Re: [PATCH] TCP: add option for silent port knocking with integrity protection

From: Christian Grothoff <redacted>
Date: Tue, 10 Dec 2013 19:35:36 +0100

Only NAT implementations that change the SQN are not supported
(those should be rare, but we have no hard data on this).

Even Linux's netfilter can and does do this, it is absolutely necessary
for tracking SIP and FTP protocols, and it's also used in our virtual
server load balancing modules.