http2: in Server, disarm connection's ReadTimeout after first request

Fix a regression from Go 1.5 to Go 1.6: when we introduced automatic
HTTP/2 support in Go 1.6, we never handled Server.ReadTimeout. If a
user set ReadTimeout, the net/http package would set the read deadline
on the connection during the TLS handshake, but then the http2 package
would never disarm it, killing the likely-still-in-use connection
after the timeout period.

This CL changes it to disarm the timeout after the first request
headers, similar to net/http.Server.

Unlike net/http.Server, we don't re-arm it on each idle period,
because the definition of idle is more complicated with HTTP/2.

No tests here for now. Tests will be in the go repo once all the knobs
are in place and this is re-bundled into std, testing both http1 and
http2.

Updates golang/go#16450 (minimal fix for now)
Updates golang/go#14204 (considering a new http1+http2 IdleTimeout knob)

Change-Id: Iaa1570c118efda7dc0a65ba84cd77885699ec8fc
Reviewed-on: https://go-review.googlesource.com/30077Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

http2/server.go

@@ -1475,6 +1475,19 @@ func (sc *serverConn) processHeaders(f *MetaHeadersFrame) error {
 		handler = new400Handler(err)
 	}
 
+	// The net/http package sets the read deadline from the
+	// http.Server.ReadTimeout during the TLS handshake, but then
+	// passes the connection off to us with the deadline already
+	// set. Disarm it here after the request headers are read, similar
+	// to how the http1 server works.
+	// Unlike http1, though, we never re-arm it yet, though.
+	// TODO(bradfitz): figure out golang.org/issue/14204
+	// (IdleTimeout) and how this relates. Maybe the default
+	// IdleTimeout is ReadTimeout.
+	if sc.hs.ReadTimeout != 0 {
+		sc.conn.SetReadDeadline(time.Time{})
+	}
+
 	go sc.runHandler(rw, req, handler)
 	return nil
 }