Hi, I've been working on IPv6 support, and one of the strangest things I find is BIO_get_accept_socket().
If bind_mode == BIO_BIND_REUSEADDR_IF_UNUSED, and bind() fails with EADDRINUSE it creates a new socket and tries to connect to the port it tried to bind() to, and if that fails tries to bind to it again but now with setting SO_REUSEADDR. Does anybody have an idea why it's trying to do that, and why we shouldn't just do SO_REUSEADDR the first time? Was there some OS that maybe did strange things when trying to use SO_REUSEADDR and it was already in use? The documentation also says: | BIO_set_bind_mode() and BIO_get_bind_mode() set and retrieve | the current bind mode. If BIO_BIND_NORMAL (the default) is set | then another socket cannot be bound to the same port. If | BIO_BIND_REUSEADDR is set then other sockets can bind to the | same port. If BIO_BIND_REUSEADDR_IF_UNUSED is set then and | attempt is first made to use BIO_BIN_NORMAL, if this fails | and the port is not in use then a second attempt is made | using BIO_BIND_REUSEADDR. The documentation is at least confusing, since it's about the address and port combination and not just the port. The main reason for using SO_REUSEADDR is that you can bind to an address / port combination that is in TIME_WAIT state, and it's recommended for server applications to always set this, and it's what I ended up doing in my new function. There are also some other cases you might want to use SO_REUSEADDR, and I suggest you read Stevens for that. In no case should it be possible to bind to the same TCP address / port from different applications, SO_REUSEADDR does not allow you to do that. But then I found some MSDN documentation that says that Windows allows others to hijack your socket when you've set SO_REUSEADDR and the results are non-deterministic. They also created an SO_EXCLUSIVEADDRUSE and I'm getting confused what it really does, but they say that server applications should set it. Anyway, is that whole logic with the connect() needed, or can I just always use SO_REUSEADDR (on non-windows hosts)? Kurt ______________________________________________________________________ OpenSSL Project http://www.openssl.org Development Mailing List openssl-dev@openssl.org Automated List Manager majord...@openssl.org
