On Thu, Aug 20, 2020 at 11:56:45PM +0200, David von Oheimb wrote: > OpenSSL has one function, namely BIO_lookup_ex(), that uses DNS lookup > functions. Since commit 28a0841bf58e3813b2e07ad22f19484308e2f70a of > 02 Feb 2016 it uses getaddrinfo(). Right, but even this is not "DNS lookup". It is hostname + service name resolution via the operating system's mechanisms for resolving hostnames and service names. This may, or may not, involve DNS lookups. There is no code in OpenSSL that *directly* performs DNS lookups. -- Viktor.