Write bits about TCP timestamps in Tails design documentation

As discussed in the “Risks of enabled/disabled TCP timestamps?” thread on tails-dev, we might want to disable TCP timestamps just to be on the safe side, but stating exactly what kind of attacks this would protect against is not that clear.

As intrigeri put it:

I’m still not convinced we can put statements as bold as “tracking the
clock down to the millisecond” in there, without thinking a bit about
how an attacker is affected by the network lag between the time a TCP
timestamp was created, and the time when they get to see the packet.

I mean, I’m weak at stats and all and you probably know better, but
learning that “some unknown time ago, the system clock was T with
a millisecond precision” does not really give me the current system
clock with a millisecond precision, does it?

Hence, marking as a research task to start with, and we can turn it into a documentation one once we’ve got the needed data.

Feature Branch: feature/6579-disable-tcp-timestamps

Parent Task: #6579 (closed)

Related issues

• Blocked by #6580 (closed)

Original created by @intrigeri on 6581 (Redmine)