Merge branch 'rds-conn-spamming'

Sowmini Varadhan says:

====================
RDS: TCP: connection spamming fixes

We have been testing the RDS-TCP code with a connection spammer
that sends incoming SYNs to the RDS listen port well after
an rds-tcp connection has been established, and found a few
race-windows that are fixed by this patch series.

Patch 1 avoids a null pointer deref when an incoming SYN
shows up when a netns is being dismantled, or when the
rds-tcp module is being unloaded.

Patch 2 addresses the case when a SYN is received after the
connection arbitration algorithm has converged: the incoming
SYN should not needlessly quiesce the transmit path, and it
should not result in needless TCP connection resets due to
re-execution of the connection arbitration logic.
====================

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