Function check_san_dns_name 

pub fn check_san_dns_name(
    cert_der: &[u8],
    server_name: &str,
) -> Result<bool, Error>

Check whether any SAN dNSName matches the given server name, without allocating.

Supports wildcard DNS names (*.example.com). Returns Ok(true) on match, Ok(false) on no match (or missing SAN extension), Err on parse failure.