Multiple connections support.

[TimonPost]

With rust-openssl we run into an issue that we have to be able to listen to multiple endpoints which we do not know in advance. We somehow have to listen like a TCP listener and create streams for incoming connections. As you know with UDP this is a bit difficult but not possible. There are some solutions to this. Either wait for rustls to finish their DTLS implementation. Or use openssl. Since this library works with openssl it will choose the second option.

Unfortunately, rust-openssl does not have implemented this dtls listening feature. See this issue for more information.

And so I am trying to implement this feature. It takes some extra work than I initially thought. It requires an update to libc, openssl-sys and OpenSSL and this library of course.

My working branches are:

libc: https://github.com/TimonPost/libc/tree/dtls_additions
rust openssl: https://github.com/TimonPost/rust-openssl/tree/dtls_listen
this library https://github.com/TimonPost/udp-dtls/tree/multiple_connections