[internal-branch.go1.21-vendor] http2: reject DATA frames after 1xx a…

…nd before final headers

When checking to see if a DATA frame can be accepted, check to
see if we have received a non-1xx header, not whether we have
received any header.

For golang/go#65927
Fixes golang/go#66254

Change-Id: Id4fae1862de6179f8fc95e02dec7d4c47a7640e1
Reviewed-on: https://go-review.googlesource.com/c/net/+/567175
Reviewed-by: Jonathan Amsterdam <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-on: https://go-review.googlesource.com/c/net/+/574855
Auto-Submit: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>

http2/transport.go

@@ -2663,7 +2663,7 @@ func (rl *clientConnReadLoop) processData(f *DataFrame) error {
 		})
 		return nil
 	}
-	if !cs.firstByte {
+	if !cs.pastHeaders {
 		cc.logf("protocol error: received DATA before a HEADERS frame")
 		rl.endStreamError(cs, StreamError{
 			StreamID: f.StreamID,