From: Martin KaFai Lau <redacted>
Date: Fri, 18 Aug 2017 13:51:36 -0700

It seems like that middle box specifically drops TCP_RST if it
does not know anything about this flow.  Since the flowlabel of the TCP_RST
(sent in TW state) is always different, it always lands to a different middle
box.  All of these TCP_RST cannot be delivered.

This really is illegal behavior.  The flow label is not a flow _KEY_
by any definition whatsoever.

Flow labels are an optimization, not a determinant for flow matching
particularly for proper TCP state processing.

I'd rather you invest all of this energy getting that vendor to fix
their kit.

Thank you.