http2: Reject incompatible TLS ALPN handshakes

[sebdeckers]

1. Only announce http/1.1 in ALPN when the fallback is allowed.
2. Immediately destroy connections that do not support HTTP/2 when the HTTP/1 fallback is not allowed. Previously these connections would instantiate an Http2Session and linger until they timed out or caused a protocol error.

Note: The Node.js API does not seem to allow rejecting TLS handshakes at the ALPN-level (as described in RFC 7301 3.2). Therefore we do not differentiate between TLS clients that failed to match an ALPN protocol, and clients that simply do not support ALPN. In practice this should make little, if any, difference. Should consider adding strict ALPN negotiation as an option to Node.js core TLS though.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

http2

[jasnell]

Updated master from nodejs/node master. This will need a rebase

[sebdeckers]

@jasnell rebased 👍

[sebdeckers]

@mcollina @jasnell As per discussion in the outdated code review I've changed this to emit an error instead of silently destroying the connection. See b900d2d. This could be pretty annoying to users, I fear, since must listen for socketError events or risk uncaught error events being thrown on a the socket (which is only accessible through the secureConnection event). Is that by design?

[mcollina]

I do not think we should emit an error event. This is a very specific case, and we should be more diligent. So maybe we should use an "unknownProtocol" event passing the socket, and if there are no listeners, we silently drop. If there is a listener (check the return value of emit()), we do nothing and it would be up to the user to decide what they want to do with this.

[sebdeckers]

@mcollina That sounds good to me. See ad8bb9d

[sebdeckers]

@jasnell Rebased and ready for review. Minor patch but introduces a new event as per above discussion.

[mcollina]

Still LGTM :).

[jasnell]

Landed!