nginx: ability to log if client supports TLS SNI?
Solution 1:
Based on the nginx documentation about variables I think the information is not available.
Citing from exactly the same documentation you reference:
$ssl_server_name
returns the server name requested through SNI (1.7.0);
Thus, if no ssl_server_name is set than the client does not send the server_name extension, which means that the client does not use SNI.