're using epoll, and that single fd can accept connections to any of those 16k IP addresses.