TLS sockets are currently using BIOs that rely on access to a socket file descriptor, namely:

BIO* bio = BIO_new_socket(callbacks_->ioHandle().fdDoNotUse(), 0);

To avoid direct use of the fd and to ensure that SslSockets can work with any type of IoHandles, probably mem BIOs should be used instead. I am willing to do the work but does anybody know if this comes with any significant downsides? Are there any better alternatives?