Re: [RFC 1/3] tcp: randomize tcp timestamp offsets for each connection

On Thu, 2016-08-25 at 11:06 +0200, Florian Westphal wrote:

So I gave this a try and it does avoid this tcp_request_sock increase,
but I feel that getting boot_time_rnd is too easy.

Fair enough, I didn't think very hard about it.

I tried a few other ideas but nothing satisfying/simpler came out of it
(e.g. i tried to also hash the isn but that gets scaled w. current
 clock so it doesn't work).

Are you more concerned wrt. complexity or the reqsk increase?

No, a reqsk increase is really fine.

I guess I was simply worrying your work would make my future submission
more tricky.

Here at Google we have been using usec resolution in TCP timestamps for
a while for all our DC traffic, and we have to upstream this at some
point.

It would be nice if the randomization was optional, because having usec
timestamps with a common base (ie no per flow random base) helps a lot
to understand the host delays at transmit time, and receive time.

I will review your patch more in depth today, thanks.