WARN: do_handshake encountered BIO error

Submitted by Daniel F

Description

I see this in logs repeatedly when DTLS handshake is performed:

0:00:00.404539920 19083 0x130ead0 WARN dtlsconnection gstdtlsconnection.c:737:openssl_poll:GstDtlsConnection@0x137dde0 do_handshake encountered BIO error

Here are additional details:
SSL_do_handshake() returned -1
SSL_get_error() returned 5 (SSL_ERROR_SYSCALL)
errno is 0 (Success)
ERR_error_string() returned "error:00000005:lib(0):func(0):DH lib"

Real sockets do not return EOF when there is no data available. Your custom BIO does this when buffer is empty. I suspect that it should not do this, to match way how sockets operate:
https://github.com/GStreamer/gst-plugins-bad/blob/3caf16a1994b55b4ca19e2d5802b6a60e0a1149c/ext/dtls/gstdtlsconnection.c#L954

Version: 1.14.0