On Feb 26, 5:54 pm, "Joshua J. Kugler" <[EMAIL PROTECTED]> wrote: > Considering that UNIX Network Programming, Vol 1 (by W. Richard Stevens) > recommends "_All_ TCP servers should specify [SO_REUSEADDR] to allow the > server to be restarted [if there are clients connected]," and that > self.allow_reuse_address = False makes restarting a server a pain if there > were connected clients, why does SocketServer default allow_reuse_address > to False? It's kind of bemusing to subclass ThreadingTCPServer just to > change one variable that arguably should have been True in the first place. > > Is there some history to this of which I'm not aware? Is there a good > reason for it to default to false? >
Yes, it is there for a good reason. Security is the primary focus of that option. If you enable that option, rogue applications can assume service processing under a number of server failure conditions. In other words, start your rogue, crash the primary service, and you now have a rogue service running. Even periodic checks will show the server is still running. Under a number of other configurations, it is also possible for the rogue service to simply start and usurp some types of IP traffic on certain OSs which would otherwise be delivered to your real server. Contrary to the book, blindly enabling SO_REUSEADDR is a very, very bad idea unless you completely understand the problem domain. I'm sure Stevens' does understand so it makes for a good choice for him. On the other hand, most people don't understand the implications so it makes for a very, very poor move from a security perspective. Long story short, it is not a bug. It is a feature. The proper default is that of the OS, which is to ensure SO_REUSEADDR is disabled unless you absoluetely understand what you're buying by enabling it. Greg -- http://mail.python.org/mailman/listinfo/python-list
