Support TLS 1.3 for okhttp transport

[voidzcy]

Our current okhttp version (2.7.4 Feb 2016) does not support TLS 1.3 https://github.com/grpc/grpc-java/blob/cb8b0679add2d389cfd15cd34e11c3577e3de2cb/okhttp/third_party/okhttp/main/java/io/grpc/okhttp/internal/ConnectionSpec.java#L60

Okhttp3 supports that. Since we don't have a short-term plan for upgrading to okhttp3, we may consider adding TLS 1.3 support to our existing okhttp transport.

[beatrausch]

Hi, whats the current state of TLS1.3 in grpc? Regards

[minopolous]

Yeah, same question we just fell over connection failures to a service which forces TLS 1.3 and found this ticket here. When specifying the latest TLS1.3 in the tlsconnectionspec call, tls1.3 connection seems to work. Is it just to add the latets version to the default setup?