How to debug a TLSv1.3 protocol problem?

[Claus Assmann]

On Tue, May 19, 2020, Matt Caswell wrote:

> > SSL_accept:error in TLSv1.3 early data

> This comes from this code in the info callback which you lifted from s_cb.c:

> Please could you modify this as follows:

> +        ERR_print_errors(bio_err);

That's basically already in the code:
while ((l = ERR_get_error_line_data((const char **) &file, &line,
		    (const char **) &data, &flags)) != 0)
  log it ...
but that does not generate any output. Even if I add
the line you suggested there's no extra output
(to make sure there would be something I also added
an BIO_fprintf() and that output is shown, so it's not
a problem with the BIO).

I guess I have to figure out how to use wireshark for this.