On Sat, 11 Sep 2004 20:45:43 -0600 "Wolfpaw - Dale Corse" <admin@xxxxxxxxxxx> wrote: > As for it being an application bug - it may be one in Mysql not > closing the sockets, but it is a Kernel Bug that allows CLOSE_WAIT > sockets to clog up the connection queues, and cause a DOS conditions > on other applications (such as Apache). Since most software used for > denial of service is badly written (intentionally) to exploit the > holes, the error should be fixed, not blamed on faulty software. If the application doesn't close it's file descriptors there is absolutely nothing the kernel can do about it. It's a resource leak, plain and simple. > That being said - below is a the proper description, and the code > used to exploit it. Hope it helps. This version is not the one > which invokes the CLOSE_WAIT state, but rather the TIME_WAIT one, > I am not able to publish the source code for the CLOSE_WAIT bug. There is nothing wrong with creating tons of TIME_WAIT sockets, they simply time out after 60 seconds (unless hit by a RESET packet or similar). This is how TCP works. > The log however clearly shows that a mysql descriptor is closed, > and then used immediately again by the socket call, which causes it > never to end up getting closed. Linux apparently has either no > timeout for CLOSE_WAIT, or it's a very very long one.. Either way > is a bad thing. Please do us all a favor and learn how TCP works. CLOSE_WAIT means simply that only one side of the TCP connection has done a close. Therefore the other end stays open until that side closes as well. There is no way to "time things out" or release the state.
