Merge branch 'mptcp-add-receive-buffer-auto-tuning'

Florian Westphal says:

====================
mptcp: add receive buffer auto-tuning

First patch extends the test script to allow for reproducible results.
Second patch adds receive auto-tuning.  Its based on what TCP is doing,
only difference is that we use the largest RTT of any of the subflows
and that we will update all subflows with the new value.

Else, we get spurious packet drops because the mptcp work queue might
not be able to move packets from subflow socket to master socket
fast enough.  Without the adjustment, TCP may drop the packets because
the subflow socket is over its rcvbuffer limit.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>