THRIFT-5996: connection check supports TLS sockets

[murfffi]

Client: go

The connection check first introduced in THRIFT-5214 now supports TLS connections using a technique from the code that initially inspired the check:
go-sql-driver/mysql#934

Testing done: new test with alongside the existing test of conn. check

[fishy]

in the jira ticket your proposal was to do this before trying to get syscallConn. is there a reason you flipped it to this approach?

I like that approach better because that way you don't have the next line that rewrites syscallConn, ok which is very error-prone (e.g. if you used ok instead of isTLS on line 45 that's a bug that's hard to spot).

[murfffi]

Thanks for the review! I agree that the version is more convoluted and thus error prone .

I wondered if it is likely that, in the future, Go team makes *tls.Config implement syscall.Conn directly, possibly to utilize https://docs.kernel.org/networking/tls-offload.html on Linux.

I though about this more and I believe that if something drastic like that happens, the syscall code may not work and we should unwrap the connection anyway.

I changed it back to the variant in JIRA. Please take another look.

[murfffi]

I reviewed golang/go#44506 - tracking kernel TLS support in Go . It is in state Proposal-Accepted but not implemented. A couple of people implemented crypto/tls forks as PoC. I think the point still stands - there is no value to check if tls.Conn implements syscall.Conn.